Amphibian populations around the world have been declining rapidly over the past two decades, particularly in upland regions of the neotropics, where a fungal pathogen that causes chytridiomycosis has decimated many regions. Despite increasing concern over these and other dramatic losses of biodiversity, little information is available on the overall ecological effects of amphibian declines. As part of the Tropical Amphibian Declines in Streams (TADS) project, I quantified major energy fluxes, secondary production, and macroinvertebrate community structure for two consecutive years in four stream reaches in the Panamanian uplands, two with healthy amphibian populations and two that had experienced amphibian declines in 1996-1997. Despite relatively high year-round inputs of allochthonous organic materials, storage of detritus in the stream channels was low compared to streams in temperate regions. Organic matter inputs and standing stocks were similar between pre- and post-decline streams, and did not differ appreciably with season. Seston export was a major energetic flux in these systems, and differences in the nutritional quality (C:N) of seston in pre- and post-decline streams suggested that the loss of tadpoles may decrease the quality of materials exported from these headwaters. At coarse scales (e.g., total abundance) macroinvertebrate assemblages were similar between pre- and post-decline sites, but there were noticeable differences in production and functional and taxonomic structure. Pre-decline reaches had higher shredder production and post-decline streams had higher scraper production. In addition, taxonomic differences between pre- and post-decline streams were also evident, with a shift from dominance of smaller scraper taxa in pre-decline sites (i.e. Psephenus) to larger-bodied scrapers such as Petrophila in post-decline reaches. Filterer production was dominated by hydropsychid caddisflies in pre-decline reaches, whereas black flies dominated filterer production in post-decline reaches. Overall, detritus and detritivores dominated energy flow in all study reaches. However, scrapers were well represented in these systems and appeared to be food-limited, particularly in pre-decline reaches where grazing tadpoles were still abundant. During the second year of my study, predicted amphibian declines began at the pre-decline site. The loss of amphibians through this year resulted in subtle shifts in macroinvertebrate functional and taxonomic structure, which correlated with changes in available food resources. Some grazing mayflies responded positively to declining tadpole populations and subsequent increased periphyton resources, suggesting a potential for some degree of functional redundancy in these systems. However, other grazers, such as the water penny beetle Psephenus, showed no response during the period of study. My results indicate that responses of remaining consumers to tadpole declines in streams may not be evident at some coarse scales (e.g., total abundance, biomass). However, differences in secondary production at the community and the functional level, along with assemblage structure changes were evident, with some individual taxa responding relatively quickly. Long-term studies in these same stream reaches will further illuminate the ultimate ecological consequences of these dramatic and sudden losses of consumer diversity.

1. Tardigrades comprise a micrometazoan phylum that is a sister group of the arthropods. 2. They are components of the meiobenthos in lotic habitats, and ≃ 50-70 species have been reported in such habitats world-wide. Approximately 800 species have been identified from all marine, freshwater, and terrestrial habitats. 3. Taxonomy is based primarily on the morphology of the claws, buccal-pharyngeal apparatus, cuticle and eggs. 4. Reproductive modes include sexual reproduction (amphimixis) and parthenogenesis. The sexual condition of individuals may be either gonochorism, unisexuality, or hermaphroditism. Moulting occurs throughout the life of the tardigrade. 5. Latent states (cryptobiosis, including encystment, anoxybiosis, cryobiosis, osmobiosis and anhydrobiosis) enable tardigrades to withstand unfavourable environmental conditions. 6. Population densities, life histories, dissemination and biogeography of freshwater species are poorly known.

Historically, whole stream open channel metabolism has been measured over short periods in conjunction with nutrient injections to assess nutrient dynamics within streams. The purpose of my study was to understand the seasonal changes in metabolism within and among streams as well as the impacts of different land use. This was addressed by monitoring nine different watersheds in the Little Tennessee River watershed in southwestern North Carolina.  The nine study watersheds were selected to represent a gradient of forested, agricultural, and developed land use / land cover types. Data loggers were deployed to collect continuous oxygen, temperature, conductivity, and stage height data from 2010-2011. I used these data to estimate gross primary production (GPP) and ecosystem respiration (ER). GPP and ER were compared to stream chemistry, light, land cover, and storms. I found that there is greater influence of local riparian land cover than watershed land cover on GPP and ER. Streams had varying annual GPP, but generally the peak in GPP occurred in late winter- early spring with lows in fall. GPP was most strongly influenced by the amount of available light, which is directly related to the amount of canopy cover. ER was much more variable than GPP within and among streams but generally peaked in summer and was lowest in the winter. ER was most strongly related to the proportion of agricultural land cover in the local riparian area. My results suggest that local riparian vegetation may have a greater impact on metabolism than mountainside development. / Master of Science

The movement of translatory waves over an erodible stream has a critical influence on the time of rise of the hydrograph which, in turn, affects the stability of the stream channel. In the present study, the movement of these flood waves is described by the one-dimensional equations of continuity and motion which are obtained by the space integration of the three-dimensional equation of continuity and Reynolds equations. The flow of suspended sediment is described by a one-dimensional dispersion equation which is derived from a three-dimensional equation of conservation of solid mass in the flow. With some modifications the one-dimensional dispersion equation is used to describe the scouring of the stream bed. Then the suspended sediment model is connected to the bed scouring model by a stochastic model which describes the bed load and the sediment transfer between the suspended sediment state and the immobile bed state. The stochastic model consists of a set of nine Kolmogorov differential equations for the probabilities of sediment transfer between different states in which a sediment particle may be. To obtain a high-accuracy approximation in the solution of the one-dimensional equations of continuity and motion, the one-step Lax-Wendroff numerical scheme is adopted. The Kolmogrov differential equations are solved directly by means of an analog computer. An analytical investigation of the stability of the approximation scheme is performed. The simulation of the model is done on a hybrid computer by incorporating into the entire model various model components and testing the effects of each component on the whole model and on the other components to see its behavior.

In this study, features of ecology, behavior, and functional morphology related to feeding activity of two populations of the amphipod Gammarus minus were compared. The two populations occupied different habitats, and I attempted to determine whether differences observed between the two populations were related to habitat. Annual production and life history of the populations were compared and their relationship to factors such as temperature, water-chemistry, and quantity of available organic matter were examined. Mouthpart and foregut morphology were compared between the two populations and between immature and mature amphipods with light and scanning electron microscopy. Measurements of structure were analyzed by linear regression. A behavioral study, comparing feeding of immature and mature G. minus, was conducted in the laboratory. Annual production of G. minus occupying a habitat characterized by the presence of watercress, gravel substrate, and constant temperature (Site 1) was 3.9 g/m² (95% C.I.: 3.2- 4.5), while that in the habitat characterized by leaf detritus and fluctuating temperatures (Site 2) was 1.8 g/m² (95% C.I.: 1.6-2.1). Breeding occurred throughout the year at Site 1, but there was a yearly cycle at Site 2. The greatest numbers of the smallest size classes of amphipod were present at Site 2 when the quantity of ash-free dry mass (AFDM) of wood and bark was greater than AFDM of leaf detritus. Of nine mouthpart and foregut structures studied, three, the number of cuspidate setae on outer plates of maxillipeds, the length of the dactyl on maxilliped palps, and the number of hook setae on the foregut ampullae, were found to be correlated with body length. Of these, rates of increase in maxilliped setae numbers and hook setae numbers were greater for immature than mature animals, and the number of hook setae for a given sized animal was generally greater for animals at Site 1 than Site 2. Animals presented with ground-up leaf material in the laboratory exhibited twenty-one recognizable behaviors. The frequencies of six behaviors were found to be statistically different between immature and mature animals. The differences suggest that immatures may prefer a food type or size other than that provided in the experiment. / Ph. D.

No description available.

<p> A brief review of the industrial methods employed to remove hydrogen sulfide from contaminated gas streams is given, with particular emphasis centred on the Stretford process.</p> <p> A summary of some recent developments in the solvent extraction of vanadium(5) is also given, together with the relevant aqueous vanadium chemistry.</p> <p> The experimental section deals with the development and optimization of an analytical procedure for vanadium(5) determination in alkaline solution. This developed procedure is then applied to the analysis of Stretford liquor.</p> / Thesis / Master of Science (MSc)

No description available.

In intermittent streams, hydrological variation is probably the single-most important factor affecting fish assemblage structure. While the response of aquatic assemblages to seasonal or annual variation in hydrology is well-known, less attention has been devoted to how assemblages respond to natural, intraseasonal drought. To explore this question, I conducted summer surveys of fish and aquatic insect assemblages occupying pool refugia in first to third order, intermittent streams in the Saline river drainage in the Ouachita highlands (central Arkansas, U.S.A.)(2001?2003). The goals of this project were: 1) to relate assemblage variability of fishes and aquatic insects to environmental gradients during summer drying of streams; 2) to characterize the variability of fish assemblages occupying pool refugia, which differed in quality along a spatial gradient; and, 3) to determine the population genetic structure of five fish species across the intermittent landscape. Hydrological variables explained significant variation in assemblage variability for fishes. In contrast, variability in aquatic insect assemblages was related to water quality variables. These patterns are similar to those observed at larger scales of space and time. As pools dried, neither fish species richness nor the slope of the species-area relationship changed. However, the structure of many assemblages was variable over time. Pools with a relatively stable hydrology were sources of reproduction and high population growth, low extinction and high immigration. Sites that exhibited a more variable hydrology (drying completely or nearly-so) were sinks characterized by population declines. The majority of sites had minimal population growth, and intermediate immigration and extinction rates, and were dubbed metapopulations. Immigration and extinction dynamics had important effects on population genetics for common fish species. Two common species had relatively high immigration rates and showed no population differentiation. Populations of three species showed differentiation that was not related to geographic distance among sites. Instead, local extinction of rare haplotypes and evidence of recent bottlenecks suggested that ecological attributes associated with summer drought affected population differentiation. It is clear that retaining the natural hydrology of stream systems contributes to the maintenance of biodiversity, and the conservation of complex demographic processes and genetic patterns.

Fish assemblage structure in lotic environments is a product of interactions between the habitat and the biota, but little is known about how deep pool habitat conditions affect distributional patterns of fish occupying them in larger warmwater streams. This study describes relationships between the habitat and the fish assemblages in deep pools of the Upper Tombigbee River, Mississippi. Pools exhibited an increase in size from headwaters to mouth. The change in the structure of fish assemblages was related significantly to increases in pool size while independent of time or other environmental conditions. A small amount of the variation in structure of fish assemblages in deep pools was accounted for by the measured environmental variables. This suggests other factors such as biotic interactions play an additional role in the forming the observed distributional patterns in fishes occupying deep pools.