Western English Channel Fixation

16th December 2008

 

A trio of scientists from PML and the National Oceanography Centre have discovered that the biological fixation of nitrogen in the marine environment may be far greater than was previously thought, and thus could quash the current school of thought on the role of shelf seas such as the English Channel and the North Sea in global nitrogen cycling.

 

A specialised, but diverse, group of organisms (diazotrophs), which include cyanobacteria and bacteria, are able to obtain their nitrogen requirements from atmospheric N2 (known as nitrogen fixation) and pass it onto other organisms. This process is particularly significant,as these organisms usually exist in nutrient poor areas of the ocean, where they help to maintain the productivity of the system.

 

Indirect evidence had indicated that N2 fixation in the marine environment may be far greater than was previously thought and recent work has proved this theory to be correct, with fixation rates now being reported at previously unprecedented levels. A pilot study at PML, to investigate the potential for nitrogen fixation in the western English Channel, demonstrated the first reported evidence of nitrogen fixation in a temperate, coastal marine environment. This was a significant find in itself, however using molecular techniques we found that the samples contained a number of previously unreported nitrogen fixing organisms.

 

A more focused examination of coastal waters close to Plymouth is planned, whereby an historical library of stored DNA samples will be interrogated to examine the potential nitrogen fixing activity on a seasonal basis and how this may vary between years. This information will be compared with long-term data sets of nutrient and primary production measurements in order to assess the contribution that nitrogen fixation makes to biological production in temperate waters.

 

If this process is found to be significant in these waters, then this will challenge existing models, budgets and predictions concerned with coastal and shelf sea carbon and nitrogen cycling. This will be of concern to all scientists who investigate marine biogeochemical cycling and agencies with responsibilities in these areas.