SS1.04 Small-scale Biophysical Coupling in Plankton Ecology
Date: Thursday, June 13, 2002
Time: 4:00:00 PM
Location: Esquimalt
 
CampbellRW, University of Victoria, Victoria, Canada, rwcampbe@uvic.ca
Dower, J, F, University of Victoria, Victoria, Canada, dower@uvic.ca
 
DEPTH DISTRIBUTIONS OF OVERWINTERING COPEPODS: THE ROLE OF BUOYANCY REGULATION
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The large calanoid copepods that dominate the mesozooplankton of high-latitude pelagic ecosystems undergo considerable annual ontogenic vertical migrations, spending much of the year overwintering in a quiescent state at depth. In general, vertical distributions are poorly described in these copepods, and it is unknown how species-specific vertical distributions are regulated. Since overwintering copepods are inactive, it has been proposed that they overwinter at a depth of neutral buoyancy (determined partially by their species-specific lipid profile). However, these lipids are more compressible than seawater and thus the depth of neutral buoyancy for an animal is not stable: if displaced up (down) from that depth, a copepod will continue to ascend (sink). Buoyancy control is not well understood in the crustacea. We will present results from experiments conducted to determine how Neocalanus plumchrus, the dominant mesozooplankter in the Northeast Pacific, modulates its buoyancy. The results, presented in the framework of a model for the buoyancy of a copepod, will be used to illustrate the relative importance of lipid and water content on buoyancy in relation to overwintering depth distributions