Award: OCE-1130284

Toxic algal blooms are proliferating at unprecedented rates worldwide. These blooms can have dramatic negative effects on marine food webs. Moreover, these blooms represent a public health problem because of human consumption of shellfish and fish contaminated with the algal toxins. Our understanding of the factors that promote and determinate these blooms, and the effects of blooms on aquatic consumers is still limited. One important determinant for bloom initiation and persistence is the rate of toxin production and how much toxin is accumulated in algal cells. The higher the cell toxin content, the worse the effect on organisms that consume the cells. This project provided novel information and insight into prey toxin production. We have shown that prey toxin production is strongly stimulated by the presence of grazers. This can be interpreted as a defense mechanism of the prey. Toxin production, however, comes at a significant cost to the prey in the form of reduced cell growth. The major implication of these findings is that understanding the dynamics of antagonistic prey interactions is essential to modeling and managing blooms of toxic algae. Specific findings of the project are: A wide variety of animals (spanning several phyla) induced saxitoxin production in the dinoflagellate Alexandrium fundyense. The induction is dramatic (3-10 fold increase in toxin content relative to prey that are not exposed to predators). Hence, this project has provided strong evidence that measuring toxin production in the absence of grazers can result in severe underestimation. An effect of evolutionary history between predator and prey on induction of toxin production. That is, predators that persistently cohabit with a prey produce a kairomone that induces toxin production, whereas no kairomone is produced by predators naive to the prey. This finding points to a novel coadaptation dynamic. The existence of algal alarm cues that can also induce toxin production. A dramatic cost to toxin production manifested as a trade-off between toxin production and cell growth rate. This is the first such demonstration for marine phytoplankton. A new method to measure simultaneously cell toxin production and cell growth so that the fitness cost of toxin production can be determined. Discovery of a novel mechanism of toxicity by the dinoflagellate Alexandrium fundyense—production of reactive oxygen species, which severely reduce survival of protist grazers. This project provided support and professional development for two graduate students, one postdoctoral investigator, and research experience for several undergraduate students. The project also reached nonacademic audiences through educational and outreach efforts. Most notably, the project provided materials and ideas for high school teachers to develop research-based curricular material to incorporate active learning activities using the concept of grazer adaptation to neurotoxic prey. Materials are available online (http://datanuggets.org/2014/08/dangerous-aquatic-prey-can-predators-adapt-to-toxic-algae/). Research from this project was also featured as part of a TV documentary series (Infestation: Water, http://www.stornowayproductions.com/productions/infestation/). Data from this project is currently in the final stages of curation from public dissemination. Data will be provided to the Biological and Chemical Oceanography Data Management Office, and data sets will be linked to tthis project 's site at: http://www.bco-dmo.org/project/561498 Last Modified: 02/04/2016 Submitted by: Hans G Dam