Rn. Head et al., A comparative study of size-fractionated mesozooplankton biomass and grazing in the North East Atlantic, J PLANK RES, 21(12), 1999, pp. 2285-2308
Measurements of biomass and grazing for three size classes of mesozooplankt
on were carried out at two drifting stations: at 59 degrees N, 20 degrees W
during a tracer release experiment, and at 37 degrees N, 19 degrees W at a
conventional drifting station. Mesozooplankton biomass at 59 degrees N did
nor vary between day and night (6.7 and 6.4 mg C m(-3) for night and day s
amples, respectively). At 37 degrees N, carbon biomass was much lower and i
n addition a diel cycle was observed (2.2 and 1.4 mg C m(-3) for night and
day samples, respectively). No one size fraction was the major contributor
to biomass at either station. At 59 degrees N, grazing was dominated by the
small size fraction for both day and night samples, and at 37 degrees N gr
azing was dominated by this size fraction during the day only. At 59 degree
s N, mean ingestion (57.1 and 91.1 mg C m(-2) day(-1) for day and night sam
ples, respectively) was much higher than at 37 degrees N (5.3 and 1.7 mg C
m(-2) day(-1) for day and night samples, respectively). Consumption of the
standing stock of phytoplankton (based on total chlorophyll a concentration
s) was higher at the southern station where 8.9% and 2.6% day(-1) of the st
anding stock was removed by night and day, respectively. Reverse diel consu
mption was observed at the northern station, where 1.5% (night) and 2.1% da
y(-1) (day) of the standing stock was removed. Comparisons are made between
the two time series, and the results are set in the context of a decade of
investigations into the role of mesozooplankton in this region of the Nort
h Atlantic.