Grand Cayman Research Articles

Renewed occurrence of schooling scalloped hammerhead (Sphyrna lewini) and of great hammerhead (S. mokarran) sharks in the Cayman Islands

The scalloped hammerhead shark (Sphyrna lewini), a critically endangered species with a decreasing global population, is characterised by its occurrence in large schools. Such schools are still observed today in the Pacific Ocean, but this is generally not the case in the Atlantic Ocean, and in the Cayman Islands not since the 1970s. Here we report a recent record of a school of S. lewini in deep water off Grand Cayman, and describe a recent, concomitant increase in numbers of the species, and its critically endangered congener, the great hammerhead (Sphyrna mokarran), around the Cayman Islands. Relative population trends and seasonal patterns were assessed using data from shallow and deep-water BRUVS, scientific longlining, citizen science projects including the Sharklogger Network and REEF, and social media reports. It appears that S. lewini may be slowly re-occupying the area, selecting and using deeper waters to school, while S. mokarran has also become less scarce than hitherto.

Benthic and fish community composition on mesophotic reefs in Grand Cayman.

Mesophotic Coral Ecosystems (MCEs) represent unique ecological habitats that range from 30 to 150 m deep, harbouring phylogenetically distinct species and offering refuge for many taxa during times of environmental stress. Yet owing to inaccessibility of ecosystems at these depths, most MCEs remain unexplored, with quantifications of ecological communities in these habitats lacking across many regions. Here, using open- and closed-circuit technical diving, we quantified benthic and fish community composition at four mesophotic reef sites (45 m depth) in Grand Cayman. We show significant differences in benthic community composition over a small spatial scale driven by disparate coverage of sponges, crustose coralline algae, and sand/rubble, yet consistent patterns of macroalgal dominance representing >50% coverage at each site and low hard coral cover at an average of 2.4%. Reef fish species richness, biomass, and density was consistent across sites, however the relative contribution of individual species to community composition differed significantly. Macrocarnivores were found to be the dominant contributors to biomass, with invertivores the most speciose, and omnivores and planktivores at the highest densities, consistent with previous descriptions of mesophotic fish assemblages in other regions. Similarly, the low hard coral cover and high macroalgae and sponge cover of the benthic communities also appear ecologically similar to several described mesophotic reefs yet is not uniform across the Caribbean. The ecological organisation of Grand Cayman's MCEs may result from a variety of factors such as isolation from other major land masses, geology, local geography, and anthropogenic activity at both the local and global scale and highlight the importance of continued exploration and documentation of MCE communities.

Insights from the 2-year-long human confinement experiment in Grand Cayman reveal the resilience of coral reef fish communities

In March 2020, the world went into lockdown to curb the spread of the novel coronavirus (SARS-CoV-2), with immediate impacts on wildlife across ecosystems. The strict 2-year long lockdown in Grand Cayman provided an unprecedented opportunity to assess how the ‘human confinement experiment’ influenced the community composition of reef fish. Using a suite of multivariate statistics, our findings revealed a stark increase in reef fish biomass during the 2 years of lockdown, especially among herbivores, including parrotfish, with drastic increases in juvenile parrotfishes identified. Additionally, when comparing baseline data of the community from 2018 to the 2 years during lockdown, over a three-fold significant increase in mean reef fish biomass was observed, with a clear shift in community composition. Our findings provide unique insights into the resilience of reef fish communities when local anthropogenic stressors are removed for an unprecedented length of time. Given the functional role of herbivores including parrotfish, our results suggest that reductions in human water-based activities have positive implications for coral reef ecosystems and should be considered in future management strategies.

Individual residency behaviours and seasonal long-distance movements in acoustically tagged Caribbean reef sharks in the Cayman Islands.

Understanding how reef-associated sharks use coastal waters through their ontogeny is important for their effective conservation and management. This study used the horizontal movements of acoustically tagged Caribbean reef sharks (Carcharhinus perezi) to examine their use of coastal space around the Cayman Islands between 2009 and 2019. A total of 39 (59.1%) tagged sharks (male = 22, female = 17, immature = 18, mature = 21) were detected on the islands wide network of acoustic receivers. The detection data were used to calculate values of Residency Index (RI), Site-Fidelity Index (SFI) and minimum linear displacement (MLD), as well as for network analysis of individual shark movements to test for differences between demographics, seasons, and diel periods. Sharks were detected for up to 1,598 days post-tagging and some individuals showed resident behaviour but the majority of tagged individuals appear to have been one-off or only occasional transient visitors to the area. Generally, individuals showed strong site-fidelity to different areas displaying linear home ranges of < 20 km. The evidence indicates that there was no pattern of diel behaviour. Tagged sharks generally showed increased movements within and between islands during the summer (April-September), which may be related to breeding activity. Some individuals even made occasional excursions across 110 km of open water > 2,000 m deep between Grand Cayman and Little Cayman. One mature female shark showed a displacement of 148.21 km, the greatest distance reported for this species. The data shows that the distances over which some sharks moved, greatly exceeded the extent of any one of the islands' marine protected areas indicating that this species may be more mobile and dispersive than previously thought. This study provides support for the blanket protection to all sharks throughout Cayman waters, which was incorporated within the National Conservation Act in 2015.

Temporal variations in Rare Earth Element distributions in the Cenozoic succession and modern sediments of the Cayman Islands

The Rare Earth Elements (REEs) in limestones and dolostones that develop on isolated oceanic islands, like the Cayman Islands, were acquired from the seawater in which they formed and various diagenetic processes that led to their lithification and, in some cases, pervasive dolomitization. Modern sediments from North Sound, Grand Cayman, contain up to 30.93 ppm ∑REEs and 45.23 ppm ∑REEs + Y, whereas modern corals contain up to 2.30 ppm ∑REEs and 3.65 ppm ∑REEs + Y. The limestones and dolostones in the Brac Formation (late Oligocene), the Cayman Formation (Miocene), and Ironshore Formation (Pleistocene) generally contain <7 ppm and <10 ppm, ∑REEs and ∑REEs + Y, respectively. In contrast, the Pedro Castle Formation (Pliocene) contains up to 14.18 ppm ∑REEs and 20.81 ppm ∑REEs + Y. The Distribution Coefficients for the REEs from the modern Cayman corals are similar to those determined for corals elsewhere in the world. In the modern sediments from North Sound there is a high correlation between the ∑REEs + Y and Fe and Al but a low correlation with Na and Mn. In contrast, the correlation between the ∑REEs + Y and other elements in the limestones of the Ironshore Formation and dolostones/limestones of the Brac Formation and Cayman Formation is low. The light REEs were >Limit of Quantification (LoQ) in most samples, whereas the medium REEs and heavy REEs were commonly <LoQ. There is no recognizable pattern to the presence/absence of the light, medium, and heavy REEs. Collectively, these data show that (1) the REEs in the limestone/dolostone succession on Grand Cayman are similar to those from Cayman Brac, (2) dolomitization does not seem to have modified the REEs of the original limestones, and (3) the content of the REEs of the limestones and dolostones of the Pedro Castle Formation is higher than those in the Brac Formation and Cayman Formation. This may indicate that the concentration of the REEs in the seawater during the Pliocene highstand was higher than those when the original sediments of the Brac Formation and Cayman Formation were deposited.

Production of phytodetritus by a coral reef sponge increases from shallow to mesophotic depths

AbstractOn Caribbean coral reefs, sponges are important members of the benthic community and have an important role in consuming particulate organic matter (POM) and dissolved organic matter (DOM), with the subsequent production of detritus that is then shunted into a process now referred to as the “sponge‐loop.” An emergent species of sponge commonly found on Caribbean coral reefs, Agelas tubulata, increases in size and growth rate from shallow (&lt; 30 m) to mesophotic depths (30–150 m) on Grand Cayman Island. A. tubulata depends largely on heterotrophy across shallow to mesophotic depths and has been shown to utilize detritus on shallow reefs. However, detritus production by A. tubulata on shallow and mesophotic coral reefs has not been previously reported. Here we show, using flow cytometry, that sponge detritus includes a previously unquantified component, phytodetritus. Sponge phytodetritus production was shown experimentally to be greater in sponges from mesophotic depths compared to sponges from shallow coral reefs. Additionally, the size range of this phytodetritus corresponds to the size range of autotrophic picoplankton, primarily prochlorophytes, known to be an important food source for filter‐feeding sponges. Given the known lability of phytodetritus, compared to other more recalcitrant components of the detrital pool, its role in the food web of mesophotic communities combined with the increased availability of live POM, may be an underappreciated component of mesophotic community carbon and nitrogen flow.

Shoreline change on a tropical island beach, Seven Mile Beach, Grand Cayman: The influence of beachrock and shore protection structures

Contemporary and near-future shoreline change is widely regarded as an issue on small tropical islands. While it is widely anticipated that sea-level rise will precipitate shoreline recession on tropical islands, studies to date record both accretion and recession at historical timescales. This study of Seven Mile Beach, Grand Cayman presents a case study of historical shoreline change in which the local geomorphic setting is shown to be an important influence on shoreline behaviour. Consistent with its leeside setting, historic shoreline analysis (1958–2019) reveals erosion on the margins and accretion in the central part of the headland-embayment beach where no beachrock is present. The beach comprises five discrete, but interlinked subcells delineated by low headlands of exposed beachrock. These headlands have emerged through shoreline recession post-1971 but once exposed have become loci of persistent erosion, suggesting a positive feedback between beachrock and waves. A Category 5 Hurricane generated waves directly opposed to long-term modes and throughout the beach, long-term patterns of shoreline change were temporarily reversed, however, the historic pattern of shoreline change was restored within 2 years. The contemporary patterns of erosion and cell development suggest a reduction in sediment supply leading to cannibalization of relict beachridges on the margins of the embayment and emergence of formerly buried beachrock. The effects of coastal structures and erosion abatement measures were assessed and recommendations for coastal management, including development setback lines are presented.

Re-connecting Communities in Biodiverse Places to their Biological Heritage: The case of iguanas on Grand Cayman

For centuries, naturalists from the Global North have traveled southwards to collect specimens of species from regions where there were many. The legacy of this is that the large natural history collections and the biodiverse regions of the world are often distant from one another. The unique and often disappearing species and ecosystems in these regions need conservation, yet much of the data on this biodiversity resides in collections and with the experts that work in them, rather than in the countries where it is needed. In this poster we zoom in on Grand Cayman, a small island in the Caribbean, facing severe threats to its endemic biodiversity - from habitat loss to introduced species. More specifically we focus on the endemic blue iguana (Cyclura lewisi) and the invasive green iguana (Iguana iguana). Specimens from the Cayman Islands are dispersed over American and European natural history collections and give data on the species present, their abundances and the interactions among those species (e.g. their food plants and parasites). Such data can be used in risk assessments and conservation planning, and the specimens themselves can inform research, such as population genetics. While the Cayman Islands are small they provide an excellent case study of the issues of conservation, society, climate and other environmental change in the tropics. Islands are highly sensitive to environmental change, but the lessons learned from them can be extended to other areas, including continents. On this poster, we describe the From Blue Iguanas to Blue Vervain project (Fig. 1), which aims to connect the biodiverse Caribbean UK Overseas Territories of Montserrat and the Cayman Islands with natural science collections around the world. We aim to learn ways to address issues of access and benefit-sharing, particularly how residents of these biodiverse places can benefit from the data and research linked to specimens originating in their islands.

Monitoring and modeling non-native invasive green iguana population response to harvesting on Grand Cayman, Cayman Islands

Registered hunters harvested over 1.3 million non-native invasive green iguanas (Iguana iguana) on Grand Cayman between October 2018 and August 2021. We used islandwide post-reproduction survey-based abundance estimates in August 2014–2021 and model-based abundance predictions for August 2022–2030 to assist natural resource managers with reassessment and modification of the harvest strategy due to diminishing returns to hunters paid per green iguana harvested. We need harvest rates > 0.600 for desired abundance ≤ 50,000 and > 0.700 for desired abundance ≤ 10,000 green iguanas. With harvest rates < 0.600, the population would likely remain above desired abundance. Without harvesting, the green iguana population would likely reach carrying capacity by August 2026.

A review of 263 years of taxonomic research on Hypoplectrus (Perciformes: Serranidae), with a redescription of Hypoplectrus affinis (Poey, 1861).

The hamlets (Hypoplectrus spp., Perciformes: Serranidae) constitute a distinctive model system for the study of a variety of ecological and evolutionary processes including the evolution and maintenance of simultaneous hermaphroditism and egg trading, sex allocation, sexual selection, social-trap, mimicry, dispersal, speciation, and adaptive radiation. Addressing such fundamental and complex processes requires a good knowledge of the taxonomy and natural history of the hamlets. Here, we review the taxonomy of the hamlets, from early ichthyological studies to the most recent species description in 2018. We report a total of 72 different binomial names for Hypoplectrus, synonymized or invalidated down to 17 unambiguously recognized species today. In addition, we redescribe Hypoplectrus affinis (Poey, 1861) as a valid species. In Bocas del Toro (Panama), this hamlet is distinct from eight sympatric congeners in terms of colour pattern, body size and behaviour. Whole-genome analysis and spawning observations indicate that it is genetically distinct from sympatric congeners and reproductively isolated through assortative pairing. Based on the colour pattern we detail in its redescription, live-fish photographs, videos, and earlier reports, H. affinis occurs in Panama, Nicaragua, Mexico, the Florida Keys, Cuba, Grand Cayman, Jamaica, the Dominican Republic, Los Roques (Venezuela), Bonaire, and Tobago. We conclude with a discussion of pending taxonomic issues in this group and the species status of the hamlets in general.

Variability in antimicrobial chemical defenses in the Caribbean sponge Agelas tubulata: implications for disease resistance and resilience

Sponges in the genus Agelas produce a diversity of bromopyrrole alkaloid secondary metabolites, some of which are known to inhibit predators and pathogens. Selective pressures on sponges to produce chemical defenses vary in time and space, often resulting in differences in the production of secondary metabolites. To characterize intraspecific variation in these compounds, we generated metabolomic profiles of the Caribbean sponge A. tubulata across spatial gradients, including multiple sites in Belize and Grand Cayman, and depths ranging from 15 to 61 m in Grand Cayman. Samples were also analyzed from a reciprocal transplant experiment across shallow (22 m) to mesophotic (61 m) reefs. We found quantitative, but not qualitative, differences in metabolite profiles across sites and depths, with 9 metabolites contributing to that variation. In addition, transplanting sponges across depths resulted in significant changes in concentrations of the metabolite sceptrin. Sponge extracts exhibited antibacterial activity against a panel of marine and human pathogens. Multiple regression analyses showed that different metabolites were associated with antibacterial activity against different pathogens. The strongest compound-specific relationship was a negative effect of oroidin on the growth of Serratia marcescens, and purified oroidin was found to inhibit S. marcescens growth in a dose-dependent manner. Overall, A. tubulata exhibits intraspecific variability in the production of antibacterial secondary metabolites across sites and depths that signals selective responses to its environment. Given the current increase in sponge densities, and incidence of disease on coral reefs, these data have implications for disease resistance and resilience of sponges in the Anthropocene.

Depth-dependent trophic strategies of Caribbean sponges on mesophotic coral reefs

Mesophotic coral reef ecosystems (MCEs) are characterized by gradients in irradiance, temperature and trophic resources. As depth increases on Caribbean mesophotic reefs, particulate organic matter increases while dissolved organic matter decreases, and the increase in particulate organic matter is directly related to the increase in sponge abundances and growth rates on MCEs. To further understand the trophic ecology of sponges, changes in microbiome composition and function, stable isotopic composition and proximate biochemical composition of 4 Caribbean reef sponges (Amphimedon compressa, Agelas tubulata, Plakortis angulospiculatus and Xestospongia muta) were quantified along a shallow to mesophotic depth gradient on Grand Cayman Island. Increases in δ15N for all sponges were observed as depth increased, indicating an increasing reliance on heterotrophic food resources. Species-specific changes in symbiotic microbial community composition were also observed as depth increased, and the predicted functional genes associated with nitrogen and carbon cycling showed species-specific changes between depths. Regardless of species-specific changes in microbiome community structure or function, or whether sponges were classified as high microbial or low microbial abundance, sponges increased their consumption of particulate organic matter with increasing depth into the lower mesophotic zone.

Helicobacter cyclurae sp. Nov., Isolated From Endangered Blue Iguanas (Cyclura lewisi)

Blue iguanas (Cyclura lewisi) are endangered reptiles found only on Grand Cayman. Previously, DNA for a novel Helicobacter species GCBI1 was detected in sick and dead iguanas. In the current study, fecal and cloacal swab samples were obtained from 25 iguanas. Through molecular and microbiological techniques, a novel Helicobacter species was cultured from feces and characterized, for whom we propose the name Helicobacter cyclurae. This novel helicobacter had a prevalence of 56% by PCR and 20% by culture in samples analyzed. The type strain MIT 16-1353 was catalase, oxidase, and gamma-glutamyl transpeptidase positive. By electron microscopy, H. cyclurae has a curved rod morphology and a single sheathed polar flagellum. Phylogenetic analysis using 16S rRNA, gyrB, and hsp60 indicated that these strains were most closely related to Helicobacter sp. 12502256-12 previously isolated from lizards. H. cyclurae has a 1.91-Mb genome with a GC content of 33.37%. There were 1,969 genes with four notable virulence genes: high temperature requirement-A protein-secreted serine protease, gamma-glutamyl transpeptidase, fibronectin/fibrinogen binding protein, and neutrophil-activating protein. Whole-genome phylogeny, average nucleotide identity, and digital DNA–DNA hybridization analysis confirmed that H. cyclurae is a novel species, and the first helicobacter cultured and characterized from blue iguanas.

Growth and feeding in the sponge Agelas tubulata from shallow to mesophotic depths on Grand Cayman Island

AbstractOn Caribbean coral reefs, sponges are important members of the benthic community and play multiple roles in ecosystem structure and function. They have an important role in benthic‐pelagic coupling, consuming particulate organic matter (POM) and dissolved organic matter (DOM) and in turn providing food in the form of sponge biomass or the release of detritus for a variety of coral reef organisms. Throughout the Caribbean, sponges show consistent increases in their abundance and growth rates as depth increases into the mesophotic zone (30–150 m). This has been hypothesized to be driven by bottom‐up forces, particularly the increased supply of nitrogen‐rich POM in mesophotic coral reef ecosystems (MCEs). Here, we tested the hypothesis that the sponge, Agelas tubulata, exhibits increased growth rates on MCEs relative to shallow reefs on Grand Cayman Island and that this is driven by bottom‐up forcing. We observed increased growth rates in mesophotic A. tubulata, compared with shallow conspecifics, despite variability in feeding on both POM and DOM. Mesophotic sponges, however, were consistently exposed to greater amounts of POM, which was seasonally variable unlike DOM. Changes in stable isotopic signatures, and higher feeding rates with increasing depth, were consistent with increasing rates of growth in sponges as depth increases. These observations support the hypothesis that mesophotic sponges have higher growth rates due to increased POM availability and consumption over time. The results of this study illustrate the crucial role that bottom‐up forcing has in the structuring of sponge communities on both shallow and mesophotic Caribbean coral reefs and the importance of POM as a source of nitrogen in sponge diets.

Dolomitization micro-conditions constraint on dolomite stoichiometry: A case study from the Miocene Huangliu Formation, Xisha Islands, South China Sea

The micro-conditions that control dolomitization processes were still not well known in natural environments. Cenozoic “island dolostones” are ideal for examining the processes since they are geologically young and have not experienced deep burial conditions. Miocene dolostones from the Xisha Islands, located in the South China Sea, are similar to those found on Grand Cayman Island, located in the Caribbean Sea. These dolostones are composed of low-Ca dolomite (LCD, < 55 mol % CaCO3; hereafter referred to as %Ca) and high-Ca dolomite (HCD, > 55 %Ca). Individual dolomite crystals are commonly formed entirely of LCD or HCD, and/or HCD cores that are encased by LCD and alternating zones of HCD and LCD (1–10 μm thick). The crystal textures indicate that the LCD and HCD are primary growth features (no obvious recrystallization) that formed as the dolomite replaced the limestone precursor. The compositional features (%Ca in LCD and HCD, average %Ca, and proportion of LCD and HCD) and geochemical parameters (O/C isotopes, Sr, Fe and Mn) of dolomite indicate that the Mg was incorporated into dolomite crystals in an orderly manner that was mainly controlled by the interaction of fluid properties and crystal structure. The fact that dolomite stoichiometry varied laterally and vertically throughout the successions shows that micro-scale physicochemical conditions played a critical role in the evolution of individual dolomite crystals. The similarities between the dolostones of the Xisha Islands and Grand Cayman, which are 15,795 km apart, indicate that the factors that control the micro- and large-scale features of these dolostones must have undergone similar processes or experienced similar physicochemical conditions despite their disparate settings.

Analysis of Bobbing Displays in the Grahami Series Anoles from Jamaica and Grand Cayman

Behavioral biologists have long been fascinated with the diversity of animal signals produced in the contexts of courtship and same-sex competition. In these contexts many lizards engage in conspicuous bobbing displays, and numerous studies have been devoted to describing these displays. Traditionally, bobbing displays are partitioned into units whose durations (and sometimes head amplitudes) are measured. Recently, Macedonia et al. (2019) introduced use of the Discrete Fourier Transform (DFT) as an alternative to unit-based variables for characterizing species-specific traits in display structure of Galápagos Lava Lizards (Microlophus spp.). The relative success of the two methods was not compared directly, however, because the homology of display units among species was uncertain. Here we overcome this problem using the “grahami series” of Anolis lizards—a monophyletic radiation of seven species on Jamaica and Grand Cayman. Our study had three primary goals. Our first goal was to discover whether DFT-based measures, unit-based measures, or their combination provided the best means to capture taxon-specific distinctiveness in display structure. To this end, we quantified bobbing displays and used nested analyses of variance (ANOVAs) to determine if particular variables were reliably superior at differentiating populations within a species. We then used principal components analysis to reduce the number of measurement variables, and entered the components into discriminant function analyses to determine which approach best discriminated among taxa. Results showed that no one type of measurement, or measurement combination, emerged as being consistently better at discriminating taxa across comparisons. Our second goal was to test a hypothesis that arose from our findings in Galápagos Lava Lizards—that the DFT may decrease in effectiveness as bobbing display structure increases in complexity. For this test we used four simple and compound display types from the species Anolis reconditus. Results of discriminant function analyses provided mixed support for the hypothesis, and we suggest that a definitive test of DFT performance and display complexity should utilize synthetic displays in which attributes of display structure are varied systematically. Last, we show how bobbing display structure maps onto alternative DNA-based phylogenies of the grahami series anoles. Whereas some species produced derived display types unanticipated from displays of more basal species in this adaptive radiation, others exhibited features that linked them to a particular population of a species in their clade.

Biochemical variability in sponges across the Caribbean basin

AbstractSponges are a diverse phylum of sessile filter‐feeding invertebrates that are abundant on Caribbean reefs and provide essential ecological services, including nutrient cycling, reef stabilization, habitat, and food for a variety of fishes and invertebrates. As prominent members of the benthic community, and thus potential food resources, factors determining the biochemical and energetic content of sponges will affect their trophic contributions to coral reef ecosystems. In order to evaluate the influence of geographic variation on biochemical composition and energetic content in the tissue of sponges, we collected several common and widespread species (Agelas conifera, Agelas tubulata, Amphimedon compressa, Aplysina cauliformis, Niphates amorpha, Niphates erecta, and Xestospongia muta) from multiple shallow reefs in four countries across the Caribbean Basin, including Belize, Curaçao, Grand Cayman, and St. Croix, U.S. Virgin Islands. In addition, we correlated inherent species‐level traits, including the production of antipredator chemical defenses and the relative abundance of microbial symbionts, with biochemical and energetic content. We found that energetic content was higher in sponges with antipredator chemical defenses, and was significantly correlated with the concentration of chemical extracts from these sponges. We also noted that sponges with high microbial abundance contained significantly more soluble protein than sponges with low microbial abundance. Finally, both biochemical and energetic content varied significantly among sponges from different locations; sponges from Grand Cayman had the highest lipid and energetic content, whereas sponges from Belize had the highest carbohydrate content but lowest energetic content. Despite similar environmental conditions at these sites, our results demonstrate that biochemical and energetic content of sponges exhibits geographic variability, with potential implications for the trophic ecology of sponges throughout the Caribbean Basin.

Cayman Islands Sea Turtle Nesting Population Increases Over 22 Years of Monitoring

Given differing trajectories of sea turtle populations worldwide, there is a need to assess and report long-term population trends and determine which conservation strategies are effective. In this study, we report on sea turtle nest monitoring in the Cayman Islands over a 22-year period. We found that green (Chelonia mydas) and loggerhead (Caretta caretta) nest numbers increased significantly across the three islands since monitoring began in 1998, but that hawksbill nest numbers remained low with a maximum of 13 nests recorded in a season. Comparing the first 5 years of nest numbers to the most recent 5 years, the greatest percentage increase in green turtle nests was in Grand Cayman from 82 to 1,005 nests (1,126%), whereas the greatest percentage increase for loggerhead turtle nests was in Little Cayman from 10 to 290 nests (3,800%). A captive breeding operation contributed to the increase in the Grand Cayman green turtle population, however, loggerhead turtles were never captive-bred, and these populations began to increase after a legal traditional turtle fishery became inactive in 2008. Although both species have shown significant signs of recovery, populations remain at a fragment of their historical level and are vulnerable to threats. Illegal harvesting occurs to this day, with multiple females taken from nesting beaches each year. For nests and hatchlings, threats include artificial lighting on nesting beaches, causing hatchlings to misorient away from the sea, and inundation of nests by seawater reducing hatch success. The impacts of lighting were found to increase over the monitoring period. Spatial data on nest distribution was used to identify critical nesting habitat for green and loggerhead turtles and is used by the Cayman Islands Department of Environment to facilitate remediation of threats related to beachside development and for targeted future management efforts.

On the efficacy and limitations of isolated carbonate platforms as “oceanic dipsticks” to reconstruct subsidence histories, a case study from the Paleogene to Neogene strata on Grand Cayman and Cayman Brac, B.W.I.

Carbonate sedimentary successions that developed on isolated oceanic islands typically comprise a series of unconformity-bounded packages of strata that reflect eustatic sea level changes superimposed on local tectonic movements. Resolving the subsidence and/or uplift of these islands, which are often assumed to have simple tectonic histories, is challenging because the tectonic movements are commonly of similar magnitudes to the eustatic oscillations. The uncertainty associated with each of the components involved in the construction of subsidence diagrams (e.g., age constraints, decompaction, eustatic sea level curves, paleobathymetry), therefore, introduces significant error margins when assessing the tectonic histories of isolated carbonate platforms. By using two end-member subsidence diagrams for the Paleogene to Neogene successions on Grand Cayman and Cayman Brac, it can be shown that their subsidence rates were heterogeneous over time and that the evolution of these islands vary significantly even though they are situated in the same basin. Although these islands, located 150 km apart, were subject to uniform changes in eustatic sea level, they have different stratigraphic architectures owing to their independent tectonic histories. From the Oligocene to the late Pliocene, the tectonic histories of Grand Cayman and Cayman Brac were analogous, and they subsided at a rate of 5.6 to 9.9 m/Myr. From the late Pliocene to ~400 ka, however, northeast Cayman Brac was uplifted by 165 m and tilted with a rotational axis offshore from the southwest end of the island, whereas Grand Cayman was uplifted by ~10 m with no rotational component. The results of this study challenge the assumption that isolated carbonate platforms have simple tectonic histories, while exploring and highlighting the common problems that are encountered with the construction of subsidence diagrams.

Systemic Helicobacter infection and associated mortalities in endangered Grand Cayman blue iguanas (Cyclura lewisi) and introduced green iguanas (Iguana iguana).

The Blue Iguana Recovery Programme maintains a captive breeding and head-starting program for endangered Grand Cayman blue iguanas (Cyclura lewisi) on Grand Cayman, Cayman Islands. In May 2015, program staff encountered two lethargic wild Grand Cayman blue iguanas within the Queen Elizabeth II Botanic Park (QEIIBP). Spiral-shaped bacteria were identified on peripheral blood smears from both animals, which molecular diagnostics identified as a novel Helicobacter species (provisionary name Helicobacter sp. GCBI1). Between March 2015 and February 2017, 11 Grand Cayman blue iguanas were identified with the infection. Two of these were found dead and nine were treated; five of the nine treated animals survived the initial infection. Phylogenetic analysis of the 16S rRNA gene suggests Helicobacter sp. GCBI1 is most closely related to Helicobacter spp. in chelonians. We developed a Taqman qPCR assay specific for Helicobacter sp. GCBI1 to screen tissue and/or blood samples from clinical cases, fecal and cloacal samples from clinically healthy Grand Cayman blue iguanas, including previously infected and recovered iguanas, and iguanas housed adjacent to clinical cases. Fecal and/or cloacal swab samples were all negative, suggesting that Grand Cayman blue iguanas do not asymptomatically carry this organism nor shed this pathogen per cloaca post infection. Retrospective analysis of a 2014 mortality event affecting green iguanas (Iguana iguana) from a separate Grand Cayman location identified Helicobacter sp. GCBI1 in two of three cases. The source of infection and mode of transmission are yet to be confirmed. Analysis of rainfall data reveal that all infections occurred during a multi-year dry period, and most occurred shortly after the first rains at the end of seasonal drought. Additionally, further screening has identified Helicobacter sp. GCBI1 from choanal swabs of clinically normal green iguanas in the QEIIBP, suggesting they could be asymptomatic carriers and a potential source of the pathogen.