Meeting Abstract
Saxitoxins (STX) are paralytic alkaloids produced by marine dinoflagellates in response to biotic and abiotic stressors yielding harmful algal blooms. Because STX impacts coastal communities to a greater extent than would be predicted by its relative abundance it has been referred to as a “molecule of keystone significance” in reference to Robert Paine’s Keystone Species Concept. Pisaster ochraceus, the predator upon which Paine’s concept was founded, inhabits waters regularly plagued by harmful algal blooms, but the effects of STX on Pisaster have not yet been investigated. Here, we used laboratory and field experiments to examine the potential consequences of STX exposure on sea star feeding, substrate attachment, and fertilization success. Pisaster exhibited similar feeding behaviors when offered non-toxic prey, STX-containing prey, or a combination of the two. Though feeding behavior is unaffected, consumption of STX poses a physiological tradeoff. Sea stars in the laboratory and field had significantly lower substrate attachment thresholds after either being exposed to or consuming STX. HPLC analysis indicated an accumulation of STX (and structural analogues) in sea star viscera, likely due to trophic transfer from toxic prey. Fertilization success tended to decrease when gametes were exposed to high, yet ecologically relevant STX concentrations. These findings suggest that the molecule of keystone significance, STX, produced during harmful algal blooms extends its impacts to rocky intertidal communities by way of the keystone predator Pisaster ochraceus.
