Functional responses of copepod nauplii using a high efficiency gut fluorescence technique
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To investigate copepod nauplii ingestion rates on phytoplankton, we have adapted the traditional gut fluorescence technique as it can be used with lower gut pigment concentrations. With the improved technique, laboratory experiments were performed to estimate functional responses for nauplii of Calanus helgolandicus and Centropages typicus. Nauplii were raised from eggs to copepodites and the experiments were performed with stages NIV-NV. Gut evacuation rates and ingestion rates were measured on Isochrysis galbana at different concentrations. Specific ingestion rates ranged between 0.038–0.244 μg C μg−1 nauplii C d−1 for C. typicus and 0.041–1.412 μg C μg−1 nauplii C d−1 for C. helgolandicus. Both species showed a type III functional response, reaching a saturation concentration at around 600 μgC l−1 for C. typicus and 800 μgC l−1 for C. helgolandicus.
KeywordsPhytoplankton Ingestion Rate Functional Response Phytoplankton Concentration Specific Ingestion Rate
This work was supported by the collaboration specific agreement between Universidad de Oviedo and Instituto Español de Oceanografia: “Control a largo plazo de las condiciones químico-biológicas en la plataforma continental de Asturias”, the Ministerio de Educacion y Ciencia (MEC) project CARPOS (REN/09532-C03–03) and a FPU grant by MEC to E.L. We are indebted to the crew of the R/V “Jose Rioja” and “Sepia” for their help to collect zooplankton and seawater. We thank the “Group of Biological Oceanography” of the University of Oviedo for their help with the sampling and their helpful assistance in the laboratory and D. Bonnet, L. Yebra and T. Smith (Plymouth Marine Laboratory) for their technical assistance and constructive criticism. We also want to thank J. L. Acuña for his useful comments on functional responses and A.G. Nicieza and J. Arrontes for their statistical assessment. All the experiments were performed in compliance with the laws of Spain and UK.
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