Viewing entries in
Student Research

Coral and Hurricane Matthew

As Hurricane Matthew made contact with the Bahamas in early October, it brought with it many threats of damage and devastation. The Cape Eleuthera Institute (CEI) was extremely fortunate in the sense that Matthew did not hit as hard as expected, but still the storm left its fair share of destruction. Coral reefs offer numerous benefits to ecosystems; one of these being that they can dissipate the power of storm waves generated by hurricanes and therefore lessen the blow of terrestrial damage. However, this absorption of wave energy does not leave the reefs unimpaired. During large storm systems such as hurricanes, corals are susceptible to fragmentation. Fragmentation is a negative effect in the sense that it can cause some stress to the coral, but on the other hand it can be a positive event because some coral species, such as Elkhorn coral (Acropora palmata) and Staghorn coral (Acropora cervicornis) use fragmentation as a form of asexual reproduction. That is, a new colony can grow from a fragment of the parent colony. Scientists across the Caribbean, including here at CEI, are using this method of growth to create coral nurseries which grow fragments to be outplanted onto damaged reefs.

Island School students aid in the monitoring and upkeep of our coral nurseries. In the above photo, students are measuring Staghorn coral (Acropora cervicornis) in order to track its growth rate. (Photo_ Brittany Munson)

As CEI continues to focus its research on the endangered Elkhorn coral (Acropora palmata) in the wild, the Coral Team went out to assess the toll Hurricane Matthew had on our local reefs. As expected, there was a decent amount of fragmentation found at Bamboo Point, where there was a large colony of Elkhorn coral with evidence of recent storm damage. Some fragments seen nearby were due to Hurricane Matthew whereas others were older and likely produced by past events. It is CEI’s hope that the newly-formed fragments will proliferate to form new colonies.

This photo displays some recent fragmentation of Elkhorn coral (Acropora palmata) caused by Hurricane Matthew. This fragmentation occurred at Bamboo Point, a site near the CEI campus. (Photo_ Reilly Edgar)

In addition to fragmentation, hurricanes have been shown to relieve thermal stress. By mixing the water column and bringing water temperatures down, storms can once again restore favorable thermal conditions and allow coral the chance to recover from bleaching events. As climate change continues and sea surface temperatures rise, coral bleaching events have become more prevalent as the coral’s symbiotic zooxanthellae are expelled. Due to a number of stressors including climate change, overfishing and pollution, coral are increasingly vulnerable. Major storm events are beneficial only once in a while, but if there are too many large storms too often it not only makes the environment uninhabitable for corals, but also can permanently damage reefs that are already existing at the upper limits of their stress tolerance.

As the 2016 hurricane season comes to an end, CEI will continue its monitoring and restoration efforts of Eleuthera’s reefs in the hopes that we can continue to enjoy the many benefits they provide!

Graduate student update from the Stingray Research Group

Molly Meadows and Ethan Wrigglesworth have joined the team as part of the Masters of Research data collection from Exeter University in the UK, under the supervision of Dr. Owen O’Shea and Dr. Lucy Hawkes. The university has been visiting CEI every January for three years as part of their field course module, creating a fantastic bond between the two institutions. So it is very exciting to have students from Exeter studying their Masters with CEI for the very first time, further expanding our relationship and connection. Ethan, Molly and the stingray team work up a large female southern stingray.

Both Molly and Ethan are researching stable isotope analysis on the two species of stingrays here in Eleuthera, the Caribbean whiptail and southern stingrays. Stable isotopes can be used to peek into the diet and ‘trophic status’ of an organism over different timescales. It basically follows the general rule of “you are what you eat”; all organic tissue has an isotopic value and, once ingested, that value can then be identified within the consumer's body tissues. They will be collecting body tissue samples from both species of stingray, as well as diet and habitat samples, all of which will be analysed back at Exeter’s facilities in the UK. They will also be studying captive rays in the wet labs here at CEI, discerning how quickly isotopic values from manipulated prey sources are assimilated into different body tissues.

Molly and Ethan brief an educational program before going out into the field (Photo by Catherine Argyrople)

This research forms part of The Island School Applied Scientific Research Class and students will be directly assisting with data collection whilst producing a side project on dietary partitioning between the two ray species.Stingrays are remarkable, ancient creatures, which play key roles as mesopredators and bioturbators within their environment, keeping ecosystems stable and healthy. Despite this, not much is actually known about this group of around 90 species, particularly the species focused on in this study. Therefore, any research on these creatures is vital, not only for the conservation of the individual species, but for the systems they inhabit as a whole. Understanding these stingrays place in the food chain will help quantify their impacts on local fisheries and ecosystems allowing more effective conservation methods to be employed.

A female southern stingray is released after being sampled for stable isotopes

 

Operation Wallacea students participate in sea turtle research

Green sea turtles (Chelonia mydas) are one of only seven remaining sea turtle species. These reptiles were classified as an endangered species on the IUCN Red list, following the abrupt decline of populations due to overexploitation and habitat loss. Although the green sea turtle  is protected in Bahamian waters, it is still of great importance to investigate the factors that influence where juveniles choose to forage, as this life cycle stage is crucial to the species’ ability to grow and thrive. Seagrass beds play a critical role within this life cycle stage acting as a key food source for the green sea turtle, and therefore vital for development. This summer, at the Cape Eleuthera Institute, Trinity College Dublin student Anna Whitaker, Oxford University student Alison Maughan and Royal Holloway University of London student Kate Rowley, aim to carry out research which could contribute to the improvement of future conservation efforts of the green sea turtle. A total number of 9 mangrove creeks were studied in this experiment. At each creek they visited, quadrats were placed and used for the investigation of seagrass structure, where percentage cover, species richness, and leaf canopy height data were collected. As well as this, environmental factors of the area, such as water depth, were studied. Samples of seagrass were also taken using a core.

Two CEI interns catching turtles with a seine net (turtle seining)

Laboratory analysis of the seagrass samples was used to identify the determinants of sea grass density. This analysis included calculating the number of leaves and shoots in each core taken. After which, the biomass of the samples were calculated by dividing out the core samples into above and below-ground matter. These seagrass samples were heated, and therefore dry weights of above and below ground seagrass matter could be taken.

In order to collect data regarding the abundance of turtles, methods including turtle seining, chasing and abundance surveys were carried out within the creeks where seagrass data had previously been collected. These methods sought to demonstrate correlations between characteristics of the seagrass and the abundance of turtles.

Measuring a captured juvenile green sea turtle (Chelonia mydas) at Half Sound, Eleuthera

Within each creek, a number of different habitat types were studied, including the mouth, silty mangroves, warm shallow waters, and seagrass meadows.

In addition, this project has collaborated with numerous programs, such as Earthwatch, allowing this research to connect with educational outreach and inspire young marine biology enthusiasts.

Sea Turtle Research Interns (front row) and Earthwatch students (back row)

The data collected will identify the fine-scale patterns of site selection and resource use of foraging grounds. This will contribute to a better and more in depth understanding of green sea turtle habitat usage. The research objectives of this study will form the basis for Alison, Kate and Anna’s undergraduate dissertation projects. We thank them for their help and wish them all the best with their studies!

 

Summer research focusing on critically endangered coral reef species

Elkhorn (Acropora palmata) and staghorn (Acropora cervicornis) corals are major reef-building corals found off the shores of Florida and throughout the Caribbean. In recent decades there has been a widespread decline in distribution and abundance of elkhorn and staghorn corals. Their decline is the product of compounding effects from local stressors and global factors linked to climate change including ocean acidification, sea level rise, coral bleaching, disease, and the increased severity of hurricanes. The loss of the Acropora species negatively affects the reef function and structure. This summer, McMaster University student, Heather Summers, in collaboration with Operation Wallacea and the Cape Eleuthera Institute, has been investigating the abundance and distribution of the Acroporid coral populations in South Eleuthera, Bahamas. Undergraduate dissertation student, Heather Summers, recording the habitat assessment score at one point along the transect.

The purpose of this study is to collect qualitative and quantitative observations of coral reefs for use in the development of a mathematical model that will help describe these complex marine ecosystems. The data collected includes benthic assessment, species abundance, bleaching status, and environmental conditions of temperature, pH, and salinity. At each site transects are laid out and benthic communities are assessed using habitat assessment scores (HAS) and the line-point-intercept method in order to quantify the coverage of live scleractinian coral and macroalgae. This research project also investigates the impact of predation and herbivory on coral health by recording the abundance of key fish families and invertebrates including Diadema antillarum, Scaridae, Acanthuridae, Pomacentridae, and Pterois. The information amassed by this research project can help inform decisions on coral nursery site selection and identify potential donor colonies for regeneration in the nursery.

Staghorn coral colony

Coral reefs are complex, dynamic marine biomes and their health is reliant upon many factors. This complexity makes coral reefs ideal platforms for the development, testing, and validation of mathematical models that can be used to help explain and predict the impacts of adverse conditions on Acropora health.

Elkhorn coral colony

If you spot any elkhorn or staghorn on Eleuthera or elsewhere throughout the Bahamas please report it to us! info@ceibahamas.org

Newcastle University Summer Research Update

Globally, sharks are among the most threatened group of species, facing some of the greatest population declines in modern history. This is exacerbated by conservative life history characteristics such as slow growth rates, late maturity ages and low number of offspring, which in turn increase their vulnerability to extinction. Turtles also exhibit similar life history characteristics, therefore assessing their importance as a food source and the significance predation has on their population can help us to further conservation efforts. This summer, Newcastle University student Massimo Casali in collaboration with the Cape Eleuthera Institute’s Shark Research and Conservation Program has been conducting a study to elucidate the importance of habitat complexity and coastal shark species on turtle abundance in different creek systems. The Bahamas offers unique opportunities to study turtles and sharks on account of a total ban being enforced since 2009 and 2011 respectively, and so this project will take advantage of the relatively untouched environment of south Eleuthera, The Bahamas. Newcastle University undergraduate student Massimo Casali holding a nurse shark prior to release

Through the use of experimental longlines, sharks are caught in close proximity to creek systems before being sampled, including the taking of morphometric data (measurements), tissue harvest for stable isotope analysis and tagging, allowing for mark-recapture assessment. So far the team has caught a total of 21 sharks represented by 5 species; nurse shark (Ginglymostoma cirratum), Caribbean reef shark (Carcharhinus perezi), blacknose shark (C. acronotus), blacktip reef shark (C. limbatus) and tiger shark (Galeocerdo cuvier). This research has also included a range of educational programmes and Island School classes enabling us to reach a broad range of budding young shark scientists.

OLYMPUS DIGITAL CAMERA

Overall, the research objectives of this study will form the basis for Massimo’s undergraduate research dissertation, that will specifically address the relationships between sea turtle and shark abundance in these biologically diverse ecosystems, considered fragile due to human induced disturbances. This will further allow conservation frameworks that will allow the management of sensitive coastal ecosystems throughout The Bahamas.

South Eleuthera offers the only mangrove creek systems on the Island - here shows Kemps Creek which borders the Grand Bahama Bank.