Downward fluxes of fatty acids and hydrocarbons during a phytoplankton bloom in the austral summer in Breid Bay, Antarctica

Vertical fluxes of fatty acids and hydrocarbons were measured in sinking particles collected by a time-series sediment trap in Breid Bay, Antarctica during the austral summer December 1985 to February 1986. Temporal variations in fatty acid fluxes were related to changes in growth of the overlying diatom population. High contents of 21:6 alkenes and 14:0, 16:0, 16:1, 20:5 acids of the sinking particles supported the idea that the source of the sinking organic matter was mainly diatoms. 21:6 Alkenes and 20:5 acids increased in the late exponential phase of the overlying diatom bloom. Branched C25 alkenes were detected in the sinking particles. Measurements of changes in the fatty acid composition of the sinking particles were shown to provide useful information on the ecophysiological status of the phytoplankton population as the bloom progressed. Unsaturated fatty acid/saturated fatty acid ratios in the sinking particles indicated active growth of diatoms during the observations. High fluxes of 20:5 acids suggested a late exponential phase and a stationary phase of the overlying diatom bloom.