Copepod grazing and its potential impact on the phytoplankton development in the Barents Sea |
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| Authors: | ULF BÅMSTEDT HANS CHRISTIAN EILERTSEN KURT S TANDE DAG SLAGSTAD HEIN RUNE SKJOLDAL |
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| Institution: | Department of Fisheries and Marine Biology, High-Technology Centre N-5020 Bergen, Norway;Norwegian College of Fisheries, University of Tromsø, P.O. Box 3083 Guleng, N-9001 Tromsø, Norway;SINTEF Automatic Control, N-7034 Trondheim-NTH, Norway;Institute of Marine Research, P.O. Box 1870 Nordnes, N-5024 Bergen, Norway |
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| Abstract: | Compiled data from published and unpublished sources on copepod grazing of the large-sized copepods in the Barents Sea give wide ranges in grazing rates. Approximate average values indicate daily rations of 7–18% for copepodite stages V and VI and considerably higher values for the earliest copepodite stages. It is demonstrated that individual variability in gut fullness of copepods from a given locality is typically very high and not closely related to variable food abundance or depth of occurrence. There is no diel feeding rhythm during the summer, and even when relating copepod grazing to a number of biotic and abiotic factors through stepwise linear regression analysis, much of the variability remains unexplained. It is suggested that feeding behaviour, food quality and feeding history of the copepods all play important roles as factors which regulate copepod grazing. Model simulations on the phytoplankton succession, using literature data on laboratory-determined growth characteristics for solitary cells and colonies of the prymnesiophyte Phaeocystis pouchetii and large diatoms, indicate that the extent of the mixed layer and selective grazing by zooplankton are important factors that may explain the occurrence of dense blooms of P. pouchetii colonies, frequently observed during the spring. |
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