Rainbow Warrior - Twenty Years After the Big Bang!
By Roger Grace
The 10th of July 1985. A fateful evening in New Zealand's history. An explosion in Auckland Harbour shook the world and changed New Zealand forever.
French Government secret service agents illegally entered the country and carried out a deliberate and carefully planned underwater terrorist attack on the Greenpeace ship "Rainbow Warrior" as she lay tied to the dock at Marsden Wharf. Minutes before there had been many people onboard. Had the explosion occurred then there would have been more than the one fatality - photographer Fernando Periera.
The events of the following weeks saw New Zealand police track down and apprehend two of those responsible. After initial denials the French Government was eventually forced to admit its involvement in this "sordid act of international state-backed terrorism" - (David Lange).
The episode sparked international outrage and severely soured relations between New Zealand and France for many years. Even today few New Zealanders who lived through that time will ever trust the French Government.
The plan of course backfired on France, who had hoped to silence Greenpeace who were about to sail to Moruroa Atoll in French Polynesia to protest at French nuclear testing there. The event in fact boosted support worldwide for Greenpeace, and the French Government were eventually forced to pay for a replacement vessel, and to contribute a substantial fund for environmental work in the Pacific. And, probably hardest of all, to make a formal apology. A few years later the French stopped their nuclear testing programme.
The Rainbow Warrior was eventually put to rest on the seabed in 1987 at the Cavalli Islands off the Northland coast. The ship then took on a new life. A succession of marine plants and animals occupied the wreck, and started an evolutionary process from a man-made piece of historical hardware to a living reef, more vibrant in its natural colours than the painted rainbow which once adorned its bow.
Only minutes after the ship finally settled to the bottom a mad scramble began to occupy fresh new living space on the artificial reef. Bare rock, or in this case hard metal surfaces, are rare in the sea. Normally every square millimetre of available surface is occupied, sometimes by layer upon layer of encrustations laid down by a succession of organisms over the years.
The sea is full of drifting larvae and algal spores, a major component of the plankton, whose primary function is to find somewhere to live. The vast majority of the larvae die before they find anywhere suitable. Many of these drifters are the dispersal phase of animals which as adults are attached permanently to one spot - bryozoans, sponges, anemones, seasquirts. The adults make a living by filtering tiny diatoms, bacteria and flagellates from the water, and probably sometimes larvae of their own species.
Settlement of organisms on fresh underwater surfaces does not operate on a simple "first come, first served" basis. It proceeds through a series of stages, each more or less dependent on the one before it, until the sequence has run its full course and a "climax" community of organisms exists. The whole process takes several years.
The early part of the succession varies depending on the season in which the surface first becomes available. The first few months on a wreck sunk in winter, for example, will be different from the early stages on a similar wreck sunk in summer. But after several years life on the two wrecks would become indistinguishable.
The first to occupy the new surfaces were marine bacteria and microalgae, which soon developed into a greenish velvety fuzz. Very quickly several types of hydroids, polychaete worms with limey tubes, and encrusting and fluffy bryozoans settled. Barnacles grew rapidly on areas where there was vigorous water movement. Within a few weeks the wreck was well on its way towards functioning as a reef.
The irregular shape and structure of a wreck provide many different microhabitats. Seaweeds, which need light for photosynthesis, are confined to the upper well-lit surfaces, whereas plankton-eating animals such as anemones, bryozoans and sponges are able to colonise more dimly lit overhangs. In fact many of these cannot compete with the fast-growing algae on upper surfaces.
The dark interior of the wreck lacks water movement, and filter-feeding animals would be starved of plankton for food. Silt often accumulates on quiet interior horizontal surfaces further hampering colonisation. Upstanding structures such as bollards and railings, on the other hand, experience constant movement of food-rich water and are keenly sought as living areas.
Gradually a variety of fishes came to inhabit the wreck, some dropping in from the plankton as juveniles and some arriving through exploratory travels from nearby natural reefs. As more attached life developed, more food became available for nibblers such as leatherjackets, and fossickers such as porae and goatfish.
On the upper surfaces and railings, sporelings of the common kelp Ecklonia radiata and colonies of white anemones staked their claim, while in shaded areas bryozoans settled then radiated outwards and began to coalesce. Gorgeous jewel anemones, each patch a different fluorescent colour from its neighbour, competed with the bryozoans for space, so that soon the ship's side was a kaleidoscope of colour - nature's hues proving more beautiful than the original painted rainbow on the hull.
Attached marine life on the Rainbow Warrior wreck has now reached a climax stage, where small localised changes are occurring all the time but there is no progression to another stage - a state of dynamic equilibrium like on natural reefs nearby. Fishes such as leatherjackets,sandagers wrasse, snapper and red pigfish, nibble away at animals attached to the ship, clearing small areas and exposing new surfaces for settlement. Thus, on a small scale, the whole succession process begins again, as opportunists move into the new spaces.
Now, twenty years after the ship first struck the bottom in Auckland Harbour, dramatic physical changes have occurred on the ship. The aluminium superstructure corroded away from the steel hull in less than ten years on the bottom. Surprisingly the wooden decking is still intact, but when it finally caves in it will expose many new settlement surfaces to water movement and new larvae. There are few of the original railings remaining, but they are prime living areas for seaweeds, anemones, and hydroid fans with their purple and white Jason nudibranchs.
Long-lived encrusting animals are now common on the wreck, including encrusting corals, solid massive bryozoans, narrow "pencil" bryozoans, and pink spikey sponges more typical of natural reefs. Large numbers of leatherjackets nibble at the vertical walls, and numerous snapper, some quite large, cruise over the decks. The dark interior seems to be overflowing with bigeyes, spilling out of doorways and other openings even in the daytime.
An unwritten code of "no fishing" on the wreck seems to be working surprisingly well for the fish. I have never seen so many large snapper on a reef except in a no-take marine reserve. But where are the crayfish? Surely there should be many of them peering out from the numerous apparently ideal crayfish lairs on the wreck. Why hasn't this wreck got official no-take status? It would provide a much higher degree of security for the fish and crayfish on the wreck. Then it could really reach its full potential.
1. The Greenpeace flagship Rainbow Warrior rests on the bottom at Marsden Wharf in Auckland Harbour in July 1985. In an ill-conceived plan to stop Greenpeace protests at nuclear testing, French terrorists planted limpet mines on the hull and sank the ship, killing photographer Fernando Periera.
2. A clear day on the Rainbow Warrior wreck at the Cavalli Islands in 1994.
3. By 1994 all that was left of the aluminium superstructure was one wall of the wheelhouse. Railings were covered with anemones and hydroids.
4. March 2005, and the railings have gone from the bowsprit. Encrusting life is lush on the hull, and a large finger sponge has grown in the last two years.
5. Leatherjackets are abundant on the wreck, nibbling at encrusting life and clearing tiny areas for new organisms to occupy.
6. Ecklonia kelp is common on the top of the wreck. Remaining railings are rich with hydroids, algae and bryozoans.
7. Nocturnal plankton-feeding bigeyes overflow from the dark interior of the wreck during the day. It is as if there is not enough room inside the wreck for the many thousands of bigeyes present.
8. Jason nudibranchs munch away at hydroid fans on the railings.
9. A grey moray peers from a hull-breather pipe on the foredeck, with masses of pencil bryozoans growing in the foreground.
10. A dwarf scorpionfish rests beside a yellow sponge at the foot of the stairs leading to the bow.