Saumweber, W.1
1Graduate School of Oceanography, University of
Rhode Island, Narragansett, RI 02882
The calanoid copepod, Calanus finmarchicus, dominates epipelagic
mesoplankton biomass in the Gulf of Maine from January to June. It
is currently believed that this large spring population develops
primarily from a seed population of diapausing animals that
overwinter in the Gulf of Maine's three deep basins: Wilkinson,
Georges, and Jordan. This seed population in turn is thought to
consist mostly of animals that developed during the previous spring
bloom and have since been in diapause for six months or more.
However, recent work with populations of C. finmarchicus in the
Eastern Atlantic suggests that the deep water in the Gulf of Maine
may be too warm for diapausing animals to survive the required six
months. To investigate this possibility, a new nitrogen specific
respiration model has been developed for diapausing stage C5 C.
finmarchicus in the Gulf of Maine. Stage C5 C. finmarchicus were
collected during July and September 2003 from Wilkinson and Georges
Basins using both a MOCNESS and the suction sampler of the Johnson
Sea Link II submersible. Metabolic rates were measured using
Winkler incubation techniques in the field and a Micro-Oxymax gas
analyzer on shore. Oxygen consumption rates measured in the field
in July and September were not significantly different but were
higher than rates measured on shore. In order to predict potential
survival time, the shore measured nitrogen specific rate was applied
to individual C. finmarchicus from the Gulf of Maine that were
caught and measured during the summer and fall of 2001. Results
suggest that diapausing animals caught in June have a survival
window of two to three months and that significant starvation
mortality will accrue by August. Strong changes in the size
distribution of C. finmarchicus between June and August and August
and November support these predictions and suggest that there is a
significant addition of animals to the diapausing population, either
from advection or a surface population that is actively reproducing.