OLI Grant: A Novel, Lipid-based Assay for Phosphorus Stress in Marine Phytoplankton

Benjamin Van Mooy, Marine Chemistry & Geochemistry
Eric Webb, Marine Chemistry & Geochemistry

Grant Funded: 2005

The subtropical ocean gyres are the largest biomes on earth and the plankton that dwell in these environments exert immense influence on global biogeochemical cycles and climate. The dominant photosynthesizing (i.e. carbon dioxide consuming) plankton in gyres are cyanobacteria, small prokaryotic cells that have adapted to growing in these locations where nutrient concentrations are vanishingly low. Despite these environmental conditions, cyanobacteria in the gyres are able to consume massive amounts of carbon dioxide and may be responsible for as much as half of the global marine productivity. Recent work has shown that the nutrient phosphate may be of key importance in determining exactly how much photosynthesis cyanobacteria are able to sustain in the gyres. To test where and when cyanobacteria are stressed by phosphorus limitation, we propose to investigate the molecular structure of intact membrane lipids in cyanobacteria. Glycolipids, which do not contain phosphorus, are key structural components of the cell membranes in cyanobacteria, and it has been suggested that these compounds are synthesized preferentially over phospholipids when cyanobacteria are stressed by phosphorus limitation.  Understanding the relative proportions of phospholipids and glycolipids in key populations of picoplankton in gyres will offer a new molecular-level means by which to determine the reliance of these populations on dissolved phosphorus. Thus, this new lipid-based assay will provide a powerful means by which to understand the economy of phosphorus in the subtropical gyres.