Results Are Starting to appear from an Antarctic scuba diving project undertaken by New Zealand scientists over the last few summers at Cape Armitage, Ross Island.
The research headed by Dr Chris Battershill (lately of Canterbury University, now of Queensland) had a dual purpose. The first was to examine subtidal ecology in a particularly harsh and unusual environment, and the second was to find out whether any of the marine organisms present produced chemicals with pharmaceutical value.
The Antarctic subtidal environment is of interest for several reasons. The water temperature is -1.9°C (dissolved salt depresses its freezing point by a few degrees). Ice cover for most of the year means light levels are very low, and this in turn prevents most phytoplankton growth. Water clarity is outstanding, due both to the absence of plankton and the lack of rivers disgorging sediment into the water.
For their diving base the New Zealand scientists use a small, heated but perched over a hole cut through the 2m thick ice. Multiple layers of Antarctic outdoor clothing (the outside summer temperature is around -15°C) have to be exchanged for special ‘dry suits’. An outer waterproof layer goes over polypropylene and cut fibre undergarments. Air is used to inflate the suit and provide extra insulation, except in the gloves, so hands always get cold first.
Scuba tanks each carry two regulators fitted with a Y-valve. This is in case one regulator freezes up. Antifreeze-filled caps cover the first stage of each regulator to reduce the risk of icing up.
Where possible, bulldozers are used to clear snow off the ice surface over an area half the size of a rugby field. These ‘windows’ allow light to penetrate the ice (which is basically transparent) giving a blue neon light effect.
Seals are not uncommon under the ice, but the range of shallow water fish is very limited. Most Antarctic fish inhabit deep water (300m+).
At shallow depths (up to 5m), ice has ground all rock faces bare of organisms.
Below the ice abrasion levels, rocky surfaces are densely covered with encrusting organisms — ascidians, anemones, tube worm colonies, bryozoans, hydroids and soft corals, but sponges are the most important and striking component of the fauna.
Giant starfish feed on sponges and anemones, some of which may reach plate size. The lack of light means that seaweeds, a major component of most hard shorelines, are sparse or absent most of the year, though during summer algae and plankton may bloom briefly in areas where ice melts. Fish have unusual, bright eye pigments to cope with the low light levels.
Colours of the organisms are more subdued than one would find in New Zealand. Predators seem to be less common than elsewhere, and growth rates of organisms are generally slow.
Preliminary results of the search for pharmacologically active compounds suggest some may be present, but the number of species producing such molecules is much lower than in temperate areas. Sponges from other regions have proved to be a particularly rich source of these compounds possibly they deter predatory animals and bacterial invaders.
The work is continuing.