New Zealand Journal of Marine and Freshwater Research abstracts
Composition of macrozooplankton assemblages associated with the formation and decay of pulses within an upwelling plume in greater Cook Strait, New Zealand
JANET M. BRADFORD-GRIEVE
ROBIN C. MURDOCH
BRUCE E. CHAPMAN
New Zealand Oceanographic Institute National Institute of Water and Atmospheric
Research Ltd
Private Bag 14 901, Kilbirnie Wellington, New Zealand
Abstract
The structure of macrozooplankton assemblages associated with an upwelling plume was studied at an active upwelling site located in greater Cook Strait, New Zealand. Zooplankton within the plume divided into five geographically coherent assemblages, generally reflecting temporal changes in the zooplankton community as the upwelled water of the plume advected from west to east into greater Cook Strait - as indicated by the movement of three separate pulses of upwelled water. Near the source of the upwelling plume, inshore zooplankton biomass decreased as did the numbers of several coastal species, and oceanic species were introduced into nearshore waters. The capacity of copepods and the euphausiid
Nyctiphanes australis to reproduce was reduced, and the diversity indices and proportion of herbivorous copepods decreased, relative to water south of the plume. Downstream from the plume source, in the eastern part of the upwelling plume, many zooplankton species were distributed in a manner reflecting the physical characteristics of the plume, whereas oceanic forms were entrained along the offshore border of the plume. The proportion of omnivorous copepods was reduced and the capacity of herbivorous copepods and
Nyctiphanes australis to reproduce increased. The abundance of selected coastal copepods was apparently related to their vulnerability to offshore transport on an upwelling coast. A comparison of the Kahurangi and Mauritanian
upwelling plumes suggests that the upwelled new nitrogen is converted to zooplankton biomass more efficiently in greater Cook Strait.
Keywords zooplankton; upwelling plume; distribution; horizontal; vertical; Cook Strait; New Zealand.
New Zealand Journal of Marine and Freshwater Research, 1993: Vol. 27: 1-22 0028-8330/93/2701-0001 $2.50/0 © The Royal Society of New Zealand 1993
Received 12 February 1992; accepted 17 November 1992
PDF file of entire paper: medium quality (2035K); (scanned from paper original: notes about this process)
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