Copepod feeding selectivity on microplankton, including the toxigenic diatoms Pseudo-nitzschia spp., in the coastal Pacific Northwest

As part of the Pacific Northwest ECOHAB project, we measured clearance rates and feeding selectivity of calanoid copepods off the coast of Washington State, USA, during fall of 2003. We tested the hypothesis that copepods discriminate amongst prey, particularly against the toxic diatoms Pseudo-nitzs...

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Bibliographic Details
Published in:Marine ecology. Progress series (Halstenbek) 2006-11, Vol.326, p.207-220
Main Authors: BRADY OLSON, M, LESSARD, Evelyn J, WONG, Chung Huen J, BERNHARDT, Megan J
Format: Article
Language:English
Subjects:
Acartia
Acartia longiremis
Animal and plant ecology
Animal, plant and microbial ecology
Biological and medical sciences
Calanus pacificus
Crustacea
Fundamental and applied biological sciences. Psychology
Invertebrates
Marine
Metridia pacifica
Oithona
Paracalanus
Prorocentrum
Pseudo-nitzschia
Pseudocalanus
Sea water ecosystems
Synecology
Thalassiosira
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Summary:As part of the Pacific Northwest ECOHAB project, we measured clearance rates and feeding selectivity of calanoid copepods off the coast of Washington State, USA, during fall of 2003. We tested the hypothesis that copepods discriminate amongst prey, particularly against the toxic diatoms Pseudo-nitzschia spp. in natural assemblages from this highly productive, upwelling environment. Seven grazing experiments were conducted across and along the shelf using the copepods Calanus pacificus, Metridia pacifica, Acartia longiremis and a small community assemblage dominated by Acartia spp., with minor contributions from Pseudocalanus spp., Paracalanus spp. and Oithona spp. Three general patterns emerged from our experiments. First, all copepods, except A. longiremis in 1 experiment, showed neutral preference or discriminated against Pseudo-nitzschia, but preference did not appear related to cellular domoic acid concentrations. Second, the dominant prey biomass contributors in each experiment were cleared at low rates relative to other prey types. In most cases the dominants were the diatom Thalassiosira spp. or the autotrophic dinoflagellates Ceratium spp. and Prorocentrum spp. The third pattern was high preference for microzooplankton. High clearance on microzooplankton can result in trophic cascades, which were evident in our size-fractionated chlorophyll data. These patterns indicate that copepods could have both direct and indirect effects on the plankton community composition on the Washington coast. However, our estimates of total potential grazing suggest that copepod grazing impact on Pseudo-nitzschia populations is negligible.
ISSN:0171-8630
1616-1599
DOI:10.3354/meps326207