An experimental analysis of harmful algae–zooplankton interactions and the ultimate defense

Emily J. Remmel, Nicole Kohmescher, James H. Larson and K. David Hambright

Limnol. Oceanogr., 56(2), 2011, 461-470 | DOI: 10.4319/lo.2011.56.2.0461

ABSTRACT: We examined effects of the invasive, toxigenic haptophyte Prymnesium parvum on grazing rates, feeding behaviors, and life-history characteristics of clonal lineages of three daphniid zooplankton species. Grazing experiments revealed similar clearance rates for P. parvum and a common green alga. Behavioral observations revealed no significant effects of P. parvum on daphniid feeding behaviors after 30 min, but major declines in appendage beat rates after 1 h. Chronic exposure (10 d) to P. parvum resulted in severe reductions in daphniid growth rates, age at first reproduction, fecundity, and survivorship at densities as low as 7750 cells mL−1. Thus, in addition to direct fish mortality during P. parvum blooms of 50,000–200,000 cells mL−1, the entire food web of an invaded system may be subjected to potentially severe negative consequences even at nonbloom densities of P. parvum.

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