Annual cycle of the production and fate of DMS and DMSP in a marine coastal system

The production of DMSP by phytoplankton and the fate through the marine system of both DMSP and DMS were followed for a period of 21 mo in the natural environment by studying a Wadden Sea tidal inlet. The major production and emission of DMS appeared to be Limited to a period of only 2 mo, which was closely linked to the presence of phytoplankton blooms. The production of DMS in the water column was not well correlated with chlorophyll a concentrations or plankton species composition. It was however, found to be closely related to the start of a Phaeocystis bloom early in spring. Contrary to our expectations, the senescence phase of this Phaeocystis bloom did not result in high DMS accumulation. It is postulated that this phenomenon could be the result of a bacterial consumption which increased with time in combination with a decreasing DMSP-lyase activity of Phaeocystis. A simple model, into which the overall DMSP consumption could be introduced, could very well imitate the measured concentrations of DMS in the water column of the natural system studied

Air exposure of coral is a significant source of dimethylsulfide (DMS) to the atmosphere

Corals are prolific producers of dimethylsulfoniopropionate (DMSP). High atmospheric concentrations of the DMSP breakdown product dimethylsulfide (DMS) have been linked to coral reefs during low tides. DMS is a potentially key sulfur source to the tropical atmosphere, but DMS emission from corals during tidal exposure is not well quantified. Here we show that gas phase DMS concentrations (DMSgas) increased by an order of magnitude when three Indo-Pacific corals were exposed to air in laboratory experiments. Upon re-submersion, an additional rapid rise in DMSgas was observed, reflecting increased production by the coral and/or dissolution of DMS-rich mucus formed by the coral during air exposure. Depletion in DMS following re-submersion was likely due to biologically-driven conversion of DMS to dimethylsulfoxide (DMSO). Fast Repetition Rate fluorometry showed downregulated photosynthesis during air exposure but rapid recovery upon re-submersion, suggesting that DMS enhances coral tolerance to oxidative stress during a process that can induce photoinhibition. We estimate that DMS emission from exposed coral reefs may be comparable in magnitude to emissions from other marine DMS hotspots. Coral DMS emission likely comprises a regular and significant source of sulfur to the tropical marine atmosphere, which is currently unrecognised in global DMS emission estimates and Earth System Models

Dimethylsulphide production by plankton communities

The trends of dimethylsulphide (DMS) production by plankton communities in mesocosm systems were studied under various conditions. The results show that the DMS concentration in the water column can be highly variable over time, even within days, and under apparently identical conditions. DMS release in the water column appears to be highly correlated with phytoplankton senescence rather than growth. The development of the DMS peak could not be attributed to the zooplankton activity. It is argued that bacterial consumption may be an important sink for DMS