Advances in Ecotoxicology of Scleractinian Corals and Other Coral Reef Organisms
Dorothy-Ellen Abigail Renegar, National Coral Reef Institute (NCRI) at Nova Southeastern University (NSU); Carys Louise Mitchelmore, University of Maryland Center for Environmental Science (UMCES); and Cheryl Hankins, U.S. Environmental Protection Agency (USEPA)
Coral reefs are keystone coastal ecosystems, supporting significant biodiversity and economic structure worldwide. Coral reefs are also highly sensitive ecosystems that can be negatively impacted, either directly or indirectly, by a combination of global climate change (ocean warming and acidification, increasing temperature) and regional stress from inputs of nutrients and an array of inorganic and organic chemicals, including contaminants of emerging concern (CECs). Multiple exposure pathways exist as these contaminants may be dissolved, associated with suspended solids in the water column, present in sediment, or taken up by biota (potential food or prey items for coral). Assessment of the impacts of these stressors on coral reefs, whether alone or in combination, is a relatively emerging field where results are frequently equivocal, in part due to variable exposure and assessment methodologies in laboratory tests. Currently, there are no standard toxicity test methods described for any coral species, which limit the ability to clearly characterize impacts or evaluate relative sensitivity across studies, chemical contaminants, species and life stages.
The goal of this session was to bring together researchers and stakeholders who are investigating or interested in the exposure, fate, effects and risk assessment of chemical contaminants in corals and other tropical marine species. The overall aim was to advance our knowledge on the occurrence of chemical contaminants on coral reefs, discuss toxicity mechanisms of action, particularly with respect to common and novel pathways, and the potential impacts of current and emerging contaminants. This session included six platform and three poster presentations, over a range of topics from standardization of coral toxicity assays to environmental levels of contaminants in coral reef environments.
The need for standardized toxicity test assays for corals to support science-based decision-making was an important theme for this session. Platform presentations by Abigail Renegar, NCRI/NSU and Peter Schupp, University of Oldenberg, shared approaches to development and validation of standardized toxicity testing protocols. Renegar presented a methodology which uses a flow-through exposure system for reliable and repeatable chronic and acute tests with the Atlantic staghorn coral, Acropora cervicornis, as a test species, and Schupp presented an approach which has resulted in a reliable method for acute testing with the common Pacific reef-building coral, Montipora digitata. Danielle Lasseigne, USEPA fellow, presented a poster on an acute exposure test assay developed with A. cervicornis, used to assess the toxicity and effects of UV filters. All three of the methods presented have significant potential for development as international testing standards, and all three authors emphasized that coral test methods must consider appropriate exposure system design and appropriate coral-specific endpoints to facilitate development of assay protocols, which incorporate regulatory best practices and population relevance. Carys Mitchelmore, UMCES, further explored this topic in a platform presentation on the challenges associated with scaling and normalization metrics, how this affects the accuracy and precision of coral health assessments, and the importance of appropriate analytical methods, which underpin the accuracy of toxicity thresholds generated.
Three presentations shared the results of toxicity assays conducted with a range of chemicals: Graduate student Austin Blakeslee, NSU, presented research on the toxicity of an oil spill herding agent to two species of Atlantic corals, data which supports spill-response decision-making, and a poster by graduate student Cailey Dorman, NSU, assessed the toxicity of arsenic to two coral species, which supports management decisions relating to the testing and disposal of arsenic-contaminated sediments in tropical coastal environments and is relevant to coastal dredging and beach renourishment projects near coral reefs. A platform presentation by Michael Morgan, Berry College, on transcriptional profiles for the tropical anemone Exaiptasia diaphana and the temperate anemone Anthropleura elegantissima exposed to anthracene demonstrated the significance of responsive genes as quantitative biomarkers of exposure for transcriptional ecotoxicology investigations.
Finally, two presentations addressed the extent of environmental contaminant concentrations on coral reefs and explored the potential role of contaminants on coral reef decline. A poster by Tim Barger, U.S. Geological Survey, presented the results of a contamination assessment of coral reefs of the Virgin Islands National Park and Coral Reef National Monument, which identified a range of organic contaminants in water, detritus, plankton, fish and coral tissues at four reef sites. Graduate student Ellen Skelton, NSU, presented research on contaminant levels on Florida’s Coral Reef, and how available contaminant concentration data aligns with available coral toxicity data, highlighting existing knowledge gaps in both environmental monitoring data and contaminant effects on corals.
These presentations from scientists and students provided an overview of novel approaches currently employed to evaluate the toxicity of corals to a range of environmental contaminants, with the common goal of establishing a much-needed standardized toxicity assay for corals. The evidence of widespread anthropogenic chemical contamination in reef environments and potential linkages to coral reef decline highlights the necessity for rapid advances in the field of coral ecotoxicology.
Authors' contact: [email protected], [email protected] and [email protected]
