Posidonia australis seagrass meadows of the Manning – Hawkesbury ecoregion
1
2
3
1. Description of the ecological community
4
1.1 Name of the ecological community
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
This advice follows the assessment of a public nomination to list the ‘Posidonia australis
seagrass beds’ as a threatened ecological community under the EPBC Act.
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
The ecological community occurs mostly within the sheltered environments of permanently
open estuaries along the warm temperate New South Wales coastline, from Wallis Lake (32°S)
to Port Hacking (34°S). The ecological community occurs wholly within the Manning Shelf
and Hawkesbury Shelf bioregions (IMCRA v4.0). Posidonia australis dominated seagrass
meadows occurring around islands within the geographic range are also included within the
ecological community.
42
43
44
45
46
47
48
The ecological community occurs as almost pure stands of Posidonia australis (monospecific
meadows) or multispecies meadows (eg. P. australis, Zostera capricorni, Halophila ovalis)
dominated by P. australis. P. australis is a slow growing, long lived seagrass species, with
persistent rhizomes and is meadow-forming (Cambridge and Kuo, 1979). Its fronds can grow to
over 80 cm long and as much as 90% of the mass of the P. australis plant may be in the roots
and rhizomes (Keough and Jenkins, 1995).
Posidonia australis is a sub-tidal meadow-forming seagrass species. The northernmost limit to
the distribution of P. australis on the east coast of Australia is Wallis Lake. Its distribution then
extends around the southern half of Australia to Shark Bay on the west coast encompassing
significant ecological and biogeographic variation. Given the close links between biodiversity
and the underlying abiotic drivers, the definition of the ecological community has been focused
on the assemblage of plants, animals and micro-organisms associated with seagrass meadows
dominated by Posidonia australis occurring in the temperate Manning Shelf and Hawkesbury
Shelf bioregions (IMCRA v4.01). Spalding et al. (2007) consider the Manning Shelf and
Hawkesbury Shelf bioregions to be a single ecoregion based on relative homogeneous species
composition and clear distinction from adjacent systems.
It is recommended that the ecological community be named Posidonia australis seagrass
meadows of the Manning-Hawkesbury ecoregion (hereafter referred to as the ecological
community). The name best describes the dominant component, structure and location
characterising the ecological community.
1.2 Location and physical environment
The ecological community typically occurs in subtidal waters where salinity is close to marine
levels (30-50◦/◦◦) (Meehan, 2001), dropping only for short periods following rainfall, at depths
ranging less than 1m to 10 m on sand and silty mud substrate (Cambridge and Kuo, 1979;
West, 1990). The ecological community is absent from brackish water (i.e. hyposaline)
conditions such as in coastal rivers and intermittently open lagoons. The ecological community
is known to occur at the following locations: Wallis Lake; Port Stephens; Lake Macquarie;
Brisbane Water; Hawkesbury River; Pittwater; Port Jackson (Sydney Harbour); Botany Bay;
Port Hacking (Creese et al., 2009); and in the lee of Broughton Island (West et al., 1989).
1.3 Vegetation
1
Integrated Marine and Coastal Bioregionalisation of Australia Version 4.0 (Commonwealth of Australia, 2006).
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
The spatial structure of the ecological community is highly variable with meadows ranging
from nearly continuous to highly fragmented meadows arranged into a mosaic of discrete
patches. Areas of bare sand or other seagrass species that occupy edges, blowouts2 and small
areas of meadows (Kirkman and Kuo, 1990) are common in both continuous and patchy3
meadows of the ecological community. In some cases, sparse meadows of the ecological
community may have an understorey of smaller seagrass species (e.g. Halophila ovalis). The
macrophyte, Ruppia, is also found growing within the ecological community (Creese et al.,
2009).
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
The ecological community provides habitat, shelter and food for a large diversity and
abundance of fauna. Posidonia australis is generally considered to provide the greatest habitat
structure of any of the seagrass species found in New South Wales (Middleton et al. 1984; Bell
and Pollard, 1989; Creese et al., 2009). The P. australis fronds and rhizome matte provide a
stable substratum for the establishment of animals as epifauna and infauna, which in turn
support higher food chains (Walker et al., 1991) directly as a food source or via detritus
formation.
The wide, strap-like leaves of Posidonia australis provide substrate for the establishment of a
diverse assemblage of benthic flora, in the form of micro and macro epiphytes4 and algae and a
complex layer of periphyton5 (Klumpp et al., 1989; Keough and Jenkins, 1995; Carruthers et
al., 2007). The epiphytes and some components of the periphyton can photosynthesise and
contribute significantly to the overall primary production of the seagrass community. The
amount of cover of epiphytes on the seagrass depends largely on the nutrients available in the
water – generally, more nutrients means more epiphytes.
1.4 Fauna
The macro-benthic fauna of the ecological community is dominated by polychaetes,
crustaceans and molluscs (Collett et al., 1984). These faunal groups process a significant
portion of the primary production of the ecological community, and provide an important food
resource for larger crustaceans, fish and birds. Common polychaetes include Armandia
intermedia, Barantolla lepte, Ceratonereis mirabilis, Eunice australis, Mediomastus
californiensis, Neanthes cricognatha, Notomastus torquatus, Onuphis sp., Prionospio
aucklandica, Prionospio cirrifera. Common crustaceans include Ampelisciphotis sp.,
Amphithoe sp., Birubius sp., Cyamodus sp., Macrobrachium intermedium, Tethygeneia sp..
Common molluscs include Anadara trapezia, Mysella sp. and Wallucina assimilis. Other
invertebrate taxa associated with the ecological community include sea anemones and
nemerteans (Collett et al., 1984).
The epibenthic fauna of the ecological community includes larger, often predatory, fish and
crustaceans. The majority of epibenthic fauna associated with the ecological community only
use it for a small part of their life history, as a temporary foraging area or refuge from
predation. The ecological community provides nursery habitat to the commercially important
Acanthopagrus australis (yellowfin bream), A. butcherii (black bream), Mugil cephalus (sea
mullet), Girella tricuspidata (luderick) (Burchmore et al., 1984; McNeill et al., 1992; West and
Jones, 2001). The most commonly sampled fish associated with the ecological community are
2
A blowout is an area in a seagrass meadow denuded of seagrass through natural or anthropogenic disturbance.
Blowouts are typically areas of instability in sediment movement, shape and size and seagrass species composition
(Kirkman, 1985).
3
Patchiness in meadows often reflects processes of recovery from disturbances, natural and human induced, as
well as the particular hydrodynamic conditions of the seagrass habitat (Duarte et al., 2006).
4 Epiphytes are larger algae that grow on seagrass fronds (Keough and Jenkins, 1995).
5 Periphyton is a thin layer of microscopic organisms such as bacteria and single-celled plants which colonise
exposed areas of the seagrass (Keough and Jenkins, 1995).
2
1
2
3
4
5
6
7
8
from the families Syngnathidae (including the protected Phyllopteryx taeniolatus (weedy
seadragon)), Clupeidae, Latridae, Monacanthidae (leatherjackets), Gobiidae (gobies),
Kyphosidae, Hemiramphidae and Mugilidae (Evans et al., pers. comm., 2014).
The ecological community also provides important foraging habitat for the NSW listed
endangered population of Eudyptula minor (little penguin) at Manly (Manly Council, 2009).
1.5 Key diagnostic characteristics and condition thresholds
9
10
11
12
13
14
15
National listing focuses legal protection on remaining patches of the ecological community that
are most functional, relatively natural (as described by the ‘Description’) and in relatively good
condition. Key diagnostic characteristics and condition thresholds assist in identifying a patch
of the threatened ecological community, determine when the EPBC Act is likely to apply to the
ecological community and to distinguish between patches of different quality. The ecological
community may exhibit various degrees of disturbance and degradation. This degree of
degradation has been taken into account in developing the condition thresholds.
16
1.5.1 Key diagnostic characteristics
17
18
19
20
The key diagnostic characteristics presented here summarise the main features of the ecological
community. These are intended to aid the identification of the ecological community, noting
that a broader description is given in the other sections. Key diagnostic characteristics for
describing the ecological community are:
21
22

Occurs from Wallis Lake (32◦S) to Port Hacking (34°S) within the Manning Shelf and
Hawkesbury Shelf bioregions (IMCRA v4).
23
24

Occurs in shallow subtidal coastal waters (<10 m) in locations with protection from
high wave energy, typically, permanently open estuaries.
25

Consists of seagrass meadows6 >1 ha and dominated7 by Posidonia australis.
26

Occurs on sand or silty-mud substrate.
27
28
1.5.2 Condition thresholds
29
30
31
32
33
34
35
36
37
38
39
40
41
Condition classes and thresholds provide guidance for when a patch of a threatened ecological
community retains sufficient conservation values to be considered as a Matter of National
Environmental Significance, as defined under the EPBC Act. This means that the referral,
assessment and compliance provisions of the EPBC Act are focussed on the most valuable
elements of the ecological community. Very degraded patches that do not meet the condition
thresholds will be largely excluded from national protection. However, it is recognised that
patches that do not meet the condition thresholds may still retain important natural values and
may be protected through State and local laws or schemes. Therefore, these patches should not
be excluded from recovery and other management actions. Suitable recovery and management
actions may improve these patches to the point that they may be regarded as part of the
ecological community fully protected under the EPBC Act. With respect to the ecological
community, management actions should, where feasible, aim to restore patches to at least meet
the good condition thresholds outlined below.
42
43
44
45
6
Seagrass meadow - a spatially contiguous area of seagrass of varying percent cover composition ranging from
nearly continuous to highly fragmented and arranged into a mosaic of discrete areas of seagrass.
7
Dominated - >50% of total seagrass cover.
3
1
2
Good condition categories and thresholds (minimum condition)
Meadow Size
Percent seagrass
cover of total
meadow area
Minimum shoot8
density of
Posidonia australis
Small (≥1 ha)
Moderate (≤10ha)
Large (>10ha)
>50%
>30%
>20%
and
and
and
100 shoots/m2
25 shoots/m2
10 shoots/m2
3
4
5
6
1.5.3 Further information to assist in determining the presence of the ecological community
and significant impacts
7
8
Patch definition
9
10
11
12
13
14
15
16
17
18
19
A patch of the ecological community is defined as a Posidonia australis dominated seagrass
meadow9. The edge of the seagrass meadow is defined as the edge of the contiguous seagrass
cover. A patch (i.e. a meadow) may include bare area or substrate (e.g. sand) or small scale
disturbances such as boat mooring and propellar scours or blowouts that do not substantially
alter the overall functionality of the meadow. Functionality here refers to ecological processes
such as the movement of fauna, dispersal of plant propagules, provision of food, habitat
attributes such as refuge or nursery function, and sediment stabilisation, all of which can
operate at small to large scales. Where a meadow does not meet the minimum good condition
thresholds it is not considered part of the ecological community for EPBC Act purposes.
20
21
22
23
24
25
Identifying the ecological community and its condition is possible at most times of the year,
however, consideration must be given to the role that season and disturbance history may play
in an assessment. For example, the ecological community exhibits seasonality of growth, with
maximum growth occurring during the spring and summer. In the autumn and winter, much of
this growth dies and is broken off. Severe storms or flooding may also cause loss of seagrass
leaves, leaving only the rhizome layer or a few leaves.
26
27
28
29
Timing of surveys should provide for a reasonable interval after a substantial disturbance
(natural or human-induced) to allow for regeneration of Posidonia species to become evident,
and be identified.
Timing of surveys
8
Shoot: a structure comprising one to multiple leaves/fronds with a surrounding sheath at the base.
Seagrass meadow: a spatially contiguous area of seagrass of varying percent cover composition ranging from
nearly continuous to highly fragmented (naturally and /or due to disturbance) and arranged into a mosaic of
discrete areas of seagrass (such that areas of seagrass occur within reasonable proximity that they may act as a
functional unit).
9
4
1
Buffer zones
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
Buffer zones enhance protection of a patch by avoiding or minimising potential disturbance
from surrounding land and sea uses or activities. While the buffer zone is not formally part of
the ecological community, it should be taken into account when considering likely significant
impacts during EPBC Act decision-making.
19
20
21
22
23
24
The ecological community can take decades to recover after major disturbance and frequently
the loss of the ecological community can lead to irreversible changes in the nature of the
environment and habitat, preventing the recovery of the ecological community (Seddon, 2004).
Significant efforts to restore the ecological community have been made, with some project
scale successes (Meehan and West, 2000; Wear, 2006). However, timeframes for recovery are
long (>20years).
25
26
27
28
29
30
While seagrass rehabilitation methods have improved significantly over the past twenty years,
no effective restoration strategies on ecologically significant scales (km2) have been
demonstrated (Wear, 2006). Therefore, the primary strategy for achieving the conservation
objective for this ecological community is to avoid further loss of the ecological community.
31
32
33
34
35
36
37
In the context of actions that may have ‘significant impacts’ and require approval under the
EPBC Act, it is important to consider the surrounding environment and seascape context of
patches that meet the condition thresholds. The following indicators should be considered when
assessing the impacts of actions or proposed actions under the EPBC Act, or when considering
recovery, management and funding priorities for a particular meadow:
 Large meadow and/or large area to boundary ratio – larger area/boundary ratios are less
exposed and more resilient to edge effect disturbances.
38
 Meadows with minimal evidence of disturbance.
39
40
 Good faunal habitat as indicated by medium density seagrass cover, refuge and contribution
to movement corridors.
41
 Presence of listed threatened or migratory species.
42
43
44
45
46
 Connectivity to other meadows or marine habitats. In particular, a meadow in an important
position between (or linking) other meadows/habitats in the seascape including meadows of
the ecological community that are outside the minimum meadow size (taking into account
that connectivity should aim to not exacerbate the incidence or spread of threats e.g.
invasive species).
47
 Minimal invasive species or where these can be managed easily.
It is recommended that an appropriately sized buffer zone be applied from the outer edge of a
patch. The size of the buffer zone should increase with increasing intensity and likely impact
of threat. The impact of a threat on the ecological community will vary with the activity type.
Impacts of some activities are localised, for example, the damage caused by boat propellers and
moorings. To avoid localised impacts, a buffer zone of 50 metres is encouraged. Impacts from
other activities can occur kilometres away in the case of plume generation from dredging or
changed hydrology due to sea wall construction. In such circumstances an appropriate buffer
zone may be in the order of several kilometres. With regards to dredging activities, the
application of buffer zones should be in line with national and state guidelines on dredging
activities.
Rehabilitation
Other significance considerations
5
1
2
 Remaining meadows in areas where the ecological community has been otherwise heavily
degraded.
3
 At the edge of the range of the ecological community.
4
5
6
 Unique variants of the ecological community.
Area critical to the survival of the ecological community
7
8
9
10
11
Areas that meet the key diagnostic characteristics and condition classes are considered critical
to the survival of the ecological community. Adequate light for photosynthesis is of critical
importance to the survival of the ecological community. Therefore, also critical to the survival
of the ecological community is the water column above the ecological community being of a
quality adequate for photosynthesis.
12
13
14
15
Additional areas such as adjoining habitats and a minimum 50 metre buffer zone, and areas that
meet the description of the ecological community but not the condition thresholds are also
considered important to the survival of the ecological community.
16
Geographic extent
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
Until more recently, the classification and mapping of seagrass habitat has not been undertaken
to the species or genus level. Consequently, an estimate of the former extent of the ecological
community is not available. However, historical aerial photography and field observations
indicate that the ecological community once had a much wider distribution near highly
urbanised and industrialised coastlines (eg. Larkum and West, 1990; Meehan, 2001) and the
most significant losses in the ecological community occurred before the 1980s (Creese et al.,
2009) when the first comprehensive investigation of NSW estuaries was done and maps produced
showing the cover of seagrass, mangrove and saltmarsh (West et al. 1985). For example, in Botany
Bay between 1942 and 1984, the ecological community is estimated to have declined more than
50% (Larkum and West, 1990).
While changes in resource use and improved management of estuarine environments over the
last decade have improved conditions for Posidonia australis growth, surveys of seagrasses in
New South Wales conducted in 1985 (West et al., 1985) and 2005 (Creese et al., 2009) show
marked declines in the extent of the ecological community at some locations. For example,
suspected losses of approximately 25% in Wallis Lake, 50% in Lake Macquarie and 30% in
Brisbane Water (Creese et al., 2009). Further, aerial imagery captured since late 2009-early
2010 of Lake Macquarie, Pittwater, Sydney Harbour, Botany Bay and Port Hacking show
losses of meadow area in ecological community of between 30-50% (Evans et al., pers. comm.,
2014).
Based on mapping by Creese et al. (2009), the current extent of the ecological community is
estimated to be 13 km2. However, the real extent of the community is likely to be much less
than this given estimates of more recent decline in the ecological community (Evans et al., pers.
comm., 2014). In addition, there are many instances where quite substantial bare patches occur
within meadows of the ecological community, often as a consequence of human activities such
as the installation of boat moorings. For example, it has been estimated that of the 99 ha of the
ecological community occurring in Lake Macquarie, at least 6 ha has been lost due to scouring
by boat moorings (Wright et al., 2013).
6
1
1.9 National context and other existing protection
2
1.9.1 Bioregional distribution
3
4
5
6
The ecological community occurs in the Manning Shelf and Hawkesbury Shelf meso-scale
bioregions (IMCRA v4.0).
1.9.2 Other existing protection
7
8
9
10

Seagrasses are protected in New South Wales under the New South Wales Fisheries
Management Act 1994 (FM Act) as fish habitat. However there is no power within
habitat protection plans to control catchment development that may cause a decline in the
health of Posidonia australis (Meehan and West, 2002).
11
12
13
14

Posidonia australis populations in Port Hacking, Botany Bay, Sydney Harbour, Pittwater,
Brisbane Waters and Lake Macquarie are listed under the FM Act as ‘endangered
populations’ due to ongoing threats leading to a very high risk of extinction in the near
future (NSW FSC, 2010).
15

The ecological community occurs within the boundaries of
16
17
-
aquatic reserves established under the FM Act (eg. Towra Point Aquatic Reserve and
North Harbour Aquatic Reserve);
18
19
-
Port Stephens-Great Lakes Marine Park established under the New South Wales Marine
Parks Act 1997;
20
21
22
-
marine areas of national parks and nature reserves (eg. Royal National Park and Towra
Point Nature Reserve) established under the New South Wales National Parks and
Wildlife Act 1974.
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
2. Description of threats
Coastal development
The distribution of the ecological community is within estuaries along a coastline hosting the
highest density of human population in Australia and the greatest degree of coastline utilisation
in terms of cities, harbours and industry (West, 1990). This makes the ecological community
susceptible to many environmental stresses caused by coastal development.
Coastal development includes construction of ports; foreshore structures such as reclamation
walls, moorings, jetties and boat ramps; buildings ranging from utility structures to highrise
apartments; and infrastructure, such as pipes and cables for the transport of gas, water and
energy. Coastal development can impact the ecological community directly through removal of
seagrass and indirectly through shading which limits the photosynthetic capacity of the
seagrass; increased runoff, sedimentation and pollution that decrease water and sediment
quality; and changes in wave or current patterns and sediment stability that lead to erosion and
burial of the seagrass.
A major source of disturbance to the ecological community in the Sydney metropolitan region
has been port and marina construction and operation. In addition to clearance of the ecological
community, the construction of ports and marinas is associated with changes in hydrology and
sediment transport patterns, involving both increased erosion and sediment accumulation along
adjacent and distant (kilometres away) coasts (Larkum and West, 1990; Meehan, 2001). These
changes can impact the ecological community by both erosion and burial associated with the
changing sedimentary dynamics (Larkum and West, 1990). The operation of ports and marinas
also entails substantial stress to the adjacent meadows of the ecological community (eg.
7
1
2
3
4
5
6
Larkum and West, 1990), due to reduced transparency and nutrient and contaminant inputs
associated with boat traffic and servicing, as well as dredging activities associated with port
and navigation-channel maintenance (Duarte, 2002; Haines and Rollason, 2010; Wright et al.,
2013).
7
Dredging
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
Dredging is carried out to maintain existing ports and navigation channels, for expansion to
allow access for larger ships and for the construction of new ports, as well as other activities
such as land reclamation, beach nourishment, laying of pipelines and cables and sand mining.
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
Activities relating to boating and storage of boats often directly remove or damage the
ecological community and also cause the fragmentation of meadows and increase the potential
for edge effects on meadows.
The ecological community can be impacted by dredging directly through physical removal at
the dredge site, or smothering by sediments at the dredge disposal site (McMahon, 2013).
Indirect impacts also occur through the generation of turbid plumes by sediment particles
which are suspended in the water column and reduce light reaching the meadows, and changes
to the hydrology of the area, wave or current patterns or sediment stability with consequent
impacts on meadow integrity and water quality (Larkum and West, 1990; McMahon, 2013). In
the case of contaminated sediment or sediments with high contents of organic matter, dredging
and resuspension may also lead to effects on water quality by the release of contaminants, an
increase in nutrient concentrations and reduced dissolved oxygen in the water column
(Erftemeijer and Lewis, 2006).
In Botany Bay between 1942 and 1984, dredging associated with the development of a port on
the northern side of Botany Bay contributed to major losses of the ecological community from
the southern foreshores of Botany Bay due to a changed wave regime. Dredging of the entrance
was undertaken to direct wave energy away from berthing facilities directing much of the
incident wave energy on to Towra Point, resulting in a 10-20% increase in wave height. The
new wave regime caused a loss of the ecological community from Towra Point both directly as
a consequence of mechanical disturbance and indirectly as a result of moving sediments
smothering the seagrasses (Larkum and West, 1990).
Boat mooring and other boating related activities
Moored boats and the ecological community favour the same sheltered conditions. Traditional
boat moorings located in the ecological community produce circular scours in the meadow as a
result of the slack chain from the mooring moving through the seagrass with each wind
direction change. While fragmentation and sand patches or ‘blowouts’ naturally occur in seagrass
beds (Kirkman and Kuo, 1990), the damage from boat moorings enhances and increases the rate at
which fragmentation occurs (West, 2011). Fragmentation across large areas of a meadow can
result in sediments becoming mobile, individual bare sand patches combining and forming larger
bare sand patches, deeper holes forming and ultimately leading to the entire meadow becoming
unstable (Kirkman, 1997; West, 2011). In Lake Macquarie, 6 hectares (0.06 square kilometres)
of the ecological community has been lost through damage from boat moorings and is equivalent to
6% of the total area of the ecological community remaining in Lake Macquarie (Wright et al.,
2013).
Scouring is also caused by boat propellers removing seagrass leaves and rhizomes (West,
2011). Often the scouring is restricted to narrow widths (up to 50cm), but it can be many
hundreds of metres in length (West, 2011). In Botany Bay, boat scours have created 17.5 km of
8
1
2
3
4
5
6
7
8
9
10
11
12
exposed edge (Wright et al., 2013) in what would otherwise be a naturally continuous meadow.
Exposed edges within seagrass meadows are more susceptible to erosion resulting in further losses
of the ecological community (Wright et al., 2013).
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
Land cleared for agricultural, residential and industrial development is a major pressure in
many New South Wales coastal catchments (eg. Umwelt, 2000; Meehan, 2001; Manly Council
2008; Haines and Rollason, 2010) and is known to result in increased inputs of eroded
sediments, nutrients and organic material to the associated estuary (Roper et al., 2011).
Increasing population in coastal catchments exacerbates the impacts of catchment disturbance
with the associated increased pollution loads in stormwater and sewage overflows, disturbance
of riparian and foreshore vegetation, litter and general degradation of the environment (Roper
et al., 2011).
40
41
42
43
44
45
46
47
48
49
50
51
52
Fishing by recreational and commercial fishers removes finfish and shellfish from the
ecological community and damage to the ecological community by boats, fishing gear and
people (eg. wading through meadows and bait digging) can also be associated with these
activities (Roper et al., 2011). Recreational fishing is regulated in all states and territories.
These regulations restrict the activities of anglers through measures such as fishing gear
restrictions; size and bag limits; and closed fishing seasons. The legal catch of a recreational
angler is unlikely to constitute a significant impact on native fish species. Some commercial
fishing methods (for example, prawn trawling) can impact the ecological community by
removal of leaf biomass and rhizomes. Under the New South Wales Fish Habit Protection Plan
No. 2, all commercial and recreational fishing gear needs to be designed and operated so as to
minimise damage to seagrass, including Posidonia australis (NSW DPI, 1997).
The ability of Posidonia australis to recover from habitat fragmentation is considered extremely
low given its slow rate of growth. The rate of revegetation of bare patches in southeast Australia
was estimated to be approximately 8.4cm decade-1 (Meehan and West, 2000). Coupled with
increasing populations along Australia's coastline and a corresponding increase in recreational
usage, fragmentation resulting from boating activities is one of the most serious and ongoing
threats to the ecological community.
Catchment disturbance
The most damaging form of pollution to the ecological community is the release of nutrients;
primarily nitrogen and phosphorus. Excess nutrients can trigger phytoplankton blooms or
excessive epiphyte growth, reducing the amount of light received for photosynthesis and
potentially smothering the ecological community (Shepherd et al., 1989; Kirkman, 1997). The
epiphytes and dead seagrass leaves fall to the substrate beneath, are broken down by bacteria
that use up oxygen, and this anoxic sediment gives off hydrogen sulphide that kills the benthic
flora and the whole seagrass ecosystem may be lost (Duarte, 2002) with subsequent changes in
habitats and the structure and function of estuarine food webs (Roper et al., 2011).
Nutrient inputs are associated with catchment disturbance as well as fertiliser application,
effluent discharges and urban stormwater. The ecological community may be impacted by
other pollutants such as industrial chemicals from factories, including heavy metals,
petrochemicals and toxic compounds that enter the sea via runoff and stormwater. The release
of sewage and industrial effluents along the northern shoreline of Botany Bay, from the 1830s
until the mid 1970s is considered to be a major factor responsible for the complete loss of the
ecological community along the northern shoreline (Larkum and West, 1990).
Fishing
9
1
Invasive Species
2
3
4
5
6
7
8
9
10
11
The invasive pest alga Caulerpa taxifolia has invaded many estuaries in New South Wales.
Recent research (Glasby, 2013) concludes that there is no evidence that C. taxifolia is driving
the loss of native seagrasses including Posidonia australis and does not appear to be preventing
the recovery of the native species. Rather, it is likely that parts of the ecological community
that are already under stress from other anthropogenic disturbances might become more
susceptible to impacts from C. taxifolia or that if the ecological community is removed,
C. taxifolia will potentially colonise the area previously occupied and prevent the complete
recovery of the ecological community (Glasby, 2013).
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
Climate change is anticipated to significantly impact the ecological community over time as it
is particularly sensitive to a wide range of environmental changes resulting from climate
change, including changes in temperature, salinity, water clarity and nutrient loads and ocean
acidification, sea level rise, as well as the frequency or severity of cyclones (Pratchett et al.,
2011).
Climate change
While the ecological community may be positively impacted by increases in atmospheric CO2
which will lead to a higher proportion of dissolved CO2 in the ocean and should favour seagrass
productivity (eg. increases in seagrass biomass, in seagrass depth limits and an enhancement of
the role of seagrass beds in carbon nutrient cycles), the ecological community is expected to be
negatively impacted by sea level rise due to increases in water depth and increased turbidity of
coastal waters due to erosion of coastlines or more frequent incidences of flooding
(Poloczanska, 2006). Additionally, sea temperatures, UV radiation and frequency of natural
disturbance regimes such as storms and cyclones are also predicted to alter, and combined their
impacts may negate the benefits of increased CO2 availability (Poloczanska, 2006).
Overall, it is expected that current anthropogenic pressures coupled with the stressors of a
changing climate will threaten the persistence and resilience of the ecological community
(Poloczanska, 2006).
10
1
3. Priority Conservation Actions
2
3.1 Conservation Objective
3
4
5
6
7
8
9
The conservation objective for the ecological community is to mitigate the risk of extinction of
the ecological community, and help recover its extent, biodiversity and function through the
protections provided under the Environment Protection and Biodiversity Conservation Act
1999 (EPBC Act) and through the implementation of the following priority conservation
actions.
3.2 Research and monitoring
10
11
Management and research priorities for the ecological community that would inform future
regional and local priority actions include:
12
High priorities:
13
14
15
 Improve reliability of indicators and predictors of seagrass ecosystem response to
environmental change (both natural and human induced).
 Identify locations of suitable donor populations for transplanting purposes.
16
17
18
19
 Research and monitor the impact of different styles of ‘seagrass friendly’ moorings on the
ecological community to ensure intended performance.
20
21
 Implement a monitoring program, including a community based seagrass monitoring
program, to monitor:
22
23
24
25
26
27
28
29
30
31
Other priorities:
the condition of the ecological community, including the extent of physical damage
to meadows, density and patchiness of meadows in the ecological community,
epiphyte loads and recovery.
o water quality (eg. levels of nutrients and water clarity) particularly after rainfall
events and following weekend boating activity.
o effectiveness of installed pollution control devices.
Investigate sediment dynamics in seagrass communities to identify the significance of
sediment stabilisation imparted by the ecological community.
o

3.3 Priority recovery and threat abatement actions
32
Habitat loss, disturbance and fragmentation
33
Highest priorities:
34
35
36
37
38
39
40
41
42
43
44
45
 Avoid further loss and fragmentation of the ecological community.
 Avoid dredging or disposing of dredge spoil in or near to the ecological community.
 Minimise loss and fragmentation of the ecological community through scouring from boat
propellers, anchors and moorings by
o relocating swing moorings in or adjacent to the ecological community. Where
relocation is not possible, replace swing moorings with ‘seagrass friendly’ moorings
(eg. screw moorings);
o providing mooring buoys in high use areas;
o introducing buffer zones; and
o introducing boating restriction zones over shallow patches of the ecological
community.
11
1
Other priorities:
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
 Control turbidity and sedimentation effects from dredging in the vicinity of the ecological
community by minimising spill, overflow and leakage from the dredges and barges;
judicious selection of dredging equipment; seasonal or tidal restrictions; turbidity limits
triggering specific management responses; and reactive monitoring.
 Avoid any changes to hydrology in corresponding coastal regions that may result in changes
to the natural hydrological regime influencing the ecological community, including training
walls, drainage and increase or decrease in run-off, salinity, or pollution.
 Design foreshore structures such as jetties, boat ramps and seawalls to avoid shading or
physical damage to the ecological community.
 Replace decking of jetties with mesh decking to allow sunlight penetration to the underlying
ecological community.
 Implement water quality management in catchments to reduce nutrient and sediment loads
into receiving estuarine environments in which the ecological community occurs.
 Maintain foreshore vegetation to act as a buffer zone.
 Encourage stormwater reuse in the local government area through detention devices and
promoting and providing incentives for installing rainwater tanks with connections to toilets
and washing machines.
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
High priorities:
 Promote opportunities for inclusion of the ecological community in any proposed reserve
tenure or other conservation management arrangements. In particular, ensure that remnants
that are of particularly high quality or important for connectivity are considered for inclusion
in reserve tenure or other marine conservation measures.
 Liaise with local councils and State authorities to ensure new coastal development, forestry
development or other activities involving substrate or vegetation disturbance do not
adversely impact on the ecological community.
 Liaise with planning authorities to ensure that planning takes the protection of the ecological
community into account, with due regard to principles for long-term conservation.
 In consultation with land and sea managers, local and state authorities and Aboriginal
groups, develop or support appropriate existing education programs, information products
and signage to help the public (in particular, boat users) recognise the presence and
importance of the ecological community, the need to manage water quality and their
responsibilities under state and local regulations and the EPBC Act.
45
46
47
 Australian and New Zealand Environment and Conservation Council, Agriculture and
Resource Management Council of Australia and New Zealand. (2000). Australian and New
Zealand Guidelines for Fresh and Marine Water Quality. Available at:
Communication and conservation information
Other priorities:
 Undertake stormwater pollution education for schools, industries and local residents in
which impacts of stormwater pollution on the ecological community and marine ecology
more generally are defined and measures to reduce stormwater are developed.
 Increase coordination between different government authorities to better manage the
ecological community, e.g. between NSW Fisheries and local councils.
3.4 Existing plans/management prescriptions
12
1
2
http://www.environment.gov.au/water/publications/quality/australian-and-new-zealandguidelines-fresh-marine-water-quality-volume-1
3
4
5
6
 Cardno (NSW/ACT) Pty Ltd. (2012). Coastal Management Plan for Brisbane Water
Estuary. Gosford City Council. Available at: http://www.gosford.nsw.gov.au/environmentand-waste/environmental-management-and-planning/estuaries/estuary-managementplanning
7
8
 Fairfull, S. (2013). Fisheries NSW Policy and Guidelines for Fish Habitat Conservation and
Management (2013 update). Available at: www.dpi.nsw.gov.au/publications
9
10
11
 Great Lakes Council. (2009). Great Lakes Water Quality Improvement Plan: Wallis, Smiths
and Myall Lakes, Forster, NSW. Available at:
http://www.greatlakes.nsw.gov.au/Environment/Plans_and_Strategies
12
13
14
 Lake Macquarie City Council. (2014). City of Lake Macquarie Environmental Sustainability
Action Plan 2012-2023. Available at:
http://www.lakemac.com.au/page.aspx?pid=109&vid=10&fid=147&ftype=True
15
16
 Manly Council. (2011). Manly Cover Coastal Zone Management Plan: Final Report.
Available at: http://www.manly.nsw.gov.au/environment/marine-and-coastal/manly-cove/
17
18
19
 Manly Council. (2008). Contarf/Bantry Bay Estuary Management Plan: Final Report.
Available at: http://www.manly.nsw.gov.au/environment/marine-and-coastal/clontarfbantry-bay-estuary-management-plan/
20
21
 Marine Parks Authority. (2010). Port Stephens – Great Lakes Marine Park Operational Plan, NSW
22
23
24
25
 NSW Department of Primary Industries. (1997). Fish Habitat Protection Plan No2:
Seagrasses. NSW DPI, Pyrmont, Sydney. Available at:
http://www.dpi.nsw.gov.au/__data/assets/pdf_file/0019/202744/Fish-habitat-protectionplan-2---Seagrass.pdf
26
27
 NSW National Parks and Wildlife Service. (2001). Towra Point Nature Reserve Plan of
Management.
28
29
 NSW National Parks and Wildlife Service. (2000). Royal National Park, Heathcote National
Park and Garawarra State Recreation Area plan of management.
30
31
 Haines, P., Fletcher, M., Rollason, V. and Coad, P. (2008). Lower Hawkesbury Estuary
Management Plan. BMT WBM Pty Ltd.
32
33
34
35
 Haines, P. and Rollason, V. (2010). Pittwater estuary management plan. Pittwater City
Council. Available at:
http://www.pittwater.nsw.gov.au/environment/water/estuaries/pittwater_estuary_manageme
nt_plan
36
37
38
 Stewart, M. and Fairfull, S. (2007). Primefact 629: Seagrasses. NSW DPI, Sydney.
Available at: http://www.dpi.nsw.gov.au/__data/assets/pdf_file/0019/203149/seagrassesprimefact-629.pdf
39
40
 Sutherland Shire Council. (2007). Port Hacking Integrated Environmental Management
Plan. Available at: www.sutherlandshire.nsw.gov.au/files/.../Port...Management_Plan.pdf
41
42
43
44
 Umwelt (Australia) Pty Ltd. (2009). Living on the edge – Port Stephens foreshore
management plan. Available at: http://www.portstephens.nsw.gov.au/environmentportstephenscd/water-quality-and-management-portstephen/1132949-port-stephens-myalllakes-estuary-manage
Marine Parks Authority, Sydney.
13
1
2
3
 Umwelt (Australia) Pty Ltd. (2000). Port Stephens and Myall Lakes estuary management
plan. Available at: http://www.portstephens.nsw.gov.au/environment-portstephenscd/waterquality-and-management-portstephen/1132949-port-stephens-myall-lakes-estuary-manage
4
5
 Wallis Lake Estuary Management Committee. (2005). Wallis Lake Estuary Management
Plan. Available at: http://www.greatlakes.nsw.gov.au/Environment/Plans_and_Strategies
6
7
 Wallis Lakes Estuary Management Committee. (2003). Wallis Lake Catchment Management
Plan. Available at: http://www.greatlakes.nsw.gov.au/Environment/Plans_and_Strategies
14
1
BIBLIOGRAPHY
2
3
BBCPEA (Botany Bay Cable Project Environmental Assessment). (2006). Molino Stewart Pty
Ltd.
4
5
6
7
Bell, JD. and Pollard, DA. (1989). Ecology of fish assemblages and fisheries associated with
seagrasses. In Biology of Seagrasses: A Treatise on the Biology of Seagrasses with
Special Reference to the Australian Region (eds AJ McComb, AWD Larkum and SA
Shepherd). Elsevier, Amsterdam.
8
9
10
Burchmore, J.J., Pollard, D.A. and Bell, J.D. (1984). Community structure and trophic
relationships of the fish fauna of an estuarine Posidonia australis seagrass habitat in Port
Hacking, New South Wales. Aquatic Botany 18: 71-87.
11
12
Cambridge, ML. and Kuo, J. (1979) Two new species of seagrasses from Australia, Posidonia
sinuosa and P. angustifolia (Posidoniaceae). Aquatic Botany 6: 307–328.
13
14
15
16
Carruthers, TJB., Dennison, WC., Kendrick, GA., Waycott, M., Walker, DI. and Cambridge,
ML. (2007). Seagrasses of south-west Australia: A conceptual synthesis of the world’s
most diverse and extensive seagrass meadows. Journal of Experimental Marine Biology
and Ecology 350: 21-45.
17
18
19
Collett, LC., Hutchings, PA., Gibbs, PJ. And Collins, AJ. (1984). A comparative study of the
macro-benthic fauna of Posidonia australis seagrass meadows in New South Wales.
Aquatic Botany 18: 111-134.
20
21
Creese, B., Glasby, T., West, G. and Gallen, C. (2009). Mapping the habitats of NSW
estuaries. Port Stephens Fisheries Institute, Industry & Investment NSW.
22
23
Commonwealth of Australia (2006). Integrated Marine and Coastal Regionalisation of
Australia Version 4.0. Department of the Environment and Heritage, Canberra, Australia.
24
Duarte CM (2002). The future of seagrass meadows. Environmental Conservation 29: 192-206.
25
26
Duarte, CM., Fourqurean, JW., Krause-Jensen, D., Olesen, B. (2006). In AWD Larkum et al.
(eds) Seagrasses: Biology , Ecology and Conservation pp271-294.
27
28
Erftemeijer, P.L.A. and Lewis, R.R.R. (2006) Environmental impacts of dredging on
seagrasses: A review. Marine Pollution Bulletin 52, 1553-1572.
29
30
31
Evans, S., Verges, A. and Poore, A. Personal communication by email, 16 February 2014,
Evolution and Ecology Research Centre, School of Biological, Earth and Environmental
Sciences, University of New South Wales.
32
33
Glasby, T. (2013) Caulerpa taxifolia in seagrass meadows: killer or opportunistic weed?
Biological Invasions 15,1017–1035.
34
35
36
37
Haines, P. and Rollason, V. (2010). Pittwater estuary management plan. Pittwater City Council.
Available at:
http://www.pittwater.nsw.gov.au/environment/water/estuaries/pittwater_estuary_manage
ment_plan
38
39
40
Keough, MJ. and Jenkins, GP. (1995). Seagrass meadows and their inhabitants. In Coastal
marine ecology of temperate Australia. (eds A.J. Underwood and M.G. Chapman).
UNSW Press.
41
42
Kirkman, H. (1985) Community structure in seagrasses in southern western Australia. Aquatic
Botany 21, 363-375.
43
44
Kirkman, H. (1997). Seagrasses of Australia. Australia: State of the Environment Technical
Paper Series (Estuaries and the Sea), Department of the Environment, Canberra.
15
1
2
Kirkman, H. and Kuo, J. (1990). Pattern and Process in southern Western Australian
seagrasses. Aquatic Botany 37, 367-382.
3
4
5
Klumpp, DW., Howard, RK. and Pollard, DA. (1989). Trophodynamics and nutritional ecology
of seagrass communities. In, Seagrass Ecosystems – an Australian Perspective. (eds
AWD. Larkum and A. McComb). Elsevier, Amsterdam.
6
7
8
Larkum, AWD. (1976). Recent research on seagrass communities in Australia. In Seagrass
Ecosystems: a scientific perspective. (eds C.P. McRoy and C. Helfferich). New York:
Marcel Dekker Inc. pp. 247-262.
9
10
Larkum, AWD. and West, RJ. (1990). Long-term changes of seagrass meadows in Botany Bay,
Australia. Aquatic Botany 37: 55-70.
11
12
Mc Mahon, K. (2013). Dredging effects on food webs. In ‘Seagrass-Watch magazine. Issue 47.
(eds L.J. McKenzie, R.L. Yoshida, R. Unsworth, R. Coles). Seagrass-Watch HQ, Cairns.
13
14
15
McNeill, S.E., Worthington, D.G., Ferrell, D.J., Bell, J.D. (1992). Consistently outstanding
recruitment of five species of fish to a seagrass bed in Botany Bay, NSW. Australian
Journal of Ecology 17: 359–365.
16
17
18
Manly Council. (2008). Contarf/Bantry Bay Estuary Management Plan: Final Report.
Available at: http://www.manly.nsw.gov.au/environment/marine-and-coastal/clontarfbantry-bay-estuary-management-plan/
19
Manly Council. (2009). Manly Cove Coastline Management Study – Final Report.
20
21
Meehan, A.J. and West, R.J. (2000). Recovery times for a damaged Posidonia australis bed in
south eastern Australia. Aquatic Botany 67: 161-167.
22
23
24
Meehan, A. (2001) Conservation status of the seagrass Posidonia australis Hook f. in south
east Australia. Ph.D thesis, Faculty of Science, University of Wollongong. Available at:
http://ro.uow.edu.au/theses/1864
25
26
27
Meehan, A.J. and West, R.J. (2002). FRDC 97/220 Final Report: Seagrasses in southern NSW
estuaries - their ecology, conservation, restoration and management. Report Series No.
2002/1.
28
29
30
Middleton, M.J., Bell, J.D., Burchmore, J.J., Pollard, D.A. and Pease, B.C. (1984). Structural
differences in the fish communities of Zostera capricorni and Posidonia australis
seagrass meadows in Botany Bay, New South Wales. Aquatic Botany 18, 89-109.
31
32
NSW DPI (New South Wales Department of Primary Industries). (1997). Fish Habitat
Protection Plan No2: Seagrasses. NSW DPI, Pyrmont, Sydney.
33
34
35
36
37
NSW FSC (New South Wales Fisheries Scientific Committee). (2010). Final Determination:
Posidonia australis as Endangered Populations in Port Hacking, Botany Bay, Sydney
Harbour, Pittwater, Brisbane Waters and Lake Macquarie NSW. Available on the internet
at: http://www.dpi.nsw.gov.au/__data/assets/pdf_file/0008/352169/FD44-Posidoniaaustralis.pdf
38
39
NSW SC (New South Wales Scientific Committee). (2000). Little penguin population, Manly
Point area - endangered population listing – Final Determination.
40
41
42
Poloczanska E.S. (2006). Impacts of climate change on seagrasses. In ‘Impacts of climate
change on Australian marine life. (eds A.J. Hobday, T.A. Okey, E.S. Poloczanska, T.J.
Kunz, A.J. Richardson). Report to the Australian Greenhouse Office, Canberra, Australia.
43
44
45
46
Pratchett M.S., Bay, L.K., Gehrke, P.C., Koehn, J.D., Osborne, K., Pressey, R.L., Sweatman,
H.P.A., Wachenfeld, D. (2011) Contribution of climate change to degradation and loss of
critical fish habitats in Australian marine and freshwater environments. Marine and
Freshwater Research 62: 1062-1081.
16
1
2
3
4
Roper, T. Creese, B. Scanes, P. Stephens, K. Williams, R. Dela-Cruz, J. Coade, G. Coates, B.
& Fraser, M. (2011). Assessing the condition of estuaries and coastal lake ecosystems in
NSW, Monitoring, evaluation and reporting program, Technical report series, Office of
Environment and Heritage, Sydney.
5
6
Seddon, S. (2004). Going with the flow: facilitating seagrass rehabilitation. Ecological
management and restoration 5(3): 167-175.
7
8
9
Shepherd, S.A., McComb, A., Bulthuis, D., Neverauskus, V., West, R.J., 1989, Chapter 15:
Decline in some Australian seagrass beds. In: Larkum, A.W.D., McComb, A. (Eds.),
Seagrass Ecosystems – an Australian perspective. Elsevier, Amsterdam.
10
11
12
SMEC. (2003). Towra Beach Nourishment. Vol. 1. Environmental Impact Statement. Prepared
for the Waterways Authority and NSW National Parks and Wildlife Service, August
2003.
13
14
15
16
Spalding, M.D., Fox, H.E., Allen, G.R., Davidson, N., Ferdana, Z.A., Finlayson, M., Halpern,
B.S., Jorge, M.A., Lombana, A., Lourie, S.A., Martin, K.D., McManus, E., Molnar, J.,
Recchia, C.A. and Robertson, J. (2007). Marine Ecoregions of the World: A
Bioregionalization of Coastal Shelf Areas. Bioscience 57(7): 573-583.
17
18
19
20
Umwelt (Australia) Pty Ltd. (2000). Port Stephens and Myall Lakes estuary management plan.
Available at: http://www.portstephens.nsw.gov.au/environment-portstephenscd/waterquality-and-management-portstephen/1132949-port-stephens-myall-lakes-estuarymanage
21
22
23
24
25
26
Walker, D.I. Hutchings, P.A. and Wells, F.E. (1991). Seagrass, sediment and infauna – a
comparison of Posidonia australis, Posidonia sinuosa and Amphibolis antarctica in
Princess Royal Harbour, south western Australia. 1. Seagrass biomass, productivity an
contribution to sediments. In ‘Proceedings of the Third International Marine Biological
Workshop: The Marine Flora and Fauna of Albany, Western Australia’. Vol 2 (ed. FE
Wells, DI Walker, H Kirkman, R Lethbridge).
27
28
29
Wear, R.J. (2006). Recent advances in research into seagrass restoration. Prepared for the
Coastal Protection Branch, Department of Environment and Heritage. SARDI Aquatic
Sciences Publication No. RD04/0038-4. SARDI Aquatic Sciences Adelaide.
30
31
West, R.J. (1990). Depth related structural and morphological variations in an Australian
Posidonia seagrass bed. Aquatic Botany 36: 153-166.
32
33
West, R.J. (2011). Impacts of recreational boating activities on the seagrass Posidonia in SE
Australia. Wetlands (Australia 26(2): 3-13.
34
35
36
West, R.J. and Jones, M.V. (2001). FRDC 97/204 Final Report: Shallow water fish
communities of New South Wales south coast estuaries. Report Series Nos. 2001/1.
Ocean and Coastal Research Centre, University of Wollongong, Australia.
37
38
West, R.J., Thorogood, C.A., Walford, T.R. and Williams, R.J. (1985). An estuarine inventory
for New South Wales, Australia. Fisheries Bulletin 2. NSW Department of Agriculture.
39
40
41
42
West R.J., Larkum A.W.D. and King R.J. (1989). Regional studies – seagrass of south eastern
Australia. In Biology of Seagrasses: A Treatise on the Biology of Seagrasses with Special
Reference to the Australian Region (eds AJ McComb, AWD Larkum, SA Shepherd).
Elsevier, Amsterdam.
43
44
45
46
Wright, A., Scanes, P. and Brennan, K. (2013). Posidonia australis mooring impact
assessment: investigating the impacts of boat moorings on the seagrass Posidonia
australis in Lake Macquarie, NSW. NSW Office of Environment and Heritage, Sydney
NSW.
47
17