Growth
of Calanus finmarchicus nauplii in source and on-Bank waters
of Georges Bank
D. J. Gifford, M. E. Sieracki, and J. R. Merrell
Calanus
finmarchicus is expatriate on Georges Bank. Populations do not
overwinter and must be recruited from off-Bank source waters each
spring. We hypothesized that naupliar growth rates would be higher in
productive on-Bank waters compared to less productive source waters
in regions adjacent to the Bank. Growth rates of laboratory-reared
nauplii were measured in experiments done in 3 source regions
(Georges Basin, Great South Channel, Scotian Shelf overflow) and 3
on-Bank regions (Bank Crest, Northeast Peak, Southern Flank) during
April and May 1997. Laboratory-reared nauplii were incubated in
microplankton assemblages from the various source and on-Bank
regions. Nauplii were harvested and preserved at the beginning of
each experiment and after 48 h incubation. Naupliar volume was
determined from optical sections which were created microscopically
using differential interference optics and image analysis. Contrary
to expectation, growth rate (as increase in biovolume) was higher in
source waters than in on-Bank waters in both April and May. The
highest growth rates (>100% increase in biovolume/d) were observed
in the Scotian Shelf overflow in both months. There was no
statistically significant relationship between growth rate and the
standing stock of chlorophyll.