Particulate dimethylsulfoniopropionate and dimethylsulfoxide inrelation to iron availability and algal community structure in thePeru Upwelling System.

摘要

The influence of iron on phytoplankton biogenic sulfur production, physiological status, and community structure in the Peruvian Upwelling System was investigated in September 2000. Vertical profiles of particulate dimethylsulfoniopropionate (DMSP sub(p)) and dimethylsulfoxide (DMSO sub(p)) were measured at stations along two transects passing from the high-iron waters of the continental shelf, across the Peru trench, to low-iron open-ocean waters. Although chlorophyll a (Chl a) biomass decreased significantly across the shelf, DMSP sub(p) and DMSO sub(p) concentrations relative to Chl a were higher at the offshore stations. These changes were associated with lower iron concentrations, as well as a shift from diatom-dominated communities to ones dominated by cryptophytes and haptophytes. The results of a shipboard iron-addition incubation experiment were similar to patterns observed on the transects. DMSP sub(p):Chl a ratios decreased with increasing iron and diatoms preferentially outgrew other taxa. The possible role of DMSP sub(p) and DMSO sub(p) as free radical scavengers was supported by the increased concentrations of these compounds measured under low-iron conditions, as well as by the positive correlations observed between these compounds and the known antioxidant beta -carotene.