Download or read book Spatial and Temporal Patterns of Habitat Use by East Pacific Green Turtles Chelonia Mydas in a Highly Urbanized Foraging Ground written by and published by . This book was released on 2012 with total page 43 pages. Available in PDF, EPUB and Kindle. Book excerpt: Green sea turtles, Chelonia mydas, utilize coastal areas as foraging grounds for the majority of their lives. Human development of coastlines is increasing, but the effects of the urbanization of foraging grounds on green turtles are poorly understood. I used both manual and automated acoustic telemetry to determine the home ranges, movement behavior, and temporal patterns of site visitation of green turtles during 2009-2011 in San Diego Bay, California, a highly urbanized temperate foraging area. The home ranges of all tracked turtles were restricted to the southern portion of San Diego Bay, where eelgrass (Zostera marina) is abundant and where human activity is the lowest within the bay. Core activity areas coincided with eelgrass distribution or occurred adjacent to the warm water-effluent outfall of a waterfront power plant. Automated monitoring of sites throughout south San Diego Bay confirmed this finding, showing that green turtles most frequently visited the outfall of the power plant and areas known to contain eelgrass. This method also elucidated that turtle presence at the power plant was strongest during the winter and at night, whereas visitation to eelgrass areas was strongest during the spring and in the daytime. Turtle visitation to a high boat traffic shipping terminal was rare but occurred almost exclusively during the daytime, the period during which human activities in the area are also the highest. Manual tracking of green turtles similarly demonstrated that individuals ranged across larger portions of south San Diego Bay during the day, during which they exhibited high swimming speeds but highly non-linear movement. Turtle activity at night was primarily restricted to the power plant's effluent outfall channel and adjacent jetty. Nighttime movement was characterized by long periods of inactivity sporadically interrupted by brief, linear movements to new resting locations. Collectively, the results of this study paint a robust picture of the spatial, diel, and seasonal patterns of habitat use by green turtles in San Diego Bay. All data support the hypothesis that south San Diego Bay serves as important turtle habitat within the bay. Further, a combination of manual and automated acoustic telemetry enables a more complete understanding of turtle spatial ecology that would not have been possible with exclusive use of one technique. Future monitoring and modeling is required to document the potential effects of changing environmental conditions, including power plant closure, on green turtles resident to San Diego Bay. This study helps to assess the data gap of how turtles use urbanized foraging areas and changing coastal ecosystems, a currently novel scenario that will likely become commonplace in the face of increasing coastal development worldwide.
Download or read book Influence of Temperature on Habitat Use by East Pacific Green Turtles chelonian Mynas in an Urbanized Environment written by Sheila Veronica Madrak and published by . This book was released on 2016 with total page 80 pages. Available in PDF, EPUB and Kindle. Book excerpt: Project Overview. Thermal characteristics of marine environments are changing rapidly on both global and local scales. Worldwide, ocean temperatures are increasing -- a trend expected to continue (Meehl et al. 2005; Bindoff et al. 2007; IPCC 2007). However, at the local level water temperature is more variable, demonstrating both warming and cooling through space and time (Hoegh-Guldberg and Bruno 2010; Kosaka and Xie 2013). Many marine organisms are adapted to specific, often highly constrained, thermal ranges. Global climate change and anthropogenic influences have already had dramatic effects on marine species (Harley et al. 2006; IPCC 2007; Hoegh-Guldberg and Bruno 2010). While large-scale changes in temperature can be attributed to shifts in the global climate regime, there are other human-mediated factors that influence local thermal conditions. One major anthropogenic influence on local marine environments is thermal effluent from power plants and industry that utilize once-through cooling (OTC) systems. The stations that use OTC systems generate waste heat, a by-product of the cooling process, which must be released into the environment (either via cooling towers or natural water source). Thus, OTC system stations alter the thermal environment proximate to their locations. Although local and global scale changes may be driven by different factors, changes to the thermal environment at the local level can provide a model system to study the effects of largescale climate change. Characterizing the responses of coastal fauna to rapid shifts in thermal conditions addresses a key gap in ecological knowledge -- understanding how populations of longlived marine vertebrates will be affected by a thermally dynamic environment that is changing at rapid rate. The fossil fuel-based South Bay Power Plant (SBPP) in San Diego, California was in operation from 1960 to 2010 and discharged warm-water effluent into southern San Diego Bay (SDB) and utilized an OTC system. East Pacific green sea turtles (Chelonia mydas), resident in SDB since at least the 1890's (Parsons 1962), have been routinely observed in the power plant outfall area since the 1960s (Stinson 1984; McDonald and Dutton 1990). Previous research suggests that these turtles used the outfall area to reduce metabolic costs and exhibit higher growth rates than other populations of green turtles (Eguchi et al. 2010, Eguchi et al. 2012). On December 31, 2009, two of the plant's four generators were permanently shut down; complete decommissioning of the plant occurred on December 31, 2010. This power plant closure provided a rare experimental opportunity to assess how rapid changes in the thermal environment will affect a resident marine turtle population in a coastal foraging area. The first chapter of my dissertation represents a review of the scientific studies that demonstrated physiological and behavioral changes across mobile aquatic reptiles utilizing these areas with heated effluent. I identify key responses to thermal effluent in reptiles in both marine and freshwater environments and present a case study from green turtles in SDB. The second chapter of my dissertation reflects my research using acoustic telemetry to monitor the changes in distribution and behavior of green turtles in response to the closure of the SBPP. The third and final chapter of my dissertation summarizes the changes of dive behavior by green turtles before and after the closure of the SBPP.
Download or read book Recovery Plan for U S Pacific Populations of the East Pacific Green Turtle Chelonia Mydas written by Pacific Sea Turtle Recovery Team (U.S.) and published by . This book was released on 1998 with total page 62 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Recovery Plan for U S Pacific Populations of the Green Turtle Chelonia Mydas written by Pacific Sea Turtle Recovery Team (U.S.) and published by . This book was released on 1998 with total page 98 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Identifying foraging and space use patterns of juvenile green sea turtles Chelonia mydas in Brewers Bay St Thomas using a fine scale positioning acoustic array written by Taylor Brunson and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: As green sea turtle (Chelonia mydas) populations in the Caribbean recover from historical overexploitation, growing environmental obstacles pose threats to the recovery of this species. The invasion of Halophila stipulacea seagrass in previously Syringodiumfiliforme and Halodule wrightii -dominated beds drastically alters the composition of green turtle foraging habitat. This change in forage supply for juvenile and adult green turtles in the Caribbean could impact their future habitat use and resource partitioning, information that conservation and management agencies use to implement protective guidelines for this species. We conducted a fine-scale tracking study of green turtles’ space use and movement patterns in Brewers Bay, St. Thomas to investigate their foraging selectivity in the mixed-species seagrass beds. The fine-scale positioning system(FPS) acoustic receiver array was deployed across ~1.5 km2 of the bay, which includes seagrass, coral reef, and sand/rock benthic habitat. Seventeen individual juvenile green sea turtles were tracked with acoustic transmitters with an estimated precision of ± 2meters. The native and invasive seagrass composition was mapped in the highest trafficked daytime area to pair with the turtles’ foraging locations. Turtles displayed typical diel patterns of movement with higher activity levels in shallow mixed-seagrass habitats during the day and lower activity levels in shallow reefs and rocky habitats at night. These movement results were linked to seagrass composition within the sampling grid using resource selection functions (RSF) to estimate turtle selection towards each seagrass species in Brewers Bay. Turtles were actively selecting the two native species, with no selection towards the invasive seagrass despite its high abundance. Interestingly, three individuals utilized foraging areas outside the sampling grid and in deeper water with monotypic invasive seagrass. This pattern of space use has not been observed in past tracking and observational studies in Brewers Bay, implying that part of this population has started modifying its foraging patterns to incorporate H. stipulacea.
Download or read book Home Range and Habitat Use of Juvenile Green Sea Turtles Chelonia Mydas in Brewers Bay St Thomas USVI written by Kari Gehrke and published by . This book was released on 2017 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt: Green turtles living in coastal foraging areas often occupy distinct home ranges within which they visit resting and foraging sites. Knowledge about the size of home ranges and movement patterns within these areas is important for sea turtle conservation. However, few data are available for the wider Caribbean. This study measured the movement pattern of five juvenile green sea turtles in Brewers Bay, St. Thomas, in the US Virgin Islands. Each turtle was fitted with a V13 acoustic transmitter and tracked from 90 to 214 days. Turtles were tracked with a fixed array of 30 acoustic receiving stations placed ~200-260 meters apart throughout Brewers Bay. Minimum convex polygon (MCP) and kernel density estimator (KDE) techniques were used to measure home range size. Home ranges were split into days vs. night times and compared by using utilization distributions (UD). Habitat classification was done in areas of high turtle activity and overlapped with home ranges. A general linear model was used to explore the relationship between the home range size (95% UD), core area size (50% UD), and potential predictors: mass. Average KDE day home range size was 63.3 Ha and average day core area was 6.9 Ha. Average KDE night home range size was 35.9 Ha and average night core area was 5.1 Ha. All five incremental area plots became asymptotic, indicating that the home range estimates are robust. There was a statistically significant relationship between core area size and predictor variable (P-value= 0.002; mass). Tracking results showed that all five turtles remained in Brewers Bay for 98% of the tracking duration. During the day turtles were located in seagrass beds and at night they moved to resting areas associated with natural and artificial coral reefs. Core areas for foraging overlapped with seagrass beds dominated by Syringodium filiforme; turtles occurred less frequently in seagrass beds with the invasive Halophila stipulacea. During the night there is less activity when compared to day time hours. Our data confirm that Brewers Bay is an important foraging and resting habitat for juvenile green sea turtles and that their foraging movements center on areas with S. filiforme. These areas in return should receive focused management for both seagrass and reefs to protect green sea turtles. With this management these areas should receive protection from recreational boaters and tourists to prevent the spread of the invasive H. stipulacea
Download or read book Synopsis of the Biological Data on the Green Turtle Chelonia Mydas Linnaeus 1758 written by Harold F. Hirth and published by . This book was released on 1997 with total page 130 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Effects of Temperature and Habitat on the Movement Patterns of Green Sea Turtles Chelonia Mydas Within an Urbanized River and Local Estuary written by Daniel Crear and published by . This book was released on 2016 with total page 80 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: Urban coastal development has led to major changes in ocean temperatures and habitats along the coastline. These alterations particularly affect coastal ectothermic marine species, such as green sea turtles, Chelonia mydas. This species has been observed north of their geographical range in the eastern Pacific; inhabiting a river and estuary that both have anthropogenically-altered water temperatures and habitats. Passive and active acoustic telemetry was used to determine how green sea turtle movements and habitat use were affected by these anthropogenically-altered sites. Turtles used both sites during the summer months, while during the winter, individuals selected for areas where warm water was discharged from power plants into the river. Further, turtles tracked in the larger river used more area than those tracked in the smaller estuary. Turtles selected habitats associated with manmade structures at both sites and eelgrass beds within the estuary to potentially rest and forage upon.
Download or read book Tracking Turtles Back in Time written by Calandra N. Turner Tomaszewicz and published by . This book was released on 2016 with total page 219 pages. Available in PDF, EPUB and Kindle. Book excerpt: Of the five species of sea turtles that inhabit the east Pacific Ocean, two, the North Pacific loggerhead (Caretta caretta) and East Pacific green turtle (Chelonia mydas), experience some of the highest rates of globally documented mortality in a productive foraging hotspot near the Baja California Peninsula (BCP), Mexico. This area, the Gulf of Ulloa, overlaps with high levels of fishing, resulting in thousands of dead turtles, many that wash up on the beach of Playa San Lázaro on the BCP. It is unknown how long loggerheads inhabit distinct regions of the North Pacific, and to what degree juvenile individuals in the population demonstrate variation in their life history patterns. Similarly, it is unknown how long green turtles occupy oceanic regions of the eastern Pacific before settling into more nearshore habitats, or how they use the Gulf of Ulloa. My research determined the residency duration at different foraging grounds within the eastern Pacific, as well as basic demographic information such as age-at-settlement, age-at-maturation, and timing of ontogenetic shifts, for these two endangered sea turtle populations. By determining life history parameters and the length of time individuals in these populations spend in distinct high-risk habitats, managers can better understand exposure to spatially explicit threats and prioritize conservation approaches. I focused particularly on duration of time spent in the high-bycatch waters of the Gulf of Ulloa. To this end, I developed a novel technique that combined skeletochronology (the study of growth and age increments in bones) with sequential stable carbon ([delta]13C) and nitrogen ([delta]15N) isotope analysis of humerus bone growth layers. Naturally occurring stable isotope gradients exist in ocean systems such that habitats and foraging behaviors can be distinguished (i.e. nearshore vs. offshore habitats or high vs. low trophic levels). Given these isotope gradients, the combination of skeletochronology with stable isotope analysis of sequentially sampled growth layers provides a multi-year record of location, diet, size, age, and annual growth of individual turtles, allowing the reconstruction of life history and long-term habitat use patterns. The combination of these techniques allowed me to address questions that could not be answered using either technique alone.
Download or read book Home Range and Habitat Use of Juvenile Green Turtles in a Shallow Tidal Environment written by Meagan Gary and published by . This book was released on 2017 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt: The home range can be further understood by examining: (1) environmental factors that are responsible for its selection, and (2) habitat use. Green turtle (Chelonia mydas) home ranges are characterized by their food abundance, distribution, and quality. The shallow water habitats of The Bahamas are important foraging sites for juvenile green turtle. The goal of this study was to determine how turtles use their home range at a tidal foraging site. I tracked turtle home range using acoustic telemetry. I conducted esophageal lavage on tracked turtles and mapped the vegetation coverage. Turtle home ranges were small, and often overlapping areas (mean ± SD= 0.64 ± 0.24 km2). Turtles consumed primarily seagrass (Thalassia testudinum), which was concentrated inside the tidal creek. This study documented the smallest recorded home ranges of juvenile green turtles and examines the combination of the effects of tide, temperature, and vegetation on green turtle home range.
Download or read book Foraging Ecology of Green Turtles Chelonia Mydas on the Texas Coast as Determined by Stable Isotope Analysis written by Catherine Concetta Theresa Gorga and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The green turtle, Chelonia mydas, is a circumglobal species that exhibits several important developmental or ontogenetic shifts throughout its life history. The first major shift occurs when juvenile turtles migrate from pelagic habitat, where they forage as omnivores, to coastal neritic habitat, where they become primarily herbivores, foraging on algae and seagrass. Anecdotal evidence and gut-content analyses suggest that juvenile green turtles in south Texas bays, such as the lower Laguna Madre and Aransas Bay, undergo an additional ontogenetic shift during this important life history stage. Evidence from stable isotope analysis (SIA) of scute tissues of green turtles from Texas' lower Laguna Madre and Aransas Bay supports an intermediate stage between this species' shift from pelagic waters to seagrass beds in neritic waters; this additional shift comprises an initial recruitment of post-pelagic juveniles to jetty habitat located on the channel passes Gulf-ward of adjacent bays before subsequently recruiting to seagrass beds in these bays. Examination of stable carbon ([delta]13C) and nitrogen ([delta]15N) isotopes in microlayers of scute tissue from several size classes of green turtles from the lower Laguna Madre and Aransas Bay was used to confirm the occurrence of two ontogenetic shifts. Smaller green turtles (35 cm SCL) exhibited more depleted [delta]13C signatures and more enriched [delta]15N signatures, consistent with jetty habitat, compared to those of larger counterparts ( 45 cm SCL) that displayed enriched [delta]13C signatures and depleted 15N signatures, consistent with seagrass habitat. Changes in the isotopic composition between these size classes indicate distinct shifts in diet. Post-pelagic juveniles first recruit to jetty habitat and forage primarily on algae, before subsequently shifting to seagrass beds and foraging primarily on seagrass. These findings indicate the use of a characteristic sequence of distinct habitats by multiple life history stages of green turtles in Texas bays, a conclusion with broad management implications for this endangered species.
Download or read book Development of a Species Distribution Model for the East Pacific Green Sea Turtle Using Ecological Geoprocessing Tools written by Roxanne Duncan and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: East Pacific green sea turtles, Chelonia mydas, play ecologically important roles in marine habitats which range from grazing (and thus regularly "mowing") algae and seagrass beds to cycling nutrients between the ocean and land. However, these important grazers have been hunted to ecological extinction in some places for their eggs, meat, and skin. The conservation initiative for the survival of sea turtles requires the protection of their primary habitats in conjunction with a decrease in their interaction with humans. One way these objectives can be met is through the creation of species distribution maps (SDMs). For this thesis, a SDM was created from a generalized additive model used to identify major feeding areas for East Pacific green turtles residing in the Galapagos Islands. The input for the model was green turtle sighting locations during a June 2010 marine life observation survey and remotely sensed values of four oceanographic parameters obtained from satellite sensors (Bathymetry, Sea Surface Temperature, Chlorophyll a, and Current Speed). Line transects of intertidal and subtidal shoreline regions of the islands of Isabela, San Cristobal, and Floreana were also completed, to describe similarities and differences in macroalgal abundance between the locations. A generalized additive model (GAM) explained 56% of the data's null deviance and had a true positive rate of 0.83. The corresponding species distribution map indicated that East Pacific green sea turtles prefer to forage in warm, low chlorophyll a, slow moving waters at depths mostly less than 250m throughout the archipelago. ANOVA analyses showed that macroalgal abundance was statistically different (p-value
Download or read book Recovery Plan for U S Pacific Populations of the East Pacific Green Turtle Chelonia Mydas written by and published by . This book was released on 1998 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Green Turtle and Hawksbill Reptilia Cheloniidae written by Brian Groombridge and published by . This book was released on 1989 with total page 612 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Bioaccumulation and Health Effects of Contaminants in the East Pacific Green Turtle Chelonia Mydas and Habitat in San Diego Bay written by Lisa M Komoroske and published by . This book was released on 2009 with total page 124 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Synopsis of Biological Data on the Green Turtle Chelonia Mydas Linnaeus 1758 written by Harold F. Hirth and published by . This book was released on 1971 with total page 88 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Spatial Distribution and Abundance of Large Green Turtles on Foraging Grounds in the Florida Keys USA written by Ryan Charles Welsh and published by . This book was released on 2019 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt: Discerning distribution, density, and abundance of organisms is essential for conservation and management of imperiled species. However, simple counts of sampled individuals are often not adequate to make such estimates, this is especially true for large and highly mobile marine animals. Green turtles (Chelonia mydas) are a highly migratory, long-lived, late-maturing, marine megafauna, that is beginning to recover from severe global population declines. Distance sampling techniques can be used to generate estimates of abundance of green turtles in foraging grounds which have been relatively unstudied in the Northeastern Atlantic basin, filling in important data gaps in a species that is of critical conservation concern. The Quicksands foraging grounds located west of Key West, Florida, USA is used by both sub-adult and adult green turtles. Standardized transects were performed 18 times between 2006-2018, and using the collected data; abundances, spatial distribution and evidence of spatial segregation were generated through density surface models and null mode analysis. Densities of foraging green turtles rival some of the largest densities known in the world. Spatial segregation of the two size classes is evident on the foraging ground and may be attributed to differing predator detection and avoidance strategies of the size classes Finally, given the high densities of animals found on the foraging grounds and the rise in general population levels of green turtles and drop in population of green turtle predators (i.e. large sharks), concern is raised for the long term sustainably of the Quicksands seagrass pastures.
