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

Laboratory experiments were conducted to simulate an environment in which t he copepod Acartia tonsa (Dana) migrates between food-abundant, low salinit y water and food-limiting, high salinity water. The goal of this study is t o understand how migratory grazers influence the dynamics of dimethylsulfon iopropionate (DMSP) in a vertically stratified water column. Results show t hat 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 bod y tissues. The percentage of ingested DMSP not incorporated into body tissu es is estimated to range from 88 to 100%; hence, the percentage of ingested DMSP transported to deep waters by actively migrating copepods is estimate d to be less than 10%. Therefore, it is suggested that grazers like A. tons a help mediate the downward flux of DMSP by producing fast sinking fecal pe llets when they are feeding in the surface waters. (C) 2000 Elsevier Scienc e B.V. All rights reserved.