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

We studied the seasonal distribution of dimethylsulfoniopropionate (DMSP) a mong seston, dissolved matter and zooplankton along a transect in eastern L ong 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 f rom particles <10 <mu>m Seston DMSP concentration did not correlate with wa ter temperature or salinity. Most of the seston DMSP appeared to have origi nated from phytoplankton. Both dissolved DMSP and dimethyl sulfide (DMS) co ncentrations remained low (<3 nM) and were highly correlated to each other (r = 0.83, p < 0.01). Assuming a steady state condition, the conversion eff iciency from dissolved DMSP to DMS was estimated to be 76%. On the other ha nd, seston DMSP concentration did not correlate with dissolved DMSP, implyi ng that the accumulation of seston DMSP and dissolved DMSP were uncoupled. Four types of copepods plus several other types of zooplankters contained D MSP. The copepod Temora longicornis 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, i n months when T. longicornis appeared in high abundance, zooplankton repres ented 14 to 72% of the total particulate DMSP. Estimated copepod body DMSP concentrations were orders of magnitude higher than seston and dissolved DM SP concentrations; thus, copepod bodies represent a sparse, but highly conc entrated source of particulate DMSP.