Transport and retention of the copepod Calanus finmarchicus during diapause in the deep Gulf of Maine

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Variability in the transport of diapausing individuals to productive shelf areas has been hypothesized to influence the abundance of the dominant copepod species Calanus finmarchicus in several regions of the North Atlantic. Using Lagrangian particle path simulations, we examined the effect of variability in environmental forcing and copepod behavior on the retention of diapausing C. finmarchicus in the deep Gulf of Maine, USA, a source region for Georges Bank. Retention in the Gulf of Maine was relatively high, > 45 % over six months, in all simulations. Copepod behavior during diapause was a greater source of uncertainty for retention than was variability in wind or Scotian Shelf inflow. Retention increased with the initial depth of diapausing copepods, and vertical positioning behavior had a strong influence on retention for simulations started at depths greater than 150 m. Variability in Scotian Shelf inflow had a greater influence on retention than did variability in alongshore winds. Both alongshore wind and Scotian Shelf inflow influenced transport from slope waters and the Northeast Channel into the deep Gulf of Maine. Transport patterns among Gulf of Maine sub-regions are in qualitative agreement with observed seasonal and spatial patterns in diapausing copepod length, which suggest persistence of early diapausers in Wilkinson Basin.