Links Between Oceanic Ozone Uptake and Ocean Biology

Dry deposition is a major sink of tropospheric ozone. Organic matter at the sea surface, which is primarily produced by marine biota such as phytoplankton, likely plays a key role in oceanic ozone deposition. This study investigates the fatty acid component of organic matter in the sea surface microlayer (SML) and underlying seawater (ULW). A solid phase extraction (SPE) method was used to extract fatty acids from SML, ULW and phytoplankton culture extracts. Overall, 150 SML and ULW samples collected off the southwestern UK coast over 18 months, and during a trans-Atlantic cruise were analysed using this method. Median total, saturated and unsaturated SML concentrations were 29.56, 11.22 and 5.56 µg L-1 respectively for the coastal samples and 15.69, 12.76 and 0.73 µg L-1 respectively for the open ocean. The measured fatty acids contributed between 0.002% - 8% of the total dissolved organic carbon. The fatty acids observed were predominantly of even carbon numbers, suggesting a phytoplankton source, with their carbon number distributions being comparable to the Phaeodactylum tricornutum and Synechococcus culture extracts and to intracellular phytoplankton fatty acid distributions reported in the literature. These results highlight the link between marine biota and seawater fatty acids and provide a better understanding of the biological and chemical drivers of marine ozone dry deposition.