Growth of Calanus finmarchicus on Georges Bank
R. G. Campbell, E. G. Durbin, and J. A. Runge
Growth
and molting rates of Calanus finmarchicus were measured in
shipboard incubations on Georges Bank during 1994, 1995, 1997, and
1999 as part of the US GLOBEC NW Atlantic / Georges Bank program.
Molting rates of copepodite stages were highly variable and not
related to chlorophyll a, but increased with temperature within a
stage. However, molting rates of naupliar stages were positively
correlated with both temperature and chlorophyll a. Growth rates of
copepodite stages were not related to temperature, but there was a
weak positive correlation with chlorophyll a. When copepods were
food limited, growth rates could be enhanced by enriching the ambient
water with a mixed phytoplankton culture while molting rates were
unchanged, which suggested that molting was not as tightly coupled to
food as growth.
During
April on the southern flank of the Bank, there were periods when food
limitation was severe. This was especially true during April 1997.
These episodes of food limitation may in part be responsible for the
patterns in abundance and stage distribution of Calanus
observed on the Bank. Food limitation may be partially responsible
for the low numbers of Calanus nauplii on the southern flank
of the Bank in May observed most years during zooplankton broadscale
surveys. However, on the crest of the Bank where Calanus
nauplii are low in abundance during most of the winter / spring
period, predation and / or advective processes appear to be more
important in controlling these patterns because we did not find
evidence that food limitation was important.