Turnover of dimethylsulfoniopropionate and dimethylsulfide in the marine environment:A mesocosm experiment

The production of dimethylsulfoniopropionate (DMSP) by marine phytoplankton and the fate of the produced DMSP and dimethylsulfide (DMS) were studied in 4 pelagic mesocosms during an algal bloom over a period of 1 mo. Bacterial numbers, concentrations of particulate and dissolved DMSP, DMS, and chlorophyll a were monitored, as well as the turnover rates of DMS and DMSP. Of the total amount of DMSP produced, only a fraction could be detected as DMS in the water column. DMS production in the water column did not necessarily correlate with algal senescence, but also occurred during the maximum of the algal bloom. The flux of DMS to the atmosphere played a minor role as a sink for DMS. Evidence is presented that shows bacterial consumption to be a major sink for DMS, under conditions of both high and low DMS water concentrations. DMSP was degraded either via cleavage or via demethylation; the results indicate a predominant role for the latter route

DMSP synthesis and exudation in phytoplankton:a modeling approach

In the marine environment, phytoplankton are the fundamental producers of dimethylsulfoniopropionate (DMSP), the precursor of the climatically active gas dimethylsulfide (DMS). DMSP is released by exudation, cell autolysis, and zooplankton grazing during phytoplankton blooms. In this study, we developed a model of phytoplankton DMSP and DMS production allowing quantification of the exudation rates of these compounds during different growth phases. The model was tested on published data from axenic cultures of Prorocentrum minimum and Phaeocystis sp.; DMSP exudation rates vary considerably between the 2 species. Model results show that P. minimum exudes around 1% d(-1) of its DMSP quota during the latent, exponential and senescent phases. This is comparable to the average exudation rate estimated from previous laboratory experiments. However, Phaeocystis sp. exudes from 3 to 11% d(-1) of its DMSP quota. For this species, DMSP exudation rates apparently show an inverse relationship with the population growth rate. The maximum DMSP exudation rate in Phaeocystis sp. is 10 times higher than previously reported DMSP or DMS exudation rates. Our results suggest that exudation may be as important as cell autolysis in the release of DMSP during Phaeocystis sp. blooms. We conclude that exudation should be incorporated in models of DMS cycling in the marine environment. Moreover, our results for Phaeocystis sp. suggest that a low and constant exudation rate, as sometimes used in models, is not suitable for all conditions

A new sensitive tracer for the determination of zooplankton grazing activity

A new tracer compound is presented for determining zooplankton grazing activity. The gut content in zooplankton is measured as beta-dimethylsulphoniopropionate (DMSP), which can be measured even in individual copepods. Species specific DMSP/Chl-a ratios allow applications in, for example, prey selectivity studies

A new sensitive tracer for the determination of zooplankton grazing activity

A new tracer compound is presented for determining zooplankton grazing activity. The gut content in zooplankton is measured as beta-dimethylsulphoniopropionate (DMSP), which can be measured even in individual copepods. Species specific DMSP/Chl-a ratios allow applications in, for example, prey selectivity studies.</p