Sea Turtle Conservation and Biology: All species of sea turtles are endangered or threatened, and in order to better protect these species we need to better understand their basic biology. This includes monitoring their population size, growth rates, and studying how sea turtles migrate across different habitats and even across ocean basins, in search of food, mates, and suitable nesting beaches. The British Virgin Islands Conservation and Fisheries Department has been studying their local sea turtle populations through their ongoing sea turtle tagging program. MANTA instructors and students are contributing to this effort during our cruise by conducting sea turtle tagging from our vessel. We capture wild turtles and mark them with uniquely numbered tags on their flippers, and subcutaneously. Basic biological information is then collected such as carapace length, width, sex, and a superficial health evaluation is performed. The turtle is then released, so that the next time that turtle is encountered (whether it’s 1 year later swimming in the ocean, or 10 years later nesting on a beach), we can determine how much it has grown, and how far it has migrated. These data are all provided to the BVI Conservation and Fisheries Department and incorporated into their long-term database.

Coral Reef Assessments: MANTA instructors and students scuba dive on coral reefs throughout the British Virgin Islands each year. We take advantage of this opportunity by conducting surveys to assess the condition of the coral reef ecosystem. Benthic surveys are performed using modified AGRRA (Atlantic and Gulf Rapid Reef Assessment) protocols to assess the relative cover of coral (live, dead, bleached, and diseased), algae, and other invertebrates, and their diversity. Fish surveys are also performed using AGRRA protocols to assess fish abundance, diversity, and size. These survey data are compared across sites that exhibit natural variability, and are subject to differing degrees of anthropogenic stressors. These data will be used to develop a long-term dataset, while serving as an effective tool to teach students these methods.

Water Quality: As populations in Caribbean island nations continue to grow, the severity of negative environmental impacts will also continue to increase. Coastal tropical habitats are typically characterized by clear, low nutrient waters. However, human activity often alters the hydrology of upland watersheds and amplifies the inputs of sediment, nutrients, toxins, and harmful bacteria and viruses into the adjacent coastal waters. These tropical coastal habitats include coral reefs, seagrass beds, and mangroves that are thriving ecosystems that are also sensitive to such environmental stressors. These impacts are a threat to the biodiversity of these ecosystems, and can compromise the functions that these habitats serve to the benefit of humans. These functions includes protecting shorelines from storms and erosion, serving as critical habitat for juvenile and adults species that are important sources of food for local people, providing a clean and safe place for locals to enjoy recreationally, and the extremely important economic role that these natural resources play in attracting tourism. In 2009 and 2010 MANTA conducted a research project to assess the water quality at reefs, harbors, and beaches around the BVIs. One of the primary focuses of this research was to measure the levels of fecal coliform bacteria in the seawater. These fecal coliforms come from releasing untreated sewage into coastal waters that are being used by locals and tourists for swimming, fishing, diving, beaching, and boating. This sewage can be discharged from land-based sources due to absent or insufficient sewage treatment facilities; or from marine sources from the thousands of boats in the BVIs that discharge their sewage waste directly into the water. While discharging marine sewage is technically illegal, there is virtually no compliance and the infrastructure actually does not exist to support compliance. Ingestion of fecal coliform bacteria can cause digestive problems, such as diarrhea and vomiting, and can be life-threatening. This is a major public health issue and results in numerous beach closures throughout the United States each year when fecal coliform concentrations become too high. However, a monitoring network like this does not currently exist in the BVIs, so the exposure levels are largely unknown. Aesthetics or the perception of the beauty and cleanliness of the BVIs could also be greatly harmed when tourists witness the direct release of sewage from boats, which would likely negatively impact a tourists’ enjoyment of the marine environment and subsequently harm the BVI economy by the loss of repeat tourists and negative publicity. Along with the public health risk of discharging sewage, the concomitant release of nutrients also poses an ecological threat to coral reefs. Higher nutrient levels promote an increase in macroalgae growth on the reef that can over-grow and kill the coral. A reduction in herbivorous fish abundance through overfishing further increases the competitive advantage that algae has. When these effects are combined with increased sedimentation rates caused by runoff and construction, the corals become less resilient to bleaching and disease and eventually die. These coral reefs are then replaced by a much less desirable algae-dominated reef which does serve these critical ecosystem functions. MANTA’s water quality research also included analysis of nutrient levels and sedimentation rates at selected sites. The degree of land use and human impacts was estimated by conducing building counts, boat counts, and estimating impervious cover (roofs, parking lots, roads, etc.) using photographs from google maps. Finally, human surveys were conducted by students and instructors to assess the opinions and beliefs about the marine environment of the BVIs. Tourists and locals were interviewed, including people who were, and were not, involved in a marine trade. These data are being analyzed, and will be provided to, and interpreted with, the BVI government, and published in the literature.

Fish Otolith Microchemistry: MANTA researchers are currently in the planning phases of a collaborative project with the BVI Conservation and Fisheries Department to use fish otolith chemistry to determine the natal origin of commercially important reef fish species. Otoliths are bones in the ear of a fish that are used for detecting sound and determining their orientation in the water. The unique water chemistry in which a fish lives leaves a spatially and temporally explicit record in the microchemistry of otolith growth bands, which are permanent rings that are deposited like tree rings each year. Otolith microchemistry is a newer method that has been proposed for identifying the natal origins of fish and examining differences in habitat utilization and migration. This works because the multivariate concentrations of various trace elements in the otolith cores of adults (which were grown during their larvae/juvenile stage) preserves a chemical record of the estuaries those individuals used as their nursery habitat as juveniles. Once you create a ground-truthed reference signature for each estuary by collecting juveniles from those locations and measuring their elemental and isotopic signature, you can link adult otolith signatures to these known locations. While encouraging results have been found using this approach, one of the obstacles is that there is significant annual variability in the natal signature within a given estuary. Therefore the reference signature measured for an estuary in a given year may not be representative of other year-class recruits, requiring periodic (or continual) recalibration of the reference signature for each nursery habitat. This approach may require an impractical amount of effort, therefore more consistent chemical signatures need to be identified. Geochemistry studies have shown that isotope patterns of many elements are extremely informative as environmental tracers. However there are few examples of this being effectively applied to fish otoliths. This is primarily because of the limited availability of high resolution isotopic instrumentation such as multicollector ICPMS to researchers in this field. One study that did measure isotopic signatures of strontium in fish otoliths showed that potentially higher geographic resolution exist when using this method, and that the isotopic signature from a given site is consistent in both sediment and fish otoliths. The isotopic signatures should show less influence from variability in environmental conditions, geochemical cycling, and biological regulation than elemental concentrations, and therefore offer much more promise for practical application to fisheries management. The proposed project will focus on developing more refined methods for identifying the natal origin of fish species using otolith microchemistry. Multicollector ICPMS will be used to investigate potential natural isotopic tags created by the otolith chemical constituents.