Dynamics of dimethylsulfoniopropionate ( DMSP ) in a migratory grazer : a laboratory simulation study

Laboratory experiments were conducted to simulate an environment in which the copepod Acartia tonsa (Dana) migrates between food-abundant, low salinity water and food-limiting, high salinity water. The goal of this study is to understand how migratory grazers influence the dynamics of dimethylsulfoniopropionate (DMSP) in a vertically stratified water column. Results show that the DMSP content of A. tonsa was determined mostly by food availability instead of salinity. Individual copepods accumulated DMSP in their bodies during feeding, but most of the ingested DMSP was not retained in their body tissues. The percentage of ingested DMSP not incorporated into body tissues is estimated to range from 88 to 100%; hence, the percentage of ingested DMSP transported to deep waters by actively migrating copepods is estimated to be less than 10%. Therefore, it is suggested that grazers like A. tonsa help mediate the downward flux of DMSP by producing fast sinking fecal pellets when they are feeding in the surface waters.  2000 Elsevier Science B.V. All rights reserved.