Alan B. Bolten's research while affiliated with University of Florida and other places
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Publications (280)
Concerns over the sustainability of green turtle grazing have become a central topic in discussions of seagrass protection. Understanding grazing plot dynamics and aging is critical to evaluating the sustainability of grazing and understanding the role green turtles play in structuring seagrass foraging habitats. We investigated grazing plot dynami...
Populations of green turtles (Chelonia mydas), a megaherbivore that consumes seagrasses via cultivation grazing, are recovering worldwide. Information on plant-mediated effects on herbivore foraging behavior is critical to understanding plant-herbivore interactions and sustainability of grazing as ecosystems continue to change. In a Caribbean seagr...
Seagrasses form productive marine ecosystems that serve as important foraging grounds for grazers. Meadow productivity is vulnerable to environmental change, however, because environmental factors often strongly regulate seagrass growth. Understanding effects of grazing and environmental driver interactions on growth dynamics is therefore needed to...
Trindade Island, Brazil, is a small, remote volcanic island located 1140 km off the coast of southeastern Brazil. The green turtle (Chelonia mydas) nesting aggregation on Trindade is genetically distinct, the largest in the southwest Atlantic, and represents the southern limit of green turtle nesting in the Atlantic. Projeto TAMAR (a Brazilian cons...
Many population models assume the physiological processes that underlie reproductive parameters in adult sea turtles occur independent of time. Under this framework, each adult has an equal contribution to population growth, and reproductive parameters are invariant. Senescence, which describes the negative effects of aging, proposes the contrary;...
Populations of the green turtle (Chelonia mydas), a mega-herbivore that consumes seagrasses, are recovering worldwide. Understanding green turtle adaptations to herbivory and responses to changes in seagrass availability will be critical to interpreting plant-herbivore interactions as green turtle populations continue to rebound. Ingesta particle s...
Reconstructing past events of hybridization and population size changes are required to understand speciation mechanisms and current patterns of genetic diversity, and ultimately contribute to species' conservation. Sea turtles are ancient species currently facing anthropogenic threats including climate change, fisheries, and illegal hunting. Five...
Recovery of green turtles (Chelonia mydas), mega-herbivores that consume seagrasses, is resulting in dramatic ecosystem-wide changes as meadows are returned to a natural grazed state. The green turtle grazing strategy, with long-term cultivation of meadows and high foraging site fidelity, is distinct from other terrestrial and aquatic mega-herbivor...
Although hydrogen isotopes (δ ² H) are commonly used as tracers of animal movement, minimal research has investigated the use of δ ² H as a proxy to quantify resource and habitat use. While carbon and nitrogen are ultimately derived from a single source (food), the proportion of hydrogen in consumer tissues originates from two distinct sources: bod...
Within the same population, nesting green turtles (Chelonia mydas) might exploit different niches by exhibiting polymorphic foraging strategies and/or inhabiting geographically distinct foraging areas. This is crucial information for the conservation of this species. Here, we used stable carbon and nitrogen isotope ratios (δ13C and δ15N) to test fo...
Within the same population, nesting green turtles (Chelonia mydas) might exploit different niches by exhibiting polymorphic foraging strategies and/or inhabiting geographically distinct foraging areas. This is crucial information for the conservation of this species. Here, we used stable carbon and nitrogen isotope ratios (δ13C and δ15N) to test fo...
Most of the knowledge about the biology, ecology, and conservation needs of sea turtles has been obtained from studies of adult females on nesting beaches and, to a lesser extent, from observations of juveniles and subadults in their foraging and development habitats. Those studies have principally sought to understand natal homing and nest site fi...
What happens in meadows after populations of natural grazers rebound following centuries of low abundance? Many seagrass ecosystems are now experiencing this phenomenon with the recovery of green turtles (Chelonia mydas), large‐bodied marine herbivores that feed on seagrasses. These seagrass ecosystems provide a rare opportunity to study ecosystem‐...
Hybridization is a fundamental evolutionary and ecological process with significant conservation ramifications. Sea turtle hybridization occurs at unusually high frequencies along the northeastern coast of Brazil. To better understand the process, we studied the reproductive output, migration patterns through satellite telemetry, and isotopic niche...
Marine turtles are challenging species to protect because they occur over large geographic scales. Tagging individual turtles at nesting beaches and foraging areas, and the resulting mark-recapture data sets have gradually enabled us to understand their migratory behaviour and dispersal. Within the Caribbean region, several turtle tagging projects...
Population assessments conducted at reproductive sites of migratory species necessitate understanding the foraging-area origins of breeding individuals. Without this information, efforts to contextualize changes in breeding populations and develop effective management strategies are compromised. We used stable isotope analysis of tissue samples col...
Priority setting approaches for widely distributed and long-lived species can be challenging. This is especially true for sea turtles, which are species of conservation concern. The aim of this study was to conduct a detailed analysis of threats to identify, quantify and prioritize the main impacts to the loggerhead (Caretta caretta) population in...
Seagrass meadows host diverse invertebrate faunal communities. Infaunal organisms residing in the sediments of meadows play important roles in the functioning of these ecosystems, such as the breakdown of organic matter. Disturbance to the benthic environment through grazing by megaherbivores, such as dugongs (Dugong dugon), can reduce infauna abun...
For stochastic growth processes, integrated mixed-effects (IME) models of capture-recapture data and size-at-age data from calcified structures such as otoliths can reduce bias in model parameters. Researchers have not fully explored the performance of IME models for simultaneously estimating the unknown ages, growth model parameters, and derived v...
Seagrass meadows buffer sediments against resuspension and erosion by reducing water velocity and attenuating wave energy, thereby promoting accumulation of sediment and associated carbon. Grazing by green turtles (Chelonia mydas) can significantly reduce the aboveground canopy in meadows. Increasing green turtle population sizes will return more s...
Understanding the population composition and dynamics of migratory megafauna at key developmental habitats is critical for conservation and management. The present study investigated whether differential recovery of Caribbean green turtle (Chelonia mydas) rookeries influenced population composition at a major juvenile feeding ground in the southern...
Increasing green turtle abundance will lead to increased grazing within seagrass habitats—ecosystems that are important for carbon sequestration and storage. However, it is not well understood how carbon dynamics in these ecosystems respond to grazing and whether a response differs among meadows or locations. We measured seagrass ecosystem metaboli...
Hawksbills (Eretmochelys imbricata) and green turtles (Chelonia mydas) are the predominant nesting sea turtle species on the beaches of Príncipe Island in the Gulf of Guinea. The extent of nesting has been largely unknown, but such information is essential for management and conservation. Our study is the first island-wide nesting assessment. Resul...
After hatching, juveniles of most sea turtle species undertake long migrations across ocean basins and remain in oceanic habitats for several years. Assessing population abundance and demographic parameters during this oceanic stage is challenging. Two long-recognized deficiencies in population assessment are (i) reliance on trends in numbers of ne...
Because somatic growth is an integrated response to variables on individual, population and ecosystem levels, growth rates have been used as indicators of change in a wide range of demographic and environmental variables. Models of sea turtle growth that relate changes in productivity to environmental changes have all focused on the mean or expecte...
In a highly heterogeneous open ocean, swirling oceanographic structures such as eddies drive ocean productivity and aggregate many predators, including oceanic sea turtles. During early life, juvenile loggerhead turtles can spend more than a decade feeding on gelatinous zooplankton in the open ocean, but the way they use mesoscale eddies is still p...
Avaiable at http://www.seaturtle.org/mtn/archives/mtn157/mtn157-5.shtml
Hawksbills, the most tropical sea turtle species. In Príncipe (1º 37’ N; 7º 23’ E) is located one of the last remaining aggregations in West Africa. Therefore, it is of high conservation value but research on their
biology and ecology remains scarce. Here we report, for the first time, data on the trophic and foraging ecology of both juvenile and a...
SWOT Report XIV features an up-to-date, comprehensive map of sea turtle distribution in the Mediterranean, a picture of loggerhead movements in the Atlantic, and expert answers to the most frequently asked questions about sea turtles.
Other articles explore the effects of red tides on turtles, best practices for transporting stranded turtles, and...
Population differentiation and diversification depend in large part on the ability and propensity of organisms to successfully disperse. However, our understanding of these processes in organisms with high dispersal ability is biased by the limited genetic resolution offered by traditional genotypic markers. Many neustonic animals disperse not only...
Sea turtle hybridization is a common phenomenon in Brazil between loggerheads (Caretta caretta) and hawksbills (Eretmochelys imbricata) as well as between loggerheads and olive ridleys (Lepidochelys olivacea). In a previous study we showed that the reproductive output of loggerhead/hawksbill hybrids is similar to that of parental species, suggestin...
Sea turtle research has received substantial focus worldwide. However, research on the immature life stages of sea turtles is still relatively limited. The latter is of particular importance, given that a large proportion of sea turtle populations comprises immature individuals. We set out to identify knowledge gaps in immature sea turtle research,...
Seagrass meadows are often comprised of diverse assemblages of seagrasses and algae. Green turtles (Chelonia mydas) are a prominent megaherbivore in seagrass meadows—capable of consuming large amounts of aboveground seagrass biomass and driving shifts in seagrass species dominance. Previous green turtle grazing studies have focused on diversity and...
Comparative syntheses of key demographic parameters are critical not only for identifying data gaps, but also for evaluating sources of heterogeneity among estimates. Because demographic studies frequently exhibit heterogeneity, evaluating sources of heterogeneity among estimates can inform biological patterns and conservation actions more broadly....
The loggerhead (Caretta caretta) is the most common sea turtle in the Azores. Since they do not nest in the area, a tagging program was started in the 1980’s to try to discover their origin. The result based on size distribution, suggested that they mainly are coming from beaches in SE United States. A collaboration between University of Florida an...
Seagrass meadows are important sites for carbon storage. Green turtles (Chelonia mydas) are marine megaherbivores that consume seagrass throughout much of their global range. With successful conservation efforts, turtle abundance will increase, leading to more meadows being returned to their natural grazed state. There is concern this may lead to a...
Neospirorchis (Digenea: "Spirorchiidae") are blood flukes of sea turtles. Trematodes tentatively identified as Neospirorchis sp. infect various sites within sea turtles inhabiting waters of the southeastern United States, but efforts to obtain specimens adequate for morphologic study has proven difficult. Two genetic targets, the internal transcrib...
Juvenile oceanic-stage sea turtles are particularly vulnerable to the increasing quantity of plastic coming into the oceans. In this study, we analysed the gastrointestinal tracts of 24 juvenile oceanic-stage loggerheads (Caretta caretta) collected off the North Atlantic subtropical gyre, in the Azores region, a key feeding ground for juvenile logg...
Somatic growth is an integrated, individual-based response to environmental conditions, especially in ectotherms. Growth dynamics of large, mobile animals are particularly useful as bio-indicators of environmental change at regional scales. We assembled growth rate data from throughout the West Atlantic for green turtles, Chelonia mydas, which are...
In 2010, an international group of 35 sea turtle researchers refined an initial list of more than 200 research questions into 20 metaquestions that were considered key for management and conservation of sea turtles. These were classified under 5 categories: reproductive biology , biogeography, population ecology, threats and conservation strategies...
Globally, sea turtle hybridization has been reported at very low frequencies. However, in Brazil, a high incidence (>40% of morphologically assigned hawksbills) of hybridization between loggerheads and hawksbills has been reported. To the best of our knowledge, this is the first analysis of the effect of hybridization on the reproductive output of...
Assessments of large-scale disasters, such as the Deepwater Horizon oil spill, are problematic because while measurements of post-disturbance conditions are common, measurements of pre-disturbance baselines are only rarely available. Without adequate observations of pre-disaster organismal and environmental conditions, it is impossible to assess th...
Sea turtles are important to healthy coastal ecosystems and their populations are known to be declining worldwide. São Tomé and Príncipe possess one of the last sea turtle aggregations in West Africa, especially for the critical endangered hawksbill species (Eretmochelys imbricata). Despite its high conservation value, local and regional informatio...
Sea turtles are of paramount importance to healthy coastal ecosystems, and their populations are known to be declining worldwide. Príncipe Island (1º 37’ N; 7º 23’ E) possesses one of the last sea turtle aggregations in West Africa. Despite its high conservation value, local and regional information on their numbers and habitats remains scarce. Her...
Somatic growth dynamics are an integrated response to environmental conditions. Hawksbill sea turtles (Eretmochelys imbricata) are long-lived, major consumers in coral reef habitats that move over broad geographic areas (hundreds to thousands of kilometers). We evaluated spatio-temporal effects on hawksbill growth dynamics over a 33-yr period and 2...
Despite its geographic isolation from large population centres, the Azores archipelago (north-eastern Atlantic) is not immune to thegrowing environmental threat of marine litter.Recent research developments suggest that many organisms are directly affected by this issue that should be addressed by consistent monitoring efforts. The goal of this stu...
Hawksbills, the most tropical sea turtle species. In Príncipe (1º 37’ N; 7º 23’ E) is located one of the last remaining aggregations in West Africa. Therefore, it is of high conservation value but research on their
biology and ecology remains scarce. Here we report, for the first time, data on the trophic and foraging ecology of both juvenile and a...
Genetic markers are often used to designate population units for management and conservation, but widespread sharing of mitochondrial DNA control-region haplotypes defined from short (<500 base-pair [bp]) sequences often limits inferences of population connectivity in marine turtles. Haplotype CM-A8, defined from 490-bp sequences, dominated the hap...
Age at maturation data are integral to understanding dynamics of threatened and endangered sea turtle populations. However, full characterization of this parameter requires information regarding variability in growth rates and both size and age at maturation potentially resulting from diverse environmental and biological influences. To address the...
Príncipe Island (140km2) has an incredible rich biodiversity. This region, together with the other Gulf of Guinea islands, was considered one of the 10 Richest Centers of Marine Endemism. The beaches are mainly used by green sea turtles ( Chelonia mydas ) and a small number of hawksbills ( Eretmochelys imbricata ) and leatherbacks ( Dermochelys cor...
Príncipe Island (140 km2) has an incredible rich biodiversity. This region, together with the other Gulf of Guinea islands, was considered one of the 10 Richest Centers of Marine Endemism. The beaches are mainly used by green sea turtles ( Chelonia mydas ) and a small number of hawksbills ( Eretmochelys imbricata ) and leatherbacks ( Dermochelys co...
Stable isotope analysis is a useful tool to track animal movements in both terrestrial and marine environments. These intrinsic markers are assimilated through the diet and may exhibit spatial gradients as a result of biogeochemical processes at the base of the food web. In the marine environment, maps to predict the spatial distribution of stable...
Carbon and nitrogen stable isotope (δ13C and δ15N) analysis has been used to elucidate foraging and migration behaviours of endangered sea turtle populations. Isotopic analysis of tissue samples from nesting females can provide information about their foraging locations before reproduction. To determine whether loggerhead (Caretta caretta) eggs pro...
RATIONALEStable isotope analysis has been used extensively to provide ecological information about diet and foraging location of many species. The difference in isotopic composition between animal tissue and its diet, or the diet-tissue discrimination factor, varies with tissue type. Therefore, direct comparisons between isotopic values of tissues...
Age at sexual maturity (AgeSM) is one of the most serious demographic data gaps for sea turtle populations. Better estimates of AgeSM and associated variance would improve evaluation of population dynamics and responses of populations to disturbances and conservation measures. A population of Kemp's ridleys Lepidochelys kempii was raised in captivi...
Many species of marine organisms go through ontogenetic shifts that occur in unknown or inaccessible locations. Finding these areas is crucial to understand connectivity and resilience of populations, both of which have conservation implications. When extrinsic markers are not suitable to track organisms, intrinsic markers can be useful to infer th...
Use of scute in biochemical studies to infer ontogenetic changes of habitat and diet in sea turtles is becoming more frequent because scute is an inert tissue with continuous growth that can record habitat and diet changes through time. Changes are detectable through biochemical markers such as stable isotopes and trace elements. These studies are...
