| Summary: | 碩士 === 國立臺灣海洋大學 === 環境生物與漁業科學學系 === 95 === Three species of copepods, Neocalanus flemingeri , Neocalanus plumchrus and Neocalanus cristatus are major components of the mesozooplankton on the shelf of the Gulf of Alaska. They grow and develop during the period of spring phytoplankton bloom (April–June). We used these three different species of copepods in 24-H incubation experiments to study the variation of copepod grazing rate on ciliates under different prey environments (dominated by microphytoplankton or picophytoplankton).
The grazing rates of copepods on ciliates in the inner shelf and mid shelf during the bloom period (dominated by microphytoplankton) were smaller than those at nonbloom station in the outer shelf waters (dominated by picoophytoplankton). The clearance rate was negatively related to prey concentration. Ciliates contributed 70-80% of copepod total ingestion in nonbloom condition, and in bloom condition copepods switched to graze >20μm Chl a (80-90% of total ingestion). Over all, the clearance rate in per weight basis was “other small copepods” > Neocalanus plumchrus > Neocalanus flemingeri > Neocalanus cristatus, i.e., clearance rate decreasing with the increase of grazer size. With the exception of Neocalanus plumchrus, which also fed on <5μm and 5-20μm Chl a, all copepods fed mostly on >20μm particles and preferred ciliates over phytoplankton in the most cases.
|
|---|
