This dissertation is from the Joint Program Degree from the College of William & Mary and University of Virginia and awarded by the University of Virginia. Provisional keys to the marine decapod crustacean zoeae of the Chesapeake Bay are presented. These keys provide distinguishing characters for the specific or generic identification of zoeae of 50 decapod species. Also, provisional classification schemes for the different morphological types of antennae and telsons exhibited by Chesapeake Bay brachyuran larvae are given, and the larval stages of each species or genus considered in the keys are briefly described. The larval development of eight Chesapeake Bay decapod species for which the larvae were previously unknown was studied in detail. All larval stages of ~rides limicola and Libinia dubia and the first zoea of Arenaeus cribrarius are described from laboratory-reared specimens, and four larval stages of Callianassa sp. A (=.Q_. major?), two of Callianassa sp. B (=C. atlantica?), one of Callianassa sp. C, four of Upogebia affinis, and three of Lepidopa websteri (?) are described from specimens taken from the plankton. Previous studies concerning the effects of temperature and salinity on larval development of Chesapeake Bay decapods are reviewed, and the results of an experiment to determine the effects of temperature and salinity on larval development of Palaemonetes vulgaris are presented • .!:• vulgaris larvae were reared in the laboratory in a factorial experiment employing three temperatures (20, 25 and 30 C) and six salinities (5, 10, 15, 20, 25 and 30 0/00). Considering survival, rate of development, and number of instars, optimal conditions for larval development were found to occur at a temperature of about 25 C in salinities of 10 to 30 0/00. Surface and bottom plankton samples taken with a Clarke-Bumpus Quantitative Plankton Sampler at monthly intervals over a two-year period were made available to me by Dr. V. G. Burrell, Jr. These samples were collected at 12 stations spread over a distance of about 80 miles from freshwater in the Pamunkey River, through the meso- and polyhaline York River, to euhaline conditions at the mouth of Chesapeake Bay. Some additional samples were collected with paired BCF Bongo samplers. Planktonic stages representing 37 species and genera of decapods were identified in these zooplankton collections. Decapod larvae were numerous throughout the estuary during the summer. However, larvae of Crangon septemspinosa were abundant in the bay from late winter throughout the spring, and peak numbers were generally of the same order of magnitude as total concentrations of larvae of the other species at the bay stations during summer.

Physoclistic fish, such as Pacific rockfishes (genus Sebastes), have closed swim bladders that help them regulate their buoyancy. When anglers catch these fish and reel them to the surface, gases within their swim bladder expand due to the decrease in pressure. This can cause their swim bladder to over inflate––a condition known as barotrauma. Overly buoyant fish experiencing barotrauma often struggle to swim back to dwelling depth if released at the ocean’s surface. These fish may experience high rates of mortality by thermal shock caused by the warmer surface temperatures, starvation, predation, or vision problems caused by barotrauma. Assisted release methods that recompress fish by returning them to depth prior to release may thus greatly improve survival of fish suffering from barotrauma. In this study, I characterized species-specific responses of four species of nearshore Pacific rockfishes (Canary Rockfish, Sebastes pinniger; Gopher Rockfish, S. carnatus; Deacon Rockfish, S. diaconus; and Blue Rockfish, S. mystinus) to rapid ascent by hook-and-line fishing from shallow depths (<40 m). I videotaped their immediate responses upon recompression using a weighted inverted milk crate to transport fish back to their initial capture depth. Fish were videotaped during their descent, as well as their release from the crate. In some individuals, barotrauma symptoms were reversed and did not show behavioral impairment upon release, indicating that even a simple, inexpensive device can be effective in relieving barotrauma symptoms. Species differences were also observed in the severity of barotrauma observed following the collection of fish from depth. Capture depth was positively correlated with the occurrence of barotrauma for Blue Rockfish and Gopher Rockfish, but not for Canary Rockfish or Deacon Rockfishes. I utilized data over an eight-year period from the California Collaborative Fisheries Research Project (CCFRP) to assess survivorship of rockfish experiencing barotrauma. A total of 20 rockfish (1 Black Rockfish, S. melanops; 2 Blue Rockfish; 12 Gopher Rockfish; 3 Copper Rockfish, S. caurinus; and 2 Kelp Rockfish, S. atrovirens) initially displaying barotrauma signs upon capture were tagged using a T-bar tag and released. It is unknown if these fish were recompressed because the CCFRP did not record this information. These 20 rockfish were recaptured days to 3 years later––indicating rockfish can survive long term after experiencing barotrauma. To minimize mortality of discarded fish in the fishery, fish recompression is recommended.

Calanoid copepods were sampled quantitatively at twelve stations in the York River estuary monthly over a two year period. Twenty-two different calanoid species were identified, with five species, Acartia tonsa, A. clausi, Eurytemora affinis, Pseudocalanus minutus and Pseudodiaptomus coronatus making up 95% of the numbers present. Several factors were investigated to determine their biological influence was the ctenophore, Mnemiopsis leidyi, a predator which reduced copepod numbers logarithmically at stations at which it occurred. Increased river flow was followed by large increases in copepod numbers and was the most important physical influence. Distribution of all calanoid species appearing in the estuary was described. Seasonal copepod abundance and the Acartia tonsa - A. clausi distribution in other North American East Coast and Gulf of Mexico estuaries was compared with that of the York River.

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Species’ foraging choices influences their somatic growth rates, age at maturity, and time spent in vulnerable early life stages. Thus, differences in population demographics are often attributed to variability either in diet type, quality or quantity ingested. Knowledge of species diet selection, though currently limited, particularly in marine environments, can enhance our understanding of the roles of species in marine ecosystem and, at a finer scale, elucidate how nutrition and diet influences their growth and productivity. Marine green turtles (Chelonia mydas) are considered to be herbivores, predominantly consuming seagrass and algae. However, recent studies have suggested that they may exhibit omnivory in certain forage areas. Using juvenile green turtles as a case study, I coupled stable isotope analysis with a diet preference index to provide insights into the selection and plasticity of their diet. The study was conducted within two sites (Bonefish Hole and South Bimini) in Bimini, Bahamas in 2016. Habitat surveys were conducted to gather habitat data and determine resource availability. A dichotomy in diet was found between the sites: at Bonefish Hole, turtles exhibited a more generalist omnivorous diet, selecting for sessile filters feeders and green algae, whereas turtles in South Bimini had a more specialist herbivorous diet, primarily consuming seagrasses and selecting for red algae, when available. The foraging dichotomy found in this study by green turtles expands our understanding of the spatial differences in their biology in the Bahamas and provides novel information for turtle foraging in Bimini. Knowledge about differences in intra-specific diet, with a focus on diet selection and potential drivers, can elucidate the factors that influence critical life history traits and ultimately inform species management. / A Thesis submitted to the Department of Earth, Ocean and Atmospheric Science in partial fulfillment of the requirements for the degree of Master of Science. / Spring Semester 2018. / April 13, 2018. / Bayesian ellipses, carbon, habitat use, MixSIAR, nitrogen, Trophic ecology / Includes bibliographical references. / Mariana MPB Fuentes, Professor Directing Thesis; Jeff Chanton, Committee Member; Rob Spencer, Committee Member; Jeffrey A. Seminoff, Committee Member.

Karenia brevis is a marine dinoflagellate commonly found in the Gulf of Mexico and important both ecologically and economically due to its production of the neurotoxin brevetoxin, which can cause respiratory illness in humans and widespread death of marine animals. K. brevis strains have previously shown to be sensitive to changes in CO2, both in terms of growth as well as toxin production. Our study aimed to understand this sensitivity by measuring underlying mechanisms, such as photosynthesis, carbon acquisition, and photophysiology. K. brevis (CCFWC-126) did not show a significant response in growth, cellular composition of carbon and nitrogen, nor in photosynthetic rates between pCO2 concentrations of 150, 400 or 780 µatm. However, a strong response in its acquisition of inorganic carbon was found. Half saturation values for CO2 increased from 1.5 to 3.3 µM, inorganic carbon preference switched from HCO3- to CO2 (14% to 56% CO2 usage), and external carbonic anhydrase activity was downregulated by 23% when comparing low and high pCO2. We conclude that K. brevis must employ an efficient and regulated carbon concentration mechanism (CCM) to maintain constant carbon fixation and growth across pCO2 levels. A positive correlation with pCO2, although not statistically significant, in cellular brevetoxin content was found. This study is the first explaining how this socioeconomically important species is able to efficiently supply inorganic carbon for photosynthesis which can potentially prolong bloom situations. This study also highlights that enhanced CO2, as projected for a future ocean, can affect underlying physiological processes of K. brevis, some of which could lead to increases in cellular brevetoxin production and therefore increased impacts on coastal ecosystems and economies. / A Thesis submitted to the Department of Earth, Ocean, and Atmospheric Science in partial fulfillment of the requirements for the degree of Master of Science. / Fall Semester 2018. / September 17, 2018. / Brevetoxins, Carbon Concentrating Mechanism, Climate Change, Ocean Acidification, Photosynthesis, Red Tides / Includes bibliographical references. / Sven Kranz, Professor Directing Thesis; Angela Knapp, Committee Member; Olivia Mason, Committee Member; Michael Stukel, Committee Member; Janie Wulff, Committee Member.