Wolfe, G. V.. COAS - Oregon State University, wolfeg@ucs.orst.edu
Levasseur, M. V.. Institut Maurice-Lamontagne, LevasseurM@dfo-mpo.gc.ca
Cantin, G. Institut Maurice-Lamontagne, CantinG2@dfo-mpo.gc.ca
Michaud, S. Institut Maurice-Lamontagne, MichaudS@dfo-mpo.gc.ca

 
MEASURING THE IMPACT OF ZOOPLANKTON GRAZING ON THE CYCLING OF ORGANIC SULFUR COMPOUNDS IN THE LABRADOR SEA
 
We adapted the dilution technique to study microzooplankton grazing of algal dimethylsulfoniopropionate (DMSP) and production of dimethyl sulfide (DMS) in the springtime Labrador Sea. Growth of algal Chl a and DMSP was generally high, while grazing rates were lower and more variable. Production and consumption of Chl a vs. DMSP sometimes diverged greatly due to their differing distributions among algal prey taxa and size class, but without knowledge of protozoan digestion rates of Chl a and DMSP we were unable to assess grazer selectivity of DMSP-containing prey with the dilution method. Grazing was not generally tied to DMS production except where Phaeocystis was abundant. However, the dilution method is poorly suited for assessing the impact of grazing on dissolved sulfur pools, due to the artifactual release of DMSP and DMS during filtration, and stimulation of their rapid microbial consumption in diluted bottles where bacterivory is reduced. Because DMS turnover was most rapid at low DMS concentrations and consumption saturated at 10 - 30 nM, we suggest that DMS consumption likely saturates more easily than eukaryotic or prokaryotic DMS production, possibly leading to the seasonal buildup of high DMS concentrations often noted in polar and subpolar waters.
 
Day: Friday, Feb. 5
Time: 11:30 - 11:45am
Location: Sweeney Center
 
Code: SS37FR1130S