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.