JR224: Chemosynthetic life in the Antarctic


Cruise diary

Tuesday 20 January 2009
Location: South Georgia Island (54°09.48S, 37°56.08W)

This morning at 0700 we travel close to South Georgia, to our first station. We are going to test SHRIMP, a piece of equipment that is towed behind the ship very slowly close to the seafloor and it takes video that is fed directly to the laboratory on the ship, so we can see what type of seabed there is in the area and what animals live there!

During this SHRIMP deployment, we will explore a little seamount that we identified earlier with the swath bathymetry. The swath bathymetry is an acoustic system that sends a sound signal from the ship down to the seafloor. The signal reflects from the bottom and this reflection is received by the ship, which is then used to produce maps of the seafloor. The seamount we observed earlier could be an interesting topographic feature that could host a  chemosynthetic habitat such as mud volcanoes.

Above: multibeam surveying reveals the seafloor bathymetry (topography of the sealfoor). Image courtesy CenSeam.

Left: The ship's track for the last 3 days.

Albatrosses – Ocean wanderers
Text and photos by Alex David Rogers

Since the early days of sail, voyagers on the Southern Ocean have been amazed and captivated by the enormous seabirds that have followed their ships. The largest of these are the wandering albatross, Diomedea exulans. My fellow scientists and I have stood watching as these enormous birds wheel over the rolling ocean appearing to almost touch the crests of the waves with their wing tips and speeding close to the James Clark Ross nearly in touching distance. When they get close you realise just how large these birds are. They have the largest wing span of any bird on Earth, at more than three and a half metres. Adult birds weigh up to 12 kg, although immature birds can be as much as 16kg when they first start flying.

Wandering albatrosses are amongst the champion ocean wanderers. They spend most of their lives at sea, returning to the sub-Antarctic islands like South Georgia, where they were born, once in every two years. Scientists working at British Antarctic Survey have tracked these birds using tiny tags and were staggered to find that they range from sub-tropical to Antarctic waters travelling distances of 10,000km in 10-20 days. Watching them fly it comes as no surprise as they glide seemingly without any effort, skimming the ocean throughout the day. At South Georgia, which we’re sailing past right now, these giant birds arrive to breed in November, although each pair will only breed every two years. A pair bond develops between male and female albatrosses over several years, part of which involves a ritualised dance after which the birds mate for life. They lay their eggs in December and as you would expect with such a large bird, the eggs do not hatch until April. The adults feed them over winter on a diet that includes squid and fish. The whole process takes more than a year and then the young birds fly out into the oceans where they take up to 10 years to mature. During this time they go through changes in colouration shifting from a dark, almost black colour to having a mainly white body with black or grey edges to the wings.

Sadly albatrosses are declining and the great wandering albatross is classed as Vulnerable on the IUCN red list (http://www.iucnredlist.org/). In South Georgia populations have undergone a rapid decline over the last 70 years. This is mainly the result of fishing. One method of fishing large fish, such as tunas, swordfish, and, in the South Atlantic and Southern Ocean, toothfish, is to deploy long lines of baited hooks. Millions of these hooks are set in the oceans every year to catch these prime fish. Unfortunately albatrosses, attracted to fishing vessels by the carrion thrown overboard, dive on the baited hooks and are dragged down to drown in the ocean. It has also been found that these birds collide with trawl net cables as well, also causing significant mortality. In places like South Georgia scientists and fisheries managers have worked with fishermen to develop methods of deploying long lines that prevent the albatrosses from becoming entangled in gear. These include not throwing bits of dead fish into the sea from the vessels, deploying the longlines at night time, and using new ways of deploying lines through special chutes or by streaming lines of ribbons or streamers over them and discouraging the birds from diving. These measures are enormously successful when adopted and not only save the albatrosses but also save the fishermen money in terms of preventing losses of catches. However, such measures are not adopted by all fisheries, especially those further north and of course illegal fishing vessels have little regard for ocean life.

These great seabirds have provided a comforting sight to sailors for hundreds of years on the cold and stormy Southern Ocean. Let’s hope that the careless behaviour of humankind does not banish them to memory or to the lines of Coleridge’s Rime of the Ancient Mariner.

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