Disease could account for Antarctic krill declines

Disease could be behind the dramatic decline in Antarctic krill – a “keystone” species in the Southern Ocean.

An exciting new collaboration between scientists at two leading marine research organisations – the Centre for Environment, Fisheries and Aquaculture Science (Cefas) and the British Antarctic Survey (BAS) – is hoping to shed light on this issue.

Krill are a major food source for everything from fish to penguins and whales. Precise reasons for their dwindling numbers are far from clear. Some scientists, however, have suggested that declines could be down to warming seas.

Long-term changes in disease prevalence may be more clearly demonstrated in polar and sub-polar regions, where the relative changes in ocean temperature are greatest over time.

Dr Grant Stentiford, Project Manager for the Cefas study and lead scientist at the European Community Reference Laboratory for Crustacean Diseases, said: “Temperature is an important factor in the onset and extent of disease in marine animals. The seasonal nature of many marine diseases demonstrates the importance of temperature in driving epidemics in our oceans.”

Grant continues: “Our experiment with BAS is unique: very little work has been carried out on the diseases that krill carry and whether they are on the increase. Disease is an important factor in the turnover of animal populations and krill are likely to be no exception. The decline in krill numbers has obvious implications for the future stability of the whole Antarctic system.”

Cefas researcher, Ruth Hicks, will join BAS scientists aboard the RRS James Clark Ross to collect Antarctic krill samples this spring. Sampling will cover a wide temperature range: from +4^o C at the tip of South America to –2^o C at the Antarctic ice sheet.

The scientists will catalogue whether different diseases occur across the geographical range being sampled. They also hope to learn whether diseases in krill have the potential to increase in severity with future changes in sea temperature and climate.

“This project is a fantastic opportunity to work alongside BAS, and with them to contribute to research in new areas of science including climate change.” said Ruth.

The data generated will be fed into stock and risk assessment models to estimate the future effects of shifting climatic regimes on disease epidemics. Estimating the sustainability of the Antarctic krill stock could also have knock-on effects to species such as seabirds and marine mammals.

Notes to editors

1. Cefas is an internationally renowned scientific research and advisory establishment, based at Lowestoft and Weymouth. Operating as an executive agency of the Department for Environment, Food and Rural Affairs (Defra), it works alongside government and other agencies, both in the UK and internationally, to play a vital role in securing healthy marine and freshwater environments for everyone’s well-being, health and prosperity.

2. The agency achieves its aims by providing evidence-based scientific advice, managing related data and information, conducting world-class scientific research, and facilitating collaborative action through international relationships. It applies its expertise and knowledge gained through over 100 years of applied science and research to fisheries management, environment and biodiversity protection, and aquaculture. For more detail about its range of activities visit www.cefas.co.uk 
3. Ruth Hicks, from Cefas’ European Community Reference Laboratory for Crustacean Diseases (www.crustaceancrl.eu), will carry out the Antarctic fieldwork. Ruth will fly down to Antarctica, via the Falkland Islands, on 8 March 2008 to join the RRS James Clark Ross. The cruise will take place during March and April.
4. Cefas is collaborating with scientists at the British Antarctic Survey (BAS: http://www.antarctica.ac.uk). The work is being carried out during BAS’ Discovery 2010 expedition (see
   www.antarctica.ac.uk/bas_research/current_programmes/discovery_2010.php).
5. BAS helped Cefas to secure funding for the latter’s involvement from the NERC Antarctic Funding Initiative and from the National Geographic Research and Exploration Grant.
6. There are serious concerns that the overall biomass of Antarctic krill has been declining rapidly over several decades. For general background about this important species, see http://en.wikipedia.org/wiki/Antarctic_krill; for a more detailed discussion about conservation, see http://www.ccamlr.org/pu/e/gen-intro.htm.
7. Back at Cefas’ Weymouth laboratory, researchers will analyse the krill samples using a range of high-tech tools and techniques:

histopathology: to assess the health of individual animals/population. This involves mounting samples in wax, cutting them very thinly, staining the sections and observing them under a microscope.
electron microscopy: a very high power view of individuals’ organs and tissues, which is particularly useful in identifying very small pathogens such as viruses. The technique is used in conjunction with histopathology to provide an initial understanding of the underlying causes of pathological changes to tissues.

molecular biology: detects the presence of specific DNA. The krill samples collected can be compared to DNA profiles of pathogens found in other known species, eg. in shrimps from warmer seas.

Press contact: Anne McClarnon
Telephone: 01502 524370 / Email: anne.mcclarnon@cefas.co.uk