The effect of thermal stress and nutrient loading on the coral – algal symbiosis in a dominant Hawaiian reef coral

Coral reefs are one of the most biodiverse and valuable ecosystems on the planet, and healthy reef systems can sustain a multitude of marine species, defend coastlines from storm surges, and provide employment for people in local communities. The health and prosperity of reef-building corals is largely attributed to the partnership with their algal symbiont, zooxanthellae. A large body of research contributes to understanding how corals and zooxanthellae respond to individual stressors. However, fewer articles clarify how multiple interacting stressors may threaten these ecosystems and disturb corals’ relationship with zooxanthellae. Therefore, this research aims to quantify changes in zooxanthellae density in corals that have been subjected to the interactive effects of thermal stress and nutrient loading. Corals were collected from two sites in Kāne ohe Bay, Hawai i, encompassing a gradient of temperature and nutrient influence. For one month, corals were subjected to four experimental treatments (Control, Heated, Nutrient, Heated + Nutrient). Fragments were collected at the beginning and end of the experiment, flash frozen in liquid nitrogen, and shipped back to TAMU-CC for subsequent analysis. Coral experimentation began with airbrushing the coral tissue to remove it from the skeleton, yielding tissue slurry used for the biological assay. The organic matter was lysed using a tissue homogenizer and then centrifuged to create coral pellets. The biological pellets were then resuspended in the phosphate-buffered saline (PBS) and vortexed to create an aliquoted subsample which could then be counted under a microscope using a hemocytometer. Upon analyzing the experimental results, it is hypothesized that the corals that underwent the Heated + Nutrient treatment may be more susceptible to bleaching due to the combined stressors. This study will aid our understanding of how corals in Kāne ohe Bay respond physically to interacting stressors