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The Florida Gulf of Mexico coast extends over both tropical and subtropical zones resulting in an intermingling of fauna typical to both zones. Cold winter water temperatures historically limited the distribution of many tropical species and allowed sub-tropical species to thrive. In the past 60 years, average winter sea surface temperatures have increased 2-3°C in the Northern Gulf of Mexico (NOAA OSPS), potentially allowing range expansion of tropical species and local extinction of subtropical species. While poleward range expansion is possible for species along the Atlantic coast, species in the Gulf of Mexico face land barriers that prevent northward movement. Distribution patterns of sponges in the Northeastern Gulf of Mexico have changed since previous studies in the 1950’s and 1960’s. A little over half of the common species (56%) are still widespread throughout the Northeastern Gulf of Mexico. Eleven species (44%) previously reported as widespread are either missing entirely or are no longer widespread throughout the region. Two species are newly reported in the Northeastern Gulf of Mexico (Niphates erecta and Haliclona curacaoensis) and eight other species are more widespread than before. Caribbean species make up most of the common species composition of the Northeastern Gulf of Mexico (de Laubenfels 1953, Little 1963, Storr 1976, current study). Due to the limited latitudinal range of the Northeastern Gulf of Mexico it is necessary to look at a wider scale to determine species’ northern range limits. When compared to the wide-scale Caribbean fauna, it appears that only a handful of Caribbean species occure in the Gulf of Mexico and the North West Atlantic. Of 90 common Caribbean species only 27% (24 species) were found in the Northeastern Gulf of Mexico and 38% (34 species) at Gray’s Reef in Georgia U.S.A. while 53% (48 species) were not found in either the Northeastern Gulf of Mexico or Gray’s Reef (Hopkinson et al. 1983, Freeman et al. 2007). While the species composition of Caribbean sponges at Gray’s Reef and in the Northeastern Gulf of Mexico is similar, each contain unique species that are not found at the other location. This may be due to a combination of biotic and abiotic factors that differ between the Atlantic and Gulf coasts of Florida, aiding the migration of some sponge species while hindering others. One species commonly found in the Northeastern Gulf of Mexico is endemic to the region. Halichondria corrugata Diaz, van Soest & Pomponi, 1993 is the most abundant sponge in shallow seagrass beds and on dockside fouling communities in the Northeastern Gulf of Mexico. The variation in abiotic conditions between these habitats and H. corrugata’s ubiquity make it an interesting system to test what aspects of ecology allow it to be so successful. H. corrugata utilizes different ecological strategies in seagrass and dock habitats. H. corrugata is flexible in its reproductive strategy, utilizes predator avoidance techniques when needed, and seems to be resilient to light variation despite being reliant on photosynthetic symbionts for supplemental nutrition. / A Thesis submitted to the Department of Biological Science in partial fulfillment of the requirements for the degree of Master of Science. / Summer Semester 2018. / June 19, 2018. / Gulf of Mexico, Halichondria corrugata, porifera, species distributions, sponge, sponge ecology / Includes bibliographical references. / Janie L. Wulff, Professor Directing Thesis; Don R. Levitan, Committee Member; Sophie J. McCoy, Committee Member.

Includes abstract. / Includes bibliographical references (p. 39-41). / Withdrawal from insurance contracts can be a significant risk for insurers. Withdrawal rates can be difficult to predict because withdrawal is influenced by a number of inter-related factors related to, inter alia, the sales process, characteristics of the insurance contract, characteristics of the contract holder, and economic variables. Existing methods used to model and predict withdrawal rates are initially reviewed. Two additional methods which have been proposed in the literature as means for modelling insurance risks are neural networks and Bayesian networks. These two methods are utilised in order to build models to compare their predictive ability with a commonly used method for modelling withdrawal rates, namely logistic regression.

The infauna of Zostera beds in the Chesapeake Bay-York River estuary and Chincoteague Bay was sampled in March and July using a corer. Sediments were fine sand or very fine sand. Sorting of sediments varied from poorly sorted to moderately well-sorted and was related to the density of Zostera at the respective stations. A total of 17 macroinvertebrate taxa was collected. Species abundance decreased up the estuary and there was a significant interaction in the number of species between stations and seasons. Faunal similarity of the areas sampled, as measured by three indices, indicated that the infauna of most Zostera beds in the Chesapeake Bay area is similar, except at the up estuary limits of Zostera distribution. Most dominant species showed some degree of patchiness. Some epifaunal species occurred. Animal density was very high, with a mean of 15,143 individuals/m2. Means for the Shannon-Weaver diversity index, equitability, and species richness were 3.43 bits/individuals, 0.43 and 27.9 species/180 individuals, respectively. 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.

Energy transformations and budget are computers for young-of-the-year blueback herring, Alosa aestivalis, in the James River, Virginia. Distribution, growth, and selective feeding are described. Fish and zooplankton collections were made at five stations in the main channel of the James RIver from June through November 1969. Two 24hr series of samples were collected in July and October 1968 in the Potomac River. A direct relationship existed between standing cropos of zooplankton and distribution, growth, and feeding of blueback herring. Zooplankton densities were highest upstream, where food consumption and growth rates were correspondingly highest. A progressive downstream decrease and upstream increase in the fish abundance occurred during teh study. Condition 9K) decreased after flooding from hurricane Camille. Blueback herring fed primarily on copepods (Eurytemora affinis, Cyclops vernalis, and Canthocamptus roberteokeri), but cladocerans (Bosmina longirostris-coregoni and Diaphanosoma brachyurum) were also important. Selection (electivity) was strongest for adult copepods and weakest for copepod nauplii. Selection for copepodites and B. longirostris-coregoni was moderate to weak. Feeding occurred only during daylight. Effect of predation on zooplankton populations is discussed. Respiration experiments were carried out in the laboratory from Nobvemer 1970 to March 1971. The regression of oxygen consumption on temperature (routine metabolism) was expressed as Log 0 = -1.4451 + 0.0548 T, where 0 = oxygen consumption (mg 02/gram wet weight/hr), and T = temperature (C). 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.

The autecology of the brackish water clam Rangia cuneata was investigated in the James River, Virginia, from February 1970 to January 1972. The reproductive cycle, combined salinity and temperature effects on embryos and larvae, and setting were studied. Histological slides were made, set collected, and temperature and salinity measurements taken from three populations living in different salinity regimes. Phases of gonad development are described. Gametogenesis started in April and from May through September clams were found in all gonadal phases. Ripe gonads were found from May to late November with no summer or inactive period. It was determined by the abundance of set that two periods of spawning occurred. The first took place in early and mid-summer, coinciding with the beginning of spawning as determined from histological sections. The second period was longer with a greater number of set and .took place in late.fall and winter, coinciding with the increased percentage of partially spawned and spent clams in the sections. Spent specimens were common in December and were present through March. Residual gametes were cytolyzed. Sex was not discernible during this last phase. A sex ratio of more females than males was found in the upstream (lower salinity) populations. The reproductive cycle was correlated to the salinity and temperature data. Temperature was important in initiating gametogenesis in the spring and mid-summer. Spawning was best correlated to changes in salinity. A salinity of 5%, was found to stimulate spawning in the laboratory. Embryos and larvae were reared at a number of salinity temperature conditions within the ranges of 0-20%, salinity and 8-32C. Salinities near 0%, were lethal in all cases. Response surfaces were computed to analyze the combined effects on survival of embryos and on survival and growth of the larvae. Optimum conditions for embryos (85% survival) were 6-10%, and 18-29C. Salinity had more effect than temperature on early development. Optimum conditions for the larvae were broader, being 2-20%,, salinity and 8-32C. However, temperature and salinity interacted to reduce survival at low salinity-high temperature and high salinity-low temperature combinations. Growth of larvae was best at high salinities and high temperatures. Several inferences are drawn from this field and laboratory study regarding Rangia's distribution and recruitment in the James River. Over its estuarine range, salinity had the greatest effect. Seasonal reductions in freshwater input (increased salinity) are needed for spawning and recruitment of the upstream populations. The amount of gametes produced and the degree of spawning were related to the total weight of the clams at the various stations. 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.

This project investigated several aspects of the autecology of the brackish water clam Rangia cuneata in the James River, Virginia. The study, conducted from August, 1970, through March, 1972, was primarily concerned with substrate and salinity effects on growth and condition index of R. cuneata. The studies were conducted in sand and mud substrates in four different salinity regimes. Monthly samples of 15 clams were collected at each of the eight stations for condition index determinations. Condition index was shown to vary seasonally, with a low point in early spring and a maximum in early fall. Values were higher in sand bottoms than in mud and decreased in both substrates in fresher water. Clams from sand bottoms showed a pronounced fall peak which was not evident at most mud stations. A field experiment to evaluate the relative importance of water associated and sediment-associated factors in determining condition index showed that some factor associated with the water pumped by the clams was most important. The hypothesis is presented that this factor may be related to the large difference in suspended solids taken in by clams in sand and mud bottoms. Growth studies were based on marked individuals planted at all eight stations and recovered after one year. Growth was measured in terms of shell length and live weight increases. In terms of both criteria, growth was greatest at the three downriver sand stations. The lowest salinity sand station showed considerably less growth, but exceeded the growth at all mud stations. Clams at the latter showed similar small increases in both length and weight. The above patterns of condition index and growth are discussed in relation to salinity structure and suspended solids in the environment and to osmotic stress and spawning activity of the clams. An explanation is offered for the large size and relatively high condition index of clams near their limit of penetration into fresh water. The potential commercial value and annual harvest of R. cuneata in the lower James River is estimated. 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.

This study is of five species of isopods common to the Dillon Beach area, each of which represents a different level in the transition toward land life. Cirolana harfordi was used as a completely marine form. Idothea (Pentidotea) wosnesenskii represents a step toward land life as it inhabits an area uncovered by most low tides. Ligia occidentalis is found in the splash zone, receiving spray from the action of the surf. This illustrates another, higher, level in the transition. Alloniscus perconvexus was the fourth species studied. It is commonly found burrowed in the sand in the area of the berm, which is the nearly level portion of the beach formed by high tidal wave action. Finally, the terrestrial form, Porcellio (Porcellion) scaber, was used to illustrate those isopods best adapted to land life. The physiological data presented in this paper includes salinity tolerances and humidity tolerances. Some information on acclimating one species to lowered salinities is also presented. The results of these experiments are used to illustrate the degrees of adaptation to land life shown by the isopods in different areas of the transition. A discussion of the adaptive morphology and behavioral characteristics is also related to the environmental situations in which each animal is found.

The research presented in this dissertation describes the influence of planktonic bacterial growth on upper ocean organic matter dynamics in the North Pacific Subtropical Gyre (NPSG). Examination of the temporal dynamics in dissolved organic matter (DOM) was coupled with investigations that targeted the influence of heterotrophic bacterial production (HBP) on organic matter fluxes in the NPSG. Nine cruises to the Hawaii Ocean Time-series field site Station ALOHA revealed that HBP accounted for a large flux of organic carbon in the upper ocean of the NPSG. HBP was significantly enhanced by sunlight, with photoenhancement of HBP accounting for 3.2 mol C m-2 yr-1, equivalent to 21% of the annual photoautotrophic production in this ecosystem. These observations suggest that HBP in the upper ocean of the oligotrophic NPSG exerts a large influence over organic matter fluxes in this ecosystem, and that a large fraction of HBP depends on sunlight. Several experiments were conducted to asses the response of heterotrophic protein production to irradiance at Station ALOHA. The results of these experiments revealed that HBP responded to irradiance similar to the response of photosynthesis to irradiance in this ecosystem. Upper ocean HBP increased with light intensity at low light fluxes (<200 mumol quanta m-2 s -1), but saturated or declined with increasing irradiance. Experiments conducted in the upper and lower photic zone revealed significant photoinhibition of bacterial production in the lower photic zone. Overall, the heterotrophic response was similar to the photosynthetic response, suggesting light-driven HBP could result from mixotrophic growth by the photoautotrophic unicellular cyanobacteria Prochlorococcus. Analyses of dissolved organic matter (DOM) inventories from 1988 to 1999 revealed multiyear increases in the inventories of dissolved organic carbon, nitrogen, and phosphorous (DOC, DON, and DOP) in the upper ocean of the NPSG. During the latter half of the observation period, rates of DOP accumulation declined, coincident with significant DOC and DON accumulation. Analyses of bacterial population dynamics between 1992 and 1999 revealed an apparent shift in the abundance of Prochlorococcus during the period of observation. These results suggest that prokaryote population structure directly influences the cycling of organic matter in this ecosystem.

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