Diel fluctuation in zooplankton grazing rate as determined from the downward vertical flux of pheopigments |
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| Authors: | N A Welschmeyer A E Copping M Vernet C J Lorenzen |
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| Institution: | (1) School of Oceanography, University of Washington, 98195 Seattle, Washington, USA;(2) Present address: The biological Laboratories, Harvard University, 16 Divinity Avenue, 02138 Cambridge, Massachusetts, USA |
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| Abstract: | The diel grazing activity of zooplankton was measured at a single study site in a temperate fjord, Dabob Bay, Washington, USA at several periods during spring, summer and fall of 1979–1981. Pheopigments were used as an indicator of herbivorous zooplankton activity. The downward vertical flux of pheopigment-containing fecal pellets was measured with sediment traps deployed over repetitive 4 h periods. Experiments were run for 24 to 36 h. A maximum in the flux of pheopigments was consistently noted within the euphotic zone during hours of darkness. Diel fluctuations in pheopigment flux showed amplitudes up to 29-fold. Nightly grazing activity accounted for 41 to 82% of the daily (24 h) grazing and was indirectly related to seasonal changes in daylength.Contribution No. 1405 from the School of Oceanography, University of Washington |
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