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Degradation examples - Part 1
by Dr J Floor Anthoni (2004)
www.seafriends.org.nz/decay/decay1.htm

The first 50 visual examples of degradation. Visit many habitats in many places around New Zealand while seeing many aspects of it.

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-- Seafriends home -- issues index -- Rev 20041210,

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f033318: a dense mat of dinoflagellate and diatom scum has settled onto the eelgrass habitat, smothering all. It is a symptom of nutrient enrichment. Scum like this can kill all grazing snails. Matapouri Estuary.

f030305: highly poisonous brown fluff appears to be a matting dinoflagellate (Ostreopsis sp.). Wherever it settles, it kills all grazers. One can find rock pools with not grazers left. It kills sea urchins. Goat Island marine reserve. Several kinds of brown fluff have been found in the colours yellow, green, brown, grey.

f039309: an environment in severe decay can appear beautiful but these drooping sponges and seasquirt mats do not belong here and have smothered more diverse life. A sign of severe eutrophication. Parengarenga Harbour.

f039326: a green algal mat on an exposed sandy bottom due to extreme eutrophication of the coastal sea. This is an open bay facing the open sea and it is only 6m deep. For algae to grow here is exceptional and they must be growing fast too. North Cape.

f039521: a mix of various suffocating growths has killed patches of the seagrass habitat in sheltered places of the harbour. Parengarenga Harbour.

f039523: plant or animal? A fast growing organism forming tough vermicelli-like threads  has become a nuisance in Parengarenga Harbour. Tiny polyps suggests a form of bryozoan.

f011302: inside harbours one can expect unusual species, even foreign species, as a result of serious degradation. Here one sees two species of a drooping seasquirt mat and black velvet sponges, all unknown. Houhora Harbour.

f011302: drooping sponges are a sure sign of serious decay. Houhora Harbour.

f039526: heavy sedimentation from mud and diatoms has smothered these orange hydroid firs whose skeletons remain as all their polyps have already disappeared. Whangarei Harbour.

f039907: parchment tubeworms have colonised large areas of the sea bottom, destroying sand and scallop habitat. But they are now providing a holdfast to legion other species as shown here. Whangarei Harbour. Parchment tubeworms are a recent phenomenon, but here to stay.

f040001: smothering algal mats looking like plastic sheets. Whangaroa Harbour.

f040013: stalked kelp covered in matting bryozoans. Normally kept clean by grazers and copious amounts of slime, these kelp plants are now dying. Whangaroa Harbour.

f040113: very sick stalked kelp completely smothered in dust and bryozoan mats. No sign of grazing here. Open terrritory where no juvenile kelp settles. This habitat is on the way out. Whangaroa Harbour.

f040020: fast growing leafy bryozoans have taken over where more varied life once stood. These bryozoans are a sure sign of very advanced degradation. Whangaroa Harbour.

f040125: under the photic zone at only 6m depth, the sponges are smothered in silt but the most hardy ones survive like the boring sponge (Clione cellata) and yellow nipple sponges (Polymastia croceus). Whangaroa Harbour.

f040123: where once a rich and colourful community stood in the plankton-rich current, their place has now been taken by dark drooping sponges and short-lived bryozoa. Whangaroa Harbour.

f041004: coralline encrusting and turfing algae smothered in mud and diatoms, waiting for a storm to cleanse it. All grazers have disappeared. There are no sea urchins left. Near Whangaroa Harbour.

f041012: smothered by mud and diatoms, this flexible weed is giving up and will most likely not be replaced. The end of a habitat. Near Whangaroa Harbour. Old organisms like this seaweed show that once conditions were much better.

f041923: smothered stalked kelp which is not eaten by grazing fish and invertebrates. The water is murky with large particles (snow or snot). The kelp's fronds feel papery rather than slimy and springy. Martins Bay.

f041924: the various species of grey sponges (Ancorina alata, etc.) are very hardy. Here they suffer a heavy dose of sedimentation. No other organisms compete for space. Martins Bay.

f033805: at the photic boundary (5-6m), various sponges are found but competition is poor. At this depth the waves still cleanse the environment. Martins Bay.

f033806: only a few metres from the place on left, and only two metres deeper, the sponges are dying and rocks remain barren with no grazers as this is below the photic zone. Martins Bay.

f041930: in a hot spot exposed to currents and some cleansing wave action, sensitive species are gradually replaced by hardy ones. Moturekareka, near Martins Bay.

f033506: decaying kelp with thin leaves infested with bryozoan mats. Where these obscure the light, holes appear in the leaves. Tawharanui marine reserve.

f033401: a sea cucumber mops up the thick dust covering the rocks and sponges. Only encrusting sponges remain. Competition for space is low. Tawharanui marine reserve.

f033628: the kelp canopy has thinned due to lack of light. Heavy sedimentation of the bottom. Open canopy. Two new year classes hesitantly appear at 14m depth. Goat Island marine reserve 2003.

f041907: sea urchins have eaten through an encrusting sponge, which is not a sign of degradation. The photo shows the white imprint on the pink paint below, which is recovering from the outside inward, even after years of slumber under a covering organism. Such imprints tell a story of past events. Little Barrier I.

f041906: the white imprint in both an encrusting sponge and the pink paint show how recently a large sponge has disappeared. In the distance more evidence of recent mortalities of old organisms. Little Barrier I.

f035923: at 15m depth, the canopy opens up allowing a new generation of kelp to hesitantly fill the gaps. But the canopy remains open. On the rocks also no competition for space. One young yellow nipple sponge shows signs of health. Very few grazing snails. Little Barrier I.

f036710: At the same place as on left, but shallower, a purple organ sponge is dying from a slime attack. Some parts are still alive but it won't survive. It is surrounded by light-hardy coralline algae as no other algae are game to settle here.

f042126: small crayfish in the highly degraded environment of Gisborne's marine reserve. No competition for space. Thick sediment deposits. No grazers. No leftover species under overhangs. Te Tapuwae o Rongokaiko marine reserve, Gisborne.

f042137: One finds only large sea urchins, no young ones. End of the sea urchins. The habitat is dusty. Little plant growth. No competition for space. Poorly grazed. This is a severely degraded habitat. Te Tapuwae marine reserve, Gisborne 2004.

f026712: stunted paua growing more slowly than the pink paint covering them. The edges on their shells curving inward. (not clearly visible on this wide angle photo). Poorly grazed rocks. Pohatu marine reserve, Christchurch.

f016124: The margin of bare shell gives an idea of growth rate relative to that of the encrusting pink paint. Here the margin is practically zero, which can be expected of old paua shells. Island Bay, Wellington.

f033821: a kelp forest dying from lack of light but the problem goes further back as this forest consists of a single year class, which points to a mass mortality before this one. Kawau Island.

f016803: in Nov/Dec 1992 the kelp forest died due to lack of light from muddy seas. In Jan 1993 cyclone Oli tore the paper thin canopies off and the kelp forest disappeared in a single night, leaving no traces or washed-up kelp. Goat Island marine reserve.

f036022: heavy deposition has not killed the left-over cup corals but others that prevented these from growing more numerous, have disappeared without a trace. No other organisms fancy this sheltered place any longer. Mimiwhangata marine reserve 2003.

f036025: a sheltered vertical wall in the current is still covered in sensitive stick bryozoa, but most have turned brown-green, a sign of death. Young soft corals settled on empty territory and hardy grey massive sponges and red carpet sponges are taking over. Mimiwhangata marine reserve.

f034401: a heavy infestation of brown fluff (here green) shows white patches where sea urchins have died. The remaining ones attempt to avoid eating the poisonous slime. Mayor Island 2003.

f034402: the vast urchin barrens no longer have urchins as they have all been killed by the poisonous brown fluff. All other grazing snails have also been killed. Sea lettuce is establishing itself. Mayor Island.

f034408: surviving sea urchins have aggregated in the gullies where they have cleaned a street from the poisonous brown fluff seen above them. Urchins are able to fast in bad times and they learn to avoid the poisonous algae. Mayor Island.

f034406: a closeup of the poisonous brown slime  (Ostreopsis sp.) shows that it covers everything while being able to resist cleansing wave action.

f034409: a sea urchin has grazed just too much of the poisonous brown slime (Ostreopsis sp.) and is folding its spines as a sign of ill health. When they do this, they will die soon. Notice that the grazed area is not at all large, about the size of two hands. Mayor Island 2003.

f034423: many stalked kelp plants have red seaweeds growing on their leaves, a sign of ill health, as normally these plants can keep themselves clean. Note how the red seaweeds have been grazed short, most likely by parore, a proof that grazing fish are still around although they avoid grazing on brown fluff. Mayor I.

f034818: sick stalked kelp looks white from an infestation by bryozoan mats. Such infestations are most likely where plants are weakened by lack of light, such as near the photic boundary which is seen in the distance. Yet the plant in the foregeground shows light green leaves with yellow margins, a sign of health. Poor Knights.

f035407: decay can have a beautiful face. Yellow zoanthid anemones are taking over a sick grey sponge, as can be seen from its colour and patches of fungal attack. Zoanthids can reproduce asexually by cloning a mat of identical copies. Kapiti Island 2003.

f036804: The kelp forest is thinning out well above its lower boundary (9m). No competition, no new recruits, no grazers, no sessile filterfeeders as the habitat is slowly occupied by turfing coralline algae. This is seen in many places, all the way to Cape Brett. This is Arid Island 2003.

f036819: a vertical wall has lost all its sessile filterfeeders and is now covered in algae. On a ledge, a number of surviving sponges are found, recovering from a recent disaster. The ones seen here all hardy ones, belonging to the inner Hauraki Gulf rather than to Arid Island. Notice stunted growth of fingersponge.

f035719: crayfish are rather cryptic and cannot always be seen during the day. However, when they moult, they leave their moults in the open and these are easily seen. The absence of moults alerted us to the disappearance of crayfish in 1998 in the Goat Island marine reserve.

f035728: this is a very small crayfish (5cm), this year's arrival. They are often found in the shallows and are a sign of hope. Because they are not taken by fishermen, they are important to observe. They grow rapidly, moving from shelter to shelter. During a night dive one can take a mental note of the number of juveniles compared to the number of adults. Goat Island marine reserve 2003.

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