Steinke, M. School of Environmental Sciences,
Malin, G. School of Environmental Sciences,
Archer, S. D.. Plymouth Marine Laboratory,
Burkill, P. H.. Plymouth Marine Laboratory,
Liss, P. S.. School of Environmental Sciences,

Microzooplankton grazing on the coccolithophorid Emiliania huxleyi can greatly enhance the production of the biogenic sulfur compound dimethylsulfide (DMS). This marine trace gas is produced through cleavage of dimethylsulfoniopropionate (DMSP), an osmolyte which accumulates to mM concentrations inside algal cells, via the enzyme DMSP lyase. During a Lagrangian study in June/July 1998 (ACSOE-North Atlantic Experiment), activity of DMSP lyase was investigated in a coccolithophorid bloom south of Iceland (approximately 60degN, 20degE). DMSP lyase activity was associated with particles >2 um in the euphotic zone and showed activities ranging from 100 to 500 nM DMS/day. In vitro enzymatic activity increased with increasing pH (pH 4-8). After gravity size fractionation of particles (0.2-2; 2-5; 5-10; 10-200 um), 70-90 % of activity was found in the fraction corresponding to 10-200 um, whereas activity in the 0.2-2 um fraction accounted for 2-25 % of the total. This may indicate a higher contribution of algal rather than bacterial DMSP lyases. A proportion of the enzyme activity was lost during filtration but remained constant after freezing in liquid nitrogen and further storage at -80degC. Sample analysis for species and pigment composition is underway, which should make further interpretations on group-specific DMSP lyase activities possible.
Day: Friday, Feb. 5
Time: 09:15 - 09:30am
Location: Sweeney Center
Code: SS37FR0915S