25 February, 2008 Press releases

Scientists have discovered Antarctic krill (Euphausia superba) living and feeding down to depths of 3000 metres in the waters around the Antarctic Peninsula. Until now this shrimp-like crustacean was thought to live only in the upper ocean.   The discovery completely changes scientists’ understanding of the major food source for fish, squid, penguins, seals and whales.

Reporting this week in the journal Current Biology, scientists from British Antarctic Survey (BAS) and the National Oceanography Centre, Southampton* (NOCS) describe how they used a deep-diving, remotely operated vehicle (RoV) known as Isis to film previously unknown behaviour of krill. Professor Andrew Clarke of the British Antarctic Survey said,

“While most krill make their living in the ocean’s surface waters, the new findings revise significantly our understanding of the depth distribution and ecology of Antarctic krill. It was a surprise to observe actively-feeding adult krill, including females that were apparently ready to spawn, close to the seabed in deep water.”

Euphausia superba (krill) from the Bellingshausen Sea continental shelf. Euphausiid crustaceans use their thoracic appendages as a suspension feeding basket. They are a very important source of prey to penguins, seals and whales and some fish.
Images taken onboard RRS James Clark Ross cruise JR230 (benthic pelagic coupling cruise).

Scientists have been studying krill since the ‘Discovery’ expeditions of the early 20 century. Oceanographic expeditions, using a combination of echo-sound techniques and collection samples in nets, indicated that the bulk of the population of adult krill is typically confined to the top 150 metres of the water column.

The grant to purchase the Isis RoV was led by Professor Paul A Tyler of NOCS. He says,
“Having the ability to use a deep-water ROV in Antarctica gave us a unique opportunity to observe the krill and also to observe the diversity of animals living at the deep-sea floor from depths of 500m down to 3500m. The importance of such observations is that, not only do we have the ability to identify species, but we can see the relations among individual species and their relationship to the ambient environment.”

The discovery holds some important lessons, Clarke continued.
“The behaviour of marine organisms – even quite ‘primitive’ ones – can be complex and more varied than we usually assume. There is still a great deal to learn about the deep sea and an important role for exploration in our attempts to understand the world we live in.”

Issued by British Antarctic Survey Press Office.

Linda Capper, tel: +44 (0)1223 221448; mob: 01174 233744; email: l.capper@bas.ac.uk

National Oceanography Centre, Southampton Press Office contact:
Kim Marshall-Brown, Tel +44(0)23 8059 6170; email: kxm@noc.soton.ac.uk

Author contacts: Professor Andrew Clarke, BAS. Tel 01223 221591; email: a.clarke@bas.ac.uk

Professor Paul Tyler, University of Southampton’s School of Ocean and Earth Science based at the National Oceanography Centre, Southampton. Tel: 44(0)23 80 592557; mob: 07905262038; email: pat8@noc.soton.ac.uk

Previously unseen movies of deep-sea krill swarms shot from the ROV are available from the BAS Press Office.

Download movie here. Stills are available also

The paper: Antarctic krill feeding at abyssal depths by Andrew Clarke and Paul Tyler is published this week in Current Biology.

Antarctic krill (Euphausia superba), feed on phytoplankton and are in turn eaten by a wide range of animals including fish, penguins, seals and whales. Phytoplankon are the starting point for the marine food chain and use photosynthesis to extract carbon from carbon dioxide.

Krill live in the open ocean, mainly in large swarms and reach particularly high numbers in Antarctica. Antarctic krill can grow up to a length of 6cm and can live for 5-6 years. They are one of the largest protein resources on Earth and can be fished easily with large nets for human consumption. The total weight of Antarctic krill is calculated between 50-150 million tonnes.

Numbers of Antarctic krill appear to have dropped by about 80% since the 1970s. The most likely explanation is a dramatic decline in winter sea-ice. Krill feed on the algae found under the surface of the sea-ice, which acts as a kind of ‘nursery’. The Antarctic Peninsula, a key breeding ground for the krill, has warmed by 2.5°C in the last 50 years, with a striking decrease in sea-ice. It is not fully understood how the loss of sea-ice there is connected to the warming, but could be behind the decline in krill.

The Cambridge-based British Antarctic Survey (BAS) is a world leader in research into global environmental issues. With an annual budget of around £40 million, five Antarctic Research Stations, two Royal Research Ships and five aircraft BAS undertakes an interdisciplinary research programme and plays an active and influential role in Antarctic affairs. BAS has joint research projects with over 40 UK universities and has more than 120 national and international collaborations. It is a component of the Natural Environment Research Council. More information about the work of the Survey can be found at: www.antarctica.ac.uk

The National Oceanography Centre, Southampton (NOCS) is one of the world’s leading institutions devoted to research, teaching and technology development in ocean and Earth science. NOCS is a collaboration between the University of Southampton and the Natural Environment Research Council.

The University of Southampton is a leading UK teaching and research institution with a global reputation for leading-edge research and scholarship.  It is one of the UK’s top 10 research universities, offering first-rate opportunities and facilities for study and research across a wide range of subjects in humanities, health, science and engineering.  The University has over 20,000 students and over 5000 staff.  Its annual turnover is in the region of £325 million.