It was the purpose of this investigation to present laboratory data concerning the assimilation of inorganic nitrogen by the aquatic actinomycetes. The strains of aquatic actinomycetes under consideration represented a cross section of those currently under culture at North Texas State University.

Mandatory Country of Origin Labeling (MCOOL) was implemented on seafood in the United States on April 4, 2005. MCOOL exempts the foodservice sector and excludes processed seafood from labeling. This dissertation contributes to understanding the economics of the MCOOL law for seafood by showing that current partial implementation may have unintended consequences both on the domestic supply chain and on trade. In other words, while labeling satisfies the market demand for information provision in one market, exemptions in the other market may create incentives for the diversion of imports, which are assumed to be lower in quality than domestic seafood, to the non-labeled sector. Analyzing alternate scenarios such as voluntary labeling shows that total welfare may be greatest under this scenario compared with partial MCOOL. Voluntary origin labeling of seafood by some U.S. retailers indicate there is no compelling market failure argument warranting MCOOL implementation. Trade between major shrimp exporters and the United States can be affected with partial MCOOL. It may lead exporters with questionable quality to change their product mix, i.e., export more processed shrimp relative to unprocessed shrimp. This work is therefore a step towards analyzing the effect of partial MCOOL policy in the seafood industry taking into consideration the nature of the industry.

The Cape Horn Biosphere Reserve, within the remote Sub-Antarctic ecoregion is a reservoir of expressions of biological and cultural diversity. Although it is considered one of 24 wilderness areas remaining in the world, it is not free from local and global threats, such as invasive species, and climate change. Field biologists and philosophers associated to the Sub-Antarctic Biocultural Conservation Program and the Omora Ethnobotanical Park, have worked to describe the region’s biocultural diversity, linking ecological and philosophical research into education, ecotourism, and conservation, through a methodology called field environmental philosophy (FEP), which integrates ecological sciences and environmental ethics through a 4-step cycle consisting of: 1) interdisciplinary research; 2) composition of metaphors; 3) design of field activities with an ecological and ethical orientation; and 4) implementation of in situ conservation areas. In this context, the purposes of this dissertation were to: 1) provide a comprehensive review of publications regarding the conservation status of aquatic and terrestrial insects at a global scale and with an emphasis in southern South America; 2) study the distribution of benthic macroinvertebrates through the sharp altitudinal gradient of the Róbalo River watershed; 3) describe the life histories of Gigantodax sp (Simuliidae: Diptera) and Meridialaris chiloeense (Leptophlebiidae: Ephemeroptera) in the Róbalo River and to assess the potential effects of climate change on their phenology; and 4) to apply FEP methodology in order to better understand and communicate the intrinsic and instrumental values of freshwater invertebrates in the Cape Horn Biosphere Reserve.

Metabolites of DDT were detected in five out of six major organs of blue crabs, Callinectes sapidus, taken from estuarine populations. Residue concentrations were highest in the hepatopancreas and below the limit of detection in the heart. Concentrations in pooled gonad samples (ovaries + testes) depended on the stage of development of the ovaries. Residue levels were low in claw and backfin muscles. Adult blue crabs were exposed for 12 hours to 0.01, 0.1, and 1.0 ppm DDT in water. No significant mortality was recorded. DDT was absorbed through the gills and transported to the hepatopancreas via the hemolymph. Biotransformation and distribution of DDT and its metabolites was regulated by the hepatopancreas. Induction of metabolic transformation of DDT to DDD and DDE occurred immediately. Storage of residues was greatest in the hepatopancreas and developing ovaries . Rates of loss of DDT residues from organs was subject to considerable variation. 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.

Zooplankton composition, distribution, biomass and biochemical constituents were determined monthly in the lower Chesapeake Bay for two years beginning in August 1971. Settled volume, dry weight, and ash-free dry weight estimates of total biomass were generally consistent in showing summer and late winter peaks. A mean dry weight peak of 258 mg/m3 in August 1971 decreased precipitously to a December low of 9 mg/m3, then increased to a March 1972 peak of 199 mg/m3. The second year mirrored this pattern, except that the passage of Tropical Storm Agnes in June 1972 lowered the summer peak values for July and August considerably. In August 1971 and again in August 1972, a total of 53 species, from four dominant major groups, were used to characterize four distinct geographical cluster zones. The summer zooplankton was dominated by cladocerans, largely Penilia avirostris and Evadne tergestina, and the copepod Acartia tonsa. Decapod larvae proved to be the most diverse summer group studied, containing 30 species in August 1971 and 33 species in August of 1972. Dominant species included Upogebia affinis, Callinectes sapidus, and Uca sp. Chaetognath peaks in September of each year consisted almost entirely of Sagitta tenuis. Winter populations contained less than half the number of taxa as summer zooplankton and were dominated by Acartia clausi. This species almost completely replaced Acartia tonsa by April of each year. The most notable effects of the lowered salinities caused by Tropical Storm Agnes in the summer of 1972 were a drastic reduction in cladoceran abundance and a compression of chaetognath distribution to the higher salinity areas near the bay mouth. Protein, the largest organic fraction of the zooplankton, usually accounted for 40-60% of the total dry weight. Mean monthly lipid values ranged from 1.9 to 9.5% of the dry weight, and carbohydrate appeared only as a minor organic fraction. 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.

Laboratory and environmental studies of striped bass (Morone saxatilis) X white perch (M. americana) and striped bass X white bass (M. chrysops) were used to-determine the feasibility of introducing these hybrids into an estuary as a supplement to natural populations of the parental species. Growth patterns, survival, and general hardiness of the hybrids were used as criteria. Growth of striped bass X white perch hybrids in the laboratory was apparently somewhat less than growth of natural populations of striped bass, but was much greater than growth of natural populations of white perch. Hybrid growth was slower than striped bass growth under the same conditions, but hybrid survival was much better than striped bass survival. The hybrids were able to survive and grow in estuarine salinities. Most hybrids matured at two years of age. Striped bass X white bass hybrids were able to adapt to an estuarine environment (the Rappahannock River, Virginia) and could successfully compete with striped bass and other resident ichthyofauna. Hybrid growth was faster than striped bass growth in the Rappahannock and was considerably faster than growth of various freshwater populations of white bass. Hybrids were caught in salinities as high as 17%. They were mature at two years of age. Both hybrids were described using meristic and morphometric characteristics. They were both found to be generally intermediate to the parental species, but in certain traits they tended to resemble one parent more closely than the other. Striped bass, white perch, and their hybrid all had a diploid chromosome number of 48. Possible karyological differences are discussed. One or both hybrids may be suitable for introduction into an estuary to supplement natural populations of striped bass and white perch, but more comprehensive environmental experiments are needed. 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.

No description available.

Amazonian freshwaters host the most diverse ichthyofauna in the world but the ecological mechanisms that generate and regulate this diversity are poorly known. I performed the first comparison of spatial and temporal patterns of fish community diversity among the four primary aquatic habitats of the Amazon (major rivers, floodplains, lowland terra firme streams, and upland shield streams) and among the three distinct chemical water types in Amazon river-floodplain systems (low-nutrient blackwaters and clearwaters, and high-nutrient whitewaters). To minimize confounding influences of geographical variation in species ranges, my study targeted one of the few parts of Amazonia (near Santarém, Brazil) where all four habitats and all three river-floodplain water types occur in close proximity. In the first of three chapters, I compare diversity and biomass between blackwater, clearwater, and whitewater rivers and floodplains. My results provide the first support for positive species-energy and biomass-energy relationships across multiple aquatic habitat types from the same biome and region. In Chapter 2 I compare patterns of temporal beta-diversity, and beta-deviations from null model simulations, to demonstrate that species turnover is positively correlated to seasonality and hydrological connectivity among the four Amazonian habitats types but is uninfluenced by water type. In Chapter 3 I compare up-river transects from the common confluence of a blackwater, Clearwater, and whitewater river to infer that abrupt gradient of water chemistry act as major barriers to fish dispersal. My results have important implications for biodiversity monitoring and conservation planning in the increasingly threatened aquatic habitats of the Amazon basin.

Despite an increased global interest in harmful algal bloom (HAB) species and eutrophication, the relationship between nutrient sources and changes in species composition or toxicity remains unclear. Stable isotopes are routinely used to identify and track nitrogen (N) sources to water bodies, as sources can be differentiated based on stable isotope values. While literature is available describing N fractionation by diatoms and coccolithophores, data are greatly lacking regarding isotope fractionation by dinoflagellates. Here we investigate the fractionation of nitrogen isotopes by saxitoxin-producing Alexandrium fundyense, to validate the use of the δ15N of particulate organic matter and identify the nitrogen source fueling a dinoflagellate bloom and its toxicity. The effects of N chemical form on isotope fractionation, toxin content, and toxicity, were investigated using isolates in single-N and mixed-N experiments. Growth on NO3-, NH4+, or urea, resulted in isotope fractionation of 2.761.48‰, 29.019.32‰, or 0.340.19‰, respectively, with the lowest cellular toxicity and toxin quotas reported during urea utilization. Toxin composition and growth rates, however, remained constant across all N treatments, showing no effects of NO3-, NH4+, or urea utilization. Alexandrium fundyense was then preconditioned to either NO3-, NH4+, or urea, and abruptly inoculated into mixed-N medium containing all three chemical forms. All treatments initially utilized NH4+ and urea upon inoculation into mixed medium, suggesting no effect of preconditioning. Cells only began utilizing NO3- after NH4+ decreased below 2-4 M in the medium. During the inhibition of NO3- uptake by NH4+ utilization, the cellular δ15N was at its lowest (-5‰), and through the course of the experiment, the δ15N continuously changed to mimic the isotope value of the most recent N source(s) being utilized. When utilizing multiple sources, the isotope signature of the cells fell between the signal of the two N sources. Together this suggests that in NO3- and urea rich environments, the 15NPOM would reliably look like the source or sources of nitrogen utilized, but that caution should be taken in NH4+ rich environments where the large value could lead to misinterpretation of the signal. Nutrients are only one factor influencing bloom dynamics, but information about the relative importance of natural or anthropogenic nutrients in the development and toxicity of bloom events is necessary to predict future shifts in phytoplankton species composition, density, and toxicity.

As the Earth undergoes continued climatic change, shifts in the cryosphere are occurring at increasingly rapid rates. As a significant proportion of global freshwater is located in the mid- to high-latitudes of the northern hemisphere and is often seasonally ice covered, it is vital to understand how surface cover quality influences biological activity in these systems. Ice and surface cover conditions have been noted to be very effective at limiting light availability, and therefore influencing the photosynthetically active radiation (PAR) available for primary production. To quantify the relationship between winter surface cover and under-ice hydroecological variables, two complimentary controlled experiments were conducted over two winter periods at the University of Calgary Aquatic Experimental Facility. Above-ground polyethylene mesocosms were utilized to remove the influence of littoral and benthic activity influences on measured biological endpoints. Two paired experimental ponds, that are hydrologically disconnected and located immediately adjacent to the mesocosm enclosures were utilized to further develop the relationships, while including a slightly more complex food web structure. Surface cover manipulations were done by either adding snow (snow-on-ice), or slushing snow (white ice), and resulted in distinct differences in under-ice light regimes, dissolved oxygen (DO) levels, but not primary production measured as chlorophyll-α values. However, in the pond systems, surface cover had minimal impact on the DO levels, with both the control and treatment systems trending towards hypoxic conditions quickly after ice-on conditions, as measured using high temporal resolution probes embedded in the ponds. Chlorophyll-α levels in the pond systems, however, was significantly different with the snow-on-ice (control) pond having lower values than the pond where snow was mechanically removed, over two adjacent winter observation periods. In the second observation period, dissolved organic carbon (DOC) values were also manipulated in the mesocosm systems, with the elevated DOC systems exhibiting a decrease in DO values when compared to control systems. The utilization of controlled experimental systems and high-resolution data loggers allowed this study to offer unique insights into the relationship between ice and surface cover composition, under-ice light regimes, and corresponding biological activity under-ice. As shifts in annual winter climatic and associated meteorological conditions are predicted to continue to occur, generally towards increased precipitation and warmer mean air temperatures, the relationships derived in the study will be valuable in understanding and potentially predicting the implications of climate variability and change on seasonally ice-covered systems / Graduate