Substrate ID Training
Global Community
Coral Reef Monitoring
Program
What is a coral reef?
Coral reefs are typified by large hard corals that build the
reef structure and support a myriad of life.
They are tropical ecosystems that rival only rainforests in
biodiversity and are important to us for:
• Food;
• Shore breaks;
• Pharmaceuticals;
• Tourism.
What conditions do reefs require?
 Low nutrient, clear water;
 Sunlight;
 Salinity around 30 – 36 ppm;
 Water temperature between 20 - 29ºC;
 More effective management than is currently in place.
Naturally subject to environmental disturbance, the
health of a coral reef can be measured in terms of its
resilience to impacts and its ability to recover from
disturbance. We can measure this health by monitoring
how they change over time.
As the disturbance – recovery regime of a coral reef is
complex, the longer time-period we have monitoring
data for, the more patterns we can see. Therefore, by
monitoring the reef each year from now, we’ll be really
helping scientists understand how the reef works in the
future.
The Reef Check Substrate Categories
HC – HARD CORAL (includes blue coral, fire coral and organ pipe coral)
*HCB – BLEACHED HARD CORAL
SC – SOFT CORAL (includes zoanthids)
*SCB – BLEACHED SOFT CORAL
NIA – NUTRIENT INDICATOR ALGAE (includes seaweed that proliferates
with high nutrient input. *Record what it is on top of e.g.
NIA/RC)
OT – OTHER
(includes other living or non-living substrata, such as,
hydroids, anemones, gorgonians and ascidians)
SP – SPONGE
RC – ROCK
(includes any surface that coral could settle onto including
rock covered with turf algae, bivalves, coralline algae and
dead coral)
RKC – RECENTLY KILLED CORAL (includes coral that has died in the last
year. Such coral will still have a white or partially white
skeleton and may be slightly overgrown with algae. *If it has
NIA on top of it then write NIA/RKC)
RB – RUBBLE
(includes dead coral of 0.5 to 15 cm diameter)
SI – SILT
(write the substrate underneath e.g. SI/RC)
SD – SAND
(includes pieces less than 0.5 cm in diameter)
*This only applies to Reef Check Queensland, Australia.
HARD CORAL
The reef builders
Reef Check code: HC
HARD CORAL
The reef-builders
Hard corals function as the main builders of coral reefs.
They are also important in providing both food and shelter
to a large number of reef organisms.
Coral reefs are naturally subjected to erosion from wave
surges and boring organisms. As hard corals lay down
more of their underlying limestone or calcium carbonate
skeleton the reef grows.
When there is a mass hard coral die-off on a reef from a
storm, crown-of-thorns starfish outburst or other impact,
the reef itself loses its ability to ‘grow’ and may be eroded
down. Additionally, the organisms reliant upon the hard
coral structures for hiding from predators will likely
decrease in abundance as their habitat is lost.
HARD CORAL
The reef-builders
Hard coral includes:
• All hard corals;
• Fire coral (Millepora);
• Blue coral (Heliopora);
• Organ pipe coral (Tubipora musica).
HARD CORAL
The reef-builders
Tentacles for catching food
using stinging cells
(nematocysts) to stun their
prey. Hard coral polyps have 6
or multiples of 6 tentacles.
Zooxanthellae algae live in
the coral’s tissue and make
food from sunlight using
photosynthesis. This food
counts for 90+% of the
coral’s food.
Mouth
Where food is
ingested and
waste excreted.
Mucus is excreted from the
coral’s surface, which
provides a limited ability to
clean itself from sediment.
Stomach.
Coral cup or
‘corallite’.
Cross section through a coral polyp
Limestone
skeleton that is
excreted by the
coral polyp. This
skeleton ‘builds’
the reefs.
HARD CORAL
The reef-builders
Most corals, as well as many other similar coral reef
organisms, are colonial. This means that individual
animals, like coral polyps, are joined to one another by a
thin layer of cells called tissue. Animals on the same
colony are typically identical genetically as they are formed
by asexual reproduction. Corals also reproduce sexually
once or twice a year (coral spawning) and the young corals
(recruits) will settle on the reef and start a new colony. By
joining one another, they can share food as well as send
messages to one another, for example, a message to close
up if there is danger.
HARD CORAL
The reef-builders
Coral Growth Forms
Corals can grow in may different shapes. For the purpose of Reef
Check, we are not interested to record the different shapes of
hard coral that we see. Therefore, do not attempt to learn these,
however, it is a good idea to be aware of them in order that we
can identify a hard coral from another reef organism or substrate.
The different growth forms are as follows:
•
•
•
•
•
•
•
•
Branching;
Plate;
Encrusting;
Massive or boulder;
Submassive or irregular;
Folios or lettuce-like;
Columnar or digitate;
Free living or mushroom.
HARD CORAL
The reef-builders
To identify hard coral use the following decision rules:
1. If it is a protruding structure, waft the water near it
with your hand.
Does it move?
Yes
It is not hard coral
and may be soft coral
or sponge
No
1. Look at the texture and try to find
the coral cups. Hard coral
texture is like sandpaper or
knobbly;
2. If the coral polyps are out, count
the tentacles. Hard coral polyps
have 6 or multiples of 6 tentacles
whereas soft corals only have 8.
HARD CORAL
The reef-builders
2. If it is an encrusting structure, look at the texture.
Does it have regular corallites and have a
sandpapery or knobbly surface?
Yes
Check it is hard
to touch and it
is probably a
hard coral.
No
1. Look at the texture, if it is smooth and a
purple, orange or red colour it is
probably coralline algae;
2. If it has holes on its surface and feels
soft to the touch it is probably either a
sponge or an ascidian;
3. If it has regular corallites but is soft to
the touch it is probably a soft coral.
HARD CORAL
The reef-builders
3. If it is an encrusting structure, gently touch to check if
it is hard or soft.
Does it feel hard and knobbly?
Yes
It is probably a
hard coral.
No
1. If it is hard and smooth, it might be
coralline algae, which goes in the rock
category for Reef Check;
2. If it is spongy, check if it is a soft coral, a
sponge or an ascidian. If it has regular
corallites but is soft to the touch it is
probably a soft coral.
HARD CORAL
The reef-builders
Branching
Photo by Jos Hill, 2002
Look at the texture. You can
see the coral cups protruding
HARD CORAL
The reef-builders
Branching
Each polyp
lives inside
this coral
cup or
corallite
Photo by Jos Hill, 2002
HARD CORAL
The reef-builders
Branching
These tube-like
projections are
the corallites in
which the coral
polyp lives.
HARD CORAL
The reef-builders
Branching
Encrusting
hard coral
Branching
hard coral
Encrusting
hard coral
Photo by Jos Hill, 2002
HARD CORAL
The reef-builders
Branching
HARD CORAL
The reef-builders
Plate
Photo by Jos Hill, 2002
HARD CORAL
The reef builders
Encrusting
Encrusting hard coral
‘hugs’ the substrate to
which it is attached and
will tend to be a few mm
thick.
Note the ‘knobbly’
texture.
Photo by Jos Hill, 2002
HARD CORAL
The reef builders
Encrusting
Note the ‘knobbly’
texture. If we could
get a closer look you
would see tiny holes
that are the corallites.
Photo by Dean Miller, 2002
HARD CORAL
The reef builders
Encrusting
Note the
knobbly/sandp
apery texture.
Photo by Dean Miller, 2002
HARD CORAL
The reef builders
Massive or boulder
The corallites on
this species are
larger than
previous examples.
This makes this
hard coral easier to
identify.
Photo by Dean Miller, 2002
HARD CORAL
The reef builders
Massive or boulder
This coral colony is
several meters in
length. Some
massive corals can
be hundreds of
years old.
Photo by Dean Miller, 2002
HARD CORAL
The reef builders
Submassive
Note the
‘knobbly’
surface.
Photo by Dean Miller, 2002
HARD CORAL
The reef builders
Submassive
Watch out for this one!
Look at this polyp.
There are 24 tentacles
(6 x 6) which means it
is a hard coral. This
particular coral feeds in
the day time so is often
mistaken for a soft
coral. If you wafted
these polyps quite hard
they will retract and
you’ll see the hard
skeleton beneath.
Photo by Dean Miller, 2002
HARD CORAL
The reef builders
Foliose or lettuce
Note the sandpaperlike texture.
Photo by Jos Hill, 2002
HARD CORAL
The reef builders
Digitate
Each of these
projections is a
corallite.
Photo by Jos Hill, 2002
HARD CORAL
The reef builders
Mushroom or free-living
Unlike other corals,
mushroom corals do not
attach itself to the reef
rock. Additionally, they
do not live in colonies,
but alone as single
polyps.
Mouth
Photo by Jos Hill, 2002
HARD CORAL
The reef builders
Watch out for this one!
Mushroom or free-living
Some types of mushroom
corals feed in the day time
and can be mistaken for
anemones. Although not
all anemones have
anemone fish in them, if
you see one of these with
no fish, give it a waft and
you’ll see the hard
skeleton underneath.
Photo by Jos Hill, 2002
HARD CORAL
The reef builders
Blue coral
Blue coral is not a true hard
coral as it has a blue argonite
skeleton instead of calcium
carbonate/limestone. However,
as its skeleton is hard, it is a
reef-builder and is, therefore,
included in the HC category for
Reef Check.
Blue coral looks like a
submassive hard coral.
Photo by Jos Hill, 2002
HARD CORAL
The reef builders
Fire coral
Notice
the tiny
hairs.
Fire coral is not a true hard
coral. In fact, it is a
hydroid. However, it has a
hard skeleton and appears
the same as a hard coral
people tend to have no
problems with identifying
this as a hard coral for Reef
Check. The only thing to
be aware of is that the tiny
hairs sting!
Photo by Dean Miller, 2002
HARD CORAL
The reef builders
Notice that this coral’s polyps
have 8 tentacles. In the next
section you will learn that soft
corals have 8 tentacles, which
can be a good way to tell them
apart from hard corals.
Organ pipe coral
Organ pipe coral is in fact a soft
coral. However, it is unusual for
soft corals in that it makes a
hard, red skeleton and is,
therefore, a reef-builder and
included in the HC category for
Reef Check.
If you see this coral, waft the
polyps gently and see them retract
into a red skeleton…but
remember that red is filtered out
of the water at shallow depths so
this skeleton may look brownish
underwater.
Photo by Jos Hill, 2002
HARD CORAL
The reef builders
Organ pipe coral
This is the organ
pipe coral skeleton.
Notice the pipes!
Photo by Jos Hill, 2002
HARD CORAL
The reef builders
Summary
• Calcium carbonate skeleton. Waft the water and it won’t move!
• Polyps have 6 or multiples of 6 tentacles, except fire coral, blue
coral and organ pipe coral, which are also included in hard coral;
• Mostly night feeders. Exceptions have large polyps and you can
count the tentacles and/or waft to see a skeleton underneath;
• Look for corallites that are fairly regularly spaced;
•Different shapes exist – don’t be caught out by encrusting hard
corals as these are sometimes overlooked;
• Look at the texture, think sandpaper or knobbly surface!
• Mushroom corals are hard corals. Don’t be caught out by those
that feed in the day and may look like anemones.
BLEACHED HARD CORAL
Global warming indicator
Reef Check code: HCB
BLEACHED HARD CORAL
Global warming indicators
Bleaching is when the zooxanthellae (algae) living in the coral’s
tissue is expelled. As this algae is also a pigment in the coral,
when it is expelled many corals appear white because we can see
their calcium carbonate skeleton through their thin tissue.
The white patch here is bleached
and the brown parts are
unbleached.
Photo by Dean Miller, 2002
BLEACHED HARD CORAL
Global warming indicators
As the zooxanthellae provide corals with 90% or more of
their total food intake, if they sustain their bleached state,
they starve. Starvation does not necessarily mean death and
many corals will recover their zooxanthellae when the
stressor is removed. However, should the stressor remain
for many days or weeks the coral’s immune and reproductive
systems may first become impaired and they may die.
BLEACHED HARD CORAL
Global warming indicators
Bleaching happens when the coral is under stress, such as, sea
surface temperatures (SSTs), which are higher than corals can
tolerate. High SSTs of 29ºC or higher frequently occur when we
have an El Niño Southern Oscillation (ENSO) weather event.
Global warming appears
to increase the
frequency and intensity
of ENSOs. As a result it
is feared that coral
bleaching events will
become more frequent
and severe as a result.
Photo by Jos Hill, 2002
BLEACHED HARD CORAL
Global warming indicators
Reef Check surveys
document bleaching on
coral reefs and this data
will help scientists
understand how reefs are
affected by this
phenomenon.
Photo by Jos Hill, 2002
BLEACHED HARD CORAL
Global warming indicators
Photo by Jos Hill, 2002
BLEACHED HARD CORAL
Global warming indicators
This coral is only
partially bleached.
This means that the
zooxanthellae algae
have only been
expelled from the
coral polyps that
appear white.
Photo by Jos Hill, 2002
BLEACHED HARD CORAL
Global warming indicators
Photo by Jos Hill, 2002
SOFT CORAL
Non-reef builders
Reef Check code: SC
SOFT CORAL
Non-reef builders
Soft corals do not build reefs as their skeleton is made from
soft tissue that is supported internally like re-enforced
concrete by a matrix of calcareous elements.
Soft corals can be identified from hard corals by wafting the
water column and the whole structure will move. Many soft
corals will also have their polyps out during the daytime
and you can count their 8, hairy tentacles. (remember hard
corals have 6 or multiples of 6 tentacles). To identify
encrusting soft corals, you can gently touch them and they
will feel spongy.
The soft coral category also includes zoanthids. These are
not true soft corals but fill the same function as non reefbuilding structures.
SOFT CORAL
Non-reef builders
To identify soft coral use the following decision rules:
1. If it is a protruding structure, waft the water near it
with your hand.
Does it move?
Yes
It is not hard coral
and may be soft coral
or sponge
No
1. Look at the texture and try to find
the coral cups. Hard coral
texture is like sandpaper or
knobbly;
2. If the coral polyps are out, count
the tentacles. Hard coral polyps
have 6 or multiples of 6 tentacles
whereas soft corals only have 8.
SOFT CORAL
Non-reef builders
2. If it is a soft, encrusting structure, look for regular
corallites or feeding polyps (many soft coral polyps are
out feeding during the day, whereas hard corals tend to
feed at night).
Does it have regular corallites or
protruding polyps?
Yes
It is probably soft coral.
If the polyps are out
check there are only 8
tentacles.
No
If it has holes larger than
1mm diameter on the
surface then it is probably
a sponge or an ascidian.
SOFT CORAL
Non-reef builders
Notice the 8
tentacles. Soft
coral tentacles
also tend to be
hairy or
feathery.
Photo by Jos Hill, 2002
SOFT CORAL
Non-reef builders
Count the
8 tentacles
Photo by Jos Hill, 2002
SOFT CORAL
Non-reef builders
This soft coral will
sway when wafted.
The ‘fluffy’ surface is
the polyps. When
these polyps are not
feeding the surface of
this coral appears
leathery.
Photo by Dean Miller, 2002
SOFT CORAL
Non-reef builders
This is a close-up of the same
type of soft coral seen in the
previous picture. Here you can
see the polyps more clearly.
This is what
the polyps of
this coral look
like from up
close. Note
the 8
tentacles.
Photo by Dean Miller, 2002
SOFT CORAL
Non-reef builders
Some soft corals
look like trees and
many can be
bright colours.
Photo by Dean Miller, 2002
SOFT CORAL
Non-reef builders
This ‘finger’ soft coral
would move when
wafted. If you look
closely you would see
tiny pin-prick holes
that are the corallites.
Photo by Dean Miller, 2002
SOFT CORAL
Non-reef builders
Photo by Jos Hill, 2002
SOFT CORAL
Non-reef builders
Photo by Jos Hill, 2002
SOFT CORAL
Non-reef builders
Photo by Jos Hill, 2002
The ‘fluffy’
appearance is
the polyps.
SOFT CORAL
Non-reef builders
Zoanthids
Zoanthids are not true soft corals, however, they can cover huge
mats of reef and because they are non-reef builders like the soft
corals, we count them under this category for Reef Check.
Zoanthids look like little cogs of
about 1cm diameter, that have a
mouth in their centre and are
surrounded by little ‘teeth-like’
tentacles.
Zoanthids can live separately as in
this picture or in colonies where they
are connected to each other just like
most corals.
Photo by Jos Hill, 2002
SOFT CORAL
Non-reef builders
Zoanthids
This picture illustrates colonial zoanthids. They appear like they
are made out of plasticine. If you waft your hand over them,
they will close up as illustrated below.
These colonial
zoanthid polyps
are ‘open’.
These colonial
zoanthid polyps
are ‘closed’.
Photo by Jos Hill, 2002
SOFT CORAL
Non-reef builders
Zoanthids
Colonial zoanthids are frequently confused with massive and
encrusting corals of the genus illustrated below. This is because
the corallites of this coral resemble the soft zoanthid polyps.
To avoid confusion you can
touch the surface and find the
coral hard and the zoanthids
soft. Or you can gently waft
your hand over the top and
see that the zoanthids will
close up but the coral’s
skeleton won’t budge.
These corallites are part of this coral’s
skeleton. Go back to the last slide to
make sure you can see the difference.
Photo by Jos Hill, 2002
SOFT CORAL
Non-reef builders
Zoanthids
These are solitary zoanthids. Although their tissue is separate
they normally occur in groups. These zoanthids will also close if
you waft your hand over them.
Photo by Jos Hill, 2002
SOFT CORAL
Non-reef builders
Zoanthids
Zoanthids tend to have brown, red or
green centres as these below.
Photo by Jos Hill, 2002
SOFT CORAL
Non-reef builders
Zoanthids
Another example of
colonial zoanthids
where some are
‘open’ and some are
‘closed’.
Photo by Jos Hill, 2002
SOFT CORAL
Non-reef builders
Summary
• Skeleton structure is soft;
• Polyps always have 8 tentacles, which are hairy;
• Polyps are often day feeders;
• Smooth texture with small, regular coral cup holes;
• Surface of some appears leathery or rubbery;
• Zoanthids most often occur in groups or joined in colonies.
They can look like cogs surrounded like teeth and colonial ones
look like they’re made from plasticine. To recognise, waft and
they will close up.
BLEACHED SOFT CORAL
Global warming indicators
Reef Check code: SCB
BLEACHED SOFT CORAL
Global warming indicators
Like hard coral, soft coral can also bleach. However, as
soft corals do not contribute to the reef structure, we are
not as concerned about this bleaching as we are about
hard corals. Nevertheless, it is still interesting to note
where bleaching occurs in order to get an idea of the affect
of global warming on soft corals and their ability to
recover.
We can measure recovery of reef organisms from
detrimental impacts by monitoring the site year after year
and comparing the survey results.
NUTRIENT INDICATOR
ALGAE
Nutrient pollution indicator
Reef Check code: NIA
**Note that this category changed from Fleshy Seaweed (FS) in 2003
NUTRIENT INDICATOR ALGAE
Nutrient pollution indicators
Firstly, note that algae can be green, red or brown!
Photo by Jos Hill, 2002
Photo by Jos Hill, 2002
Photo by Jos Hill, 2002
NUTRIENT INDICATOR ALGAE
Nutrient pollution indicators
Note the
fleshy body
of this algae.
Photo by Jos Hill, 2002
Coral reefs are naturally ‘oligotrophic’ or nutrientpoor environments and nutrients that become
‘available’ from dying animals and plants are
quickly re-used and recycled into the living reef
organisms. This leaves the surrounding waters
nutrient-poor.
We all know that lots of nutrients, such as
nitrates and phosphates help plants grow.
Indeed, high nutrient conditions on a reef helps
algae grow fast. Although algae on reefs is both
natural and an important source of food for
herbivores, in unnaturally high nutrient
conditions, algae can out-compete coral, smother
it and block the sunlight that is essential for 90%
or more of its food. Therefore, proliferation of
many types of algae is an indicator of nutrient
pollution.
NUTRIENT INDICATOR ALGAE
Nutrient pollution indicators
Nutrient pollution can occur when farming practices on
land use fertilizers. These fertilizers run-off into the sea
and increase the nutrient levels on the reefs.
It is important to not that although most kinds of algae can
proliferate in high nutrient conditions, there are types of
algae that are not indicators of nutrient pollution. These
include Sargassum sp., Turbinaria sp., Halimeda sp.,
coralline algae and turf algae. Sargassum and turbinaria
tend to proliferate then practically disappear seasonally.
These algae can be recognised by having thick, leathery and
spiky leaves. Sargassum also has little air bladders that
hold it upright.
NUTRIENT INDICATOR ALGAE
Nutrient pollution indicators
Halimeda looks like chains of flat, green discs. Coralline algae
looks like a thin purple, orange or red covering on the reef
surface and turf algae is like a short (few mm tall), wiry grass.
If we see these algae on the reef, just look at what is below and
note its presence in the comments section of the survey sheet.
IMPORTANT! This
is halimeda and
NOT a nutrient
indicator algae!
Photo by Jos Hill, 2002
NUTRIENT INDICATOR ALGAE
Nutrient pollution indicators
This algae is like a turf
algae, however, it has a
jelly/fleshy coating that is
more than just a few mm of
wiry turf. This is, therefore,
included in nutrient
indicator algae.
If you are unsure whether it
is turf algae (and therefore
just noted in the comments
section) or nutrient
indicator algae, look for a
fleshy ‘halo’.
Photo by Jos Hill, 2002
NUTRIENT INDICATOR ALGAE
Nutrient pollution indicators
This algae is
fleshy, therefore
counted as
nutrient
indicator algae.
Photo by Jos Hill, 2002
NUTRIENT INDICATOR ALGAE
Nutrient pollution indicators
Red and fleshy algae.
If this is allowed to
proliferate as it might
in high nutrient
conditions, it can
smother the coral and
prevent light to
penetrate. Lack of
light prevents the
zooxanthellae algae
inside the coral from
photosynthesising.
Photo by Jos Hill, 2002
NUTRIENT INDICATOR ALGAE
Nutrient pollution indicators
See how this fleshy
algae is competing
with the branching
coral for space and
light.
Photo by Jos Hill, 2002
NUTRIENT INDICATOR ALGAE
Nutrient pollution indicators
This algae is
beginning to
smother the
branching hard
coral.
Photo by Jos Hill, 2002
NUTRIENT INDICATOR ALGAE
Nutrient pollution indicators
This algae, which
looks like pencil
shavings, can
proliferate in high
nutrient conditions.
Photo by Jos Hill, 2002
NUTRIENT INDICATOR ALGAE
Nutrient pollution indicators
This red algae
grows like
little red
leaves.
Photo by Jos Hill, 2002
NUTRIENT INDICATOR ALGAE
Nutrient pollution indicators
As this fleshy brown algae
grows over the dead coral,
it can smother the
surface and prevent baby
corals from establishing
themselves by blocking
out the sunlight.
Photo by Jos Hill, 2002
NUTRIENT INDICATOR ALGAE
Nutrient pollution indicators
Summary
• The aim is to record blooms of fleshy algae that may be
responding to a high level of nutrient input;
• . Examples of these types of algae are Ulva, various blue
green algae, and bubble algae as illustrated here;
• Algae that are a normal part of a healthy reef, such as
Sargassum sp., should NOT be recorded as NIA. Instead,
record the substrate directly beneath the algae and note
this in the comments section;
• Turf and coralline algae go under rock and halimeda goes
under ‘other’.
SPONGE
Sewage pollution indicator
Reef Check code: SP
SPONGE
Sewage pollution indicator
Sponges are very simple animals and are filter feeders that
clean the water of bacteria and other suspended organic
particles. They work like suction pumps and can filter large
quantities of water in a day.
As they are simple animals, they have no nervous network and
so will not react if you waft your hand over their holes!
Neither do they have a system for cleaning their outer surface
from particles from the water column that get sucked there as
the sponge filters the water. Instead, little sea cucumbers do
this job for them and you may see some sponges covered by
little white worm-like sea cucumbers. Other sponges may be
covered with a thin layer of silt.
Sponge texture tends to be matt rather than shiny.
SPONGE
Sewage pollution indicator
You’d expect to see more sponges
in areas of strong currents where
more food will be brought their
way in the water column.
Sponges are very common
components of coral reefs,
although they tend not to make up
a large percentage of the reef
surface in the Indo-Pacific.
Extensive coverage of sponge may
indicate sewage pollution, as they
are able to proliferate where there
is more food. Extensive sponge
growth takes up space from hard
corals.
Photo from Undersea Explorer, 2002
SPONGE
Sewage pollution indicator
Sponges come in ALL shapes, sizes and colours!
They can be confused with ascidians (see the ‘other’ category).
Their tissue is fairly stiff and their skeleton is similar to that of
soft corals, a matrix of hard elements called spicules. Patterns
of these spicules can often be seen from the surface like
splinters in the tissue or irregular lumps over the surface.
SPONGE
Sewage pollution indicator
The network of small
canals lead to a larger
canal that leads to the
ostia opening.
Small, irregularly
spaced holes called
ostia cover the sponge
surface.
They lead to a network
of canals, which are
lined with collar cells.
These cells create the
suction current and
sieve out organic debris
(food) from the water.
Water pumped out through
the larger holes, this is called
an osculum.
Water is sucked into the
ostia by a suction
current that is created
by the collar cells that
line the internal canals.
The sponge surface is
a matt texture. And
may be covered with
silt and other organic
debris that is too
large to fit into the
ostia.
Cross section through a sponge
SPONGE
Sewage pollution indicator
To identify sponge use the following decision rules:
1. If it is a protruding structure, waft the water near it
with your hand.
Does it move?
Yes
It is not hard coral
and may be soft coral
or sponge.
No
1. Look at the texture and try to find
the coral cups. Hard coral
texture is like sandpaper or
knobbly;
2. If the coral polyps are out, count
the tentacles. Hard coral polyps
have 6 or multiples of 6 tentacles
whereas soft corals only have 8.
SPONGE
Sewage pollution indicator
2. If it is a soft, encrusting structure, look for irregular
holes. THINK IRREGULAR is probably the best advise
you can use to recognise sponges!
Does it have irregular holes?
Yes
It is probably sponge or an
ascidian. To tell these apart,
waft the holes. If there is NO
reaction it is probably a
sponge. If the holes close up
– it is an ascidian!
No
If it has regular holes less
than 1mm diameter then
it is probably a soft coral.
SPONGE
Sewage pollution indicator
Look at the matt surface,
which is covered in little
spikes from the spicules
in its skeleton.
Notice how it
cannot clean this
debris out.
Photo by Jos Hill, 2002
SPONGE
Sewage pollution indicator
Note the holes (osculum).
These are distributed in
an irregular fashion over
the sponge body.
Note the irregular,
matt surface and
irregular shape
Photo by Jos Hill, 2002
SPONGE
Sewage pollution indicator
Note these holes.
They are fairly
regularly spaced over
this sponge.
Note the spiky
surface.
Photo by Jos Hill, 2002
SPONGE
Sewage pollution indicator
Note the
irregular, spiky
surface.
Note irregularly
spaced holes.
Photo by Jos Hill, 2002
SPONGE
Sewage pollution indicator
Note irregular, spiky
surface.
Photo by Jos Hill, 2002
SPONGE
Sewage pollution indicator
In a silty environment,
sponges may frequently
be covered in a layer of
silt.
Note irregular and spiky
surface with irregularly
spaced holes.
Photo by Jos Hill, 2002
SPONGE
Sewage pollution indicator
Spiky, irregular,
holey surface.
Irregular and
matt surface with
one large hole.
Photo by Jos Hill, 2002
This is an
ascidian NOT a
sponge. See
‘Other’
SPONGE
Sewage pollution indicator
Summary
• Huge range of colours;
• Surface often matt or dull;
• Simple organisms with no set shape. Think IRREGULAR!
• Can assume a variety of shapes and sizes from small encrusting
animals to large tube, barrel or foliose forms;
• To tell these from hard corals, waft and they will sway. To tell
them from soft corals, look closely at the surface for irregular
texture, covered in different sized holes. These holes will NOT close
up if you waft your hand over them.
• To tell an encrusting sponge or soft coral from hard coral, look
how ‘thick’ the structure is on the reef. Sponges and soft corals
will be thicker.
OTHER
Not indicators of impacts
Reef Check code: OT
OTHER
Not indicators of impacts
This category contains both living and non-living elements of
a coral reef that do not serve as indicators of human impacts
for the Reef Check survey.
Some of the members of the ‘other’ category can be confused
with members of the soft coral and sponge categories. It is,
therefore, important to familiarise yourselves with these in
order to avoid making these misidentifications.
OTHER
Not indicators of impacts
This category can include the following – although
this is not an exhaustive list!
• Ascidians;
• Hydroids;
• Anemones;
• Coralliomorphs;
• Gorgonians;
• Clams (but the shell comes under Rock).
OTHER
Not indicators of impacts
Ascidians
These holes will
close up if you
waft your hand
over them.
Ascidians (or tunicates or sea
squirts) can easily be confused
with encrusting sponges
because or their irregular
growth. They are also filter
feeders and so are covered in
inhalant and exhalent holes.
However, they are much more
complex organisms than
sponges and the holes will
CLOSE if you waft your hand
over them. Sponges will not
do this!
Photo by Jos Hill, 2002
OTHER
Not indicators of impacts
Ascidians
Solitary as well as colonial
ascidians exist. Solitary
ascidians are often easier
to recognise as they look
like little bells. These
solitary ascidians can
occur in groups but their
tissue is not joined (like
the zoanthids).
Photo by Jos Hill, 2002
OTHER
Not indicators of impacts
Ascidians
Inhalant and exhalant
holes. Waft and these
will close.
Photo by Jos Hill, 2002
OTHER
Not indicators of impacts
Ascidians
These ascidians
look like little bells.
Waft over the holes
and they will close!
Photo by Jos Hill, 2002
OTHER
Not indicators of impacts
Ascidians
These little yellow
organisms are also
ascidians. Waft and the
holes will close.
Photo by Jos Hill, 2002
Ascidians tend to have a
more shiny surface than
a sponge. The holes will
close when wafted.
OTHER
Not indicators of impacts
Ascidians
This is quite
common on the
Great Barrier Reef.
Most people just
have to learn this
one – but it helps
to describe it like
snot!
Photo by Jos Hill, 2002
OTHER
Not indicators of impacts
Hydroids
Hydroids are related to coral. They look
like feathers or ferns and are often called
stinging hydroids because they STING!
Don’t touch!
Photo by Jos Hill, 2002
OTHER
Not indicators of impacts
Hydroids
Photo by Jos Hill, 2002
OTHER
Not indicators of impacts
Anemones
Anemones are also
related to coral. They
frequently have
anemone fish living in
them – however, not
always. Be careful not
to confuse these with
the mushroom corals!
Photo by Jos Hill, 2002
OTHER
Not indicators of impacts
Anemones
Photo by Jos Hill, 2002
OTHER
Not indicators of impacts
Gorgonians
Gorgonians are
actually soft corals
but come under the
‘Other’ category for
Reef Check. They are
common in areas of
high current where
they position
themselves against
the current and filter
out food from the
water that travels
across them.
Photo by Dean Miller, 2002
OTHER
Not indicators of impacts
Non-nutrient indicator seaweed
Halimeda is a green algae
that excretes a calcium
carbonate ‘skeleton’, which
makes it difficult to digest
by many herbivores and so
serves as protection from
many algae-eating
organisms. Halimeda is
common on some reefs and
is not counted as a nutrient
indicator seaweed.
Therefore, put it in ‘Other’.
Photo by Jos Hill, 2002
OTHER
Not indicators of impacts
Coralliomorphs
Photo by Jos Hill, 2002
Coralliomorphs look like
anemones. As both these
belong in ‘Other’ there is no
need to differentiate between
the two.
ROCK
Hard substratum
Reef Check code: RC
ROCK
Hard substratum
Rock can be defined as any hard substratum that is either
bare rock or covered in turf algae or encrusting coralline
algae, barnacles, oysters etc. Rock also includes dead coral
that is more than 1 year old, i.e. is worn down so that few
corallite structures are visible, and covered with a thick layer
of encrusting organisms and/or algae.
• Turf algae is like wiry turf no more than a few millimeters
long;
• Coralline algae is encrusting and looks like lichen that is
pink, purple, orange or red;
Rock is important because it is a hard substratum on which
new coral or other organisms can settle.
ROCK
Hard substratum
The whole of this picture would be classified as rock
This is coralline
algae, therefore,
rock for Reef
Check.
Photo by Jos Hill, 2002
ROCK
Hard substratum
This
has a
think
layer of
silt
Photo by Jos Hill, 2002
ROCK
Hard substratum
The whole of this picture would be classified as rock
This pink is
coralline algae
(rock for Reef
Check)
Photo by Jos Hill, 2002
ROCK
Hard substratum
Rock
This is actually hard
coral. The little
bumps are the
corallites. The ‘holelike’ ones are
irregularities. If you
gave this a gentle
touch, you would see
that it was hard
coral rather than a
sponge or ascidian.
Photo by Jos Hill, 2002
ROCK
Hard substratum
This is broken dead coral
(rubble). It is classed as rock
because it has encrusting
organisms growing on it so that
it is now consolidated rather
than lose. Had it been lose
rubble that could be moved
around it would go in the
rubble category.
This is sponge.
Look at the spiky
texture.
Photo by Jos Hill, 2002
ROCK
Hard substratum
The shell of this
clam would
come under
rock.
Photo by Dean Miller, 2002
ROCK
Hard substratum
The corallites of this dead coral are
very eroded. This is therefore rock.
These are
ascidians.
Photo by Jos Hill, 2002
ROCK
Hard substratum
The corallites of this
dead coral are very
eroded. This would
come under rock.
Photo by Jos Hill, 2002
ROCK
Hard substratum
Again, the corallites of
this dead coral are very
eroded. This is,
therefore, rock.
Photo by Jos Hill, 2002
ROCK
Hard substratum
Summary
This includes:
• Bare rock;
• Turf and coralline algae;
• Barnacles or oysters etc;
• Coral that has been dead for over a year;
• Rubble that has been ‘cemented’ together by coralline algae.
Recently Killed Coral
Indicator of recent disturbance
Reef Check code: RKC
RECENTLY KILLED CORAL
Indicator of recent disturbance
The aim here is to record recent mortalities in hard corals. It is
important to be able to identify recently killed coral from coral
skeletons of coral that has been dead for a while. The following
guidelines may help with the identification of this category:
• Killed during the last year. This means that corallites will not be
very eroded. If the corallites have been eroded down and are covered
in encrusting organisms and/or are a dull grey colour, then it is
classified as rock;
• The skeleton may still be white if very recently killed because it is
made out of limestone. It may be slightly overgrown by algae as this
may not take long to settle. Look under the algae for corallites that
are not eroded and/or whitish skeleton;
• If it is slightly grown over with algae – note it as NIA/RKC or
OT/RKC depending on whether it is nutrient indicator algae or other
algae.
RECENTLY KILLED CORAL
Indicator of recent disturbance
If you look closely, the corallites
are only slightly eroded here. This
would be on the borderline of RKC
and nearly rock.
This is very eroded and
covered in coralline
algae. This would come
under rock.
This part has died very recently
as it only has a very thin layer of
algae covering it. This algae is
not thick enough to count as
algae so just put RKC.
This looks white like it has
very recently died.
This part is still alive
hard coral.
Photo by Jos Hill, 2002
RECENTLY KILLED CORAL
Indicator of recent disturbance
This ‘halo’ of jellylike algae is cyanobacteria which is a
nutrient indicator
algae. Put NIA/RKC
on the survey form
here.
Note the skeleton is
still white, so this is
very recently killed.
Photo by Jos Hill, 2002
RECENTLY KILLED CORAL
Indicator of recent disturbance
This photo was taken in
March 2002 when there
was severe bleaching on
the Great Barrier Reef.
This white part is either
bleached and still alive or
recently killed. It is hard
to tell – however, seeing
that the rest of this
branching hard coral
colony is recently killed,
you can assume that this
part is also.
Photo by Jos Hill, 2002
This part is recently
killed but now
covered in a thin
layer of algae. Here
you can put
NIA/RKC.
RECENTLY KILLED CORAL
Indicator of recent disturbance
Live hard coral
This photo was taken a
couple of weeks after
bleaching hit this area.
Apparently all this NIA
only took a couple of
weeks to cover this
coral! In other areas it
can take a lot longer. A
close look at this coral
will show that the
corallites were not
eroded and white
underneath. Therefore,
put NIA/RKC.
Photo by Jos Hill, 2002
RECENTLY KILLED CORAL
Indicator of recent disturbance
This nutrient indicator
algae has not taken
long to partially cover
the recently killed
coral. Put NIA/RKC
for the areas covered
with this algae.
This is recently
killed. Note the
white skeleton.
Photo by Jos Hill, 2002
RECENTLY KILLED CORAL
Indicator of recent disturbance
This algae is too
thin to worry
about. Put RKC.
This algae is
starting to get
‘fleshy’. Put
NIA/RKC
here.
Photo by Jos Hill, 2002
RECENTLY KILLED CORAL
Indicator of recent disturbance
Summary
This includes coral that has died in the last year (recently).
This can be a difficult category to define – therefore note the
following:
• Corallites are not eroded much;
• Some white skeleton showing;
• Only partially grown over with encrusting algae – where
corallites and/or white skeleton is still visible;
• If it is slightly grown over with algae – note it as NIA/RKC
or OT/RKC depending on whether it is nutrient indicator
algae or other algae.
RUBBLE
Unconsolidated material
Reef Check code: RB
RUBBLE
Unconsolidated material
Rubble is classed as rocks between 0.5
and 15 cm diameter. If it is larger than
15 cm it is rock, smaller than 0.5 cm
and it is sand.
As rubble is unattached
to the reef, wave action
will make it tumble
around, which may
knock off any new corals
that have settled.
Photo by Dean Miller, 2002
When rubble has been
‘cemented’ together by
coralline algae, we call it
rock as it is no longer
unstable.
SILT
Indicator of soil erosion or dredging
Reef Check code: SI
SILT
Indicator of soil erosion or dredging
Tap this and it will rise from the
reef in a little cloud.
Photo by Jos Hill, 2002
Silt is sediment that remains in
suspension if disturbed. Note
that these are practical definitions
not geo-technical. Often, silt is
present on top of other indicators
such as rock. In these instances,
silt is recorded if the silt layer is
thicker than 1 mm or covers the
underlying substratum such that
you cannot observe the color. If
the color of the underlying
substrate can be discerned, then
the contact will be the underlying
substrate NOT silt.
SILT
Indicator of soil erosion or dredging
One way to double check that it is
silt is to tap it and it will come up
from the substrata like a cloud.
Photo by Jos Hill, 2002
SILT
Indicator of soil erosion or dredging
Remember if you can’t see the
substrate colour underneath,
it is silt.
Nutrient indicator
algae.
Photo by Jos Hill, 2002
SAND
Non-reef area
Reef Check code: SD
SAND
Non-reef area
Sand is a natural component of coral reefs. This category
helps us to see when the transect hits a sandy patch inbetween the reef area.
If you are unsure as to whether it is sand or silt, pick a bit
up and drop it. If if falls straight to the ground, it is sand.
If it forms a cloud in the water column, it is silt.
Phew! Well done!
This presentation was produced by Jos
Hill, 2003©. Any questions, please
contact Jos at
jocelyn.hill@jcu.edu.au
Ph: +61 (0) 7 4721 5001
Mob: +61 (0) 415 446 646
www.ReefCheck.org