2 August 2004

Researchers uncover change in Earth's waters

University of Dundee's Professor John Raven, together with a team of scientists from the USA and Canada, have published a paper in the journal Science reporting progress of a five year project that could help predict the future patterns of biodiversity in the sea and interactions with global climate change.

Supported by a four million dollar grant from the US National Science Foundation under the Biocomplexity program, the research concerns phytoplankton in the ocean.

Phytoplankton are tiny organisms, one millionth to one thousandth of a metre in maximum dimension, which are suspended in the surface of the ocean. They use energy from sunlight in the process of photosynthesis to make organic matter and oxygen from carbon dioxide, water and nutrients such as nitrogen and phosphorus. These organisms are responsible for almost half of the photosynthesis that occurs on Earth and are major food sources for other organisms in the ocean. Without them there would be no fish, whales or penguins in the Earth's waters.

The scientists have discovered that over the last 250 million years there has been a replacement of green-coloured phytoplankton, related to green plants on land. by brown-coloured phytoplankton that are more closely related to the malaria parasite and the organism causing potato blight. The team believe that one reason for this could be natural changes in the trace metals in the ocean.

The team have also shown that the most important brown phytoplankton, the diatoms, is linked in some way to grasses on land. Diatoms assimilate approximately 20 billion tonnes of carbon each year, which is about the same as grasses (including cereals) assimilate on land. They both also contain silica, which is the component in grasses that wears down sheep’s teeth. The researchers suggest that silica could be the key to understanding the parallels between the spread of grasses on land and the increase in diatoms in the sea over the last 40 million years.

The work has improved understanding of the evolution of the phytoplankton and its relation to global phenomena in the past, including major geological events such as the formation of the Atlantic Ocean. The findings will be important in predicting long-term changes in the biology of the seas in relation to changes in the climate and other environmental factors.

Professor Raven is a Principal Investigator in the Division of Environmental Science in the School of Life Sciences.

For further information please contact Professor John Raven on 01382 344281

By Angela Durcan, Press Officer 01382 344910, out of hours: 07968298585, a.durcan@dundee.ac.uk