TRANSFER OF HARMFUL ALGAL TOXINS FROM GRAZERS TO PREDATORS

As harmful algal blooms become more common and intense, the production of cyanotoxins, like microcystins, becomes more problematic. These toxins unequivocally impact aquatic ecosystems, but there is no current consensus on if or how these toxins are transferred through food webs. We used an experimental aquatic ecosystem including Microcystis, the herbivorous zooplankter, Daphnia pulex, and predatory Enallagma damselfly larvae, to test the hypothesis that microcystin would be transferred across trophic levels. We then examined the mechanism for this transfer, testing for the relative contribution of microcystin transferred from Daphnia gut contents versus microcystin in Daphnia tissue. Then we estimated the efficiency of toxin transfer between Daphnia and Enallagma. Overall, we found that microcystin was transferred across trophic levels in this system, but concentrations decreased with increasing trophic level, a process known as biodilution. Nearly all the toxin transferred from Daphnia to Enallagma came not from Daphnia gut contents, but from Daphnia tissue. A surprisingly high fraction of microcystin consumed by Enallagma in the form of microcystin-contaminated Daphnia was incorporated into the tissue of Enallagma. Together, these results demonstrate that the transfer of toxins serves as another mechanism through which food webs, both aquatic and terrestrial, may be negatively impacted by harmful algal blooms.

Presentation Preference: Oral

Primary Presenter: Jessica Beyer, University of Oklahoma (beyer@ou.edu)

Authors:

Dani Glidewell, University of Oklahoma  (daniglidewell@gmail.com)

K. David Hambright, University of Oklahoma  (dhambright@ou.edu)