Collaborative Research: Unraveling parasite, host, and environmental drivers of Diadematidae scuticociliatosis, a globally significant marine disease

About This Grant

Marine mass mortality events can drastically alter the structure and function of marine habitats, shifting the balance between organisms and leading to ecosystem degradation. The long-spined sea urchin Diadema antillarum plays a critical role in Caribbean coral reefs by maintaining the balance between corals and algae. Mass mortality of this urchin species has been linked to a pathogenic ciliate from the Diadema scuticociliatosis Philaster clade (DaScPc). Despite identifying the agent responsible, we still lack a fundamental understanding of the disease and its progression. By combining field monitoring, laboratory experiments, and molecular approaches, this project investigates how DaScPc, environmental conditions, and the microbiomes of Diadema interact to shape disease outcomes. These findings will be essential for predicting and potentially mitigating future urchin die-offs, thereby protecting the sensitive coral reef habitats they inhabit. This project includes the training and mentoring of graduate, undergraduate and high school students across four institutions, and the development of a global network of collaborators to facilitate monitoring and early detection of the disease. This project addresses two major questions surrounding mass mortality of the long-spined sea urchin Diadema antillarum. Aim 1 identifies environmental reservoirs of DaScPc and explores the environmental factors influencing its emergence and spread. This team conducts systematic time-series surveys of DaScPc presence in urchins, macroalgae, and corals in the U.S. Virgin Islands while monitoring physicochemical oceanographic conditions, host densities, and indicators of biological productivity. Additionally, field and experimental work assesses the potential reemergence of DaScPc from corals and other sympatric surfaces and its subsequent infection dynamics in Diadema. Aim 2 defines the growth conditions of DaScPc and determines how environmental factors and host microbiomes influence parasite-host interactions. This team assesses the effects of salinity, temperature, and nutrients on DaScPc growth and behavior in the laboratory. Co-culture experiments with bacterial strains isolated from the reef evaluates whether these microbes serve as prey or antagonists. Finally, this project characterizes the microbiomes of healthy urchins from unaffected sites and conducts experiments to determine how microbiome variation alters DaScPc-Diadema relationships. This integrative approach advances our understanding of the interactions among marine pathogens, hosts, and the environment, and provides critical tools for predicting and mitigating future outbreaks of marine diseases. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.