Bochdansky, A. B.. Queen's University, bochdans@biology.queensu.ca
Deibel, D. B.. Ocean Sciences Centre, Memorial University of Newfoundland, ddeibel@morgan.ucs.mun.ca
Bushell, V. Ocean Sciences Centre, Memorial University of Newfoundland, vivian@cs.mun.ca

 
INTERACTIONS OF CALANUS AND FRAGILARIOPSIS DURING THE SPRING BLOOM: CLEARANCE RATE REDUCTION DUE TO LONGER DIATOM CHAINS?
 
Fragilariopsis and Calanus are key genera in global material and energy fluxes warranting closer examination of the dynamics of their interaction. During the spring diatom bloom on the Grand Banks off Newfoundland, the phytoplankton community was dominated by Fragilariopsis (> 95 % of total cells) and the copepod community >1 mm by Calanus (ca. 80% by number). In bottle incubations at in situ temperatures in the dark, Fragilariopsis was cleared by copepods at the same rate as other phytoplankton genera. However, carbon-specific clearance rates of Calanus were two-fold higher at an on-shelf time series station (90 m) than at a second station at the shelf break (2,300 m). Phytoplankton species composition and temperature were similar at the two stations, but food concentration was 50% higher at the shelf break. This difference in food concentration does not seem sufficient to explain the difference in clearance rates indicating that other factors are involved. Since we found evidence of the copepods breaking long chains of Fragilariopsis into smaller fragments, we hypothesize that reduced clearance rates are at least partly due to the longer handling time associated with the 3-times longer chain length at the shelf break station.
 
Day: Tuesday, Feb. 2
Time: Poster
Location: Sweeney Center
 
Code: SS01TU0809S