Acrylic acid : the forgotten part of the dimethyl sulphide story

Acrylic acid in the marine environment is thought to originate mainly from the algal osmolyte dimethylsulphoniopropionate (OMSP). Enzymatic cleavage of this precursor has shown to produce the climate active sulphur gas dimethylsulphide (OMS) and acrylic acid. Whereas OMS and DMSP have attracted a lot of scientific interest over the years, the roles and fate of acrylic acid in the marine environment are poorly understood. To investigate these in more detail, an HPLC method has been developed which allows the direct analysis of acrylic acid in seawater. The method has a detection limit of 5-1 OnM and enables differentiation between the dissolved and particulate fractions of acrylic acid. This allowed an in-depth study into the acrylic acid production characteristics of several Emiliania huxleyi strains during growth and senescence and their subsequent classification into high and low acrylic acid producers. Grazing and viral lysis of OMSP-containing cells increases the production of OMS. The concomitant formation of acrylic acid in these processes has often been assumed and laboratory experiments now confirmed this hypothesis. Further research focused on the suggested grazer deterrent effects of acrylic acid and experiments with the microzooplankton grazer Oxyrrhis marina indicated that these were highly dependent on length and levels of exposure. Whilst high acrylate additions to cultures of 0. marina and its prey Dunaliella tertiolecta increased grazer growth rates in the short term (12-24 hours), they resulted in grazing and growth rate reductions in the long-term (1-5 days). Field studies investigated the occurrence of acrylic acid in the natural environment. During a research cruise in the Norwegian and Greenland Sea depth profiles were taken which show for the first time the distribution of this compound within the water column. A mesocosm experiment emphasised the importance of bacterial communities in controlling acrylic acid levels in the natural environment and identified it as an important carbon source for bacterial growth.