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Description and use of an improved method for determining estuarine zooplankton grazing rates on phytoplankton

Description and use of an improved method for determining estuarine zooplankton grazing rates on... 227 54 54 4 4 F. B. Griffiths J. Caperon CSIRO Division of Fisheries and Oceanography P.O. Box 21 2230 Cronulla New South Wales Australia Hawaii Institute of Marine Biology University of Hawaii Coconut Island P.O. Box 1346 96744 Kaneohe Hawaii USA Abstract A method of rapidly determining zooplankton grazing rates on natural mixed phytoplankton populations using 14 C is described. The method simplifies the design of grazing experiments as the grazing time can be kept short enough to prevent recycling of the isotope, and growth of the phytoplankton substrate. Very high specific activity, 14 C-labelled phytoplankton concentrated either by centrifugation or sieving, may be used either as the sole grazing substrate, or as a tracer in natural mixed phytoplankton. Zooplankton, confined in glass jars at either ambient, or higher than ambient concentrations, are permitted to feed on the phytoplankton for periods of 30 min and 2 h, and are then separated by sieving. The zooplankton community grazing rate, or, if the samples are sorted into species, the individual species grazing rates, can be determined after scintillation counting of the zooplankton. The rate of appearance of 14 C-labelled phytoplankton in the zooplankton is an estimate of the grazing rate, and the slope of the line joining the grazing rates at various phytoplankton concentrations gives an estimate of the grazing rate constant for the zooplankton population. The method provides a quick way of obtaining both zooplankton population, and individual species grazing rates on natural mixed phytoplankton. In two experiments, labelled phytoplankton was used as the sole grazing substrate in concentrations ranging between 0.4 and 5 times ambient levels. Grazing rate constants, for net-caught zooplankton concentrated to 46 times (Experiment 1) and 28 times (Experiment, 2) ambient estuarine levels were-0.14and-0.12 of the phytoplankton standing stock per day, respectively. There was a linear increase in the amount of phytoplankton grazed with an increase in phytoplankton concentration up to four times ambient phytoplankton levels. When tracer amounts of labelled phytoplankton were added to samples containing both phytoplankton and zooplankton at ambient concentrations the grazing rate constants were-0.28 and-0.42 of the phytoplankton standing stock per day. We conclude that zooplankton grazing was the major control factor of phytoplankton population size during October–November 1975 in South West Arm, Port Hacking, near Sydney, Australia. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Marine Biology Springer Journals

Description and use of an improved method for determining estuarine zooplankton grazing rates on phytoplankton

Griffiths, F.; Caperon, J.
Marine Biology , Volume 54 (4) – Oct 1, 1979
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References (23)

Publisher
Springer Journals
Copyright
Copyright © 1979 by Springer-Verlag
Subject
Life Sciences; Biomedicine general; Oceanography; Ecology; Microbiology; Zoology
ISSN
0025-3162
eISSN
1432-1793
DOI
10.1007/BF00395436
Publisher site
See Article on Publisher Site

Abstract

227 54 54 4 4 F. B. Griffiths J. Caperon CSIRO Division of Fisheries and Oceanography P.O. Box 21 2230 Cronulla New South Wales Australia Hawaii Institute of Marine Biology University of Hawaii Coconut Island P.O. Box 1346 96744 Kaneohe Hawaii USA Abstract A method of rapidly determining zooplankton grazing rates on natural mixed phytoplankton populations using 14 C is described. The method simplifies the design of grazing experiments as the grazing time can be kept short enough to prevent recycling of the isotope, and growth of the phytoplankton substrate. Very high specific activity, 14 C-labelled phytoplankton concentrated either by centrifugation or sieving, may be used either as the sole grazing substrate, or as a tracer in natural mixed phytoplankton. Zooplankton, confined in glass jars at either ambient, or higher than ambient concentrations, are permitted to feed on the phytoplankton for periods of 30 min and 2 h, and are then separated by sieving. The zooplankton community grazing rate, or, if the samples are sorted into species, the individual species grazing rates, can be determined after scintillation counting of the zooplankton. The rate of appearance of 14 C-labelled phytoplankton in the zooplankton is an estimate of the grazing rate, and the slope of the line joining the grazing rates at various phytoplankton concentrations gives an estimate of the grazing rate constant for the zooplankton population. The method provides a quick way of obtaining both zooplankton population, and individual species grazing rates on natural mixed phytoplankton. In two experiments, labelled phytoplankton was used as the sole grazing substrate in concentrations ranging between 0.4 and 5 times ambient levels. Grazing rate constants, for net-caught zooplankton concentrated to 46 times (Experiment 1) and 28 times (Experiment, 2) ambient estuarine levels were-0.14and-0.12 of the phytoplankton standing stock per day, respectively. There was a linear increase in the amount of phytoplankton grazed with an increase in phytoplankton concentration up to four times ambient phytoplankton levels. When tracer amounts of labelled phytoplankton were added to samples containing both phytoplankton and zooplankton at ambient concentrations the grazing rate constants were-0.28 and-0.42 of the phytoplankton standing stock per day. We conclude that zooplankton grazing was the major control factor of phytoplankton population size during October–November 1975 in South West Arm, Port Hacking, near Sydney, Australia.

Journal

Marine Biology – Springer Journals

Published: Oct 1, 1979

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