Publication Date



Open access

Embargo Period


Degree Type


Degree Name

Master of Science (MS)


Marine Biology and Ecology (Marine)

Date of Defense


First Committee Member

Larry E. Brand

Second Committee Member

Kathleen Rein

Third Committee Member

Andrew C. Baker


Phycotoxins are secondary metabolites produced by dinoflagellates and other algae. Despite their notorious role in neurotoxicity to higher trophic level species, it is still unknown why algae produce phycotoxins. This study reviewed the available literature, that forms our current knowledge on the potential ecological roles of phycotoxins. It also experimentally examined three untested hypotheses. First, the role of phycotoxins in chemical defense against bacteria was tested. The second hypothesis examined the role of toxins in dissipating excess energy from intense light. Lastly, the role of toxins in alleviating copper toxicity was tested. Two bloom-forming toxic dinoflagellates (Alexandrium catenella a saxitoxin producer, and Karenia brevis a brevetoxin producer) were selected for this work. With A. catenella, three high toxic strains, one low toxic strain, and two nontoxic strains were selected. With K.brevis one high toxic and one low toxic strain were chosen. The difference in toxicity was used to determine if toxic strains were more resistant to stress than the nontoxic strains of the same species. This research did not find evidence that toxin production provides an advantage to toxic algae against the three tested stress factors. Instead, the results show that nontoxic strains were consistently more resistant to stress than the toxic strains in both species. Toxic algae vulnerability may be the result of higher energy and nutrient allocation to toxin production.


Algae; Phytoplankton; Harmful Algal Blooms; Phycotoxins; Chemical defense; Energy dissipation; Copper toxicity