Seasonal distribution of DMSP among seston, dissolved matter and zooplankton along a transect in the Long Island Sound estuary

Abstract

We studied the seasonal distribution of dimethylsulfoniopropionate (DMSP) among seston, dissolved matter and zooplankton along a transect in eastern Long Island Sound. The seston DMSP concentration (1 to 52 nM) was comparable to that reported for some estuaries. Most of the seston DMSP was derived from particles <10 μm. Seston DMSP concentration did not correlate with water temperature or salinity. Most of the seston DMSP appeared to have originated from phytoplankton. Both dissolved DMSP and dimethyl sulfide (DMS) concentrations remained low (< 3 nM) and were highly correlated to each other (r = 0.83, p < 0.01). Assuming a steady state condition, the conversion efficiency from dissolved DMSP to DMS was estimated to be 76%. On the other hand, seston DMSP concentration did not correlate with dissolved DMSP, implying that the accumulation of seston DMSP and dissolved DMSP were uncoupled. Four types of copepods plus several other types of zooplankters contained DMSP. The copepod Temora tongicornis contained 2.8 nmol DMSP per individual, the highest among the zooplankters. For most of the year, zooplankton were a negligible component of particulate DMSP in the water column. However, in months when T. longicornis appeared in high abundance, zooplankton represented 14 to 72% of the total particulate DMSP. Estimated copepod body DMSP concentrations were orders of magnitude higher than seston and dissolved DMSP concentrations; thus, copepod bodies represent a sparse, but highly concentrated source of particulate DMSP.