Project: Cellular physiological mechanisms for coral calcification and photosynthesis: extending lab-based models to the field

Description from NSF award abstract:
Coral reefs are amongst the most biodiverse and productive ecosystems in the world, providing millions of dollars of ecosystem services to coastal communities. There is growing concern about the future of coral reefs and the impact of anthropogenic stressors including eutrophication, ocean acidification, warming and sea level rise. However, the lack of knowledge of fundamental coral cellular mechanisms limits our ability to understand and predict responses and to implement appropriate management decisions. This proposal will use a combination of field and laboratory experiments to use immunological techniques to study coral cellular responses to environmental conditions. This project will focus on processes related to calcification, photosynthesis and nutrient uptake and test in nature the relevance of mechanistic models obtained from laboratory experiments. Results from this study could help generate biomarkers for future physiological, ecological and interdisciplinary studies. To maximize the scientific, societal and educational impacts of this research, a coordinated set of activities will include: (1) Training of one graduate student in molecular, cellular, and ecological research. (2) Dissemination of results through journals, conferences and undergraduate and graduate physiology courses. (3) Partnering with the Birch Aquarium at Scripps to build awareness of coral reef biology, ecology and conservation issues and disseminate the findings of this study to the general public. These activities will reach hundreds of thousands of children and adults that attend Birch annually, and millions of viewers through online resources. (4) Engage and train undergraduate students from underrepresented minorities through the Scripps Undergraduate Research Fellowship summer program.

This research will use recently developed immunological techniques to localize and quantity proteins in specific coral cell types and determine coral responses to environmental conditions at the cellular level. One enzyme of interest is the vacuolar proton ATPase (VHA), which was recently found in the symbiosome membrane of gastrodermal cells and identified as essential for the coral's symbiotic algae to concentrate CO2 for photosynthesis. Another enzyme, the sodium/potassium ATPase (NKA), was immunolocalized to calicoblastic cells suggesting a role in calcification. Additionally, NKA was found in cells in corals from the Complex but not the Robust clades, suggesting a role in nutrient uptake only in the former. In the project a series of field and manipulative aquarium studies will be used to determine the physiological roles of VHA and NKA in two coral species, one from each clade. Specifically, this research will: (1) Localize and quantify VHA and NKA in specific tissue layers of Acropora cervicornis and Orbicella annularis from 1 and 5m depth at a lagoonal and an open ocean exposed reef in Bocas del Toro, Panama. (2) Correlate potential differences in VHA and NKA to light, pH, and nutrient levels at the different field sites and depths, to study evolutionary adaptation to environmental conditions. (3) Perform one-year reciprocal transplantations to examine chronic acclimatization. (4) Perform one-month reciprocal transplantations to examine acute acclimatization. (5) In a flowing seawater system expose corals to a range of environmentally relevant nutrient, light and pH levels to determine if any of the single factors are causing changes in the cellular responses. In addition to characterizing responses to environmental conditions on a broad temporal scale from evolutionary, chronic, to acute exposure, this research will examine potential cellular mechanistic differences between Robust and Complex corals. The long-term goal is to generate biomarkers based on specific cellular physiology processes to explain and predict effects of environmental stress (e.g. eutrophication, ocean acidification, and sea level rise) on coral homeostatic responses.