Lethal and sublethal effects of the toxic dinoflagellate, Alexandrium fundyense on three species of larval fish

The toxic dinoflagellate Alexandrium fundyense, produces paralytic shellfish poisoning (PSP; saxitoxin and its derivatives) toxins and has been implicated in fish kills during bloom events. Alexandrium is at the base of the aquatic food web, and is consumed by a variety of organisms, which can accumulate the toxin. Alexandrium occurs temporally and spatially in estuaries with larval fish during summer and fall. We investigated lethal and sublethal effects of PSP-toxin exposure from toxic, Alexandrium fundyense on larval stage sheepshead minnow, Cyprinodon variegatus and mummichog, Fundulus heteroclitus, and newly-settled winter flounder, Pseudopleuronectes americanus using several different Alexandrium → copepod → fish food chains.; Copepods were exposed to toxic A. fundyense, while control copepods were fed a non-toxic strain of A. tamerense. Following exposure, toxic copepods were fed to fish. First-feeding sheepshead minnow larvae were also exposed to Alexandrium cells directly.; In mortality experiments fish were fed 1 toxic copepod every 15 minutes until mortality occurred. Symptoms of lethal PSP-toxin exposure included erratic swimming, loss of equilibrium and death. All three fish species experienced these symptoms, including sheepshead minnows exposed directly to toxic cells.; Sublethal exposures to PSP-toxins were followed by prey capture, predator avoidance, and swimming performance experiments. Respiration rate and gut evacuation rate was also determined for winter flounder and sheepshead minnow. Cell selection ability was also investigated in sheepshead minnow larvae exposed directly to Alexandrium. All three species exhibited sublethal effects from vector-mediated exposure and first-feeding Cyprinodon larvae were highly sensitive to direct exposure. Winter flounder and mummichogs exhibited reduced swimming performance. Predator avoidance ability of winter flounder was also affected; as was prey capture ability of mummichogs. Direct exposure to toxic cells reduced prey capture and predator avoidance response in sheepshead minnow, which did not differentiate between toxic and non-toxic Alexandrium cells.; PSP-toxin exposure induced both lethal and sublethal (behavioral) effects on all three species tested. Behavioral abnormalities that reduced prey capture or predator avoidance ability can impact larval survival and could facilitate the transmission of PSP toxins through the food web. This study provides baseline information on sublethal effects of PSP-toxin exposure, which is currently lacking in the literature.