Kills of adult herring occurred in two locations in the southwestern Bay of Fundy in July 1979 during a bloom of the toxic dinoflagellate Gonyaulax excavata. Fish showed the same symptoms as in a herring kill linked to G. excavata toxins in 1976. Herring stomachs contained G. excavata toxins (66–245 μg/100 g guts), the cladoceran Evadne nordmanni, and yellow-brown material probably of algal origin. At the time of the kills the zooplankton community was overwhelmingly dominated by E. nordmanni. Furthermore, bioassays showed the presence of G. excavata toxins in the zooplankters (18 μg/g wet plankton). Combined with evidence from the 1976 kill in which pteropods were vectors of the toxins, and with results from recent field and laboratory studies, these new observations and results substantiate that (1) G. excavata toxins can, and do, cause herring kills in nature with planktonic herbivores, E. nordmanni in this case, acting as vectors, and (2) the toxin transfer mechanism is a general phenomenon among herbivorous zooplankton. Similar food chain events may affect finfish in other areas of the world which experience blooms of toxic dinoflagellates.Key words: dinoflagellate toxins, Gonyaulax excavata, herring kills, Clupea harengus harengus, cladoceran, Evadne nordmanni, red tides, zooplankton, fish kills
Digestion and alteration of the biochemical constituents of a diatom (Thalassiosira weisflogii) ingested by an herbivorous zooplankton (Calanus pacificus)
