Graduate Thesis Or Dissertation
 

Transport of the copepod, Calanus finmarchicus, in the northwest Atlantic during diapause

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  • The copepod Calanus finmarchicus is the most important and biomass dominant mesozooplankter in the temperate-boreal North Atlantic. C. finmarchicus has an overwintering phase, termed diapause, during which it descends to great depths (300-2000m) and is metabolically quiescent for up to ten months. Changes in the currents at depth due to climate variation may influence the spring distribution and abundance of C. finmarchicus. We evaluated the potential transport of C. finmarchicus during diapause in the Labrador Sea and the Scotian Shelf under positive and negative North Atlantic Oscillation (NAO) index conditions with a coupled bio-physical individual-based model (IBM). The physical simulation was a basin-scale ROMS model using mean forcing for 1980-1993 (1962-1971) from NCEP/NCAR re-analysis fields to generate idealized positive (negative) NAO conditions. The biological IBM consisted of a particle-tracking model with simulated biological behavior. We modeled four mechanisms that have been proposed for diapause emergence: an external, photoperiod-dependent emergence trigger and three internal, temperature-controlled lipid consumption triggers. Copepods were seeded in the Labrador Sea and the Scotian Shelf for positive and negative NAO climatic conditions. An internal, lipid-based diapause emergence trigger based on Saumweber and Durbin (2006; Deep Sea Res. II, 53 (23-24), 2597-2617) best reproduced field observations of the dates of C. finmarchicus appearance at the surface following diapause. The phase of the NAO had an effect on potential transport distance of C. finmarchicus during diapause on the Scotian Slope, and in the northeastern Atlantic. In the Labrador Sea, the phase of the NAO had little effect on potential transport and duration of diapause.
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