Prey switching by Acartia clausi

Experimental evidence and implications of intraguild predation assessed by a model

Ingrid Gismervik*, Tom Andersen

*Corresponding author for this work

    Research output: Contribution to journalArticle

    79 Citations (Scopus)


    Switching between algal (Thalassiosira weissflogii) and ciliate (Strobilidium undinum) food by the marine copepod Acartia clausi was investigated in the laboratory by short incubation experiments with 14C-labeled prey. A. clausi displayed a Holling type 3 functional response (which differed significantly from a type 2 response, p < 0.05) for ciliates when there was a constant abundance of algae present, and likewise for algae when there was a constant abundance of ciliates present. The results were implemented in a mathematical model to investigate the effect of different functional responses on a simple food web comprised of nutrient, algae, ciliates and copepods. In the model, ciliates and copepods competed for resources (algae) and ciliates were also prey for copepods. This blend of predation and competition among copepods and ciliates corresponds to intraguild predation as defined by Polis and Holt (1992; Trends Ecol Evol 7:151-154). Stable solutions with all state variables present were found over a range of nutrient concentrations when the copepods displayed type 3 functional responses. On the contrary, when copepods displayed type 2 responses, such stable solutions were only found at very low input nutrient concentrations. Coexistence of ciliates and copepods further required that ciliates had a lower threshold prey concentration for positive net growth than copepods.

    Original languageEnglish
    Pages (from-to)247-259
    Number of pages13
    JournalMarine Ecology Progress Series
    Publication statusPublished - 16 Oct 1997


    • Acartia clausi
    • Algae
    • Ciliates
    • Coexistence
    • Copepods
    • Intraguild predation
    • Model
    • Prey switching
    • Stability

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