Abstract
Thermal anomalies caused by anthropogenic climate change have been shown to trigger a breakdown of the symbiotic relationship between reef-building corals and their algal symbionts (Family Symbiodiniaceae) (Hughes et al. 2018). The photosynthetic machinery of these single-celled algae begins to collapse under the effects of chronic heat stress, which leads to the proliferation of highly unstable oxygen radicals (Reactive Oxygen Species, or ROS) that can damage DNA and cellular membranes (Lesser 1997). Several studies have correlated high amounts of intracellular ROS in the coral host with accelerated bleaching and eventually mortality (Lesser 1997, Weis 2008). The exact timing of the mechanistic breakdown of photosystems and subsequent accumulation of intracellular ROS, however, has not been well studied between coral and symbiont. Additionally, varying densities of symbionts have played a part in observed ROS levels in the coral host (Gardner et al 2017), as well as variations in the exact mosaic of symbiont clades found in the host (Krueger et al 2015). Here, changes in antioxidant capacity of critical Atlantic reef-building stony corals Orbicella faveolata, Acropora cervicornis, and Montastrea cavernosa were measured as they underwent thermal stress by determining relative concentrations of antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), and glutathione reductase (GsX) present within the coral host.