9403426 Lessard This project will investigate the bioenergetics, growth and prey preferences of representative heterotrophic dinoflagellates and ciliates in batch cultures to define the trophic roles of each group and to determine how these two groups of potential competitors coexist in the marine plankton. A systematic investigation will be done on the bioenergetics and food preferences in a large number of representative heterotrophic dinoflagellates and ciliates using a 14C-radiotracing method which will include direct measures of egestion and excretion of organic matter. Information on gross growth efficiencies, maximal growth rates, and the effects of temperature and food quality will be obtained under strictly comparable conditions. Careful evaluation of the carbon: volume relationship of thecate and athecate dinoflagellates will also be undertaken, as this is an important but uncertain parameter, which greatly affects estimates of gross growth efficiencies and biomass estimations.
