Jim Hendee

2015

2016

Whereas thermal stress has been proposed as the main physiological driver behind mass coral bleaching events, new evidence is emerging that suggests that poor water quality may have a strong synergistic effect, to the extent that corals which regularly experience poor water quality conditions seem less resistant to thermal stress (e.g., Woolridge, 2009). A direct link between algal symbiont density and bleaching severity has been hypothesized (Cunning and Baker, 2013), in which corals with higher densities of algal symbionts are more vulnerable to coral bleaching. Therefore, environmental conditions that increase algal symbiont densities, such as elevated nutrients, are likely to exacerbate climate change-induced coral bleaching. To further test this hypothesis, we propose to investigate the synergistic effects of nutrient enrichment and elevated SST on the ecology, genetics and photophysiology of two Caribbean corals with contrasting life-history reproductive strategies (Orbicella faveolata and Porites astreoides), during early stages of life, critical for the successful recruitment and survival to adult stage. Until recently, investigations generally focused on testing the effects of both of these stressors (elevated nutrients and temperatures) individually, preventing the identification of any additive or synergistic effects, and making future predictions about climate change difficult. However, our plan is to expose newly-settled and juvenile corals from proposed species to various nutrient concentrations and then thermally stress these to (1) quantitatively monitor how corals change the density of their symbionts in response to changes in nutrients and how these changes subsequently affect thermal tolerance, (2) assess how bleaching susceptibility may depend on the genetic identity of the coral or its algal symbionts and (3) monitor the photosynthetic efficiency of corals prior, during and post-thermal stress. Overall, this information is critical for managers in the US and Caribbean regions because it is expected to provide empirical evidence that might support the implementation of environmental policies which improve water quality and increase reef resilience. Furthermore, because one of the focal species (O. faveolata) has been recently proposed for listing as endangered under the U.S. Endangered Species Act (ESA), this information is critical for managers in the US and wider Caribbean and has enormous potential for outreach and local media interest. The affiliated CRCP project (#797) entitled “Gamete/larval fitness of ESA listed and candidate corals” to team member Dr. Margaret Miller will provide permits through the FKNMS to collect O. faveolata larvae and facilities to rear and culture larvae, with the advantage that over the years past efforts have resulted in high survival of larvae for at least >1 month after settlement. A second affiliated project entitled "Climate change and nutrient stressor interactions and their effects on coral health and fitness of ESA priority species" proposed by Dr. Cheryl Woodley will provide direct comparisons to our work (i.e., pre-settlement vs. post-settlement nutrient and temperature interactions) for the species O. faveolata.

This project is expected to provide many short and long-term benefits, including: (1) Providing the first empirical evidence of synergistic effects of nutrient enrichment and elevated temperatures for Caribbean corals during early stages of life. (2) Providing critical information for a species recently listed as endangered, with enormous potential for outreach and local media interest. (3) Providing some of the necessary information that managers need to support the implementation of environmental policies aimed at increasing reef resilience by improving water quality. (4) Helping develop a set of hypotheses that might be easily tested at numerous other sites in the US and wider Caribbean, particularly those that regularly experience high levels of terrestrial runoff. (5) Allowing the identification of the most susceptible (or resistant) coral/algal genotype combinations. To our knowledge, this is the first study that combines a genetic component of both partners when assessing thermal tolerance.

• Florida

Land-based Sources of Pollution (LBSP)

Closed

Funding Ended

https://www.coris.noaa.gov/search/rest/find/document?searchText=projectNumber%3A1117%20OR%20projectTitle%3A"Synergistic%20effects%20of%20eutrophication%20and%20elevated%20SST%20in%20the%20early%20life%20stages%20of%20two%20Caribbean%20corals"&start=1&max=10&f=searchPage