The toxin-producing harmful algal bloom (HAB) species Alexandrium monilatum has long been associated with finfish and shellfish mortalities in the Gulf of Mexico. In the summer of 2007, A. monilatum re-emerged as a bloom-forming species in the Chesapeake Bay. Over the last decade, late summer blooms of A. monilatum have been expanding in range in the lower Chesapeake Bay and have reached record-high densities, particularly in the lower York River. This dinoflagellate species overwinters in the sediments as a resting cyst, and upon excystment under suitable environmental conditions produces blooms the following summer. The research presented here includes the first mapping and quantification of resting cysts of A. monilatum in surface sediments in the Chesapeake Bay using quantitative real-time polymerase chain reaction (qPCR) assays. A systematic grid sampling design was employed to collect pre-bloom sediments in the southwestern portion of the Chesapeake Bay each year from 2014-2016. Cysts were widespread in the bottom sediments and sediment cyst density increased from 2014-2016, reaching as high as 90,000 cysts/cc in the York River channel. A multiple linear regression was used to model cyst density using environmental parameters. Sediment type was a strong predictor of cyst density, with higher cyst densities found at sites with more fine sediments (silts and clays). Laboratory HAB toxicity bioassay methods were used to investigate potential adverse health impacts of A. monilatum on adult triploid eastern oysters, Crassostrea virginica. Oyster behavior and mortality were monitored and routine paraffin histology was performed to analyze tissue damage. Oysters did not exhibit mortality or tissue damage in a 48-hour fed toxicity bioassay. However, a 96-hour unfed toxicity bioassay led to 67% mortality, and erosion of the gill and mantle epithelial tissues in 94% of oysters exposed to A. monilatum (live cell or lysate). In the summer of 2015, oysters were deployed in the lower York River to assess effects of exposure before, during, and after a natural A. monilatum bloom. A subsample of six live oysters was collected weekly for two months and processed for histology. There was no mortality of deployed oysters, but minor epithelial erosion of the mantle was seen in half of the oysters sampled during the peak of the A. monilatum bloom from early to mid-August. Field and laboratory results showed that C. virginica did occasionally consume A. monilatum, and exposure of C. virginica to live A. monilatum or lysate could lead to epithelial erosion of external tissues and mortality. It is clear from the findings of this research that A. monilatum has established itself in the York River region of the Chesapeake Bay and that at least under laboratory conditions, persistent exposure to A. monilatum (live or lysate) can have serious potential health impacts on adult oysters.

With temperatures rising globally, assessing the possible impacts of the changing climate becomes more and more urgent. Ectotherms are excellent indicators of potential climatic ramifications on biodiversity because of their heavy reliance on the environment for their thermoregulation. Studies have historically looked at thermal tolerance values to establish predictive models for population and species extinctions. In chapter 1, we looked at recent studies that suggest that thermal tolerance may be a plastic trait and test the effects empirically. Most studies are based on captive lizards acclimated to laboratory conditions that do not necessarily reflect natural environments, and if thermal tolerance is plastic and affected by the recent thermal history of the animal, then the data may not be accurate. We tested the critical thermal maximum of the western fence lizard, Sceloporus occidentalis, in all four seasons, both under field (same-day) and short (two-day) lab-acclimated conditions. We found that thermal tolerance varied seasonally, with the lowest values in the summer in both same-day and two-day acclimated lizards. Additionally, we found that the thermal tolerance of lizards tested on the same day was higher in spring than in fall, but two days of acclimation to lab conditions eliminated this difference. We also tested the thermal tolerance of lizards housed at several constant acclimation temperatures for one or three weeks and compared these values to those of lizards housed in a terrarium allowing thermoregulation, and to same-day lizards. While the thermal tolerance of all lab-acclimated lizards was higher than that of same-day lizards, there was no significant difference in thermal tolerance among any of the acclimation treatments. Overall, our results show that thermal tolerance may be plastic in some situations in S. occidentalis, but that this species overall shows little plasticity in response to acclimation. In chapter 2, we evaluated the thermal environment of S.occidentalis using operative temperature models. Using operative temperature models combined with field lizard body temperatures and a lab-determined selected body temperature range, we evaluated the thermal environment of Sceloporus occidentalis to identify habitat quality, thermoregulatory effectiveness, and thermal exploitation index. Additionally, we used two predictive climate change models at a 1°C and 2°C increase to project the potential changes in habitat quality in the future. The thermal quality was highest for shady microhabitats, lowest for sunny microhabitats, and intermediate for mixed sunny/shady microhabitats. S. occidentalis were able to maintain their body temperatures in their Tset range for 6 hours, indicating the ability to exploit multiple microhabitats. Neither climate change scenario (1°C or 2°C increase) placed S. occidentalis at risk of extinction, likely because the coastal field site has a relatively mild climate. However, both scenarios greatly decreased the thermal quality of the environment, causing S. occidentalis to lose up to 2.5 hours of activity time per day. This highlights that even animals that inhabit mild climates are likely to experience sub-lethal effects of climate change.

An increasing number of habitats are affected by anthropogenic noise pollution, which is often louder, has a different frequency emphasis, and may occur over a different temporal scale, than natural noise. An increasing number of studies indicate that acoustically-communicating animals in such areas can modify their vocalizations in order to make themselves heard over the noise, but many questions still remain, including: How taxonomically widespread is vocal flexibility in response to anthropogenic noise, and do all vocally flexible species employ the same mechanisms to escape acoustic masking? Are there fitness repercussions for living, communicating, and breeding in noisy habitats? and, can particular habitat features be used to predict environmental noise levels and sound propagation characteristics? Here, I present data collected from the breeding territories of eastern bluebirds (Sialia sialis ) to address each of these questions. My results add another species to the list of those who are able to avoid acoustic masking by modifying temporal and spectral traits of vocalizations. I also show that anthropogenic noise is associated with changes in several eastern bluebird breeding parameters. Finally, I demonstrate that both anthropogenic noise levels and sound propagation traits can be predicted by particular habitat characteristics.

Immature foraging sea turtles occupy Chesapeake Bay, Virginia annually from May through November. Telemetry was used to monitor the movements and behavior of loggerhead, Caretta caretta, and Kemp's ridley, Lepidochelys kempi, turtles during 1981-1985. Both species utilized the estuary for summer foraging, but exhibited habitat-preference and behavioral differences that amounted to resource partitioning between the species. Loggerheads oriented towards major river outflows and tended to move along channel sides with the tidal flow while ridleys occupied shallower foraging areas and did not range as far with the tide. Strong site tenacity was displayed by both species once foraging areas were established. Differences were apparent in respiratory behavior; ridleys remained on the surface for longer and underwater for shorter periods than loggerheads. Ridleys had a tendency to stay on the surface longer during daylight than night hours, whereas loggerheads surfaced and submerged longer during night than daylight. Estimates of daylight respiration behavior of loggerheads (surface to dive time ratio of 1:17) were used to adjust estimates of population size. Replicated aerial surveys for loggerheads yielded an unadjusted mean population over 1982-1985 of 423. A respiration adjustment factor which accounts for turtles unseen because they are below the surface (17 turtles below the surface for every one seen at the surface) yielded an average annual estimate of 7905. Reported mortality is a small percentage (1.4) of the adjusted population estimate. Mark-recapture, aerial survey and biotelemetric techniques were used in 1980 and 1982-1985 to elucidate migrations of loggerheads and ridleys which are incapable of overwintering in Chesapeake Bay. For both species, the period of residence in the Bay was correlated with water temperature. Migrations to the Bay were linked to vernal warming; the heaviest concentrations of turtles were found south of the 18 C isotherm. Fall migration was linked less strongly with declining water temperature and appeared to be related to the onset of winter storms. Migrating loggerheads remained nearshore in southerly currents in the fall. Contact with most telemetered loggerheads was broken in the vicinity of Cape Hatteras, North Carolina. A satellite-tracked loggerhead spent two months in the vicinity of the Gulf Stream offshore before contact was broken.

Plants species interactions via pollinators are a model system to understand the mechanisms that generate plant diversity in nature. However, most studies have focused on plant-plant interactions via pollinator attraction while ignoring the role of plant-plant interactions via pollen transfer. Heterospecific pollen transfer (henceforth HP) can be common and have negative fitness effects. Negative HP fitness effects may prompt the evolution of adaptive strategies to minimize them. However, the extent of spatial variation in HP load size within and among populations, a tenet for natural selection, remains unexplored. Such knowledge would hence constitute a first step in advancing our understanding of the importance of HP transfer as an evolutionary force promoting plant diversification. For instance, the opportunity for natural selection would only be expected under strong among population variation in HP load size. In this study we aim to answer the following specific questions: Is there variation in the amount and diversity of HP load in Lobelia siphilitica? How is the variation partitioned across different levels of organization (populations, individuals, and flowers among an individual)? Greater among-population variance would suggest that community attributes, such as plant density and diversity are the major drivers of HP load size. Greater among-plant variance would indicate plant traits that affect pollinator foraging behavior may play an important role. Greater variance among flowers within an individual plant, would suggest stochastic events may underlie variation in HP load size and diversity. In order to test these hypotheses, samples of the native perennial Lobelia siphilitica were taken from 10 populations in the Northeast Tennessee region (500 total). The styles were processed in the lab and pollen grains counted separating them into two categories, heterospecific and conspecific pollen. There was variation in the amount and diversity of HP load received. Populations are expected to have the largest variation among them due to different environments (disturbance levels, pollinators, plant communities, etc.) Since populations are expected to have the largest variation in HP received, they are also expected to have the greatest opportunity for natural selection to act. Looking at HP receipt within-species is important for identifying the mechanisms that can generate diversity in plant communities.

Studies were carried out to quantify abundance, mortality, and variability in these parameters, during settlement and recruitment of bivalve mollusks, using the oyster, Crassostrea virginica, as a primary model species. Most work was undertaken in the York River, Chesapeake Bay, Virginia, with additional work in the Indian River, Florida. The period chosen, in the bivalve early life history, was from the late planktonic larva to the early benthic juvenile. Studies were designed to specifically examine (a) abundance of late-stage larvae in the plankton, (b) the relationship between larval abundance and settlement, and (c) mortality immediately following settlement. Variability in abundance or mortality was also examined at each of these stages. It was found that, of larvae in the plankton with the morphological characteristics of competency-to-settle, about 80% would settle within 24 hours, under laboratory conditions. Temporal variation in abundance of planktonic larvae was high and apparently random, but separate species covaried in observed abundance. Time of day and tidal phase had little or no effect on larval distribution, but late stage larvae showed a consistent depth preference, which varied depending on species. Crassostrea late larvae tended to be most abundant near the benthos, both at the Virginia site and at the Florida site. The relationship between planktonic abundance and settlement density of Crassostrea was weak, within one order of magnitude of variation in larval abundance, although the same relationship for a sympatric species in Florida, Ostrea equestris, was significant. Settlement onto a natural oyster reef was more variable but not significantly lower than settlement onto adjacent defaunated shell substrate. The increased variability could not be accounted for by coverage by dominant fouling macroorganisms. Mortality of newly-settled juvenile Crassostrea was high, with near 100% mortality within 28 days on a natural oyster reef, with high but significantly lower (about 96%) mortality on previously defaunated shell substrate over the same time.

Mesozooplankton function as microbial microhabitats and can support concentrations of bacteria orders of magnitude higher than in the surrounding water. These zooplankton-associated bacteria can have much higher production rates than their free-living counterparts. Portions of the zooplankton microhabitat may also be anoxic and provide refuge for anaerobic bacteria and their associated processes within the oxygenated water column. Despite their common presence in the marine environment, zooplankton-associated bacteria are largely ignored by microbial ecologists and zooplankton ecologists alike. Consequently, factors which influence zooplanktonassociated bacterial abundance, community composition and function, and how zooplankton-associated bacteria compare to free-living bacteria are not well known. The goal of my research was to investigate which environmental parameters and zooplanktonspecific characteristics influenced the zooplankton-associated bacterial abundance, community composition and function. During a year-long field study in the York River, VA, free-living bacteria concentration peaked in the summer, while zooplanktonassociated bacteria concentration peaked in both summer and winter. There were no relationships between number of bacteria per individual zooplankter and zooplankter size. Ambient ammonium concentration was the one environmental parameter that correlated with all zooplankton-associated bacterial concentrations. In laboratory experiments, copepods raised in high ammonium concentration had high concentrations of loosely attached bacteria, while copepods raised in low ammonium concentration supported fewer, firmly attached bacteria, suggesting greater exchange between free-living and zooplankton-associated bacterial communities in nutrient rich systems. Zooplankton-associated bacterial communities were genetically distinct from free-living bacterial communities and utilized a wider array of carbon substrates. Changes in ambient environmental conditions played a larger role than zooplankton-characteristics in shaping zooplankton-associated bacterial community composition and function. Additionally, the potential importance of zooplankton guts as anoxic microhabitats was evaluated by comparing carbon substrate usage by the total bacterial (epibiotic + gut) and gut bacterial communities of the calanoid copepod Acartia tonsa under aerobic and anaerobic conditions. Gut bacteria were responsible for a large portion of the microbial activity associated with the copepod under both aerobic and anaerobic conditions. A larger variety of substrate subsets were used by zooplankton-associated bacteria than free-living bacteria under anaerobic conditions, suggesting that each zooplankton group selects for a specific combination of bacteria. In fact, some zooplankton-associated bacteria were not detected in the surrounding water and utilized substrates not used by free-living bacteria. These results highlight that zooplankton act as micro bial hotspots and zooplankton-associated bacteria are an important part of the total bacterial abundance, diversity and functionality in aquatic systems.

Approximately 40% of the bottom of Chesapeake Bay is less than 2.0 m in depth and many of these broad shoal environments are bordered by wetlands. The vegetated and nonvegetated subtidal and intertidal environment is a dynamic mosaic of highly productive estuarine habitats linked by the exchange of waterborne materials. This study developed simulation models of primary production and material exchange for four littoral zone habitats of the Goodwin Islands National Estuarine Research Reserve (NERR) in lower Chesapeake Bay. Field studies were conducted to determine the sediment biogeochemical and biomass characteristics of sandy shoal, seagrass, silt-mud, and marsh habitats. Ecological models were developed for each habitat based upon their position and ecological characteristics. The models simulate the dynamics of phytoplankton, particulate and dissolved organic carbon, dissolved inorganic nitrogen, sediment microalgae, Zostera marina, and Spartina alterniflora. Following sensitivity analysis and validation the models were used to estimate annual primary production, nitrogen processes, and material exchange. The net annual rate of phytoplankton production was 66.0, sediment microalgae ranged 101-169, Zostera marina community production was approximately 350 gC m&\sp{lcub}-2{rcub}& yr&\sp{lcub}-1{rcub}&, and Spartina alterniflora shoots and root-rhizomes produced 1150 gC m&\sp{lcub}-2{rcub}& yr&\sp{lcub}-1{rcub}& (gC m&\sp{lcub}-2{rcub}& yr&\sp{lcub}-1{rcub}&). Nitrogen uptake was in excess of demand in phytoplankton while the reverse was true for the macrophytes. The marsh habitat accounted for 43% of the total annual primary production for the ecosystem despite being the smallest habitat while the largest habitat (nonvegetated subtidal) required 52% of the total ecosystem nitrogen demand. All four habitats imported phytoplankton, particulate organic carbon, and dissolved inorganic nitrogen annually. While the intertidal habitats imported dissolved organic carbon the subtidal habitats showed net annual export. These models were developed to assess ecosystem structure, function, and change in the littoral zone of Chesapeake Bay. Ecosystem structure was assessed through field research and model development. Ecosystem function was assessed by using the model to generate annual producer, habitat, and ecosystem carbon and nitrogen budgets. The model is currently being used to investigate the interactive effects of water quality, primary production, and habitat composition in order to assess potential change in the estuary.

The purpose of this study was to investigate the relationship between the fall proportion of fawns among fawns and does in a mule deer population and two measures of productivity, the spring recruitment rate and the reproductive performance as measured in the fall. The spring recruitment rate was defined to be the number of fawns per doe which were recruited into the population at 1 year of age. The reproductive performance was defined to be the number of fawns produced per doe 2 years or older which survive to a specified time. The relationships between these quantities were measured by calculating linear coefficients of correlation from data generated by a projection matrix model of a mule deer population. A coefficient of correlation of 0.86 was found between the fall proportion of fawns and the rate at which fawns are recruited into the spring population. A coefficient of correlation of 0.89 was found between the fall proportion of fawns and the reproductive performance as measured in the fall. The effect of misclassifying fawns as does and does as fawns on estimates of the proportion of fawns among fawns and does was also investigated. A comparison was made between the expected values of two estimates of the fall proportion, one with misclassification and one without misclassification. The misclassification of fawns and does was found to bias estimates of the proportion of fawns. The bias was found to be a function of the amount of misclassification and the actual proportion of fawns .

This study was conducted to examine coyote behavioral responses to novel stimuli in familiar and unfamiliar environments and the implications of this behavior with regard to specific coyote management and research techniques. A series of pen studies with captive coyotes was undertaken at the U.S. Fish and Wildlife Service's Predator Ecology and Behavior Project research site, Logan, Utah, to observe the range and type of behaviors coyotes showed towards small novel objects and standard scent stations in familiar and unfamiliar 1-ha enclosures. The initial response to these novel stimuli in familiar environments was one of neophobia and caution, whereas in the unfamiliar environment these same stimuli were readily approached and investigated. Field studies were undertaken at the Idaho National Engineering Laboratory and Freer, Texas, to examine coyote visitation to scent stations inside, peripheral to, and outside their defined home ranges. Radio-collared coyotes were monitored to determine home range use and movement patterns, with relocations plotted on computer graphic maps and gridded base maps. Modified scent-station survey lines were run and visitations by marked coyotes plotted with respect to home range zone. Marked coyotes visited a greater percentage of scent stations peripheral to and outside their home ranges than inside. The socio-spatial distribution of coyotes, home range size, and percentage of road comprising home range zones influenced differential scent-station visitation rates. The importance of understanding the influences of animal behavior on wildlife management and research techniques is discussed.