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A special place New Zealand occupies a special place in the World's natural affairs, as can be seen from the map on right. This is a view of the globe centred on the South Pole. Three main continents can be seen extending hesitantly southward: South America, Africa and Australia. But they are separated by insurmountable distances, reason why their flora and fauna differ completely. Also their marine environments have nothing in common, even though marine creatures could swim from one continent to the other. The reason they cannot do so, is that they won't survive the trip, as the blue seas are water deserts, with too little food. Only the largest of marine creatures, having enough spare fat, and the advantage of scale, can make it (whales).

This diagram sketches the basic currents around New Zealand (See oceanography/New Zealand). As mentioned before, the South Pacific ocean circulation (gyre) pushes warm water down Australia's eastern shore, where some splits off along the tropical front (TF), as it meets cooler water travelling north. Importantly, it shows that the general direction of all currents is eastward. On the map, three subtropical island groups can be seen, from W to E: Lord Howe Island, Norfolk Island and the Kermadec Islands. The direction of the current suggests that eggs and larvae of marine species travel mainly eastward, and that the reverse is unlikely. It can explain why Australia has practically no NZ species, but NZ has some Australian species. Note also how the sub-antarctic islands are isolated from NZ by the Sub Tropical Front (STF).

The net effect is that like the deserts on land (yellow), similar deserts are found in the oceans (deep blue) at roughly the same latitudes, as shown by this satellite image of actual chlorophyll concentrations, representing the amount of plant life, on which all other life depends. Tucked away in the righthand margin is NZ, blessed by rather high fertility in its seas. But the Kermadecs lie just outside, as the detail map below shows.

This map is an enlargement of the one above, with left and right margins joined. It shows how New Zealand's seas are relatively productive, with a peak off Kaikoura, east off the South Island. The Kermadecs jut out into the blue desert, but some peculiar mixing is noticeable. Experimenting around the ocean ridges of the Hawaiian chain of islands, scientists have discovered [1] that the tide wave, which raises and lowers the water along continents twice daily in the rhythm of the moon, causes deep currents when hitting the Hawaiian ridge head-on. These currents disturb the deep thermocline, bringing nutrients to the surface. A similar situation is likely present at the Kermadecs, and indeed, satellite images [2] have shown a noticeable distortion in the tide wave,which causes local ocean currents and swirls. When diving the Kermadecs, these strong currents are very noticeable. The conclusion is that, although the Kermadecs are located in a blue water desert, a slow supply of nutrients makes it to the surface, supporting not too abundant life.

[1] Hawaii Ocean Mixing Experiment (HOME). Rob Pinkel, Scripps Institution of Oceanography.
[2] Egbert G and Ray (2001). Global distribution of barotropic tidal loss. In: Aspects of deep ocean mixing, Chris Garrett and Louis St Laurent. http://maelstrom.seos.uvic.ca/people/lous/japan/paper.html
 
 

Along sizeable land masses, such as New Zealand, most of the nutrients in the sea originate from the land. Rocks weather to form soil. In the process, nutrients are dissolved and washed into the sea. Farming exacerbates the situation and soil loss even more so. These nutrients feed the phytoplankton of the sea and the seaweeds on the rocks, on which all animal life depends. The land mass also provides the mechanisms to keep nutrients from straying into the abyss of the deep sea: A continental shelf, the stage for abundant life. The sea soil here returns nutrients from dead organisms and wastes to the water. Shelter from winds, which makes the sea winds stronger than the land winds, resulting in sea surface currents returning nutrients to the shore. Ocean currents, following the continental slope, rotate in such a way that they bring deep nutrients back onto the continental shelf. Current eddies branching from the ocean currents, bring nutrients back.

For a small land mass like Raoul Island, these factors are almost negligible, reason why nutrients originating from the island, are quickly lost. Small islands like this surrounded by a blue ocean desert, are thus destined to look more like a desert than a fertile ground under water, which makes life there difficult, but sea birds may play an important role.

The diagram shows how sea birds can play an important role in recycling island nutrients. It is an advantage enjoyed by outlying islands, because rats, cats and stoats have driven sea birds off the mainland, allowing them to congregate on safe, offshore islands. Due to ocean mixing near islands, which is still poorly understood, there is a slow upward trickle of nutrients from the deep. Add to this those from island erosion and volcanism and bird droppings. Rains wash the nutrients down, causing phytoplankton to bloom in pockets around the island and further down-stream (left). Living from this phytoplankton, shrimps multiply their numbers, and these are eaten by fish. Both fish and shrimps are caught by sea birds, who spend some time on the island, emptying their guts overnight. In the cycle, the sea soil, and planktonic bacteria in the water help to recycle nutrients from dead animals and wastes. But overall, some (or most?) nutrients are lost to deeper water.
How large the influence of birds is on this nutrient cycle, is unknown. It would be interesting to monitor the fish life around Raoul, as its bird numbers increase. It could well be possible that this has a large and beneficial effect on the sea life there, but there is yet another factor.

We noticed symptoms of (serious) environmental stress. How is this possible in a pristine environment so far removed from human influence? Would global pollution be to blame? The volcano perhaps?
Stress on the natural environment is hard to quantify, and very few people would be able to recognise it as such (See also the chapter on Marine Conservation and principles of degradation). But a number of stress indicators can be observed clearly, and taken together, form a picture, even if this is only a mental picture. The stress symptoms we observed were the following:

• Few juvenile organisms and missing year classes. The juveniles of almost every marine organism are usually the most sensitive to pollution and other stresses. Spawning is a delicate event that can go wrong in any of its many stages. When successful all along this chain, it results in recruitment (juveniles settling from their planktonic stage). Year classes are sometimes hard to assess, but one can almost always distinguish five age groups: this year's babies, last year's juveniles, young adults, mature adults and old adults. What we observed was that there was ample evidence of (serious) recruitment failure in all organisms observed.
• Large sessile organisms removed but not replaced: Open space on the rocks is very precious real estate. In a healthy environment, it is almost instantaneously occupied, often immediately with opportunistic invasive species like barnacles, seasquirts, bryozoa. Because such opportunistic species don't live long, but reproduce fast, the rock space eventually becomes available again, during which time more permanent species have found it. We found an unusually large part of the rocks unoccupied. Ironically, the Kermadecs have hardly any invasive species. Even the barnacles there live with restraint!
• No schools of small pelagic fish: We found no schools of pelagic silver fish like pilchard, koheru, jack mackerel, trevally, and their fast and voracious predators. But here and there a kingfish was seen, although looking thin and emaciated. Also a small pod of dolphins keeps a presence here and a small school of northern kahawai.
• Poorly grazed algae: Although there are grazers like drummers, turtles, sea urchins, top shells and others, many rocks remained poorly grazed. Such an observation may point to poor replacement, or a recent mass die-off, but it may also be a normal situation after good growth in summer (we were there in autumn). We suspected slow replacement of grazers who died recently.

The small size of the islands poses another problem, that of insufficient habitat space. Although the marine reserve proper measures 7480km2, this is overwhelmingly empty seawater. Raoul with its 31km2 land area, has probably no more than 20km of rocky shore, including all the islets around it. Most of this consists of boulders bordered by a shallow sandy bottom, razed by ferocious waves. For the giant limpet, which grows with densities of 2-6/m2, perhaps only 10km of suitable habitat is available. Its zone is only two metre or so wide, so a quick estimate of their numbers is ~30,000. This is a small number for a viable population, particularly for a grazer, on which other species should feed. It must not be surprising then, that they do not appear to have natural enemies, and that they grow very old. To increase their survival chance, the large females carry small males on their backs!

Take the giant groupers. They are top predators, living in the slow lane, but also growing very old. Nobody has surveyed their numbers, but my own estimate is 20/km, or a total of 200, plus an equal number of small ones. The large males are certainly sporadic. They are all born female, and change into a male at 1m length (40 years old). This makes them rather vulnerable to exploitation.

It follows then that the gene pool (variability within a species) of the species at the Kermadecs is rather homogenous, because:

• There are only few of each species.
• They can't migrate and mix with other gene pools.

Scientists have sampled the coral species at the Kermadecs, and found that at Raoul in shallow water of 1-6m depth, the coral cover can reach 20-40%. South of Raoul, the coral cover reduces dramatically to less than 1%.
There are 17 hermatypic (zooxanthellate) species and 7 ahermatypic at Raoul, but only 2 hermatypic and 2 ahermatypic at l'Esperance. It shows that even corals are not very successful at this latitude and loneliness.
Of the close to 400 species of mollusc found, some 20% is thought to be endemic, and all other species are probably stragglers (allopatric), not normally breeding here.

The one really successful marine creature is a coralline alga (Lithtohamnion sp. =stone-leaf), or popularly called pink paint. It is found as a major cover on all rocks and all depths we could dive to. Look for it in the many photographs in our photo galleries.

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Reader pleas note that all of the above has not (yet) been supported by scientific study and experiment. It follows from oceanographic facts for the area, and personal observations. Please e-mail me should you have additional or corrective knowledge. - Dr J Floor Anthoni

f031028: Abundant coral life is observed in shallow waters, made up of few coral species. They do not grow fast enough to create coral reefs. Notice the rivers of poorly grazed red algae and the recently vacated homing spots of sea urchins (dark spots), who created these patches and rivers of red algae. In the backgrund a small school of northern kahawai.

f031408: Giant limpets (Scutellastra kermadecensis) are crowding for space, but some of their homing spots have been vacated. A large number of year classes is absent. Notice how these animals are restricted to a very small homing range (hand-sized) and also a narrow habitat zone(around low tide level). They appear able to graze the limestony pink paint, from which they may derive calcium for their thick shells.

f031419: A formation of hard basalt rock at a depth suitable for both hard and soft corals. The area is dominated by pink paint and fierce grazers like the brown urchin (bottom left) and top shells (bottom right). This area  is grazed to the maximum, perhaps preventing corals from settling.

f031506: Under overhangs and on the roofs of caves, one can study the fragile and varied communities of the deep reef, which is beyond diving range in these clear waters. In the centre a yellow and a brown featherstar, a purple gorgonian, surrounded by yellow tube corals.

f031312: A dense school of blue maomao has arrived out of sheer curiosity. They catch zooplankton in the currents around promontories, but a diver is a rare sight for them. Dense schools of fish are found, but they are not common. Amongst the blue maomao, one can find a related species, the blue knifefish. Blue maomao are excellent survivors, able to switch to a plant diet in case of zooplankton shortages.

f031704: The gentle giant groupers gave the motivation for creating a marine reserve here, because even a few fishermen could have wiped them out, as has happened elsewhere. They are inquisitive and intelligent creatures, often underestimated by us. Here a snorkeldiver hands out some food to gain trust, but these fish thrive on more personal interaction. Born female, the grouper changes into a male at the whopping size of 1m! Consequently there are very few mature males.

f031325: A rocky pinnacle is covered in corals, down to where the large crown of thorns star can reach, because higher up, it is knocked back by wave action. This star is not particularly a voracious predator, and their numbers are low, but because the corals recover very slowly, it has nonetheless a major influence on this habitat. Below the star some fleshy corals in which it is not interested, possibly because its stomach has adapted to particular types of coral. As it turns out, these are also the fastest growing ones. In all, this star may have a beneficial influence on the diversity of the coral habitat. Recruitment of young organisms into the vacant areas is poor.

f031334: The shaded side of the pinnacle shown left, shows the rock cover in a gradient from light (top) to dark (bottom). Corals able to grow in poor light, have zooxanthella with dark, almost grey pigment (top right). Some of these look like grey encrusting sponges (middle right), competing with true orange encrusting sponges. Then comes a band of fleshy corals, who live deeper but still need sunlight, and finally the rock is left bare, covered in pink paint and short algae. This image, like the one on left, shows a lot of vacant space, which has been left unoccupied for a very long time.

Plants
Raoul is densely covered in a climax forest of Pohutukawa (Metrosideros kermadecensis), Karaka and Nikau palm (Nikau Rhopalostylis baueriana), from the cliff face to the top of Mount Moumoukai at 516m. The mountains catch more moisture and here one finds a rich variety of mosses (52), ferns, lichens and fungi (89). The forest community here includes Ascarina lucida, Melycitus ramiflorus and Pteris comans.
The native forest hosts 113 native (NZ) vascular plants of which 23 are endemic! The understorey of the forest consists mainly of Myrsine kermadecensis; Lobelia anceps, Poa polyphylla, Coprosma acutifolia, Coriaria arborea.
The coastal vegetation consists mainly of: Myosporum obscurum, Coprosma petiolata, Asplenium obtusatum, Cyperus ustulatus, Disphyma australe, Scirpus nodosus.

Sea birds
Many sea birds have evolved to migrate vast distances, and the Kermadec's isolation is no real obstacle to their distribution. But when they gather in their millions, they also need to be fed, which requires a rich source of food nearby.
Historic accounts talk of millions of breeding seabirds in some seasons, but they have been discouraged by the introduced predators. Still present are 14 species, including 10 that breed nowhere else in NZ, like the Kermadec petrel (Pterodroma neglecta/ cervicalis) and the black-winged petrel (Pterodroma nigripennis). There are 3 endemic breeders.
It is not known how many uniques species lived here before the introduction of alien predators, but the following three species have been extirpated (destroyed completely):

• the Kermadec parakeet (Cyanoramphus novaezelandia cyanurus)
• the New Zealand pigeon (Hemiphaga novaeseelandia)
• the spotless crake (Porzana tabuensis)

Here are some of the sea and water birds and their seasons:

• The masked gannet or blue-faced booby (Sula dactylatra) is a large bird that does not build a nest but lays its two eggs in a hollow in the ground, from August-November. A number of these birds are resident here, and they are the first ones to meet when approaching the Kermadecs. The photo on right is that of a masked gannet.
• The red tailed tropic bird (Phaethon rubricauda) (Maori: amokura) arrives in October and lays eggs in December - January. They lay a single egg in the holes in the cliff. The parent bird is beautifully pink with a red beak and one long red feather in its tail. some of these are resident.
• Godwits and curlews are noticed in Spring and Autumn, probably on their journey from Siberia to NZ and back.
• The wide awake terns or sooty terns (Sterna fuscata) arrive in August and leave in December. They are very noisy at night, keeping one 'wideawake', and used to settle on beaches like Denham Bay, laying and brooding a single egg.
• White capped noddy or lesser noddy (Anous minutus) arrive in great numbers during spring. They make nests of seaweed and leaves in the branches of trees, low to the ground. This tern has a black body and silver-grey patch on the top of the head.
• Kingfishers (Halcyon sancta) burrow holes in cliffs for nests, the young ones appearing in October.
• Grey duck (black duck) (Anas superciliosa):  a small number is found in the crater lakes.

Passerines (perching birds like sparrows):

• Tui (Prosthemadera novaeseelandiae), the same species as in NZ. They nest in the fronds of Nikau palms, building nests of grass, sticks and mud. The young appear in November.
• Silver-eye (Zosterops lateralis).
• Red crowned parakeet (Cyanoramphus novaezelandiae?) (Maori: kakariki): very numerous on all islands. They breed in holes in the cliffs or in hollows of trees.
• Introduced: Starlings, blackbirds and thrushes and two other species.

Bees:
Raoul has native bees which are black and very ferocious. They find rich supplies of nectar from the pohutukawa trees, which have a much longer flowering season than the NZ variety. Their honey is of the finest grade, some large hives yielding over 30 litres!

Whales:
The Kermadecs lie along the migration paths of humpback whales and sperm whales, seen in numbers in the months of October and November.