Degradation examples - Part 2 by Dr J Floor Anthoni (2004)
The second 50 visual examples of degradation,
beginning with various aspects of plankton blooms
For comments, corrections or suggestins, please e-mail
the author Dr Floor Anthoni.
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-- Seafriends home -- issues
index -- Rev 20041210,
f212406: the sea in the Goat Island marine reserve now often
looks like this, with mud soiling the water and threatening sea life. But
once the mud has been cleared away, its nutrients fertilise the sea, resulting
in dense plankton blooms which also threaten for a long time afterwards.
Goat Island 1999.
f014321: all the coastal trees have been killed by the possum,
introduced from Australia. Once the roots let go, the soil slips into the
sea and it won't take long before the whole coast reverts to barren rock.
In 20 years from now, people won't even remember what it once looked like.
This land is managed by DoC. Cape Brett 1997.
f011204: a mixed school of trevally and kahawai is frothing
the water, with birds working from above. This used to be very common with
schools up to one hectare in size, counting tens of thousands of individuals.
Now it has become a rare sight, as schools are also much smaller. Cape
f990208: a small school of young trevally and blue maomao
(4 years old) feeding on the surface, pushing their backs out of the water
while swimming furiously. Such schools disappeared in 1992 and again in
2001. Poor Knights 1999.
f942018: left image of a panorama showing a red tide of the
plankton dinoflagellate Noctiluca scintilans or sea spark. Sea spark
is common around our coasts, all year long, as it is easy to see during
night dives. Leigh.
f942019: the righthand image of a panorama. Usually in the
warm months of February to April, one would see some of these red tides.
But they have become more common and more intensive lately, also appearing
throughout the year.
f942017: red tides are the most spectacular of plankton blooms
because they also give light at night. But they are not poisonous and seldom
kill fish. Leigh 1994.
f002306: as this underwater photo shows, the sea spark dinoflagellates
which can swim, concentrate at the surface in a wind-blown thin layer.
These tiny plants consist of jelly. Goat Island.
f003724: during periods of red tides, jellyfish like this
blue jelly Cyanea lamarcki can become really big. The photo shows
one measuring one metre across. As the dark eggmass underneath fills a
whole bucket, they can breed a plague. Goat Island 1995.
f033522: jellyfish scyphistoma polyps have attached to a
bare rock under an overhang. Each polyp can produce up to one hundred new
jellyfish, so this patch alone can spawn a whole jellyfish plague. When
bare rock becomes available due to sponges dying earlier on, jellyfish
can indeed proliferate profusely. It is a powerful indicator of degradation.
Leigh 2003 .
f011134: phytoplankton can grow very fast, often in patches
with sharp boundaries. Here is a brown bloom rapidly growing into the still
clear green water. Mimiwhangata Hr.
f011118: a deep red plankton bloom that could well be poisonous.
Such patches are good indicators of impending decay. Bay of Islands Dec
f970421: the plankton blooms so thick that it looks like
an oil spill, threatening the toheroa clams in the beach. This is a sure
sign of eutrophication. Westcoast off Dargaville 1997.
f202317: for those who do not dive, health warnings like
these are sure signs of degradation. Keep an eye out for them. Kaipara
f002004: a mass mortality of pilchard (Sardinops neopilchardus)
happened in July 1995 over a large area, outside the Hauraki Gulf. Wind-blown
to the shore, fish beached like this. Leigh.
f001727: what remained of the pilchard washup the day before.
These fish disappeared in two days. Remember that most dead fish sink while
no more than 5-10% float. So what washes up on beaches is but a small part
of the whole disaster. Leigh Harbour, Jul 1995.
f991027: these are scrape marks of parore (see right), cleaning
the rocks from detritus rich in diatoms. Remarkable is that underneath
the dust one does not find pink paint but only bare rock, an indication
of severe degradation. Long Bay 1999.
f017816: parore (Girella tricuspidata) is an important
reef fish, because it cleans plants and rocks from invasive algae. Many
have been lost from Goat Island due to a disease and degradation. Many
of these fish were seen with white welts on their bodies.
f990833: in a small area of the beach, these dead blue penguins
minor) were found. Whangapoua Beach, Coromandel 1999.
peng09: a mass mortality occurred at Goat Island. These birds
washed up after a beach cleanup the day before. since this event, penguin
numbers have been declining sharply, as also the breeding colonies of gulls
and terns on Goat Island disappeared. Goat Island.
f211016: a dense bed of empty parchment tubes washed up to
become a nuisance to bathers. Long Bay 2001.
f211017: closeup of the mess of empty parchment tubes. Long
Bay beach and marine reserve.
f021017: underwater, parchment worms can be very effective
at converting a sandy habitat to a thick cake of cemented tubeworms. What
they need is a thin layer of mud to start them off on the sand. Leigh 1999.
f025805: a parchment worm (Chaetopterus variopedatus)
carefully peeled out of its tube and photographed under water. It is a
complicated bristleworm. Leigh 2000.
f035907: smothered flexible weed (Carpophyllum flexuosum)
and strange dark purple finger sponges and massive sponges. Port Fitzroy,
Gt Barrier I 2003.
In the most degraded of all habitats, one often sees
strange sponges, as if these do not belong in New Zealand.
In colder waters, the undaria seaweed is spreading. Such
propagation success may be related to degradation as space becomes available
to settle on. Undaria pinatifolia is, like garden weeds, an annual
plant, dying at the end of one year and sprouting again from its
offspring. Wellington 2003. Photo Rob Marshall.
f005121: a bed of large atrina fan mussels trap mud
in between them while providing an artificial substrate for filterfeeders
like these short-lived soft corals (Alcyonium sp.). There is only
one year class and they are all dead, a sure sign that this is the end
of it. Mouth of the Mahurangi Harbour 1995.
f026711: Five large paua on this picture, yet the rocks remain
poorly grazed. The paua are all of same age and none is growing well as
shown by their growth margins. Nowhere can juveniles or other year classes
be found. This is certain degradation and spells the end of paua. Flea
Bay marine reserve near Christchurch 2000.
f017315: a trove of golden golfball sponges (Tethyia
aurantium) is being cleaned by a single sea cucumber (Stichopus
mollis) (1998) However, in 2002 these rocks proved to be barren.
The end of a habitat. Near Martins Bay, Hauraki Gulf.
f017316: two sea cucmbers are cleaning a boring sponge (Clione
celata) while other sponges await their turn: the red meatball sponge
aaptos) and yellow nipple sponge (Polymastia croceus). Years
ago one could rely on sea cucumbers not being harvested, but they now fill
an Asian need. Near Martins Bay, Hauraki Gulf.
f017305: a sea cucumber on a very dirty patch. Martins Bay.
Depositon and algal growth of this magnitude is almost always fatal.
f042007: once its stipe has gone, a kelp plant dies back
completely while rotting away. The last bits to go are its holdfast of
spreading 'roots', which take 6 months before disappearing. After that,
there still remain the white imprints on the pink paint below.
f033509: this stalked kelp (Ecklonia radiata) has
lost its self defence, allowing grey mats of bryozoa and other infestations
to cover it all over. From this kind of infestation it will not recover.
In the background the whole kelp forest looks similar. Leigh Jan 2003.
f042706: the kelp forest's lower boundary is dying while
juveniles are absent or insufficient. It means that the lower boundary
is shifting upward as the water has become dirtier, a sure sign of degradation.
Poor Knights 2004.
f017115: The kelp is dying back as no recruits are present.
Also only the most hardy of sponges are found underneath, as the others
have died. One of the most beautiful reefs, Floor's Reef in the Goat Island
marine reserve has become a shadow of its former glory. Goat Island marine
f033816: the old kelp is dying from lack of light and the
young kelp is too sparse to replace it. At the same time coralline algae
take over on the rocks. There are no sponges or filterfeeders or grazers
below. This will become barren rock. Flat Island Kawau I 2003.
f003713: sand dahlia anemones can grow larger than a hand
in various beautiful colours. They survive the wave-washed sand which also
keeps them clean. But they are disappearing, as also they are becoming
smaller. Near Goat Island 1995.
f003710: beautiful sand dahlias (Isocradactis magna)
tucked safely in between the cracks of solid rock. Hardy to sand blasting,
these anemones are sensitive to degradation. Near Goat Island.
f036114: Brachiopod lamp shells on a rocky wall
are a sign of health, particularly when several year classes can be distinguished
as on this photo. Whangamumu Hr near Cape Brett.
f025912: dead Brachiopod lamp shells on a vertical
wall. In the Goat Island marine reserve nearly every vertical wall that
is turned away from the light, used to be covered in these but they have
all disappeared. Notice the very few small red lampshells. Near Leigh 2000.
f029923: underneath the kelp forest one should find a dense
mat of life, particularly near currents, as shown here. On closer inspection,
all animals shown here are short-lived, a sign of alarm. However, elsewhere
the situation is far worse as competition for space has ended, even though
more planktonic food is available. Poor Knights marine reserve.
f030216: on this vertical wall one finds sessile filterfeeders.
They are all short-lived, and competition for space is rather weak, showing
much empty territory. Yet there is ample food for all and also shelter.
Brachiopod lamp shells used to live here. Goat Island marine reserve 2002.
f030218 orange compound mushroom seasquirts conquering space
underneath an ailing kelp canopy. There is much sediment and little competition.
Goat Island marine reserve.
f033409: various species of sponge occupy a sandy flat under
the kelp forest, where also goatfish sleep. It would be a sign of health
but no sponge is older than 3 years, perhaps due to a recent disaster.
Tawharanui marine reserve, 2003
f036608: this rock is covered in sponges whereas the area
around is not, because it juts out in the current and above the sand. Yet
competition for space is not fierce. Some sponges are older than 10 years,
a good sign. Left-over species. Near Leigh.
f041036: these carpet fanworms have become rare, as they
disappeared from 5 of 6 places I knew. But here they thrive in a degrading
harbour because dredging for scallops has diminished as few scallops are
left. Whangaroa Hr 2004.
f022901: a diver shows how an orange nipple sponge (Polymastia
granulosa) withdraws its nipples when touched. It also does this when
'unhappy', a sign of stress. These large sponges were once common everywhere
down from 6m depth. They even occurred in the Channel and around Shag Rock,
together with the yellow nipple sponge Polymastia croceus which
prefers deeper water. Goat Island marine reserve 2002.
f036017: this orange nipple sponge was able to grow large
because it had no competition for space. But it has withdrawn its nipples
as a sign of stress. This is the urchin barren zone, but urchins have left.
One dead urchin below. Mimiwhangata marine park 2003.
f040629: on a pinnacle, exposed to the sea, one finds this
dense mat of life as jewel anemones in all colours conquer space from a
sick boring sponge. Good and bad signs. Cavalli Islands Truelove Reef.
f036018: dense life and fierce competition with few old species
(stick bryozoa, still looking sick) but these are the leftover species,
found only in the most favourable places. It shows what once lived everywhere,
a confirmation of degradation. Mimiwhangata marine park 2003.