Science

Chemosynthetic ecosystems south of the Polar Front: ecology and biogeography


RRS James Cook  cruise 80 from Punta Arenas (Chile) to the eastern Scotia Sea and then going to Montevideo (Uruguay).

Since the discovery of the first hydrothermal vents in 1977 there has been a continuous interest in the discovery of these enigmatic ecosystems in the deep sea. For the 30 years after the initial discoveries, vents were discovered in the East and NE Pacific, the Atlantic, the SW Pacific and finally in the Indian Ocean. However, because of the constraints on using manned submersibles in relatively calm conditions most of the discoveries were at generally low latitudes in the major oceans. With the advent of scientific remotely operated vehicles (ROVs) it became possible to think about exploring for vents and seeps at higher latitudes. A group of us from the Universities of Southampton, Bristol, Newcastle and Oxford, and the National Oceanography Centre and the British Antarctic Survey proposed a programme to explore for hydrothermal vents south of the Polar Front in the Southern Ocean. We called this programme ‘Chemosynthetic ecosystems in the Southern Ocean’ (ChEsSo).

Our first exploration cruise was in January/February 2009 on board the RRS James Clark Ross  during which we used Conductivity, Temperature and Depth samplers (CTDs) and a photographic frame for finding the vents. It was a slow business but eventually we found vents at ~2500m along segments E2 and E9 of the East Scotia Ridge, part of a back-arc basin system to the southeast of South Georgia. On the same cruise we found volcanic craters (~1200m depth) associated with the Kemp seamount at the very southern end of the South Sandwich Islands. It is interesting to note that the South Sandwich Islands were discovered by James Cook in 1775 and thus it was therefore very fitting that we returned to the vent sites in January and February 2010 on board the RRS James Cook  carrying the ROV Isis  . Using the ROV Isis  we were able to video, photograph and collect the remarkable animals living at the first hydrothermal vents discovered in the Southern Ocean. The animals were unlike any found at previous hydrothermal vents, the dominant one being a lithodid crab with a hairy chest that became known as the ‘hoff crab’. In the crater discovered in 2009 we found hot seeps and again a specialised chemosynthetically-driven fauna.

In January 2011 we extended our exploration to the Bransfield Strait. However, disaster struck on the first launch of the ROV Isis  when the vehicle was severely damaged. As a result we had to modify our 2011 programme severely. To complete the research programme, Isis  had to be rebuilt and the present voyage on the RRS James Cook  is to return to the eastern Scotia Sea and complete our programme with the new ROV.

Our plan for this cruise is to steam from Punta Arenas (Chile) to E9 (see map), then onto the two craters at the southern end of the South Sandwich Islands and then north to E2. We will then steam to Montevideo in Uruguay. However, already we have had to modify our plans as Station E9, and the crater stations are still covered by ice after a very hard ice season. So we are on our way direct to E2!

Our sampling plan is to map the area using swath bathymetry on the ROV and then carefully video and photograph the vent sites and the fauna. We will then be collecting samples using the ROV and CTD for a variety of chemical and biological analyses to be carried out when we are back in the UK.

We very much hope you will be able to follow us over the next few weeks as we explore these hydrothermal systems. We will be exploring throughout the festive season and sending back some of the amazing images we collect.

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