Kermadec Islands - images of seascapes

by Dr J Floor Anthoni (2002)
The seascapes of the Kermadecs look barren with their low profile, slow growing corals and extensive barren rocks, grazed by sea urchins. Yet, here hides a variety of life that has adapted to living in this harsh environment. 

The first impression when seeing the underwater landscape, is that of barrenness. Compared to the densely clad rocky shore of the New Zealand main islands, the Kermadec shores appear barren, because the organisms clinging to their rocks are smaller. Instead of large seaweeds (macroalgae), one finds corals interspersed with matting green and red algae. The water is too cold for corals to form extensive reefs, but it is clear, allowing for over 30m visibility. The water moves relentlessly, powered by large swells curving around the islands while penetrating every sheltered nook. Sea currents are unexpectedly strong, and planktonic food is scarce. Yet one can encounter dense schools of fish as well as large predators. The rocks are volcanic, and often too soft to give a safe holdfast to large organisms like corals and sponges, but glorious exceptions can be found.

See also the gallery of corals, for identifying the various species.

Note! for best printed results, set your page up with a left margin of 1.5cm (0.6") and right margin of 1.0cm (0.4")
-- home -- issues index -- marine reserves index -- kermadecs index -- site map -- Rev:20020624,20020719,

f031027: Grey knife fish swimming close to the surface
f031027: A snorkeldiver views a school of grey knife fish close to the surface. Although knifefish swim around freely, they are not blue sea pelagic, but stay around the bubble-impregnated wild waters close to shore. These provide protection and also planktonic food, which is richer close to the sruface.
f031312: Dense schools of fish near promontories
f031312: Around promontories, the currents run surprisingly fast, reason why blue maomao and demoiselles are found here, often in dense schools. These two schools came to meet us, just out of interest for the divers, who provide rare entertainment in these waters.

f031028: Coral seascape
f031028: Between 2 and 6m deep, the rocks are covered in a mosaic of corals and short algae. The water movement here is too strong for sea urchins, and also the crown of thorns star can't survive here. Thus the slow growing corals are allowed to grow old, almost entirely covering all space. Notice that the gaps in between, are ocasionally grazed by urchins, making way for rivers of red hairy algae.
f031029: Coral seascape in turbulent water
f031029: Another picture of this shallow habitat zone. Notice that there are only few species of hard coral. The dark red spots are homing sites of sea urchins, which have died recently. Notice also the yellow-green colouring of the coral polyps, which, although extended, do not extend any tentacles. They just soak up the maximum amount of sunlight they can get.

f031030: Corals, green seaweeds and red algae
f031030: Just around the 6m boundary, hardy green seaweeds are able to grow next to the red algae. Notice how these do not show signs of grazing. The Kermadecs have a few resident green turtles that are able to feed on this type of seaweed.
f031230: Tightly woven mats of green and red algae
f031230: The most successful red and green algae grow by sending out runners (stolons), which sprout new plants at intervals, while also attaching to the rock at various points. This photo shows a complicated turf of creeping green and red seaweeds, which can grow very old. Again, no sign of grazing.

f031328: A large fruit bowl coral
f031328: A large fruit bowl coral grows below the boundary where most hard corals end, at 6-8m. It is surrounded by short red algae and by soft corals. At the top of the image, a barren zone of dead coral skeletons, grazed by urchins.
f031404: Brown soft corals and grey hard corals
f031404: A deep and sheltered pocket at 6m depth shows a dark grey coral (on left), capable of living in conditions of reduced light, better suited to soft corals shown in the foreground. The fish in the background are various species of drummer.

f031325: Sunlit side of a rock face with COT star
f031325: On the sunlit side of a pinnacle rising to 5m depth, one sees the sharp boundary between the live hard corals above, and the barren urchin zone below, with a pied urchin mid-left. In the foreground the notorious crown of thorns (COT) star, which is partly responsible for the death of the hard corals in this zone.
f031334: Shaded side of a rock face
f031334: The shaded side of the pinnacle shows a radically different environment of dark coloured corals (top), soft corals (below) and encrusting sponges amongst the varied red algae. A toadstool grouper rests near the centre, under a protruding hard coral.

f031121: close-up of shaded wall
f031121: This close-up of the shaded side of a shallow wall, shows encrusting orange spongess, pink coralline algae and various other short algae. All the white specks and blobs are composite seasquirts. Invisible to the human eye, a variety of well camouflaged crabs and snails can be found.
f032005: a fast growing purple opportunistic sponge.
f032005: Fast growing opportunistic organisms like this mauve encrusting sponge (or colonial seasquirt?), are not common on the Kermadecs. Notice the large barnacles and solitary corals top left, and small barnacles bottom centre. One must have extraordinary defences to thwart an invading and smothering blanket like this.

f031414: A bared rock face slowly recovering
f031414: A large area of hard coral has, over time, been killed by the crown of thorns star, then grazed flat by the powerful jaws of sea urchins. But in the process, the barren and levelled rock invites young corals (bottom centre) to reoccupy the lost ground. It appears that the teamwork of COT stars and urchins maintains a high level of biodiversity.
f031408: Giant Kermadec limpets in the wavewash
f031408: Above the zone of hard corals, in the heavy wave wash, one finds the unique Kermadec giant limpet, maintaining its own habitat zone, which is bounded sharply, as can be seen here. Above this limpet zone, one finds a narrow band of large barnacles (Balanus sp.). The heavy waves did not allow us to take photographs.

f031411: Barren rock, corals, weeds and fish
f031411: At Meyer Island, the shallows have a pleasant degree of playfulness: grooved and rounded rocks alternated by shallow canyons. In such an environment, the zonation patterns become blurred, and one finds a great variety of organisms living together in apparent confusion. It is of course, a playground for fishes. In the picture three grey drummers, one bluefish (No 2 from left) and one green wrasse (right).
f031419: Barren hard basaltic rock
f031419: If organisms wish to grow old, they must settle on hard rock like this ancient basalt flow, which is in short supply at the Kermadecs.  The rock here is covered in pink paint, grazed by brown urchins and top shells. Here and there a coral colony has been able to sprout. The top of the formation is covered in brown fleshy coral.

f031824: Purple urchin and top shell
f031824: Two important grazers of the Kermadecs, the purple urchin and top shell. Notice how the purple urchin folds its spines in a special way to reduce water drag: in ten clusters all around, and pointing downward to the rock face.
f031422: Plate corals on hard basaltic rock
f031422: This area of hard rock has been colonised by plate corals, possibly all at the same time (same age) . Notice how the rock in the foreground has recently been bared, possibly by the removal of such a  plate coral.

f031425: A garden of lush soft corals in a sheltered, shallow place
f031425: In a sheltered gully, we found this garden of soft corals. Notice the large area of white water above, saturated with tiny bubbles that reflect the sunlight. As a consequence, it is much darker here under this foam umbrella, than outside it. Hence the absence of hard corals, which need much sunlight.
f031406: Algae, corals and grazing brown urchins
f031406: A garden of green seaweeds, brown urchins and encrusting yellow coral. There is little sign of grazing by fishes.

f031005: Crown of thorns star and dead corals
f031005: A birds-eye view of the rock shows a crown of thorns star and a trail of dead white corals. The whitest one above, must have provided its most recent meal, because green algae have not settled on it yet. Although the COT star does not eat voraciously, it still causes much damage becaue the corals repair or replace themselves only very slowly.
f031237: Tubefeet and stomach of COT star
f031237: The under side of a COT star shows its bright yellow tube feet, and also its peculiar stomach, which it is withdrawing fast. Rather than resembling a plastic bag as in other starfish, it has lobes designed to engulf a coral polyp each. In this manner it can dine out on many coral polyps in a single sitting. The COT star is a very specialised feeder, and fortunately prefers the fastest growing corals, thus enhancing biodiversity on the reef.

f031200: Fruit bowl coral damaged by anchor chain
f031200: A fruit bowl coral has been damaged by the anchor chain of a visiting ship. Fortunately, it had died long before, and is now covered in green algae, a rich picking ground for various species of hermit crab.
f031510: Caves and overhangs are in short supply
f031510: The rocky shore of the Kermadecs extends along the abyssal slope down into the 10km deep Kermadec Trench. On elevated rocks, a most colourful and delicate fauna of filterfeeders is found, like these gorgonian corals. Under overhangs and at the ceilings of caves (here 27m deep), divers can obtain a sneak preview of this most amazing and colourful deep-sea habitat. In the photo three striped boarfish and a masked moki (Cheilodactylus sp.) (bottom-right).