The Dynamic Interaction of Nutrient Pollution and Seawater Temperature on Reef Corals: Is Nutrient Enrichment Undermining Coral Resilience?

EPA Grant Number: FP917794
Title: The Dynamic Interaction of Nutrient Pollution and Seawater Temperature on Reef Corals: Is Nutrient Enrichment Undermining Coral Resilience?
Investigators: Wall, Christopher Bennett
Institution: University of Hawaii at Manoa
EPA Project Officer: Lee, Sonja
Project Period: September 1, 2015 through August 31, 2018
Project Amount: $132,000
RFA: STAR Graduate Fellowships (2015) RFA Text |  Recipients Lists
Research Category: Academic Fellowships

Objective:

Local nutrient pollution and global ocean warming threaten coral reefs by disrupting the symbiosis between reef corals and their symbiont algae (Symbiodinium spp.). Nutrient pollution alters the exchange of metabolites between host and symbiont and can increase the sensitivity of corals to thermal stress, thereby affecting the ability for corals to respond to regional and global environmental change. This research will use field and laboratory experiments to test for nutrient and temperature effects on the performance, bleaching, and nutrition of reef corals and Symbiodinium to offer insights on the response of corals to changing environmental conditions.

Approach:

I will use carbon and nitrogen stable isotopes (d13C, d15N) to test for effects of temperature and nutrient on reef coral nutrition and the autotrophic performance of genetically distinct Symbiodinium types. In a field experiment I will test for nutrient effects on the nutritional modes of corals across a gradient of human impacted reefs in Kaneohe Bay, Hawaii. I will then design a laboratory experiment to test for nutrient and temperature effects on the fixation, exchange, and storage of autotrophic metabolites among coral species and Symbiodinium clades. Data will be used to construct mass balanced carbon budgets, stable isotope mixing models, and trophic relationship for corals under changing environmental conditions.

Expected Results:

The interaction of nutrient pollution and temperature stress affects the function of the coral-algae symbiosis and shapes ecological outcomes for coral reefs. Nutrient pollution destabilizes reef corals by favoring the retention of autotrophic metabolites by the symbiont at the expense of the host, while temperature stress disrupts symbiont photosynthesis and drastically reduces autotrophic nutrition available to the host. Corals display alternative strategies for coping with environmental stress, including shifting modes of nutrition (autotrophy vs. heterotrophy) and associating with stress tolerant and functionally distinct Symbiodinium partners. However, the capacity to be flexible in nutrient acquisition or in symbiont partnerships is not shared among all coral taxa. By evaluating nutritional flexibility and autotrophic performance among reef corals and symbiont types it will be possible to identify whether nutrient and temperature effects on reef corals are conserved or dependent on species or host-symbiont combinations.

Supplemental Keywords:

coral reefs, Symbiodinium, nitrogen, pollution, temperature, bleaching, isotopes, ecology, autotrophy, heterotrophy, nutrition

Progress and Final Reports:

  • 2016
  • 2017
  • Final