Can grazers help reduce the frequency and abundance of harmful algal blooms? We are considerably closer to the answer to this "top down control" question because of some recent work comparing grazing rates of copepod grazing on toxic and non toxic strains of the same algal species. As it turns out, if the toxin is a neurotoxin, copepods can detect toxic cells before they are ingested. Neurotoxins cause copepods to shut down their feeding activity.
On a non toxic strain of the same algal species, feeding continues. If the algal toxins are not neurotoxins, but rather cytotoxins that disrupt membranes, copepod grazing is not significantly different on the toxic and non toxic algae. The data from this study will inform a species specific harmful algal bloom models to help predict the formation and persistence of blooms.