New Zealand Journal of Marine and Freshwater Research abstracts
Biomass, carbon ingestion, and ammonia excretion by zooplankton associated with an upwelling plume in western Cook Strait, New Zealand
MARK R. JAMES1 VAUGHAN H. WILKINSON2
Taupo Research Laboratory
Department of Scientific and Industrial Research
P. O. Box 415, Taupo, New Zealand
2Fisheries Management Division Ministry of Agriculture and Fisheries P. O. Box 3437, Auckland, New Zealand
Abstract
The biomass, elemental composition, and rates of ingestion and excretion by macrozoo-plankon associated with the upwelling plume off the north-west coast of the South Island, New Zealand, were investigated in March-April 1983. Ingestion and excretion rates of the major zoo-plankton species were combined with abundance data to determine the spatial and temporal variability which may influence phytoplankton dynamics in the plume system. Zooplankton biomass near Cape Kahurangi was dominated by small copepods like
Acartia ensifera (up to 60%). In the South Tar-anaki Bight, larval and adult forms of the euphau-siid
Nyctiphanes australis commonly contributed up to 60% of biomass. However, the carbon ingestion and ammonia excretion patterns of
N. australis were spatially displaced from those of the total zooplankton community in the South Taranaki Bight because of higher weight-specific metabolic rates for the smaller copepods. Close to the focus of the upwelling near the Kahurangi Shoals, grazing pressure on the phytoplankton was high, but as the upwelled water was adverted into the Taranaki Bight, carbon production exceeded utilisation by zooplankton. Relatively high rates of ammonia excretion were also associated with peak zooplankton biomass near the Kahurangi Shoals and in the eastern Taranaki Bight.
Keywords elemental composition; excretion; metabolic rates; O: N ratio; upwelling; West Coast; zooplankton
New Zealand Journal of Marine and Freshwater Research, 1988, Vol. 22: 249-257 Crown copyright 1988Received 18 June 1987; accepted 22 September 1987
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