The effect of the toxic dinoflagellate Alexandrium fundyense on the fitness of the calanoid copepod Calanus finmarchicus

Abstract

<p class="first" id="P1">Inshore and offshore waters of the Gulf of Maine (USA) have spring/summer harmful algal blooms (HABs) of the toxic dinoflagellate <i>Alexandrium fundyense</i>, which is responsible for paralytic shellfish poisoning (PSP) in humans. The calanoid copepod <i>Calanus finmarchicus</i> co-occurs with <i>A. fundyense</i> during the seasonal blooms. At that time, <i>C. finmarchicus</i> population abundances are high, dominated by immature copepods preparing for diapause, and by actively-reproducing adults. High survival has been reported for copepods exposed to toxic <i>A. fundyense</i>, but little is known about possible sublethal effects. In this study, <i>C. finmarchicus</i> adult females were fed either a control diet of non-toxic <i>Rhodomonas</i> spp. or one of two diets containing either low dose (LD) or high dose (HD) levels (50 and 200 cells mL ⁻¹, respectively) of toxic <i>A. fundyense</i> for a total of 7 days in two independent experiments. As expected, ingestion of the dinoflagellate had no effect on copepod survival and grazing activity. However, significant reductions of egg production and egg viability were observed in <i>C. finmarchicus</i> females fed on either experimental diet. After the 7-day experiment, total nauplius production by females on the LD and HD diets was reduced by 35% to 75% compared to the control females. These results suggest that blooms of <i>A. fundyense</i> in the Gulf of Maine may be an environmental challenge for <i>C. finmarchicus</i> populations, with a potential negative effect on copepod recruitment. </p>