Conserving Corals: The Effects of Manganese and Zinc on Orbicella faveolata Recovery and Resilience to Stress

Abstract

Coral conservation and restoration efforts rely on our ability to successfully support coral health amidst an onslaught of anthropogenic stressors. Unprecedented bleaching events in recent decades have decimated live coral cover. The species of focus in this study is a reef building Caribbean coral, Orbicella faveolata which serves as a backbone to the coral reef ecosystem. There are multiple conservation efforts currently in place to save reefs, yet the success of these efforts is low and understudied. A compelling area of research is using trace metals at nanomolar concentrations to enhance the physiological processes and resilience of corals. This study was designed to elucidate the efficacy of trace metals, specifically Manganese (Mn) and Zinc (Zn), for improving growth and photosynthetic health of coral fragments under ambient and thermal stress conditions. Experiments were conducted in eight aquaria tanks over a period of 12 weeks. Four treatments in duplicate were synthesized into tiles, attached to coral micro fragments, and placed into tanks. At 6 weeks, four tanks were heated to 33C thermal stress conditions. We measured buoyant weight and polyp counts to understand the effects of trace metals on growth. We additionally measured pulse amplitude fluorometry (PAM) to assess changes in photosynthetic health. These measurements provide insight into whether trace metals can improve coral health under normal conditions and coral resilience under stress. We demonstrate in this study that Mn and Zn can maintain coral photosynthetic health under thermal stress, potentially boosting resilience. As a pilot study, this experiment lays the foundation for a future body of work using trace metals to improve coral physiology in response to climate change.