LIPID BIOMARKERS FOR HETEROTROPHIC ALTERATION OF SUSPENDED PARTICULATE ORGANIC-MATTER IN OXYGENATED AND ANOXIC WATER COLUMNS OF THE OCEAN

The fatty acid, sterol and hydrocarbon composition of suspended partic les from the central North Pacific VERTEX IV site and from the Black S ea were used to investigate the abundance of biomarkers produced by he terotrophic alteration of particulate organic matter (POM). At the oce anic VERTEX site, bacterial alteration of organic matter did not contr ibute significant amounts of diagnostic lipids to particles, whereas z ooplankton did leave a marked imprint on particulate lipids. In contra st, in the anoxic zone of the Black Sea there were significant lipid i ndicators of bacterial decomposition of POM. Most of these were derive d from anaerobic sulfate-reducing and phototrophic sulfur bacteria. A comparison of the two sites and their lipid distributions indicates th at it may be difficult to use lipid biomarkers to assess the importanc e of bacterial decomposition of organic matter in the open ocean, as l ipids from these bacteria are not readily distinguished from the more abundant planktonic lipids.