E. Gaard, The zooplankton community structure in relation to its biological and physical environment on the Faroe shelf, 1989-1997, J PLANK RES, 21(6), 1999, pp. 1133-1152
The Faroe shelf water is separated from the offshore water by a persistent
tidal front, which surrounds the islands. This shelf water contains a nerit
ic zooplankton community, which, regarding species composition, production,
seasonal development and environmental conditions, is quite different from
that in the surrounding ocean. While during spring and summer the zooplank
ton in the oceanic environment are dominated by the copepod Calanus finmarc
hicus, the zooplankton in the shelf water are largely dominated by neritic
copepods, mainly Acartia longiremis and Temora longicornis. Calanus finmarc
hicus occurs in interannually highly variable abundance in the Faroe shelf
ecosystem. Meroplanktonic larvae, mainly Balanus spp. and decapod larvae, a
re also common in the shelf water during spring and summer. During the peri
od presented (1989-1997), the Faroe shelf ecosystem has undergone very larg
e changes in abundance of different zooplankton species. The midsummer abun
dance of C.finmarchicus, which originally is advected into the shelf from t
he open ocean, fluctuated from similar to 400 copepods m(-3) in 1989 to sim
ilar to 25 copepods m(-3) in 1994, and at the same time the neritic zooplan
kton increased from similar to 120 m(-3) in 1989 to 450 m(-3) in 1994. Cons
equently, the midsummer biomass in the shelf fluctuated by a factor of 10 d
uring the same period. It is presumed that this variability between oceanic
- and neritic-dominated zooplankton, their sizes and their biomass has grea
tly affected the entire pelagic ecosystem.