Tracking losses of brevetoxins on exposure to phytoplankton competitors: Ecological impacts

The frequent occurrence of devastating blooms of the harmful dinoflagellate Karenia brevis in the Gulf of Mexico has motivated research into bloom dynamics and potential mitigation strategies. The use of competing phytoplankton to lower waterborne concentrations of the most abundant and toxic brevetoxins produced during these blooms has been proposed. However the ecological impacts of using such biocontrol agents have not been addressed. This study investigated the impact on marine invertebrates of lowered brevetoxin concentrations due to the presence of competing phytoplankton. Even at low brevetoxin concentrations, the presence of the common diatom Skeletonema grethae ameliorated harmful toxic effects of brevetoxins upon the brine shrimp, Artemia salina, and reduced the incidence of negative physiological and morphological responses of the sea anemone Aiptasia pallida. In addition, brevetoxin biotransformation products formed by competing phytoplankton appear to be non-toxic or do not trigger the same physiological responses as brevetoxins in the model organisms used. These findings may impact the interpretation of ecotoxicological data gathered during bloom events, since the presence of phytoplankton competitors in Karenia blooms is likely to reduce the harmful effects seen on many marine invertebrates.

► Phytoplankton competitors lower waterborne concentrations of brevetoxins-1 and -2.
► We address some subsequent ecological impacts of using such a biocontrol agent.
► Skeletonema grethae ameliorated harmful effects of PbTx-2 on marine invertebrates.
► Biotransformation products formed by S. grethae are non-toxic to these marine invertebrates.
► Phytoplankton competitors in Karenia blooms are likely to reduce harmful effects.