Parks Victoria Technical Paper Series No. 56
Reef Surveys at Twelve Apostles Marine
National Park and The Arches Marine
Sanctuary
Matt Edmunds
Penny Pickett
Anthony Judd
Australian Marine Ecology Pty Ltd
June 2010
Parks Victoria Technical Series No. 56
Twelve Apostles Reef Survey
EXECUTIVE SUMMARY
The initial survey objective was to expand the Parks Victoria Subtidal Reef Monitoring
Program (SRMP) to provide baseline biological information from the Twelve Apostles Marine
National Park and The Arches Marine Sanctuary. The SRMP monitoring program uses
standardised underwater visual census techniques for long-term monitoring of reef biota
throughout Victoria and elsewhere in southern Australia, undertaken by divers. From 2003 to
2005, it was found that diving surveys were not going to be feasible in this region due to the
high exposure of the coastline to the prevailing weather, turbulent seas and diveable reefs
which were often too close to shoreline cliffs. Only one site was successfully surveyed using
the SRMP methods during this period.
During the same period of time, substantial advancements were made in the technology and
techniques for surveying the flora and fauna of deep marine habitats. These developments
included the use of easily deployed remotely operated vehicles (ROV) with sophisticated
underwater navigation systems, as well as developed protocols for the collection of biological
data from the underwater video on the ROV. These methods were implemented with success
at the Port Phillip Heads Marine National Park. Thus, with little prior success to undertake
SRMP monitoring within the Twelve Apostles Marine National Park and The Arches Marine
Sanctuary, the focus of this project was altered to use an ROV and the associated methods
to describe the biota of deeper habitats within the parks.
Seven (7) sites in the Twelve Apostles Marine National Park and four (4) sites in and near
The Arches Marine Sanctuary were surveyed using a standardised quantitative ROV video
survey technique. These were surveyed between June and August 2006 and ranged in depth
from 18 to 45 m depth. A total of 924 still-frames were captured from the video footage and
processed to provide percent cover abundance data on plants and animals attached to the
reef (sessile biota), including seaweeds, sponges, corals and ascidians (sea squirts).
A multivariate statistical analysis indicated there were approximately seven major
assemblage types in the region, with intergrades between these assemblage types also
occurring. The shallower sites (18-25 m depth) were dominated by seaweeds with a strong
component of larger brown algae, particularly the kelp species, Ecklonia radiata, thallose red
algae and encrusting coralline algae. The abundance of the brown algae decreased with
depth, with the canopy thinning to form a Ecklonia kelp ‘park’ at approximately 30-35 m
depth. The larger brown alga, Seirococcus axillaris, was a small but notable component of
the community at The Arches Marine Sanctuary sites, but was not present on shallower reefs
sites within the Twelve Apostles Marine National Park. The thallose red algal species were
similar to those observed on shallow subtidal reefs in Victoria, including: Phacelocarpus
peperocarpus, Plocamium mertensii, Gelidium asperum and Sonderopelta coriacea. The
abundance of sessile invertebrates on the reef tops increased with depth, particularly the
abundances of the isidid gorgonian, Pteronisis spp., erect sponges, and the large hydroid
fan, Solanderia fusca. At the two deepest sites surveyed; both 45 m in depth; contained
assemblages dominated by a variety of sponge colonies, bryozoans, coral and ascidians,
with only a very low abundance of seaweed.
As observed elsewhere in Victoria, the benthic assemblages were heterogeneous or patchy,
within each site. These patches of different assemblages were generally associated with
obviously different microhabitat structures, such as reef tops (horizontal surfaces), ledge
edges, vertical walls and caverns under ledges. Assemblages within these microhabitats
were replicated between sites. This indicated that assemblage structure is strongly
influenced or determined by environmental conditions.
An important outcome from this study was the provision and archiving of data and
information on existing conditions at the Twelve Apostles and The Arches marine protected
areas. The surveys undertaken can be replicated in the future to monitor the biological
condition of these areas over time. In addition, the data obtained is comparable with surveys
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Twelve Apostles Reef Survey
from other deep reefs in Victoria, including Port Phillip Heads Marine National Park and
Wilsons Promontory Marine National Park, facilitating a better understanding of the ecology
of deep reefs in Victoria.
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CONTENTS
EXECUTIVE
SUMMARY............................................................................................II
CONTENTS..............................................................................................................
IV
INDEX OF FIGURES AND TABLES........................................................................ VI
1 INTRODUCTION .................................................................................................. 1
1.1 Marine Protected Areas in the Twelve Apostles Region................................................... 1
1.1.1 Twelve Apostles Marine National Park ....................................................................................1
1.1.2 The Arches Marine Sanctuary .................................................................................................1
1.2 Subtidal Reef Monitoring Program ................................................................................... 2
1.3 Marine Habitat Mapping .................................................................................................. 2
1.4 Deep Reef Biota Surveys ................................................................................................ 2
1.5 Objectives ....................................................................................................................... 3
2
METHODS ........................................................................................................... 4
2.1 Survey Techniques ......................................................................................................... 4
2.2 Diving Survey – Underwater Visual Census .................................................................... 5
2.2.1 General Methods ......................................................................................................................5
2.2.2 Method 1 – Mobile Fishes and Cephalopods ...........................................................................7
2.2.3 Method 2 – Invertebrates and Cryptic Fishes ..........................................................................7
2.2.4 Method 3 – Macroalgae ...........................................................................................................8
2.2.5 Method 4 – Macrocystis ...........................................................................................................8
2.3 Towed Video Survey - Habitat Mapping........................................................................... 8
2.4 ROV Survey – Underwater Video Census .................................................................... 10
2.4.1 ROV Survey Sites ..................................................................................................................10
2.4.2 ROV Equipment ....................................................................................................................10
2.4.3 ROV Transects ......................................................................................................................13
2.5 Quantitative Video Analysis .......................................................................................... 16
2.5.1 Video Frame Capture ............................................................................................................16
2.5.2 Points-Cover Estimation ........................................................................................................16
2.5.3 Classification .........................................................................................................................18
2.5.4 Points Standardisation and Data Pooling ..............................................................................20
2.5.5 Data Summaries ....................................................................................................................20
2.5.6 Taxonomic Richness and Diversity .......................................................................................20
2.5.7 Community Analysis ..............................................................................................................21
2.5.8 Database ...............................................................................................................................21
3
RESULTS ......................................................................................................... 22
3.1 Regional Flora and Fauna ............................................................................................ 22
3.2 Site Observations ......................................................................................................... 23
3.2.1 Twelve Apostles MNP, Site 3801, 45 m Depth .....................................................................23
3.2.2 Twelve Apostles MNP, Site 3802, 45 m Depth .....................................................................26
3.2.3 Twelve Apostles MNP, Site 3803, 35 m Depth .....................................................................29
3.2.4 Twelve Apostles MNP, Site 3804, 45 m Depth ......................................................................32
3.2.5 Twelve Apostles MNP, Site 3805, 27-45 m Depth ................................................................34
3.2.6 Twelve Apostles MNP, Site 3806, 37 m Depth ......................................................................36
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3.2.7 Twelve Apostles MNP, Site 3807, 20 m Depth ......................................................................39
3.2.8 The Arches MS, Site 3831, 18 m Depth ................................................................................42
3.2.9 The Arches MS, Site 3832, 17-20 m Depth ...........................................................................45
3.2.10 The Arches MS, Site 3833, 25 m Depth ................................................................................48
3.2.11 The Arches MS, Site 3834, 27 m Depth ................................................................................50
3.3 Site Comparisons ......................................................................................................... 52
3.4 Assemblage Structures ................................................................................................ 57
3.5 Assemblage Distributions ............................................................................................. 62
ACKNOWLEDGMENTS .......................................................................................... 63
REFERENCES ........................................................................................................ 64
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INDEX OF FIGURES AND TABLES
FIGURES
Figure 1. Locations of the Twelve Apostles Marine National Park and The Arches
Marine Sanctuary ..................................................................................................... 1
Figure 2. Location of the ROV and diving survey sites at Twelve Apostles Marine
National Park and The Arches Marine Sanctuary ..................................................... 6
Figure 3. Biologist-diver with transect reel.............................................................................. 8
Figure 4. The cover of macrophytes is measured by the number of points intersecting
each species on the quadrat grid ............................................................................. 8
Figure 5. Underwater video towfish........................................................................................ 9
Figure 6. Location of the towed-video transects (red lines) at the Twelve Apostles
Marine National Park ..............................................................................................10
Figure 7. Remotely operated vehicle (ROV) and tether. Scanning sonar and sonar
tracking devices are mounted on top of the vehicle .................................................11
Figure 8. Screen capture from the scanning sonar: a reef wall is 6 m in front of the ROV
and extends 24 m to the left and right .....................................................................12
Figure 9. Remotely operated vehicle (ROV) instrument system ............................................12
Figure 10. Remotely operated vehicle instrument station ......................................................13
Figure 11. Location of ROV tracks for reef surveys at eastern Twelve Apostles MNP ...........14
Figure 12. Location of ROV tracks for reef surveys at western Twelve Apostles MNP...........15
Figure 13. Location of ROV tracks for reef surveys at The Arches Marine Sanctuary,
26th August 2006 .....................................................................................................15
Figure 14. Example screen of the BioPoints software for determining points-cover
abundance of sessile organisms .............................................................................17
Figure 15. Standardised sponge morphological types, after Bell and Barnes (2001).
Characteristic taxa are given where possible ..........................................................19
Figure 16. Site 3801: ‘Taco’ sponge .....................................................................................24
Figure 17. Site 3801: Hydroid fan, Solandaria fusca (right), and bryozoan colony (left) .........24
Figure 18. Site 3801: Example frames used for abundance analysis ....................................25
Figure 19. Site 3802: Typical assemblage with a variety of erect and encrusting
sponges, gorgonian fans, Mopsella zimmeri (yellow wiry strictures in centre)
and ascidian, Pyura spinifera (stalked structure in centre) .......................................26
Figure 20. Site 3802: Hydroid fan, Solandaria fusca, and arborescent orange sponge ..........27
Figure 21. Site 3802: Stony coral, Plesiastria versipora, colonies..........................................27
Figure 22. Site 3802: Example frames used for abundance analysis, Twelve Apostles
MNP .......................................................................................................................28
Figure 23. Site 3803: Isidid gorgonian, Pteronisis sp. (yellow) ...............................................30
Figure 24. Site 3803: Encrusting coralline algae and fleshy thallose red algae. Solitary
ascidians, Herdmania momus, are present upper left, Twelve Apostles MNP..........30
Figure 25. Site 3803: Example frames used for abundance analysis, Twelve Apostles
MNP .......................................................................................................................31
Figure 26. Site 3804: Thallose red algae, predominantly, Pterocladia lucida. Patches of
pink encrusting coralline algae are also visible ........................................................32
Figure 27. Site 3804: Example frames used for abundance analysis, Twelve Apostles
MNP .......................................................................................................................33
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Figure 28. Site 3805: Mixed red algal and sponge assemblage in foreground. There is
a southern rock lobster, Jasus edwardsii, present in the crevice to the right,
Twelve Apostles MNP ............................................................................................34
Figure 29. Site 3805: Example frames used for abundance analysis, Twelve Apostles
MNP ......................................................................................................................35
Figure 30. Erect ruffled grey sponge with central part of colony missing ..............................37
Figure 31. Site 3806: Cup sponge with thallose red alga, likely to be Callophyllus
rangiferina, Twelve Apostles MNP .........................................................................37
Figure 32. Site 3806: Example frames used for abundance analysis, Twelve Apostles
MNP ......................................................................................................................38
Figure 33. Site 3807: Southern rock lobster, Jasus edwardsii, foraging amongst
thallose red algae. Brown kelp, Ecklonia radiate, is in the background, Twelve
Apostles MNP ........................................................................................................40
Figure 34. Site 3807: Typical reef top habitat with kelp, Ecklonia abundance, thallose
red algae and pink encrusting coralline algae. Note the strong wave surge
which sweeps the kelp fronds over the reef top, Twelve Apostles MNP ..................40
Figure 35. Site 3807: Example frames used for abundance analysis, Twelve Apostles
MNP ......................................................................................................................41
Figure 36. Site 3831: Thallose red alga, Melanthallia obtusata, and brown kelp,
Ecklonia radiate, The Arches MS ...........................................................................43
Figure 37. Site 3831: Reef wall fauna under upper ledges of wall including encrusting
and massive sponges and gorgonian fans, Mopsella spp., The Arches MS ............43
Figure 38. Site 3831: Example frames used for abundance analysis, The Arches MS .........44
Figure 39. Site 3832: Example frames used for abundance analysis, The Arches MS .........46
Figure 40. Site 3833: Example frames used for abundance analysis, The Arches MS .........49
Figure 41. Site 3834: Example frames used for abundance analysis, The Arches MS .........51
Figure 42. Differences in community structure between sites in the Twelve Apostles
Marine National Park and The Arches Marine Sanctuary. Site medioids from
MDS ordination of all frames (two dimensions, Kruskall Stress = 0.17). Site
medioids were determined as the frame with the smallest Bray-Curtis distance
from the site centroid (means of species abundances) ...........................................56
Figure 43. Relative variations in community structures in sampled frames within and
between sites. Magenta symbols indicate frames sampled from that site.
Twelve Apostles Marine National Park ...................................................................58
Figure 44. Relative variations in community structures in sampled frames within and
between sites at The Arches Marine Sanctuary. Magenta symbols indicate
frames sampled from that site. Multidimensional scaling ordination of all
frames (two dimensions, Kruskall Stress = 0.17) ....................................................59
Figure 45. Classification of frames by assemblage type based on recurring clusters
between sites (Figures 32 and 33) .........................................................................59
TABLES
Table 1. Site survey details for the Twelve Apostles Marine National Park and The
Arches Marine Sanctuary ........................................................................................ 7
Table 2. Site details for towed-video surveys in the Twelve Apostles Marine National
Park ........................................................................................................................ 9
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Table 3. Standardised index of sponge classification categories for sponge
morphological types, i.e. type of shapes, structures and forms, after Bell and
Barnes (2001). Numbers refer to the coding system................................................20
Table 4. Site 3832: Abundance of fishes (per 1000 m2) at The Arches Marine
Sanctuary, diving survey, April 2004 .......................................................................47
Table 5. Site 3832: Percentage cover of algae at The Arches MS, diving survey, April
2004. ......................................................................................................................47
Table 6. Site 3832: Abundance of invertebrates at The Arches, diving survey, April
2004. ......................................................................................................................47
Table 7. Quantitative ROV data (BioPoints frames): percent cover of sessile plants and
animals at surveyed sites in the Twelve Apostles Marine National Park. Empty
cell indicates taxon not present ...............................................................................52
Table 8. Quantitative ROV data (BioPoints frames): percent cover of sessile plants and
animals at surveyed sites in The Arches Marine Sanctuary. Empty cell
indicates taxon not present .....................................................................................55
Table 9. Diversity statistics for BioPoints frames abundance data pooled by site ..................56
Table 10. Mean taxon abundances for identified assemblages in the Twelve Apostles
Marine National Park and The Arches Marine Sanctuary ........................................60
Table 11. Diversity statistics for frames abundances pooled by assemblage type. Hill’s
N2 statistic is an indicator of the number of dominant species in the
assemblage ............................................................................................................62
Table 12. Percent occurrence of different assemblage types at each site based on
classified frames .....................................................................................................62
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INTRODUCTION
1.1 Marine Protected Areas in the Twelve Apostles Region
1.1.1 Twelve Apostles Marine National Park
Following proposals from the Environment Conservation Council (ECC 2000), the Twelve
Apostles Marine National Park (MNP) was declared on the 16th November 2002. The Twelve
Apostles MNP encompasses 7500 hectares between Broken Head and Pebble Point, from
the high water mark to the limit of Victorian waters, approximately 3 nautical miles offshore
(Figure 1). Two areas, Gibson Steps Beach and Point Ronald to Rivernook, are excluded
from the park. Reef habitats within the Marine National Park include deep canyons, fissures,
gutters and sloping reefs as well as bombie and pinnacle type structures. This area supports
the highest diversity of marine invertebrates on limestone in Victoria (ECC, 2000). The level
of protection for marine environments within Marine National Parks includes prohibition of all
forms of recreational and commercial fishing.
1.1.2 The Arches Marine Sanctuary
The recommendations of the Environment Conservation Council (ECC) included the
reservation of a new sanctuary at The Arches (ECC 2000). The Arches Marine Sanctuary
(MS) was declared on the 16th November 2002 and encompasses 45 hectares found
offshore from Port Campbell (Figure 1). The area is named for its remarkable subtidal
limestone formations including arches, tunnels and canyons. These structures provide
physical habitat for a range of sessile invertebrate assemblages (ECC 2000). The level of
protection for marine environments within the Marine Sanctuary also prohibits all forms of
recreational and commercial fishing.
Figure 1. Locations of the Twelve Apostles Marine National Park and The Arches Marine Sanctuary.
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1.2 Subtidal Reef Monitoring Program
An important aspect in the management and conservation of Victorian marine natural
resources and assets is assessing the condition of the ecosystem and how this changes over
time. Combined with an understanding of ecosystem processes, this information can be used
to manage any threats or pressures on the environment to ensure ecosystem sustainability.
Consequently, the Victorian Government has established a long-term Subtidal Reef
Monitoring Program (SRMP). The primary objective of the SRMP is to provide information on
the status of Victorian reef flora and fauna, focussing on macroalgae, macroinvertebrates
and fish (Edmunds & Hart 2003). This includes monitoring the nature and magnitude of
trends in species abundances, species diversity and community structure. This is achieved
through regular surveys at locations throughout Victoria, encompassing both representative
and unique habitats and communities.
An initial objective of this study was to expand the subtidal reef monitoring program into the
Twelve Apostles MNP and Arches MS. This monitoring program involves diving to survey
fishes, invertebrates and seaweeds between depths of 5 to 15 m. During the course of 2004
and 2005, attempts were made to set up diving sites in the region, but were largely
unsuccessful for the following reasons:
•
Nearly all diveable reef habitats are close inshore near cliffs, making them generally
unsafe for boat navigation and diving because of swell and surf conditions.
•
All sites are subject to a large degree of ground surge, making dive surveys very difficult.
•
The coast is highly exposed and there were few days with suitable weather, sea, swell
and underwater visibility conditions suitable for diving surveys.
Only one site located at The Arches MS was surveyed, but the data collection was restricted
by 3 m ground surge and low visibility. The results are presented in this report. Following
these experiences, it was deemed impractical to implement a diving survey of the region.
Over the same period, remote video survey techniques were developed and standardised,
providing a robust means for deeper reef surveys.
1.3 Marine Habitat Mapping
In 2005 and 2006, Parks Victoria commissioned a comprehensive seabed habitat mapping
project which encompassed the Twelve Apostles Marine National Park. The habitat mapping
work involved high resolution bathymetry mapping using a multi-beam echo sounder and
mapping of general habitat types (e.g. sand, reef, kelp bed, sponge garden, etc.) using towed
video. These maps contributed to the fieldwork for this program and the methods are
described in this report. The resulting information was then delivered to Deakin University for
processing along with all the other data collected. The results are reported elsewhere.
An important outcome from this work was that most of the habitats in the Twelve Apostles
MNP are deep (> 20 m) and below practical diving limits. The main habitats included eastern
and western reef regions, separated by a sandy central region.
1.4 Deep Reef Biota Surveys
Underwater video and camera methods are the only practical way to survey flora and fauna
of deep habitats (non-destructively). Technological advances over the last few years have
resulted in the development of smaller remotely operated vehicles (ROV) that can be readily
deployed from small vessels and ships. These vehicles have an underwater video camera
and directional thrusters, which enable a surface operator (ROV pilot) to manoeuvre
precisely over identified areas to provide close-up images of habitats, communities and
species. At the same time, a robust system for collecting and analysing quantitative data on
deep reef species was developed and standardised (Edmunds et al. 2006). This
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standardised operating procedure was implemented to survey selected sites at the Twelve
Apostles MNP and The Arches MS.
1.5 Objectives
The principal objectives of this study were to:
1. Collect and archive data and information on the existing conditions within the Twelve
Apostles Marine National Park and The Arches Marine Sanctuary.
2. Describe reef species, communities and habitats and their distribution within the Twelve
Apostles Marine National Park and The Arches Marine Sanctuary.
To meet these objectives, the scope of work and associated tasks were:
1. Shallow reef surveys, using diver visual census, of selected representative and reference
sites areas within the Twelve Apostles Marine National Park and The Arches Marine
Sanctuary.
2. Seabed habitat mapping using a towed video camera within the Twelve Apostles Marine
National Park and The Arches Marine Sanctuary, the collected data to be delivered to
Deakin University for processing and analysis.
3. Deep reef surveys, using a remotely operated vehicle (ROV), of specified representative
areas within the Twelve Apostles Marine National Park and The Arches Marine
Sanctuary.
4. Quantitative analysis of still-frames from the ROV footage to determine abundances of
deep reef fauna.
5. Analysis and description of habitats, community assemblages, species and their
distribution within the Twelve Apostles Marine National Park and The Arches Marine
Sanctuary.
This report details the various diving, towed video and remotely operated vehicle surveys.
Results are provided for the diving and ROV surveys only.
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METHODS
2.1 Survey Techniques
It was originally planned to survey the flora and fauna of the Twelve Apostles region using a
highly standardised diving visual census technique. This technique, also known as the EdgarBarrett method, is used for long-term monitoring of sites throughout southern Australia,
including Victoria. In Victoria, these surveys form part of the Subtidal Reef Monitoring
Program (SRMP; Edmunds & Hart 2003). The advantages of this technique are that it is
non-destructive, it provides quantitative data on a large number of species and provides
data comparable between sites and over time. Implementation of this technique would
have provided standardised data as a base-line snap shot of biological conditions in the
region of marine protected areas. It would also have provided valuable biogeographic
information to better understand changes in communities along the coastline, from scales of
sub-kilometre to 100s of kilometres.
After various attempts to survey the region by diving, it was realised that the initial plan was
not feasible. The principal reasons for this were because the bathymetry was such that most
reefs of divable depth were in close to shore at the base of cliffs with high exposure of the
coastline to the prevailing westerly and southwesterly winds and swells. The proximity of the
potential dive sites to the shore made them inaccessible or unnavigable because of breaking
waves and backwash from the cliffs. The sites themselves were also largely inaccessible
because of the large degree of ground surge from long-period waves. Although the diving
sites were deemed unpractical, attempts were made to mobilise on the infrequent suitable
days to at least obtain a single baseline dataset. Suitable conditions for diving surveys were
defined as:
•
During daylight
•
Less than 20-25 knots of wind from the exposed directions
•
Less than 1.5-2.0 m seas
•
Less than 1.5-2.5 m swell (which produces ground swell)
•
More than 4-5 m of underwater visibility
•
Conditions deemed safe by the vessel skipper.
Suitable days did occur, but these invariably occurred at times which were problematic for
other reasons. Survey attempts were sometimes aborted after travelling to the site to ensure
personnel and equipment were not exposed to any significant risks. The most common
causes of aborted mobilisations were: bad sea and ground surge conditions; poor
underwater visibility; and equipment problems. Over the period from mid-2003 to end of
2005, there was only one, partially successful dive at The Arches.
During 2005 and 2006, Parks Victoria commissioned habitat surveys of the Twelve Apostles
Marine National Park. These included:
•
High resolution bathymetry mapping using a multibeam echosounder.
•
The general distributions of major habitat types, including sand, reef, kelp beds, kelp
park and sponge gardens using towed video transects.
This study identified extensive deep reef areas in the western and eastern regions of the
Twelve Apostles Marine National Park, separated by sandy habitats in between. Over the
same period, standardised deep reef quantitative survey techniques were developed and
tested with success in other deep reef habitats in Victoria (Edmunds et al. 2006). These
methods use remotely operated vehicles to video the substratum at a standardised scale.
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Frames are then captured from the video and analysed to determine the percent cover of the
various types of flora and fauna.
It was decided by Parks Victoria and Australian Marine Ecology to refocus the survey efforts
from diving surveys to deep reef surveys using the quantitative remotely operated vehicle
(ROV) sampling methods. Although this meant the Subtidal Reef Monitoring Program would
not be implemented in the region, there were advantages of better descriptions of the
predominant habitat types (which are mostly below diving depths) and the data would be
directly comparable with similar surveys on deep reefs in the Port Phillip Heads Marine
National Park and the Wilsons Promontory Marine National Park (Edmunds et al. 2006b).
While the team was mobilised in the area with survey equipment, additional towed video
footage was collected along transects required by Parks Victoria.
The methods are provided below for the three survey techniques used in this study –
underwater visual census by diving, towed video surveys and ROV video surveys. Data are
not presented for the towed video survey. This data contributed to a larger collaborative
study for Parks Victoria and was submitted to Deakin University for processing and analysis
(Holmes et al. 2007). The limited amount of diving data collected was presented in the
results, but the focus of the results section is on observations’ from the ROV surveys,
including qualitative and quantitative information.
2.2 Diving Survey – Underwater Visual Census
2.2.1 General Methods
As discussed above in Section 2.1; only one site was surveyed by underwater visual census
(by scientific divers). This site was Site 3802, near The Arches Marine Sanctuary, and was
surveyed on the 15th April 2004 (Figure 2; Table 1). The conditions on this dive were less
than suitable, with underwater visibility of 3-4 m, ground surge of up to 3 m and was very
dark underwater because of poor visibility and heavily overcast surface conditions.
The standardised diving reef survey technique of Edgar-Barrett (Edmunds & Hart 2003) was
applied, however the depth limits on diving time (18 m depth) meant only two 50 m transects
rather than four transects were surveyed. The site was marked with a buoy and the position
fixed using a GPS. A 100 m numbered and weighted transect line was run along the isobath
from the buoy (Figure 2). The resulting 100 m line was divided into two contiguous 50 m
sections of transect (T4 and T3 using standardised orientation).
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Figure 2. Location of the ROV and diving survey sites at Twelve Apostles Marine National Park and
The Arches Marine Sanctuary
Note: The Marine Park boundaries are outlined in blue.
For each transect, four different census methods were used:
1. The abundance and size structure of large fishes.
2. The abundance of cryptic fishes and benthic invertebrates.
3. The percent cover of macroalgae.
4. The density of string-kelp Macrocystis plants.
Excerpts from the standard operating procedure follow.
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Table 1. Site survey details for the Twelve Apostles Marine National Park and The Arches Marine
Sanctuary.
Region
Site
Date
Method
Depth
Video
Shot
Frames
Twelve Apostles
3801
26-06-06
ROV
45 m
180
1
79
3802
26-06-06
ROV
45 m
180
2
54
3803
26-06-06
ROV
35 m
181
3
46
3803
26-06-06
ROV
35 m
181
4
59
3804
26-08-06
ROV
45 m
196
4
127
3805
20-07-06
ROV
27 m
144
2
2
20-07-06
ROV
27 m
144
3
33
20-07-06
ROV
27 m
144
4
32
26-08-06
ROV
27 m
196
3
97
3806
26-08-06
ROV
37 m
197
5
152
3807
26-08-06
ROV
20 m
197
6
49
3831
26-08-06
ROV
18 m
198
1
53
3832
15-04-04
Diving
17 m
26-08-06
ROV
20 m
198
2
51
3833
26-08-06
ROV
25 m
199
3
52
3834
26-08-06
ROV
27 m
199
4
49
The Arches
n/a
Note: The Video and Shot columns refer to the footage identification system for the ROV surveys. The
Frames column is the number of frames analysed from the video footage from a site.
2.2.2 Method 1 – Mobile Fishes and Cephalopods
The densities of mobile large fishes and cephalopods are estimated by a diver swimming up
one side of each 50 m section of one transect, and then back along the other. The diver
records the number and estimated size-class of fish, within 5 m of each side of the line. The
size-classes for fish are 25, 50, 75, 100, 125, 150, 200, 250, 300, 350, 375, 400, 500, 625,
750, 875 and 1000+ mm. Each diver has size-marks on an underwater slate to enable
calibration of size estimates. The data for easily sexed species are recorded separately for
males and female/juveniles. Such species include the blue-throated wrasse Notolabrus
tetricus, herring cale Odax cyanomelas, barber perch Caesioperca rasor, rosy wrasse
Pseudolabrus psittaculus and some monacanthids. Two 10 x 50 m sections of the transect
are surveyed using a census for mobile fish.
2.2.3 Method 2 – Invertebrates and Cryptic Fishes
Cryptic fishes and megafaunal invertebrates (non-sessile: e.g. large molluscs, echinoderms,
& crustaceans) are counted along the transect lines used for the fish survey. A diver counts
animals within 1 m of one side of the line (two 1 x 50 m sections of the transect). A pole
carried by the diver is used to standardise the 1 m distance. The maximum length of abalone
and the carapace length and sex of rock lobsters are measured in situ using vernier callipers
whenever possible. Selected specimens are collected for identification and preservation in a
reference collection.
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Figure 3. Biologist-diver with transect reel.
2.2.4 Method 3 – Macroalgae
The area covered by macroalgal species is quantified by placing a 0.25 m2 quadrat at 10 m
intervals along the transect line and determining the percent cover of all plant species. The
quadrat is divided into a grid of 7 x 7 perpendicular wires, giving 50 points where the wires
intersect (including one corner; Figure 4). Cover is estimated by counting the number of
times each species occurs directly under the 50 positions on the quadrat (1.25 m2 for each of
the 50 m sections of the transect line). Selected specimens are collected for identification
and preservation in a reference collection.
2.2.5 Method 4 – Macrocystis
In addition to macroalgal cover, the density of Giant kelp, Macrocystis angustifolia plants, is
estimated. While swimming along the 100 m transect line, a diver counts all observable
plants within 5 m either side of the line, for each 10 m section of the transect (giving counts
for 100 m2). No Macrocystis plants were observed during this survey.
Figure 4. The cover of macrophytes is measured by the number of points intersecting each species
on the quadrat grid.
2.3 Towed Video Survey - Habitat Mapping
Towed video transects used an underwater video camera mounted obliquely (45º) in a 1 m
long towfish (Figure 5). The towfish has vertical stabilisers and adjustable weight system
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allowing it to be towed stably behind a vessel moving at speeds of up to 4 knots. The depth
is controlled by the length of rope and speed of the vessel.
Six transects were surveyed, located both within and to the east of The Twelves Apostles
Marine National Park, on the 26th – 27th July 2006 (Table 2; Figure 6). The video footage was
recorded on mini DV tape while the vessel GPS position and other data was logged by a
computer. The track logs and video footage was provided to Parks Victoria as the primary
deliverables.
Stabiliser fins
Camera cable and rope
Towing bridle
Nose cone
Lead weight
Camera
Figure 5. Underwater video towfish.
Table 2. Site details for towed-video surveys in the Twelve Apostles Marine National Park.
Region
Twelve Apostles
Date
Site
Method
Video
Shot
26-07-06
TV1
Towed-video
182
1
26-07-06
TV1
Towed-video
183/184
2
26-07-06
TV1
Towed-video
184
3
26-07-06
TV2
Towed-video
184
4
26-07-06
TV2
Towed-video
184
5
26-07-06
TV2
Towed-video
185
6
26-07-06
TV2
Towed-video
186
7
26-07-06
TV2
Towed-video
187
8
26-07-06
TV4
Towed-video
187
9
27-07-06
TV4
Towed-video
187/188
1
27-07-06
TV7
Towed-video
188/189/190
2
27-07-06
TV6
Towed-video
190/191
3
27-07-06
TV5
Towed-video
192/193
4
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Figure 6. Location of the towed-video transects (red lines) at the Twelve Apostles Marine National
Park.
Note: The Marine Park boundary is outlined in blue.
2.4 ROV Survey – Underwater Video Census
2.4.1 ROV Survey Sites
The survey sites were selected prior to undertaking the fieldwork, in conjunction with Parks
Victoria. The sites were positioned to provide representative information from the areas. The
site selection also included areas of interest based on features apparent from the fine-scale
bathymetry and towed video. Seven sites were surveyed in the Twelves Apostles Marine
National Park and four sites were surveyed near The Arches Marine Sanctuary (Table 1;
Figure 2). The survey period was from June to August 2006.
2.4.2 ROV Equipment
A small Seabotix LBV 150S2 remotely operated vehicle (ROV) was used for the deep habitat
surveys (Figure 7). This type of ROV had distinct advantages over many other types of ROV:
•
It is easily handled and deployed: weighing only 11 kg, it does not require heavy lifting
apparatus on the surface vessel and is safe in terms of manual handling.
•
Maximum operating depth/distance of 150 m.
•
High manoeuvrability provided by four thrusters – two forward, one vertical and one
lateral (forward/reverse, left/right, up/down, side-to-side).
•
High thrust to drag ratio (combined forward thrust of 7 kg and low drag tether of 7.6 mm
in diameter) enabling operation in slow currents.
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•
Minimal power requirements and electrical safety features – input power is from 650
watts from power supply of 240 VAC 50 Hz (safety features include isolated power
supply, ground fault interrupter, line insulation monitor, residual current monitor and leak
detectors).
•
High resolution colour video – super HAD chip with 570 lines of resolution, 0.2 lux of
light limit, 3.6 mm lens, auto iris and manual focus.
•
Camera is mounted to a rotating chassis to provide 270º field of vision – enabling
inspection of horizontal, sloped and vertical surfaces.
To assist with navigation, a 360º scanning sonar (Tritech Micron) was mounted on top of the
ROV (Figure 8). This system enabled detection and imaging of substratum structures beyond
the range of visibility, facilitating navigation among and around reef features.
A sonar tracking system (TrackLink USBL) was used to determine the position of the ROV
underwater relative to the vessel. This system consisted of a small hydrophone array
mounted on a pole beneath the hull of the surface vessel and a transponder mounted on the
ROV (Figure 9). In addition to the scanning sonar, the navigation system also consisted of a
differential GPS, electronic compass, and pitch and roll sensors (Figure 10). These vesselmounted instruments and the Tracklink USBL data were input to a mapping and logging
software program, ROVPOS. This software calculated the absolute position of the ROV and
plotted the ROV track on pre-prepared charts of bathymetry and survey waypoints (Figures 9
and 10). The ROVPOS software also logged the ROV and ship instrument data to a
computer hard drive.
Two Seabotix parallel lasers, mounted 50 mm apart, were fitted to the rotating camera
chassis of the ROV to provide a means of scaling the field of view and capture the
appropriate frame size. During the transect surveys, the ROV was positioned at a distance
from the substratum such that the laser spots aligned with marks on the video screen,
providing a standardised image height of 0.5 m.
Figure 7. Remotely operated vehicle (ROV) and tether. Scanning sonar and sonar tracking devices
are mounted on top of the vehicle.
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Figure 8. Screen capture from the scanning sonar: a reef wall is 6 m in front of the ROV and extends
24 m to the left and right.
Monitor
ROV Video
Monitor
Scanning Sonar
Monitor
ROVPOS
TrackLink
Monitor
Wheelhouse
ROVPOS
Video Duplicator
Digital Video
Recorder
(hard drive, DVD
and mini DV tape)
Hand Controller
Computer
Data Logging
(hard drive)
Twin Monitor
Video Card
ROV Power Unit
Tritech Scanner
ROVPO
S
TrackLink
Norman Is
USBL
Transceiver
Vertical
Reference Unit
(compass,
pitch and roll)
NMEA
Multiplexor
Sounder
GPS
Differential
Receiver
Vehicle
Figure 9. Remotely operated vehicle (ROV) instrument system.
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Figure 10. Remotely operated vehicle instrument station.
Rear (left to right): digital video recorder, recording monitor and ROV surface power unit; ROVPOS
mapping unit, integrating GPS and sonar tracking devices; scanning imaging sonar for detecting
features beyond the visibility range; ROV video monitor. Front (left to right): ROV hand controller,
keyboard and mouse to control software systems and log notes with track data, two-way radios for
communication with tether managers on back deck and skipper in wheelhouse; clapper board and shot
log for tagging video records.
2.4.3 ROV Transects
The ROV survey methods followed the standardised methods of Edmunds et al. (2006). The
vessel was first positioned above the site using the vessel’s GPS. The ROV was then
deployed from the vessel and maneuvered to the starting point using the scanning sonar,
ROVPOS positioning system and visual cues. The ROV was then maneuvered as slowly as
possible, countering the surge as much as possible, along the selected reef isobath.
At the Twelve Apostles MNP and The Arches MS survey areas, the substratum was
generally stepped with 1-3 m high ridges and gullies over a slight gradient; consequently
there was no clear orientation in terms of the reef slope or any obvious path along or
transverse to the isobath. Instead, the ROV was maneuvered haphazardly about the site with
the purpose of sampling as many and as much of each microhabitat type as possible
(Figures 11 to 13). These included:
•
Reef tops
•
Reef slopes
•
Ledge edges
•
Vertical walls
•
Caverns
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•
Twelve Apostles Reef Survey
Floors of depressions and gullies.
The ROV was navigated sideways when filming walls and forwards when filming flatter
sections. The camera was tilted with substratum aspect changes to maintain a perpendicular
viewing angle as much as possible. The ROV was also maneuvered to a fixed distance from
the substratum (as much as possible) to standardise the field of view to 0.7 x 0.5 m. The
correct distance was determined using a pair of in – built lasers and calibration marks on the
surface monitor. The transect was filmed at an average speed of approximately 1-2 minutes
per 10 m wherever possible. The position of the ROV was logged at 1-4 second intervals
throughout each deployment using TrackLink and ROVPOS.
The video of each transect was recorded with a time stamp onto a hard drive of a digital
video recorder (MPEG-2, XP format). The position of the ROV, surface vessel and other data
were logged to a computer hard drive by the ROVPOS software. Video footage was dubbed
onto mini DV tapes (SP format) and DVDs. Each tape was given a unique identification
number and each ROV deployment was given an identification number (e.g. the video tape
number plus the shot number).
Figure 11. Location of ROV tracks for reef surveys at eastern Twelve Apostles MNP.
Note: The underlying map depicts the fine scale bathymetry, showing reef flats, steps and gullies.
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Figure 12. Location of ROV tracks for reef surveys at western Twelve Apostles MNP.
Note: The Marine Park boundary is outlined in blue. The underlying map depicts the fine scale
bathymetry, showing reef flats, steps and gullies.
th
Figure 13. Location of ROV tracks for reef surveys at The Arches Marine Sanctuary, 26 August
2006.
Note: The Marine Sanctuary boundary is outlined in blue. There is currently no fine-scale bathymetry
data for this area.
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2.5 Quantitative Video Analysis
2.5.1 Video Frame Capture
Still frames were captured in consecutive sequence from the mini-DV tapes of ROV footage
using Sony TRV950 and VX2000 video cameras. The resolution of each frame was 640 x
480 pixels. An image was captured if it met the following criteria:
•
The distance to the substratum was correct – calibration points were marked on the
video monitor that aligned with the ROV laser spots at the correct distance.
•
The camera lamp illuminated the frame sufficiently to the edges.
•
The field of view did not overlap with a previously captured frame.
•
The footage (or the biota therein) was steady enough to capture a image sharp enough
for biota identification.
Along a transect, the taped video footage aims to capture as many frames as possible
provided that they met the criteria above. In other words, the sampling strategy was to
opportunistically maximise the data return rather than select frames at random or regular
intervals. The frames consequently varied in terms of separation distance, type of substratum
and biota, and orientation of substratum. Some types of microhabitats were unavoidably
under-represented in the frames, specifically those where the ROV could not be manoeuvred
safely, such as underneath overhangs and in crevices. On average, three frames were
captured from every minute of video footage. The frames were then used to determine the
percentage cover and spatial distribution of sessile plants and animals, as well as other
substratum features.
2.5.2 Points-Cover Estimation
The percent coverage of each identifiable component was determined using a points-cover
method, following Barrett et al. (2002a). The points-assessment and data recording were
facilitated by the software BioPoints (Australian Marine Ecology proprietary software). This
software is similar to PointCount, used for the Florida Keys Coral Reef Monitoring Project
(Eaken et al. 2002) and AVTAS, used for Great Barrier Reef Long-Term Monitoring Program
(Page et al. 2001).
A video frame is displayed on the screen with 50 randomly positioned dots on the image
(Figure 14). The microhabitat type was described by the observer, selected from a pull-down
list of categories, including:
•
Horizontal surface
•
Reef slope
•
Vertical rock face
•
Cavern/crevice
•
Ledge edge/reef break
•
Stones/broken rock
•
Patchy rock and sediments (among others)
The species or morphotype under each dot was then identified and entered by selecting the
taxon from a hierarchical menu (tree list) beside the frame and clicking on the appropriate dot
on the frame or the appropriately numbered button below the frame (Figure 14).
BioPoints saves the observer’s identifications of organisms and microhabitats in output files.
The points-data for each frame includes the pixel coordinates of every point and its
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identification. Once all points were classified, BioPoints compiled and formatted the data,
producing abundance data tables (percent cover by frame and site) for statistical analysis
and reporting.
A distinct advantage of the BioPoints software was that it enables users to browse between
frames (in sequence) to facilitate a consistent classification of morphotypes between frames,
and sites. On returning to a particular frame, BioPoints reloaded the existing data entered for
that frame, including the same positions for each dot. The selection of pre-defined categories
of organisms, including species and morphotypes, also assisted in reducing observer error in
the points-classification. Another distinct advantage of BioPoints was that no typing was
required – providing efficiency of data entry through point-and-click procedures and
eliminating a source of error.
Figure 14. Example screen of the BioPoints software for determining points-cover abundance of
sessile organisms.
Fifty random points are laid over each frame (large photograph). The taxon underlying a set
of points is selected from a drop-down list or tree-view on the right-hand side. The taxon is
assigned to each point by clicking on the point on the frame or the buttons underneath the
frame. The buttons change from blue to white when the associated point is assigned a taxon
and the button name changes to that taxon name. The details of the selected taxon are given
in the lower right of the screen, including representative photographs in the species
database.
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2.5.3 Classification
A standardised organism identification scheme was used with BioPoints. Organism
identification for each point was to the lowest taxon possible; however, there are many
species that cannot be visually identified from a video frame and many others that are not
described (particularly sponges). A hierarchical classification scheme was applied where an
organism can be identified according to both taxonomic and morphological features, with
each ‘taxon’ having a unique number code. This classification scheme was developed by
Australian Marine Ecology from a database of subtidal reef organisms and codes initially
developed by Neville Barrett and Graham Edgar (Tasmanian Aquaculture and Fisheries
Institute).
The Australian Marine Ecology database includes descriptions and photographs of each
‘taxon’ to assist with identification and appear on the screen when a taxon is selected from
the hierarchical menu. Hard-copy identification guides were also provided to the observers to
facilitate standardised classification. New taxa were added to the database and the
identification guides as they were encountered in the study.
The most abundant group that cannot generally be identified beyond morphotype is sponges.
In this case, a scheme established by Bell and Barnes (2001) was used, which is based on
the growth form, texture and colour of the colony (Figure 15; Table 3).
Standardised methods were applied to deal with unusual or ambiguous cases:
•
Where one organism had overgrown another, the uppermost organism was identified,
e.g. a sponge on top of a sea squirt.
•
When the point fell on a fish or a piece of drifting seaweed, the point was classified as
“unknown” because fixed items on the substratum were obscured from view.
•
If the location was not illuminated sufficiently (e.g. occasionally at the margin of a frame),
the point was classified as “unknown”.
•
If the area was out of scale (e.g. substratum visible in the distance beyond a ledge), the
point was classified as “unknown”.
•
If the area overlapped partially with a previous frame, the point was classified as
“unknown”.
To aid identification, the original video footage was often consulted to view organisms from
different angles and to judge their stiffness and movement in the flow of the current. As such,
the observers did the BioPoints analysis with DVD-copies of the ROV video footage running
simultaneously for frequent cross checking.
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1. Encrusting (EN), e.g. Darwinella sp
2. Massive (MA), e.g. Chondropsis sp
3. Globular (GL), e.g. Tethya sp
4. Pedunculate (PE)
5. Tubular (TU), e.g.Siphonochalina sp.
6. Flabellate (FL), e.g. Echinoclathria
leporina.
7. Cup (CU), e.g. Carteriospongia
caliciformis.
8. Arborescent (AR), e.g. Crella sp
9. Papillate (PA), e.g. Polymastia sp.
Figure 15. Standardised sponge morphological types, after Bell and Barnes (2001). Characteristic
taxa are given where possible.
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Table 3. Standardised index of sponge classification categories for sponge morphological types, i.e.
type of shapes, structures and forms, after Bell and Barnes (2001). Numbers refer to the coding
system.
Morphotype
Texture
Colour
3000. Encrusting (EN)
0. Smooth (smo)
1. W hite (W)
3100. Massive (MA)
30. Ruffled (ruf)
2. Yellow (Y)
3200. Globular (GL)
60. Spiky (spi)
3. Orange (O)
3300. Pedunculate (PE)
80. Reticulated (ret)
4. Pink (P)
3400. Tubular (TU)
90. Oscules visible (osc)
5. Red (R)
3500. Flabellate (FL)
6. Green (GR)
3600. Flabellate folded (FLf)
7. Purple (PU)
3700. Cup (CU)
8. Blue (BL)
3800. Arborescent (AR)
9. Brown (BR)
3900. Papillate (PA)
10. Grey (G)
11. Black (B)
2.5.4 Points Standardisation and Data Pooling
Prior to analysis, the points-cover of each taxon within each quadrat was corrected for any
points in the frame that could not be classified (“unknown”, database category 999). This
occurred where the substratum was poorly illuminated, beyond the field of view (into the
frame) or hidden by fish or drift seaweed. In such cases, the points-cover of each identifiable
category was standardised to a sum of 50 points.
A large number of taxa were recorded, most of which were in very low abundances and
observed infrequently. For the community analyses, abundances of sponge colour types
were pooled for each morphology and texture category (i.e. colours were ignored).
Categories distinguished by visually obvious characteristics and given a separate database
code were not pooled into the generic morphotype categories. This resulted in 63 taxa and
morphotypes from 924 suitable frames.
2.5.5 Data Summaries
Mean abundances (percent cover) were calculated for each taxon/morphotype at each site
and selected groups of frames (assemblage types).
2.5.6 Taxonomic Richness and Diversity
Taxonomic richness was determined by the number of species and morphotypes within the
frames analysed. Taxonomic (and morphological) diversity was calculated using Hill’s N2 as
an indicator (Krebs 1999). This can be considered as an approximation of the number of
dominant species in the community. Hill’s N2 is calculated as the reciprocal of Simpson’s
Index (Hill’s N2 = 1/DSimpson), which measures the probability that two individuals randomly
selected from a sample will belong to the same taxon:
N2 =
1
2
∑
pi
20
(1)
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where pi is the proportion of taxon/morphotype i in the assemblage. Hill’s N2 provides more
weighting for common species, as opposed to the weighting of rarer species (Krebs 1999)
and was chosen for its suitability to assess changes in dominant taxa.
2.5.7 Community Analysis
A Bray-Curtis dissimilarity matrix (Bray & Curtis 1957) was first constructed using differences
in abundances of the 63 taxa between each of the 924 frames. A two-dimensional
multidimensional scaling (MDS) ordination was sought from the ranked Bray-Curtis matrix.
Patterns in assemblage structure within and between sites were examined using plots of the
MDS ordination.
2.5.8 Database
The points abundance data for each frame was archived in a database, along with tables on
sampling details, frame positions and the species list.
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3
Twelve Apostles Reef Survey
RESULTS
3.1 Regional Flora and Fauna
The flora and fauna present in the Twelve Apostles and The Arches region was described
from qualitative and quantitative observations from the diving and ROV surveys (Section 3.2;
Tables 4 to 8). The flora and fauna of the region was generally composed of thallose red
seaweeds, encrusting coralline algae, brown seaweeds and a variety of sessile
invertebrates, most of which were sponges.
The predominant brown seaweed was the common kelp, Ecklonia radiata, which was more
abundant on shallower reefs, but present to depths of 35 m. Some shallower sites had
contributions to the canopy by other large brown algae, Seirococcus axillaris, and to a lesser
extent, Phyllospora comosa. Smaller brown algae included Carpomitra costatum and
Homoeostrichus sp., generally present in sandier areas.
There was a large component of thallose red algae at most sites with the abundant species
being typical of the Flindersion biogeographical province. These included: Phacelocarpus
peperocarpus, Melanthalia obtusata, Gelidium asperum, Plocamium mertensii, Callophyllus
rangiferina, Ballia callitricha, Sonderopelta coriacea and Haliptilon roseum.
There were small patches of green algae at most sites, predominantly Caulerpa flexilis, but
Caulerpa cactoides/annulata and Codium sp. were also present in the region.
There were over 30 distinguishable types of sponges observed, based on morphology and
texture. The most common types were encrusting ruffled, massive ruffled, massive
reticulated and arborescent ruffled sponges. A distinctive sponge present was the ‘taco’
sponge seen in Figure 16 (resembling a stalked Mexican taco), which is also known to occur
at Point Addis, but not on deep reefs further to the east, such as Port Phillip Heads or
Wilsons Promontory. Holopsamma laminaefavosa is a distinctive sponge of the Port Phillip
Heads region but was in very low abundance at Twelve Apostles and The Arches.
Common hydroids observed were the distinctly red hydroid, Halopteris glutinosa, the feathery
brown hydroid, Gymnangium superbum, and the large fan-like, Solandaria fusca.
The yellow soft coral, Parazoanthus sp., was only observed in the sampled frames at one
site. This species is generally more prevalent under ledges and in caves – microhabitats that
were not sampled extensively during this survey – and is likely to be more prevalent than the
data indicates. The soft coral, Erythropodium hicksoni, was common in the region, forming
large sheets over the substratum at some sites. A stony coral, Plesiastrea versipora, was
observed at one site – this is a species not often observed on cool temperate deep reefs.
Common erect corals included the gorgonians, Mopsella spp., Acabaria sp. and Pteronisis
spp. The seawhip, Primnoella australasiae, was observed at one site but was not a
characteristic component of the invertebrate fauna in the region.
Bryozoans were observed at most sites, particularly arborescent (bushy) and erect plate
(non-fenestrate) forms.
The ascidian, Herdmania momus, was common at most sites. Other ascidians were likely to
be common but are generally not readily distinguishable within the sampled video frames.
Observed mobile invertebrates included the southern rock lobster, Jasus edwardsii, and the
seastars, Nepanthia troughtoni, Plectaster decanus, Echinaster arcystatus, Nectria
macrobrachia and other Nectria species.
Commonly observed fishes were typical of the Otway Bioregion, including: the wrasses,
Notolabrus tetricus, Pseudolabrus psittaculus and Pictilabrus laticlavius; the morwongs,
Cheilodactylus nigripes and Dactylophora nigricans; sweep, Scorpis aequipinnis; perches,
Caesioperca rasor and Caesioperca lepidoptera; marble fish, Aplodactylus arctidens; and
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bullseye, Pempheris multiradiata. Leatherjackets, Monacanthidae, were present at some
sites but were generally not as abundant as on shallower reefs in Victoria. Larger fish sighted
included bastard trumpeter, Latridopsis forsteri, and blue morwong, Nemadactylus
valenciennesi.
3.2 Site Observations
3.2.1 Twelve Apostles MNP, Site 3801, 45 m Depth
Substratum structure
Low to medium profile reef. Reef surface highly fractured or
crenulated with cracks 0.3 to 1.5 m deep. Small ledges and
overhangs present (< 1 m in size). Small patches of rubble and
trapped sediments present under low ledges and in crevices.
Seaweeds
Seaweeds were present in very low abundances. Observed
species included, Callophycus rangiferina, Plocamium mertensii,
Rhyodymenia australis and Sonderopelta coriacea.
Sponges
A large variety of sponges, particularly erect and encrusting
sponges were present on the rock tops, with encrusting forms also
in sheets on the sides of rocks in places. Most sponges were in the
order of 5-20 cm high, but some were up to 50 cm high. There
were few sessile organisms inhabiting the surfaces under ledges.
Notable sponges include the stalked ‘taco’ sponge, including a very
large specimen of approximately 50 cm, cup sponges, tube
sponges and a ‘blue’ sponge.
Other sessile
invertebrates
The gorgonian corals, Mopsella and Acabaria, were abundant in
crevices along the rock sides. Pteronisis fans were abundant on
the rock tops, along with the hydroid fan, Solandaria fusca.
Herdmania momus and Pyura spinifera common.
Mobile fauna
Seastars included, Echinaster arcystatus and Nectria sp. Fishes
included, Notolabrus tetricus, Pseudolabrus psittaculus,
Nemadactylus valenciennesi, Caesioperca rasor, Caesioperca
lepidoptera, Meuschenia scaber and Pempheris multiradiata.
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Figure 16. Site 3801: ‘Taco’ sponge.
Figure 17. Site 3801: Hydroid fan, Solandaria fusca (right), and bryozoan colony (left).
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a. 6427 - Assemblage b
b. 6419 - Assemblage b
c. 6378 - Assemblage c
d. 6414 - Assemblage c
e. 6433 - Intermediate assemblage
f. 6387 - Intermediate assemblage
Figure 18. Site 3801: Example frames used for abundance analysis.
25
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3.2.2 Twelve Apostles MNP, Site 3802, 45 m Depth
Substratum structure
Low profile, dissected reef approximately 20-50 cm high,
interspersed by sand. No ledges or overhangs present.
Seaweeds
Seaweeds were exceptionally low in abundance.
Sponges
A large variety of sponges, particularly erect and encrusting
sponges were present on the rock tops. Most sponges were in the
order of 5-15 cm high, but some were up to 40 cm high. Notable
specimens included a large red arborescent sponge.
Other sessile
invertebrates
The gorgonian corals, Mopsella and Acabari,a were not as
abundant as there were fewer suitable crevices along the rock
sides. Pteronisis fans were abundant on the rock tops, along with
the hydroid fan, Solandaria fusca. Herdmania momus and Pyura
spinifera common.
Mobile fauna
Seastars included, Echinaster arcystatus and Nectria sp. Fishes
included Pseudolabrus psittaculus, Caesioperca rasor and
Caesioperca lepidoptera.
Figure 19. Site 3802: Typical assemblage with a variety of erect and encrusting sponges, gorgonian
fans, Mopsella zimmeri (yellow wiry strictures in centre) and ascidian, Pyura spinifera (stalked
structure in centre).
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Figure 20. Site 3802: Hydroid fan, Solandaria fusca, and arborescent orange sponge.
Figure 21. Site 3802: Stony coral, Plesiastria versipora, colonies.
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a. 6494 - Assemblage a
b. 6468 - Assemblage a
c. 6471 - Assemblage a
d. 6479 - Assemblage a
e. 6461 - Assemblage b
f. 6452 - Assemblage c
Figure 22. Site 3802: Example frames used for abundance analysis, Twelve Apostles MNP.
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3.2.3 Twelve Apostles MNP, Site 3803, 35 m Depth
Substratum structure
Medium profile reef with relatively smooth rocky slopes
interspersed by sandy gutters. Some gutters have vertical rock
faces 1-2 m high with ledges and undercuts in the face.
Seaweeds
Seaweeds were present in moderate abundances. Observed
species included, Phacelocarpus peperocarpus, Callophycus
rangiferina, Plocamium mertensii, Rhyodymenia australis,
Rhodymenia obtusata, Ptilonia australasica and Sonderopelta
coriacea. Encrusting coralline algae were common. Caulerpa
cactoides (possibly C. annulata) was present with sparsely
dispersed rhizomes. Occasional patches of Caulerpa flexilis were
present.
Sponges
There was a reasonable variety of sponges present, both erect
and encrusting, but had a much lower cover than the seaweeds.
Notable forms included the ‘taco’ sponge, unusual purple and grey
reticulated sponges
Other sessile
invertebrates
Pteronisis fans were abundant on the rock tops amongst the
seaweed thalli. The seawhip, Primnoella australasiae, was
conspicuous, but present in sparse abundances. The solitary
ascidian, Herdmania momus, was very abundant.
An unusual sighting was a patch of encrusting soft coral,
Erythropodium hicksoni, which was present on a reef top in a patch
approximately 2-3 m across.
Gorgonian fans, Mopsella spp. were present in the ledges of
vertical rock faces adjacent to the sandy gutters. The feathery
hydroid, Gymnangium superbum, was abundant along the reef
tops at the edge of the sandy gutters.
Mobile fauna
Seastars included, Nectria sp. and Tosia australis. Observed fish
were, Notolabrus tetricus.
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Figure 23. Site 3803: Isidid gorgonian, Pteronisis sp. (yellow).
Figure 24. Site 3803: Encrusting coralline algae and fleshy thallose red algae. Solitary ascidians,
Herdmania momus, are present upper left, Twelve Apostles MNP.
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a. 6524 - Assemblage d
b. 6595 - Assemblage d
c. 6509 - Assemblage d
d. 6519 - Assemblage e
e. 6545 – Assemblage e
f. 6532 - Assemblage e
Figure 25. Site 3803: Example frames used for abundance analysis, Twelve Apostles MNP.
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3.2.4 Twelve Apostles MNP, Site 3804, 45 m Depth
Substratum structure
Low profile reef with relatively smooth rocky slopes.
Seaweeds
Thallose red seaweeds covered approximately half the
substratum. Sonderopelta coriacea was particularly abundant,
along with, Phacelocarpus peperocarpus and Plocamium
mertensii. Encrusting coralline algae were common.
Sponges
There was a reasonable variety of sponges present, both erect
and encrusting, but abundances were low and erect forms were
sparsely distributed.
Other sessile
invertebrates
Pteronisis fans were present but not conspicuous. The solitary
ascidian, Herdmania momus was abundant.
Mobile fauna
Seastars included, Nectria sp. and Tosia australis. Observed fish
were, Nemadactylus valenciennesi, Aplodactylus arctidens and
Caesioperca rasor.
Figure 26. Site 3804: Thallose red algae, predominantly, Pterocladia lucida. Patches of pink
encrusting coralline algae are also visible.
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a. 7162 – Assemblage d
b. 7159 – Assemblage d
c. 7134 – Assemblage e
d. 7172 – Assemblage e
e. 7226 – Assemblage e
f. 7204 – Assemblage e
Figure 27. Site 3804: Example frames used for abundance analysis, Twelve Apostles MNP.
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3.2.5 Twelve Apostles MNP, Site 3805, 27-45 m Depth
Substratum structure
Flat-topped and sloped reef ridges, several metres high,
interspersed by gullies with vertical reef walls and undercut ledges.
Sand was present in small patches in the bottom of some gullies.
Seaweeds
The common brown kelp, Ecklonia radiata, formed small stands,
covering 10-20 % of the substratum on average. There was a high
abundance of thallose red seaweeds covering approximately half
the substratum. Abundant species included, Phacelocarpus
peperocarpus, Plocamium mertensii, Plocamium angustum,
Pterocladia lucida, Rhodymenia australis, Ballia callitricha and
Sonderopelta coriacea. Encrusting coralline algae were common.
Other species of brown algae were sparsely present, including
Homoeostrichus sp.
Sponges
Abundances of sponges were very low and erect forms were only
observed on the vertical wall faces.
Other sessile
invertebrates
Mopsella and Pteronisis fans were present but only on the vertical
reef faces. The solitary ascidian, Herdmania momus was
abundant.
Mobile fauna
Seastars included Nectria spp., Plectaster decanus and Nepanthia
troughtoni. Crustaceans were Jasus edwardsii. Observed fish were
Caesioperca rasor, Pempheris multiradiata, Scorpis aequipinnis,
Nemadactylus valenciennesi, Notolabrus tetricus and Pictilabrus
laticlavius.
Figure 28. Site 3805: Mixed red algal and sponge assemblage in foreground. There is a southern rock
lobster, Jasus edwardsii, present in the crevice to the right, Twelve Apostles MNP.
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a. 7098 – Assemblage c
b. 7732 – Assemblage e
c. 7716 – Assemblage e
d. 7049 – Assemblage e
e. 7724 – Assemblage f
f. 7672 – Assemblage f
Figure 29. Site 3805: Example frames used for abundance analysis, Twelve Apostles MNP.
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3.2.6 Twelve Apostles MNP, Site 3806, 37 m Depth
Substratum structure
Low profile reef, reasonably textured with outcrops and hollows up
to 0.5 m high. Bare rubble, gravel and sand present in some
hollows with indications of rumbling effects of the rubble around the
hollows. There were occasional steps in the reef of approximately
1-2 m high. Some of the steps were undercut into open caverns,
which were largely devoid of sessile biota. Sand gullies were
present in some areas of the reef. Many flat areas of reef were
partially inundated with sand, which filled hollows between rocks.
Seaweeds
The kelp Ecklonia, was common covering 10-20 % of the
substratum. There was a high abundance of thallose red seaweeds
covering over half the substratum. Abundant species included,
Melanthalia obtusata, Pterocladia lucida, Rhodymenia australis,
Gelidium asperum, Phacelocarpus peperocarpus, Plocamium
mertensii, Plocamium dilatatum, Callophyllus rangiferina, and
Sonderopelta coriacea. Encrusting coralline algae were common.
Small brown algae, including, Capomitra costata and
Homoeostrichus sp., were relatively common but in low
abundance. Small patches of the green alga, Caulerpa flexili,s
were observed.
Sponges
Abundances of sponges were low, but erect forms were sparsely
scattered over the reef, tending to more common near ledge
edges. A distinctive observation was a large erect ruffled grey
sponge, Figure 30, aligned vertically on a reef face with its central
part missing from an apparent disturbance in the past.
Other sessile
invertebrates
Mopsella fans were present but only on the vertical reef faces. The
solitary ascidian, Herdmania momus,was moderately abundant.
Pteronisis was present among the thallose algae on the reef tops,
but was more prevalent on the vertical reef faces. A large colony of
the hard coral, Plesiastria versipor,a and a large colony of the soft
cora,l Erythropodium hicksoni, were observed at this site.
Mobile fauna
Observed seastars included Nectria spp. Observed fish were
Caesioperca rasor, Cheilodactylus nigripes and Caesioperca rasor.
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Figure 30. Erect ruffled grey sponge with central part of colony missing.
Figure 31. Site 3806: Cup sponge with thallose red alga, likely to be Callophyllus rangiferina, Twelve
Apostles MNP.
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a. 7345 – Assemblage c
b. 7266 – Assemblage d
c. 7294 – Assemblage e
d. 7257 – Assemblage e
e. 7373 – Assemblage e
f. 7361 – Assemblage f
Figure 32. Site 3806: Example frames used for abundance analysis, Twelve Apostles MNP.
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3.2.7 Twelve Apostles MNP, Site 3807, 20 m Depth
Substratum structure
The reef consisted of flat areas of bedrock interspersed by steps
and gullies, 1-3 m deep. There was considerable erosion and
undercutting of the reef faces near these steps, creating
substratum complexity. There were little to no sessile biota inside
the larger caverns. Sand accumulation was on some of the lower
reef areas.
Seaweeds
A high abundance of thallose red seaweeds covering
approximately half the substratum. Abundant species included,
Phacelocarpus peperocarpus, Plocamium mertensii, Plocamium
dilatatum, Callophyllus rangiferina, and Sonderopelta coriacea.
Encrusting coralline algae were common. Small brown algae,
including what was probably, Dictyopteris acrostichoides,
Capomitra costata and Homoeostrichus sp. were relatively
common but in low abundance. The kelp, Ecklonia, was absent.
One small patch of the green, Caulerpa flexilis was observed.
Sponges
Sponges were rarely observed at this site, those seen were
located on the ledge edges.
Other sessile
invertebrates
The solitary ascidian, Herdmania momus, and arborescent
bryozoans were the only commonly observed sessile invertebrates
at this site. Low abundances of Mopsella gorgonians and
bryozoans were observed on the ledge edges.
Mobile fauna
Observed seastars included, Nectria spp. A southern rock lobster,
Jasus edwardsii, was observed foraging on top of the reef (Figure
33). Observed fishes were, Pseudolabrus psittaculus, Parma
victoriae and Notolabrus tetricus.
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Figure 33. Site 3807: Southern rock lobster, Jasus edwardsii, foraging amongst thallose red algae.
Brown kelp, Ecklonia radiate, is in the background, Twelve Apostles MNP.
Figure 34. Site 3807: Typical reef top habitat with kelp, Ecklonia abundance, thallose red algae and
pink encrusting coralline algae. Note the strong wave surge which sweeps the kelp fronds over the
reef top, Twelve Apostles MNP.
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a. 7420 – Assemblage e
b. 7437 – Assemblage e
c. 7417 – Assemblage f
d. 7405 – Assemblage f
e. 7439 – Assemblage f
f. 7446 – Assemblage g
Figure 35. Site 3807: Example frames used for abundance analysis, Twelve Apostles MNP.
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3.2.8 The Arches MS, Site 3831, 18 m Depth
Substratum structure
Medium to high profile reef with flat-topped ridges and gullies with
2-3 m high steps and ledges. Reef faces highly eroded to form
crevices, smaller ledges and undercuts, supporting sessile
invertebrate fauna. Some rocky rubble present in the gullies, but
the substratum was predominantly patchy reef and sand.
Seaweeds
The reef tops were covered by a high abundance of brown kelp,
Ecklonia radiata, brown alga Seirococcus axillaris, variety of
thallose red algae and encrusting coralline algae (Figure 36). The
thallose red algae included, Phacelocarpus peperocarpus,
Gelidium asperum, Melanthalia obtusata, Pterocladia lucida,
Callophyllus rangiferina, and the erect coralline, Haliptilon roseum.
Sonderopelta coriacea, was present, but not very abudant. Smaller
brown thallose algae were also present, including what appeared
to be Homoeostrichus.
The Ecklonia spp. on the reef tops had very long fronds, typical of
high water movement sites.
Sponges
Sponges were only observed on the ledge edges. Most colonies
were encrusting or of low profile, less than 10 cm high.
Other sessile
invertebrates
Nearly all sessile invertebrates were observed on or under the
ledges comprising the vertical reef faces (Figure 37). Commonly
observed colonies included gorgonians, Mopsella and Acabaria
and the encrusting soft coral, Erythropodium hicksoni. Colonies of
the feathery hydroid, Gymnangium superbum, were present on the
upper ledge edges, at the edge of the seaweed assemblages.
Mobile fauna
Observed seastars included, Nepanthia troughtoni. A southern
rock lobster, Jasus edwardsii, was observed in the crevice at the
base of a reef wall. Observed fishes were, Aplodactylus arctidens,
Notolabrus tetricus, Acanthaluteres vittiger, Meuschenia
flavolineata, Pseudolabrus psittaculus, Pictilabrus laticlavius,
Caesioperca rasor, Pempheris multiradiata.
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Figure 36. Site 3831: Thallose red alga, Melanthallia obtusata, and brown kelp, Ecklonia radiate, The
Arches MS.
Figure 37. Site 3831: Reef wall fauna under upper ledges of wall including encrusting and massive
sponges and gorgonian fans, Mopsella spp., The Arches MS.
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a. 7468 – Assemblage c
b. 7489 – Assemblage c
c. 7501 – Assemblage e
d. 7483 – Assemblage e
e. 7475 – Assemblage f
f. 7477 – Assemblage f
Figure 38. Site 3831: Example frames used for abundance analysis, The Arches MS.
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3.2.9 The Arches MS, Site 3832, 17-20 m Depth
Substratum structure
Medium to high profile reef with flat-topped ridges and gullies with
2-3 m high steps and ledges. There were extensive smooth, flat
areas between steps and gullies. The reef faces were highly
eroded to form crevices, smaller ledges and undercuts, supporting
sessile invertebrate fauna, although there tended to be little
colonisation in the lower caverns because of what appeared to be
scouring.
Seaweeds
The reef tops were covered by a high abundance of brown kelp,
Ecklonia radiata, brown alga, Seirococcus axillaris, a variety of
thallose red algae and encrusting coralline algae. The thallose red
algae included: Ptilonia australasica, Plocamium mertensii,
Sonderopelta coriacea, Phacelocarpus peperocarpus, Melanthalia
obtusata, and the erect coralline, Haliptilon roseum, was present,
but not very abundant. Smaller brown thallose algae were also
present; including what appeared to be, Homoeostrichus sp.
Sponges
Sponges were only observed on the ledge edges. Most colonies
were encrusting or of low profile, less than 10 cm high.
Other sessile
invertebrates
Nearly all sessile invertebrates were observed on or under the
ledges comprising the vertical reef faces. Mopsella and Herdmania
momus were the only conspicuous invertebrates apart from
sponges.
Mobile fauna
Observed seastars included, Nectria macrobrachia and Nepanthia
troughtoni. Observed fish were Notolabrus tetricus, Pictilabrus
laticlavius, Odax cyanomelas, Caesioperca rasor, Scorpis
aequipinnis, Cheilodactylus nigripes and Aplodactylus arctidens.
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a. 7516 – Assemblage c
b. 7525 – Assemblage c
d. 7530 – Assemblage e
e. 7538 – Assemblage e
f. 7553 – Assemblage f
g. 7558 – Assemblage f
Figure 39. Site 3832: Example frames used for abundance analysis, The Arches MS.
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2
Table 4. Site 3832: Abundance of fishes (per 1000 m ) at The Arches Marine Sanctuary, diving
survey, April 2004.
Species
%
male
Length (mm)
n
mean
sd
Aplodactylus
arctidens
n/a
1
375
0
Caesioperca
rasor
100
1
200
0
Cheilodactylus
nigripes
n/a
2
300
0
Odax
cyanomelas
0
1
375
0
Pictilabrus
laticlavius
100
1
150
0
Scorpis
aequipinnis
n/a
4
238
25
Length Class (mm)
100
125
150
200
250
300
350
375
1
1
2
1
1
1
3
Table 5. Site 3832: Percentage cover of algae at The Arches MS, diving survey, April 2004.
Species
Percent cover
Ecklonia radiata
61.4
Seirococcus axillaris
5.4
Encrusting corallines
16.8
Pterocladia lucida
18.2
Ballia callitricha
12.6
Gelidium asperum
2.4
Phacelocarpus peperocarpos
1.8
Melanthalia obtusata
1.6
Melanthalia abscissa
1.2
Nizymenia australis
1.6
Hemineura frondosa
1.2
Plocamium angustum
1.4
Plocamium mertensii
1.2
Plocamium dilatatum
0.6
Rhodymenia obtusa
0.8
Haliptilon roseum
0.8
Laurencia elata
0.4
Other thallose red alga
5.2
Table 6. Site 3832: Abundance of invertebrates at The Arches, diving survey, April 2004.
Species
Count (per 100 m2)
Nepanthia troughtoni
4
Nectria macrobranchia
1
Heliocidaris erythrogramma
1
Turbo undulatus
2
47
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3.2.10
Twelve Apostles Reef Survey
The Arches MS, Site 3833, 25 m Depth
Substratum structure
Highly structured high profile reef with flat-topped ridges and
gullies with 1-3 m high steps and ledges. The vertical walls of the
reef were deeply undercut with the upper ledges protruding
substantially over the gullies. There were some smooth, flat areas
between steps and gullies. The reef faces were highly eroded to
form crevices, smaller ledges and undercuts, supporting sessile
invertebrate fauna, although there tended to be little colonisation in
the lower caverns because of what appeared to be scouring. There
were some patches of sand and rubble in the gullies.
Seaweeds
The reef tops were covered by a high abundance of brown kelp,
Ecklonia radiata, (30-50% cover), brown alga Phyllospora comosa
(10-20 % cover), a variety of thallose red algae and encrusting
coralline algae. The thallose red algae included, Sonderopelta
coriacea, Phacelocarpus peperocarpus, Pterocladia lucida,
Plocamium angustum, Plocamium dilatatum, Plocamium mertensii,
Gelidium spp. and Melanthallia obtusata. The erect coralline,
Haliptilon roseum was present, but not very abundant. The brown
alga, Seirococcus was not present and green algae present
included, Codium sp., Caulerpa flexilis and Caulerpa cactoides.
Sponges
Sponges were only observed on the ledge edges. Most colonies
were encrusting or of low profile, less than 10 cm high.
Other sessile
invertebrates
Nearly all sessile invertebrates were observed on or under the
ledges comprising the vertical reef faces. Mopsella and Herdmania
momus were the only conspicuous invertebrates apart from
sponges. One patch of encrusting soft coral Erythropodium
hicksoni was observed at the base of a wall. Pteronisis was not
observed.
Mobile fauna
Observed seastars included, Nepanthia troughtoni. Observed fish
were, Scorpis aequipinni and Notolabrus tetricus.
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a. 7596 – Assemblage c
b. 7582 – Assemblage c
c. 7559 – Assemblage e
d. 7571 – Assemblage e
e. 7597 – Assemblage f
f. 7598 – Assemblage f
Figure 40. Site 3833: Example frames used for abundance analysis, The Arches MS.
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3.2.11
Twelve Apostles Reef Survey
The Arches MS, Site 3834, 27 m Depth
Substratum structure
Highly structured medium to high profile reef of ridges and gullies
with 1-3 m high steps and ledges. The vertical walls of the reef
were deeply undercut with the upper ledges protruding over the
gullies. The reef faces were highly eroded to form crevices, smaller
ledges and undercuts, supporting sessile invertebrate fauna,
although there tended to be little colonisation in the lower caverns
because of what appeared to be scouring. There were some
patches of sand and rubble in the gullies.
Seaweeds
The reef tops were covered by a high abundance of brown kelp
Ecklonia radiata (30-50% cover), brown alga, Sierococcus axillaris
(< 10 % cover), a variety of thallose red algae and encrusting
coralline algae. The thallose red algae included, Sonderopelta
coriacea, Phacelocarpus peperocarpus, Pterocladia lucida, Ballia
callitricha, Plocamium angustum, Plocamium dilatatum, Plocamium
mertensii, Gelidium spp. and Melanthallia obtusata. The erect
coralline, Haliptilon roseum, and brown alga, Homoeostichus, were
also present.
Sponges
Sponges were only observed on the ledge edges. Most colonies
were encrusting or of low profile, less than 10 cm high.
Other sessile
invertebrates
Nearly all sessile invertebrates were observed on or under the
ledges comprising the vertical reef faces. Mopsella and Herdmania
momus were the only conspicuous invertebrates apart from
sponges, although Mopsella was not very abundant compared to
other sites surveyed. Pteronisis was not observed. Patches of
Erythropodium hicksoni were observed on some ledge edges.
Mobile fauna
Observed seastars included, Nectria macrobrachia and Tosia
magnifica. Observed fish were Scorpis aequipinnis, Caesioperca
rasor, Notolabrus tetricus, Latridopsis forsteri, Cheilodactylus
nigripes and Dactylophora nigicans.
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a. 7654 – Assemblage c
b. 7659 – Assemblage c
c. 7643 – Assemblage d
d. 7634 – Assemblage e
e. 7632 – Assemblage f
f. 7636 – Assemblage g
Figure 41. Site 3834: Example frames used for abundance analysis, The Arches MS.
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3.3 Site Comparisons
The two deeper, eastern sites sampled in the Twelve Apostles MNP (Sites 3801 and 3802)
were substantially different to the sites in the western region of the MNP (Figure 42; Table 7).
This was largely because of a low abundance of seaweeds and a much higher abundance
and diversity of sponges and cnidarians.
The western Twelve Apostles MNP sites were differentiated in having a dominance of red
seaweeds, with sponges and encrusting coralline algae also being important components
(Figure 42; Table 7).
The Arches MS sites were differentiated in having a dominance of both thallose red algae
and brown seaweeds, in addition to sponge and encrusting coralline algae components
(Table 8). The larger brown alga, Seirococcus axillaris, was only observed at The Arches
sites.
Taxonomic richness and diversity was highest at the two eastern Twelve Apostles MNP sites
(3801 and 3802; Table 8). This was largely because of high abundances of a variety of
different sponges. Taxonomic richness was lowest at the algal-dominated sites, particularly
at The Arches MS. It should be noted that the diversity statistics did not include different red
algal species, which cannot be differentiated at the scale of the frames analysis. The
taxonomic richness of sessile invertebrates was relatively lower at the sampled sites within
The Arches MS.
An important observation from the ROV surveys was that each site had a heterogeneous
patchwork of assemblages. Assemblage structures varied over scales of metres to 10s
metres, usually in accordance with different substratum microhabitats, such as horizontal
reef tops, vertical faces, ledge edges and proximity to sand. The large sample sizes from
each site enabled more comprehensive assessment of assemblage structures present within
and between sites.
Table 7. Quantitative ROV data (BioPoints frames): percent cover of sessile plants and animals at
surveyed sites in the Twelve Apostles Marine National Park. Empty cell indicates taxon not present.
Twelve Apostles MNP (% cover)
Taxon
Site
3801
3802
3803
3804
3805
3806
3807
n
79
54
105
127
153
152
49
Seaweeds
Chlorophyta
2.38
0.36
0.86
Rhodophyta (ex. Corallines)
10.10
0.50
56.00
64.48
50.21
52.97
54.39
Corallines
4.10
0.43
7.75
4.28
11.59
7.34
9.41
Phaeophyta
0.13
7.56
Algal turf
22.00
0.04
Porifera (sponges)
Sponges - encrusting smooth
Sponges - encrusting ruffled
0.16
22.33
10.07
5.20
15.95
12.68
11.85
Sponges - encrusting spiky
Sponges - encrusting reticulated
2.31
0.04
0.20
0.02
0.07
0.04
Sponges - encrusting osculated
0.04
0.01
0.03
Textured Yellow Sponge
0.02
0.03
0.14
0.03
2.04
0.61
Sponges - massive smooth
0.03
0.07
Sponges - massive ruffled
9.67
16.46
52
4.70
1.63
0.29
Parks Victoria Technical Series No. 56
Twelve Apostles Reef Survey
Table 7. (continued)
Twelve Apostles MNP (% cover)
Taxon
Site
3801
3802
3803
3804
3805
3806
3807
n
79
54
105
127
153
152
49
Vanessa Sponge
0.09
Sponges - massive spiky
0.28
0.64
Sponges - massive reticulated
1.20
Sponges - massive osculated
0.80
3.02
0.39
0.03
0.29
0.03
0.03
0.05
Purple Squat Bulb Sponge
0.04
Sponges - globular smooth
Sponges - globular ruffled
0.02
0.25
0.13
0.19
Tethya bergquistae
0.08
0.01
0.02
Sponges - globular reticulated
0.03
0.01
0.03
Sponges - globular osculated
0.04
0.06
0.01
Sponges - pedunculate ruffled
0.06
0.59
0.10
0.08
Sponges - tubular ruffled
0.13
0.06
0.12
0.02
0.01
Holopsamma laminaefavosa
0.08
Sponges - flabellate smooth
Sponges - flabellate ruffled
0.17
0.27
0.39
0.11
Sponges - flabellate osculated
Taco sponge
0.54
0.02
Sponges - flabellate folded ruffled
0.56
Sponges - flabellate folded reticulated
0.78
Sponges - cup ruffled
0.47
0.63
0.03
0.03
0.04
0.01
0.16
0.01
0.05
0.29
Sponges - cup osculated
0.30
0.39
0.05
Sponges - arborescent ruffled
0.72
2.80
0.15
0.02
Sponges - papillate ruffled
0.06
0.63
0.13
0.02
Unknown cnidarian
0.72
0.04
Unidentified hydroids
0.54
0.33
Unidentified hydroid/bryozoan
0.19
0.28
0.03
0.01
Cnidaria (hydroids, anemones,
corals)
Unknown Cnidarian Fan
0.01
0.01
0.08
0.06
H. australe/ S. indivisus/ S. robusta
0.01
Halopteris glutinosa
2.13
0.70
Solandaria fusca
0.29
1.24
Gymnangium superbum
0.88
1.81
Parazoanthus spp.
0.04
1.48
Plesiastrea versipora
0.45
Erythropodium hicksoni
0.29
0.54
2.43
Mopsella spp.
1.00
0.13
0.39
Acabaria spp.
0.29
2.35
0.10
Pteronisis spp.
0.29
1.85
2.33
53
0.11
0.10
0.01
0.30
0.07
Parks Victoria Technical Series No. 56
Twelve Apostles Reef Survey
Table 7. (continued)
Twelve Apostles MNP (% cover)
Taxon
Site
3801
3802
3803
3804
3805
3806
3807
n
79
54
105
127
153
152
49
0.24
0.05
0.12
Primnoella australasiae
Gorgonian - other
0.10
0.05
Bryozoa
Unknown Arborescent Bryozoan
0.09
0.44
2.12
Encrusting bryozoan brown
0.03
Bryozoan - Erect folded, no holes
1.72
Triphyllozoon moniliferum
0.05
0.19
0.28
0.12
0.03
Chordata (ascidians)
Unidentified colonial ascidian
0.04
Unidentified solitary ascidian
Herdmania momus
0.05
0.02
0.01
0.38
0.07
1.14
0.09
0.13
0.07
29.66
29.50
3.77
0.53
9.96
13.14
3.39
2.30
7.82
2.45
Pyura spp.
Other Features
Unidentified biota
Sand
7.10
Shell piece/grit
Rubble
1.38
Bare bedrock
0.14
54
19.85
2.11
0.93
0.08
9.54
0.43
1.12
0.16
2.08
2.07
3.47
Parks Victoria Technical Series No. 56
Twelve Apostles Reef Survey
Table 8. Quantitative ROV data (BioPoints frames): percent cover of sessile plants and animals at
surveyed sites in The Arches Marine Sanctuary. Empty cell indicates taxon not present.
The Arches Marine Sanctuary (% cover)
Taxon
Site
3831
3832
n
53
51
3833
52
3834
49
Seaweeds
Chlorophyta
0.73
Rhodophyta (ex. Corallines)
25.96
30.24
38.52
27.73
Corallines
5.66
10.37
6.35
5.59
Phaeophyta
24.49
22.86
11.17
19.18
Algal turf
0.85
Porifera (sponges)
Sponges - encrusting smooth
0.04
Sponges - encrusting ruffled
15.02
Sponges - encrusting reticulated
0.62
Sponges - encrusting osculated
0.06
Sponges - massive smooth
0.21
Sponges - massive ruffled
1.36
Sponges - massive reticulated
0.32
1.15
29.22
11.15
36.90
0.90
1.63
1.22
Sponges - massive osculated
0.04
Sponges - globular ruffled
0.04
Holopsamma laminaefavosa
0.31
Sponges - flabellate ruffled
0.25
Sponges - flabellate folded ruffled
0.04
0.16
Sponges - papillate ruffled
0.06
2.47
0.10
Cnidaria (hydroids, anemones, corals)
Unknown Cnidarian Fan
0.09
Unknown cnidarian
0.34
Unidentified hydroid/bryozoans
0.43
H. australe/ S. indivisus/ S. robusta
0.32
Erythropodium hicksoni
1.92
Mopsella spp.
2.09
Acabaria spp.
1.13
Unknown Gorgonian Fan
0.12
1.65
1.06
1.38
0.59
0.20
Bryozoa
Unidentified bryozoans
0.04
Unknown Arborescent Bryozoan
0.04
Bryozoan - Erect folded, no holes
0.13
0.33
Chordata (ascidians)
Unidentified Sponge/Colonial Ascidian
0.10
Herdmania momus
0.11
55
0.48
0.04
Parks Victoria Technical Series No. 56
Twelve Apostles Reef Survey
Table 8. (continued)
The Arches Marine Sanctuary (% cover)
Taxon
Site
3831
3832
n
53
51
52
49
Pyura spp.
3833
3834
0.04
Other Features
Unidentified biota
10.19
0.10
18.15
0.76
Sand
2.38
0.16
2.77
2.24
3.25
2.98
Rubble
Bare bedrock
4.87
1.08
0.82
Table 9. Diversity statistics for BioPoints frames abundance data pooled by site.
Twelve Apostles MNP
Site
The Arches MS
3801
3802
3803
3804
3805
3806
3807
3831
3832
3833
3834
No. Taxa
31
30
30
29
22
27
10
24
13
14
8
Hills N2
4.79
5.44
2.51
1.77
2.46
1.89
2.26
4.25
3.94
3.15
3.37
3801
3804
3834
3806
3803
3832
3805
3833
3831
3802
3807
Figure 42. Differences in community structure between sites in the Twelve Apostles Marine National
Park and The Arches Marine Sanctuary. Site medioids from MDS ordination of all frames (two
dimensions, Kruskall Stress = 0.17). Site medioids were determined as the frame with the smallest
Bray-Curtis distance from the site centroid (means of species abundances).
56
Parks Victoria Technical Series No. 56
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3.4 Assemblage Structures
Multidimensional scaling ordination of individual frames indicated clusters of different
assemblage structures (Figures 32 and 33). The predominant clusters were around the
perimeter of the plot, to the left, upper left, upper right and lower right (Figures 43 and 44).
Although these clusters were well separated from one another, there were frames with
intergrades in assemblage structures, being present between the clusters. In short, there
were distinctly different assemblage types observed, but there was a continuum of structures
between these different types.
The clustering patterns of frames from each site indicated substantial heterogeneity of
assemblage structures present, which was consistent with the qualitative observations of
patches of assemblages associated with different microhabitats. For example, Site 3805
(Figure 43) has frames represented in the top-left, right and lower-right clusters of the MDS.
In addition, clustering patterns were replicated between some sites, indicating a recurrence
of particular assemblage structures between sites.
Based on different and recurring clusters between sites, there were approximately seven
distinguishable assemblage structures (recognising these clusters were on a continuum of
observed and possible structures. These clusters are indicated in Figure 45. The average
abundances of taxa and morphotypes of these clusters are provided in Table 42.
The characteristics of these assemblages were:
Assemblage a Dominance of sponges, particularly massive ruffled, encrusting ruffled,
massive reticulated and arborescent ruffled forms. Corals ,Parazoanthus
sp. and Pteronisis sp., characteristic components. Little to no seaweeds
present.
Assemblage b
Dominance of sponges, mostly massive ruffled and encrusting ruffled
forms. Soft coral, Erythropodium, and red seaweeds common.
Assemblage c
Dominance of encrusting ruffled sponges with a lesser component of
massive ruffled sponges. Red seaweeds common.
Assemblage d
Dominance of red seaweeds and encrusting ruffled sponges.
Assemblage e
Dominance of red seaweeds and coralline algae. Encrusting ruffled
sponges common.
Assemblage f
Dominance of red seaweeds, coralline algae and brown seaweed,
Ecklonia radiata. Green seaweeds and sponges common.
Assemblage g
Brown seaweed, Ecklonia radiate, dominant. Thallose red and coralline
algae common. Very low abundance of sessile invertebrates.
Example frames of each of these assemblages are presented in the previous Section 3.2.
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Parks Victoria Technical Series No. 56
Twelve Apostles Reef Survey
Site 3801
Site 3802
Site 3803
Site 3804
Site 3805
Site 3806
Site 3807
Figure 43. Relative variations in community structures in sampled frames within and between sites.
Magenta symbols indicate frames sampled from that site. Twelve Apostles Marine National Park.
Note: Multidimensional scaling ordination of all frames (two dimensions, Kruskall Stress = 0.17).
58
Parks Victoria Technical Series No. 56
Twelve Apostles Reef Survey
Site 3831
Site 3832
Site 3833
Site 3834
Figure 44. Relative variations in community structures in sampled frames within and between sites at
The Arches Marine Sanctuary. Magenta symbols indicate frames sampled from that site.
Multidimensional scaling ordination of all frames (two dimensions, Kruskall Stress = 0.17).
c
d
e
a
b
f
g
Figure 45. Classification of frames by assemblage type based on recurring clusters between sites
(Figures 32 and 33).
59
Parks Victoria Technical Series No. 56
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Table 10. Mean taxon abundances for identified assemblages in the Twelve Apostles Marine National
Park and The Arches Marine Sanctuary.
Taxon
Assemblage
a
b
c
Chlorophyta
d
e
f
0.32
0.1
0.65
g
Rhodophyta
4.16
5.12
63.74
64.74
43.64
16.26
Corallines
5
1.97
2.04
9.24
12.44
17.82
Phaeophyta
1.37
0.29
0.26
2.12
26.54
59.38
Algal turf
0.21
0.02
0.09
0.38
4.54
0.33
Sponges - encrusting smooth
Sponges - encrusting ruffled
0.23
4.78
12.11
54.85
21.09
Sponges - encrusting spiky
0.01
Sponges - encrusting reticulated
0.32
0.35
0.04
0.02
0.03
0.01
0.01
0.02
0.01
0.11
0.04
0.03
4.95
1.28
1.44
0.25
0.03
0.02
1.11
0.22
0.01
1.18
0.15
0.01
Sponges - encrusting osculated
Textured Yellow Sponge
Sponges - massive smooth
0.11
Sponges - massive ruffled
19.25
14.95
Vanessa Sponge
0.15
Sponges - massive spiky
Sponges - massive reticulated
4.08
Sponges - massive osculated
0.04
Purple Squat Bulb Sponge
0.01
Sponges - globular smooth
0.01
Sponges - globular ruffled
0.14
0.26
0.1
Tethya bergquistae
Sponges - globular reticulated
0.02
0.08
0.05
Sponges - pedunculate ruffled
0.56
0.21
0.04
Sponges - tubular ruffled
0.08
0.11
0.05
Holopsamma laminaefavosa
0.01
0.03
0.02
0.02
0.04
0.18
Sponges - flabellate smooth
0.25
Sponges - flabellate ruffled
0.25
0.16
0.3
Sponges - flabellate osculated
Taco sponge
0.13
0.07
Sponges - flabellate folded ruffled
0.11
0.21
0.25
Sponges - flabellate folded
reticulated
0.5
0.39
0.08
Sponges - cup ruffled
1.44
0.34
0.05
Sponges - cup osculated
Sponges - papillate ruffled
0.04
0.03
Sponges - globular osculated
Sponges - arborescent ruffled
0.01
0.06
0.01
0.01
0.02
0.02
0.01
0.26
0.29
0.04
3.11
1.26
0.38
0.71
1.21
60
0.06
0.03
0.02
0.02
Parks Victoria Technical Series No. 56
Twelve Apostles Reef Survey
Table 10. (continued)
Taxon
Assemblage
a
b
c
Unknown cnidarian fan
d
e
0.58
Hydroids
0.06
Unidentified hydroid/bryozoan
0.33
0.34
0.1
0.21
0.52
0.08
H. australe/ S. indivisus/ S. robusta
0.23
0.06
0.09
0.01
Halopteris glutinosa
0.61
1.95
0.73
Solandaria fusca
1.33
2.05
0.2
0.01
0.19
0.06
Gymnangium superbum
0.01
Erythropodium hicksoni
0.06
2.16
1.17
Mopsella spp.
0.14
1.26
1.28
Acabaria sp.
1.58
1.11
0.68
Pteronisis spp.
2.92
0.89
0.56
Primnoella australasiae
Unknown gorgonian fan
0.09
Other bryozoa
0.02
0.17
Encrusting bryozoan brown
Bryozoan - Erect folded, no holes
0.18
2.22
Plesiastrea versipora
Unknown arborescent bryozoan
0.42
0.46
0.11
0.03
0.55
0.17
0.05
0.01
0.34
0.22
0.02
0.31
0.13
0.64
1.13
Triphyllozoon moniliferum
0.21
0.08
Unidentified sponge/colonial ascidian
0.13
Unidentified colonial ascidian
0.04
Unidentified solitary ascidian
0.01
0.02
0.3
0.17
0.22
0.32
0.1
0.65
Herdmania momus
g
0.04
Unknown cnidarian
Parazoanthus sp.
f
0.19
0.58
Pyura spp.
0.14
0.02
Chlorophyta
Rhodophyta
4.16
5.12
63.74
64.74
43.64
16.26
Corallines
5
1.97
2.04
9.24
12.44
17.82
Phaeophyta
1.37
0.29
0.26
2.12
26.54
59.38
Algal turf
0.21
0.02
0.09
0.38
4.54
0.33
Sponges - encrusting smooth
Sponges - encrusting ruffled
0.23
4.78
12.11
61
54.85
21.09
Parks Victoria Technical Series No. 56
Twelve Apostles Reef Survey
Table 11. Diversity statistics for frames abundances pooled by assemblage type. Hill’s N2 statistic is
an indicator of the number of dominant species in the assemblage.
Assemblage
a
b
c
d
e
f
g
No. Taxa
27
32
42
33
35
14
4
Hills N2
4.70
7.27
1.99
1.84
1.62
2.59
2.14
3.5 Assemblage Distributions
The percentage frequency of frames classified by assemblage type is provided in Table 12.
There were considerable differences in the proportions of cover of different assemblage
types between sites. The predominant locations of assemblages were:
Assemblage a
Eastern deep MNP, Site 3802.
Assemblage b
Eastern deep MNP, Sites 3801, 3802.
Assemblage c
Eastern deep MNP, MS, Sites 3801, 3802, 3831, 3832, 3833, 3834.
Assemblage d
Western MNP, Sites 3803, 3804, 3806, 3834;
Assemblage e
Western MNP, MS, Sites 3803, 3804, 3805, 3806, 3807, 3831, 3832,
3833, 3834.
Assemblage f
Western MNP, MS shallower, Sites 3805, 3807, 3831, 3832, 3833, 3834.
Assemblage g
The Arches MS, Sites 3831, 3832, 3834.
Table 12. Percent occurrence of different assemblage types at each site based on classified frames.
Assemblage types (% of frames)
N
Site
a
b
c
d
e
f
3801
3
25
39
3802
61
19
17
3803
1
2
2
16
46
1
54
39
6
8
53
11
3806
7
17
59
5
3807
2
2
29
43
3804
3805
1
g
1
Int.
Frames
33
80
4
54
30
105
6
127
18
152
13
152
8
16
49
3
3
3831
2
25
2
11
28
13
19
53
3832
4
29
8
12
18
22
8
51
3833
4
15
6
33
12
6
25
52
33
14
10
12
10
20
49
3834
Note: (int.) refers to integrade assemblage; and (N) is the number of frames analysed at that site.
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ACKNOWLEDGMENTS
This project was funded by Parks Victoria and supervised by Dr Anthony Boxshall.
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Parks Victoria Technical Series No. 56
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64
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