The investigators requested RAPID funding to assess the impact of the 2010 Caribbean bleaching event on coral gene expression, immune function and coral reef communities. 2010 is currently tracking as the warmest year ever on record, potentially creating one of the largest thermal anomalies in the Caribbean basin and in the southeastern Caribbean, exceeding the previous record-breaking temperatures of 2005. These investigators will perform coral surveys at selected sites in the southeastern Caribbean and sample collections in Puerto Rico during and after this transient event to compare coral health measures with previously collected pre-event data. The study will integrate several levels of data, from remote temperature sensing satellite records, to coral health, cover and diversity surveys, to studies of individual coral immune function and microbial assemblages. The scale of this thermal event is significant enough that the investigators hypothesize levels of disease will increase following this event, as was observed after the 2005 Caribbean bleaching event and the 2002 Australian bleaching event. The RAPID study will also test the hypothesis that this large scale thermal anomaly will stress corals in Puerto Rico and down-regulate immune gene expression in thermally sensitive species (Montastrea spp), but potentially up-regulate expression in a thermally resilient species (Gorgonia ventalina). The investigators also hypothesize that this expected level of coral bleaching will change the surface microbial communities of both species toward more Vibrio-based communities, and this is the first step in increased disease susceptibility to opportunistic pathogens.
Intellectual merit: This project is relevant to an understanding of the resilience of marine ecosystems and the impact of ocean warming events on coral physiology and biodiversity. Current understanding of the impacts of warm thermal anomalies is largely restricted to the bleaching response of the corals themselves, with much less known about how warm temperatures change the functioning of the coral holobiont via the microbial constituents and/or the immune responses of corals. There is tremendous value in following the physiology and gene expression of corals in the field through an extreme and transient event like this. Laboratory studies could never truly duplicate these field conditions, particularly with respect to disruptions to the natural resident microbial community that is so critical to the coral holobiont. This RAPID project will focus on objectives for which pre-event data/samples exist: 1) Monitoring levels of coral disease, coral species diversity and coral cover in Puerto Rico, Grenada, Trinidad, the Mexican Yucatan, and Panama. 2) Assessment of coral immune responses and immune gene expression in a resilient gorgonian (Gorgonia ventalina) and a susceptible scleractinian (Montastraea spp). Sampling will occur pre-bleaching, during the heating event and after recovery. 3) Assessment of changes in total microbial community before, during and after the heating event in the two above mentioned species.
Broader Impacts: The dramatic visual impacts of coral bleaching will be captured in photos and videos that, when used in website, media and lecture outlets will help to garner public interest in coral health (e.g. www.cnn.com/2010/OPINION/09/27/harvell.coral.reefs/index.html). This interest will then be leveraged to raise public understanding of more subtle climate impacts in the ocean. Through this RAPID project the investigators will build upon ongoing local public outreach programs with the Ithaca Science center, Paleontological Research Institution, Science Cabaret, Arlington Independent School District as well as national outreach such as the "Expanding your Horizons" program and the "Sally Ride Science Festival for Girls". This work also embodies many of the objectives of the Cornell Center for Sustainable Futures, and for this reason, the center will contribute matching funds to this project.
RAPID funding was requested to assess the integrated impact of the 2010 Caribbean bleaching event on coral reef communities, coral gene expression, immune function and microbial communities. 2010 was the warmest year on record, and created a large thermal anomaly in the Caribbean basin and in the southeastern Caribbean, exceeding in the south-east the previous record-breaking warm temperature period of 2005. The study integrated ecological surveys that documented high coral mortality in the most impacted region of the southeastern Caribbean, with remote sensed temperature data, with coral health and immune function, and bacterial assemblages. The ecological impact was highly significant, with a 25-36% reduction in live coral cover in some of the previously healthier coral reefs in the southern Caribbean, significant increases in coral disease, and changes in coral microbial communities. Results from the reefs affected indicate that (1) fifty two species of hard corals, 12 octocorals and many other species from other important reef animals showed bleaching signs; (2) the proportion of coral colonies showing bleaching signs (prevalence) associated with the high thermal stress varied between 28 and 39% across the four localities; (3) similarly to the 2005 event in the northeastern Caribbean, an outbreak of a white plague-like disease (WPD) impacted several localities in the southern Caribbean and produced fast and significant coral mortality; (4) Caribbean yellow band disease (CYBD), a chronic problem in most Caribbean coral reefs since the late 1990’s, increased in all reefs surveyed (Curacao, Grenada and Grand Cayman), except in Puerto Rico, where this disease was declining by the time of the thermal event; (5) the combined impact of bleaching and infectious diseases produced an average coral mortality of 25% in less than 3 months in Curacao, a significant and fast loss of live coral tissue, reproductive output, and productivity for these communities. For the surviving corals, we detected large-scale changes in immune function and composition of associated bacteria. Both Orbicella spp. and G. ventalina immune responses (measured by biochemical assays) were depressed during the bleaching event. Orbicella spp. gene expression indicates short-term changes during the bleaching event. In addition, the bleached hard corals exhibited changes in algal symbionts during and after the bleaching event. Contrary to our original hypothesis that seafans would not be significantly affected, G. ventalina immune gene expression was highly down-regulated during the bleaching event as compared to pre- and post-event sampling. Although sampled from the same locations and time periods, Orbicella spp. and G. ventalina bacterial communities are significantly different from one another. G. ventalina bacteria moved towards a disparate, less diverse community from pre- to post- event and did not rapidly recover following the event. This project has generated 10 new scientific publications to date and will produce at least 4 more. This study resulted in significant broader impacts at three levels: 1) training of future science leaders, 2) educating the general public about massive climate impacts to coral reefs through a large new museum exhibit, and 3) conveying information from this study into national climate strategy documents. This project provided unique training to post-docs (1 female postdoc), graduate students (4 female PhD students, 3 male PhD student), and undergraduates (3 minority undergraduates, 6 other undergraduates) that was outside of their previous areas of expertise and knowledge. Because this project is utilizing new emerging approaches, these young scientists are gaining valuable skills that will be transferable to future research projects and positions. This project also contributes fundamentally to human resources and development by training minority and female undergraduates and through near-peer mentoring amoung undergraduates, graduates and postdocs. All lab members met as a team once per week to share progress. The Harvell-lab Coral Aquarium room, started as a NSF-funded research facility, has been donated to The Museum of the Earth for a substantial coral reef and climate impact display that is funded through a private donor and is having widespread educational impact in this highly visited public museum. Finally, as one of the lead authors on the US Climate Change Assessment Oceans report, Harvell was able to integrate information about the impacts detected through this project into a broad policy-relevent document, which will be used to develop national strategies to respond to climate change.
