HEMATOLOGIC AND BIOCHEMICAL VALUES OF FREE-RANGING HAWKSBILL SEA TURTLES (ERETMOCHELYS IMBRICATA) IN GLOVER'S REEF, BELIZE.

Blood samples were obtained from the dorsal cervical sinus of free-ranging hawksbill sea turtles (Eretmochelys imbricata) collected at Glover's Reef Marine Reserve, 42 km east of the coast of Belize, for hematology and plasma biochemistry analysis. Unknown sex, subadult turtles (N = 32) were sampled in 2013 (n = 22) and 2017 (n = 10). To provide a more robust data set, parameters that did not have statistically significant differences were pooled and treated as a single population. Eleven hematologic parameters were evaluated; of these, five were pooled. Twenty-three plasma biochemical parameters were evaluated; of these, 15 were pooled. The PCV observed in this study (mean 33.44%) was double that observed in two studies of juvenile hawksbills in Dubai (means 17% and 16%), whereas the total WBC count was half that observed in immature and adult hawksbills sampled in the Galápagos (mean 2.91 × 103 versus 5.3 × 103/µl). Total protein and albumin were lower than regionally similar, adult female hawksbills in Brazil (means 3.36 versus 5.45 g/dl and 0.93 versus 2.11 g/dl, respectively). Globulins were higher (mean 2.43 versus 1.06 and 0.5 g/dl), driving the albumin:globulin ratio lower than that observed in two studies of juvenile hawksbills in Dubai (0.4:1 versus 1.1:1 and 1:1, respectively). These findings represent a geographically distinct population from previous reports, highlight the variability in blood parameters from disparate populations, and reaffirm the vital importance of considering a multitude of variables when interpreting reptilian blood values. The similarities in the majority of values observed in 2013 and 2017 provide confidence in the stability of these parameters in this population.

Macroalgae reveal nitrogen enrichment and elevated N:P ratios on the Belize Barrier Reef.

Macroalgal blooms are increasing on the Belize Barrier Reef (BBR) as scleractinian coral cover declines. Although some have attributed this to reduced grazing, the role of land-based nutrient pollution has not been assessed. Nutrient enrichment was quantified through macroalgal tissue analysis from Belize City to the offshore fore reef and at several central BBR lagoon sites. These recent data were compared to baseline data from the 1980s. Significant nearshore-to-offshore gradients of %N, %P and δ13C in macroalgae all indicated land-based sources of these nutrients. Macroalgal δ15N values were generally enriched in nearshore waters where values matched those reported for human sewage. Notably, the N:P ratios of recent macroalgae measurements were elevated at all sites, more than two-fold higher than values from the 1980s (~30: 1 to 70:1). These results support the hypothesis that nitrogen enrichment from land-based sources has increased phosphorus limitation driving macroalgal blooms and coral stress on the BBR.

Predator Diet and Trophic Position Modified with Altered Habitat Morphology.

Empirical patterns that emerge from an examination of food webs over gradients of environmental variation can help to predict the implications of anthropogenic disturbance on ecosystems. This "dynamic food web approach" is rarely applied at the coastal margin where aquatic and terrestrial systems are coupled and human development activities are often concentrated. We propose a simple model of ghost crab (Ocypode quadrata) feeding that predicts changing dominant prey (Emerita talpoida, Talorchestia sp., Donax variablis) along a gradient of beach morphology and test this model using a suite of 16 beaches along the Florida, USA coast. Assessment of beaches included quantification of morphological features (width, sediments, slope), macrophyte wrack, macro-invertebrate prey and active ghost crab burrows. Stable isotope analysis of carbon ((13)C/(12)C) and nitrogen ((15)N/(14)N) and the SIAR mixing model were used to determine dietary composition of ghost crabs at each beach. The variation in habitat conditions displayed with increasing beach width was accompanied by quantifiable shifts in ghost crab diet and trophic position. Patterns of ghost crab diet were consistent with differences recorded across the beach width gradient with respect to the availability of preferred micro-habitats of principal macro-invertebrate prey. Values obtained for trophic position also suggests that the generalist ghost crab assembles and augments its diet in fundamentally different ways as habitat morphology varies across a highly dynamic ecosystem. Our results offer support for a functional response in the trophic architecture of a common food web compartment (ghost crabs, macro-invertebrate prey) across well-known beach morphologies. More importantly, our "dynamic food web approach" serves as a basis for evaluating how globally wide-spread sandy beach ecosystems should respond to a variety of anthropogenic impacts including beach grooming, beach re-nourishment, introduction of non-native or feral predators and human traffic on beaches.