Underwater

Forest and Bird, Issue 293, 1 August 1999, Page 27

Underwater

by

and

and

Jenny

Tony Enderby

WARREN FARRELLY

MALCOLM

Protecting the Acheron

Passage,

Zealand’s great natural wonders, recognized by having World Heritage Park status. Yet the unique world beneath the waters of its fiords is largely unprotected. Unlike the mountains surrounding the fiords, only two small areas — Piopiotahi in Milford Sound and Te Awaatu Channel in Doubtful Sound — have marine reserve status. Some of the fiords, such as Dusky and Doubtful sounds, are home to bottlenose dolphin pods. The dolphins often ride the bow of any boat travelling through the area. Yet, while this is an inspiring sight, it is the underwater world which makes Fiordland different from anywhere else. Fiordland’s heavy rainfall sends huge amounts of fresh water, carrying tannin from fallen vegetation, into the fiords. This discoloured fresh water does not mix with the salt water but sits on top, filtering out sunlight from the salt water beneath. Although the tannin is the colour of cold tea, divers looking back to the surface see the sun as a vivid emerald glow. The water temperature varies, with the fresh water normally at least three degrees colder than the salt water below it. It is the lack of sunlight which makes Fiordland’s waters unique. Species like black coral, normally found in other seas at depths of 50 metres or more, live here in less than 10 metres of water. The Acheron Passage between Breaksea Sound, Dusky Sound and Resolution Island has magnificent black coral. These animal National Park is one of New

colonies grow very slowly, with some hundreds of years old. They live from the shallows below the fresh water down to beyond diveable depths. The largest tree we’ve seen was three metres in height and probably as wide, but they grow to twice that size. Black coral and the beautiful red coral, also found in Fiordland, are both protected in New Zealand. (Overseas black coral is highly prized and used for making jewellery.) The shiny black trunks resemble ebony and are carved into ornaments which sell for high prices. Underwater, the name black coral is a misnomer. The first view a diver gets after passing through the fresh water layer is a glowing white tree against the green water.

The flowery polyps of the black coral are white and cover almost every living part of the tree. They are extended to catch minute food particles that drift past in the current. For divers, the Acheron Passage is an easy drift-dive, but good buoyancy is essential. The passage drops vertically to over 100 metres and a poorly weighted diver crashing down a cliff can do much damage to the fragile black coral colonies. Currently only a small number of divers visit the area. Most of the charter boat operators taking dive parties are very environmentally conscious, trying to educate those diving on the wall to be careful and not to take or damage anything. Numerous small invertebrates make their homes amongst the branches of black coral. Snake stars are found on almost every tree, wrapped tightly around the branches during the day. At night they unravel and start to feed. Snake stars live in a symbiotic relationship with the black coral, cleaning off unwanted particles and microscopic plankton. Their colours range from yellow to red, some plain and others patterned. On our dives we found beautiful yellow anemones with brilliant blue centres on some of the dead branches. Lower on the trunk were several tiger shells with the animals fully extended even though it was daylight. Scarlet wrasse hovered around the black coral during the day, but at night we found them sleeping among the branches, safe from the predators of the open water. Although the fish life was sparser than on some of our shallower dives there were still good schools of butterfly perch and tarakihi drifting below us. Blue cod, leatherjackets, and sea perch (Jock Stewarts) sat on the walls and the occasional big conger eel glared from a hole in the cliff face. The many vertical cracks in the wall

were home to crayfish. We had heard stories of ‘hundreds of crays’ here but the most we saw in any hole was about ten. The fiord walls are a mosaic of colour with yellow and orange sponges, zoanthids, gorgonians and hydroids. Living amongst these are a wide variety of shells, sea stars and nudibranchs. The aptly-named circular saw shell lives here in big numbers. Huge horse mussels, normally found on mudflats, live attached to the walls. The brilliantly coloured nudibranch Jason mirabilis also found in the north, grazes on the Solanderia hydroid. To us, the Acheron Passage portrays the magnificent underwater world of Fiordland. The black coral for which the area is acclaimed is at its best here. The accompanying life is largely also unspoilt. It will be increased pressure from divers, fishermen and sightseers that will cause damage to the fragile underwater environment of the fiords. Currently the major damage is totally natural. Huge avalanches of rocks and trees fall from high on the hillsides into the fiords. These take with them everything in their path, both above and below the water, but as with all natural disasters nature eventually restores everything to its original condition. But what about the future of the fiords? Should more of the Fiordland underwater world have marine reserve status? While the corals of Fiordland are protected, their habitat also needs protection. There are many parts of the sounds that could be considered for marine reserves. In our view the Acheron Passage with its black coral inhabitants, is one obvious area for consideration. JENNY and TONY ENDERBY are underwater photographers based at Leigh in lower Northland. Their last story in Forest & Bird was about mangroves (February 1998).

Exploring Long Sound, with Warren Farrelly and Malcom Struthers ong Sound is a sinuous narrow fiord. It begins at an impressive waterfall in Cascade Basin, 26 kilometres inland, and ends as the most southern of Preservation Inlet’s waterways. On a fine sunny day, its still surface mirrors perfect reflections of gaunt rock, trees and overhanging mountains. Mostly though, cloud blots out the lot. Everything in this place centres on weather. For instance, the northwest wind which funnels down Long Sound whips up individual williwaws at 60 kilometres an hour. When this same wind rises to a scream, at about 120 kilometres an hour, the individual williwaws come together as a 20-30 metre vertical blanket of raised water careering towards us. We had three days of this in one storm. Diving in the narrows of Long Sound ranks with the best in Fiordland (and elsewhere). Because the narrows were once only a branch of a greater glacier, the bottom here is shallow enough to be diveable. It gave us the chance to find some different, delicate and extremely rare marine life, of the kind usually only encountered at much greater depths. The outer curve of the fiord wall is steep and swept by strong tidal currents. The inner wall by contrast has less tidal current and is easily diveable at all times. Many rock pinnacles exist on this side, further breaking down the tidal movement. The inner wall of the fiord and all these pinnacles are coated in red coral. Sometimes this coral is a brilliant cochineal red and chunky. It can also be the palest pink colour and very delicate. This variability in colour and shape makes for some interesting pat-

terns and perhaps indicates a range of different species or sub-species. On one dive we found red coral growing on brachiopod shells. When wiped with our exhaust bubbles these ancient shells would close, wafting the red coral wands in a progressively upward wave of motion. In other places, fish would perch among the red coral, creating striking colour and texture patterns. Red coral was also found growing out of black coral trees. The contrast between the white external colour of the much bigger black coral and the squat red coral is eye-catching. Add wandering anemones, yellow gorgonians, snake stars, and other sea creatures and you have a diver’s heaven — somewhat moderated by a water temperature of 9-10 degrees Celsius. Rare marine life, much of it not found anywhere else, is common here. Leaving the rock wall and pinnacles took us out over the sloping bottom of loose sediment. Here the rare life included several species of sea pen. We eventually found three different species in this area. No other Fiordland dive provides more than one. The typical and most common sea pen in Long Sound is a stout, dense, pink/apricot coloured beast attached to the bottom by a foot. Its branches are like plane aerofoils that direct water across and into the waiting anemone tentacles on the lee edge of each branch. This sea pen swivels to face always into the current of the moment. Ken Grange, having studied these, believes them

to be a different but closely related species from the larger, less dense and less colourful ones found in some other fiords. On our first trip into Long Sound in January 1995 we found a very different sea pen. This one was white and smallish. It had fewer branches which each ended in a single large anemone with long tentacles. It is a beautiful, delicate-shaped sea pen the main trunk of which is transparent.All its internal organs are visible, and so is its descending lunch. Our second dive holiday to the area, from December 1997 to January 1998 , gave us four specimens of a third type of sea pen. These were much harder to find, being very scattered and low in density. In the photos they are apricot in colour, with a ‘vein’ from the foot to the top of the main stem. The ‘vein’ we thought was blue until the photos proved that wrong. This sea pen was more feather-like than the first Long Sound one. Its ‘aerofoils’ are more widely spaced, very thin but wide, with rows of delicate anemones along its back edge. Like all sea pens this one could rotate toward the current. iving Long Sound is more than red and sea pens. For instance we also dived a rock wall that was dramatically undercut. It was a pitch black dive for the sloping rock ceiling above let no light through. Marine life was not prolific; in fact it was sparse but interestingly different. Gorgonians here had so many snake stars entwined in them that they looked like intricate Celtic knot tapestries. A different and lone snake star pho-

tographed on the dive proved to be a new species for New Zealand. Its legs have colour bands, similar to another snake star found in Acheron Passage. Surely other unusual lifeforms will also be found here. In more than nine weeks of diving Long Sound we have no more than probed its secret places. We know a little of what is there, particularly in the narrows, but much more remains to be explored. Yet, already, it has proved a place too unusual and unique to risk, and risks do exist. Fishing for crayfish with pots along the red coral walls could cause considerable damage to that coral. Sea pens could be uprooted and destroyed by dredging. Clumsy divers would likewise pose problems to the fragile corals and sea pens. At present, luckily, it is undisturbed and all but pristine, but for how long? It is certain that more and more people, including divers, will find their way into Long Sound. Protection is needed now before damage changes this unique, complex, and fascinating underwater world. The best protection would be a marine reserve extending the full length of Long Sound, from the entrance at Colt Head to its headwaters at Cascade Basin. This would help the grouper to grow large again, and protect all the other marine species, some of which are undoubtedly yet to be found and described.

are divers and underwater

photographers who live and teach in Northland.