Comparisons of Video Plankton Recorder & MOCNESS
Measurements of Zooplankton from a Stratified Region of Georges
Mark C. Benfield, Cabell S. Davis, Peter H. Wiebe, Scott M.
Gallager, R. Gregory Lough, and Nancy J. Copley.
Abstract for AGU 1996.
A two-vessel exercise was conducted over the southern flank of
Georges Bank during the onset of
vernal startification in May 1992. The Video Plankton Recorder
(VPR), a towed video system, was used to map out the fine-scale
distributions of zooplankton to a depth of 70 m along a trackline
which described a regular grid (3.5 x 4.5 km) in Lagrangian space.
A second vessel following a parallel course conducted
MultipleOpening/Closing Net and Environmental Sensing System
(MOCNESS) sampling during the last section of the grid which
provided an opportunity to compare data from the two systems. Both
the VPR and MOCNESS provided similar data on the taxonomic
composition of the plankton which was numerically dominated by
copepods (Calanus, Pseudocalanus, Oithona), pteropods (Limacina)
and larvacenans (Oikopleura). The absence of rare (<43.1 m^-3)
species from the VPR data set was a consequence of the small volume
sampled (0.0694 m^3) by the highmagnification comera while fragile
gelatinous taxa were undersampled by the MOCNESS. Estimates of
copepod and pteropod concentrations were comparable for the two
gear types. The VPR represents a powerful tool for rapid surveys of
the micro- to fine-scale structure of zooplankton assemblages
either alone, or in conjunction with other sampling techniqes.