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ESF in the keys

Dr. Mark Teece Associate Professor of Chemistry

Biogeochemistry of Coral Reefs & Environmental Chemistry

Research Abstract

How will corals respond to future changes in the ocean resulting from global climate change and decreases in water quality?

The decline in global coral reef conditions and the limited prospects of recovery of reefs leads us to ask: How will corals respond to future decreases in water quality resulting from increasing coastal development and changes in oceanic chemistry including temperature and acidity associated with global climate change? Scleractinian or hard corals provide the framework of coral reefs and they obtain their metabolic requirements for fats and proteins from their symbiotic zooxanthellae or from feeding heterotrophically on plankton, zooplankton, or dissolved organic matter. Under ideal conditions, corals can obtain up to 100% of their nutritional requirements from their symbionts. We have shown that corals on less than ideal inshore habitats with higher levels of nutrients (DIN and TP), TOC, turbidity, and light attenuation have faster overhanggrowth rates and lower rates of mortality compared to corals from offshore habitats with lower nutrient and turbidity levels. In fact, inshore patch reefs exhibit some of the healthiest coral populations. Further, healthy populations of Scleractinian corals growing on deep reef habitats (> 40 m) with limited light availability have also been documented. These findings have led to the hypothesis that inshore and deep reef habitats provide an expanded heterotrophic niche for corals that will be tested in the proposed project.

The objectives of this project are to document: (1) the relative contribution of autotrophic and heterotrophic sources of nutrition and the nutritional status of corals under different environmental conditions (i.e. depth and nutrient gradients); and (2) the role of nutritional sources and status on coral growth and survivorship. These goals will be accomplished using a combination of controlled growth experiments, field collections from inshore, offshore, and deep reef habitats, and reciprocal transplants of corals in different reef communities. Coral growth rates and the relative contributions of heterotrophic feeding on satisfying metabolic needs of the coral host will be documented using molecular-level biochemical and stable isotopic techniques. The naturally occurring stable isotope compositions of essential amino acids and essential omega-3 fatty acids in corals will be measured as a direct probe to evaluate heterotrophic feeding capacities of corals with diverse life-history strategies (i.e., broadcasters, brooders). By showing the relative importance of planktonic sources of nutrition in satisfying the metabolic requirements of corals, the role of dietary sources on coral resistance and resilience will be assessed, providing important insights into how corals may adaptively respond to changes in water quality and global climate change by switching their trophic mode under adverse environmental conditions.

The proposed research has important implications for the future survival of reefs in Florida and elsewhere where coastal development has increased land-based sources of stressors. Also, the potential documentation of physiological mechanisms that may enhance coral resistance to stress and resilience rates (i.e., return to a pre-disturbance state) can be a useful tool for the future design of Marine Protected Areas. These proposed research explicitly addresses research priorities identified by NOAA’s Coral Reef Ecosystem Research Plan at both regional and jurisdictional-wide levels by: (1) developing a better understanding of the role changes in water quality on coral reef ecosystem status; (2) developing tools to forecast the impacts from and responses of reef communities to anthropogenic and natural stressors; and (3) documenting potential physiological mechanisms that can influence coral resistance and resilience to stress.

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