This dissertation has two overall objectives: first, to demonstrate the utility of paleozoological data for ongoing and future mussel-conservation efforts in Texas and second, to evaluate whether simple measures of habitat (e.g., water depth, velocity and particle size) are important for demonstrating the within-habitat spatial separation of mussels. Although these topics may seem disparate, both are important for increasing our understanding of unionid ecology and biogeography. Chapters 1 through 3 examine the use of paleozoological data for mussel conservation. Although these types of data are not new they have rarely been used in mussel conservation efforts within Texas. This is unfortunate because paleozoological data can provide an excellent record of the mussel fauna prior to wide-scale modern impacts and in areas where historical survey data are lacking. Chapter 4 examines whether assessments of microhabitat for mussels using simple measures of habitat (e.g., water velocity, depth and particle size) are useful. Recent studies have suggested that these measures do not explain the mussel distribution in flowing streams. If this is correct, instream flow studies using this approach need to be revised. Results of Chapter 4 indicate that mussels in the lower Brazos River basin are constrained in distribution by the availability of heterogenous substrate. Appendix A, details the first account of a living population of Truncilla macrodon, which is a candidate species for the Endangered Species Act (ESA). The population was found while conducting mussel instream flow studies in the lower Brazos River basin.

Global warming in response to increasing levels of atmospheric CO2 concentration (pCO2) has generated concern over the effects of increasing surface temperature on the hydrologic cycle. Investigating precipitation dynamics during past ‘greenhouse’ intervals provide important insights necessary to better constrain potential future climate scenarios. The Late Cretaceous greenhouse is characterized by elevated pCO2 and surface temperatures, with a prolonged cooling trend which initiated in the late Campanian and an associated 4th-order sea-level regression recorded in the Western Interior Seaway (WIS), providing an opportunity to examine the hydrologic cycle under conditions of changing temperature and sea-level. This study uses a sclerochronologic approach to examine δ18O and δ13C values in freshwater bivalves collected from two horizons separated by ~800 ka, to reconstruct the late Maastrichtian hydrology at a locality along the western shoreline of the WIS. To ensure the presence of primary calcium carbonate, valves were examined using Scanning Electron Microscopy (SEM). Bivalve δ18O and δ13C values reflecting coastal river compositions range from -10.5 to -2.8‰ and -8.2 to 5.6‰, respectively. A positive correlation between δ18O and δ13C values found in specimens lower in the section, reveals that the lowest δ18O values occurred during times of peak summer soil respiration, whereas the highest δ13C values of 5.6‰ record a marine influence, supporting rainout during a summer monsoon as the cause for the lowest δ18O values recorded in this group. The valves collected higher in the section have an alternating correlation between δ18O and δ13C and plot closer to high elevation precipitation values on a mixing diagram. The loss of the summer monsoon between the two unionid groups is likely in response to decreasing surface temperatures and the retreat of the seaway, providing insight into the potential for increased intensity of modern monsoons in response to increasing surface temperatures and sea-level rise.

Freshwater burrowing mussels (unionids) play a vital role in freshwater ecosystems through nutrient cycling and promoting biodiversity. They have unique life histories directly related to aquatic vertebrates during an obligate parasitic larval stage, known as glochidia. Human interference has largely impacted mussel populations causing them to become the most endangered group of animals in North America. Genetic data has revealed taxonomic issues related to valve morphology, such as valve plasticity and cryptic speciation, that has caused identification issues in the field. Using both genetic and morphometric methods, I determined the phylogenetic placement of an isolated population of mussels within the tribe Lampsilini. I also investigated whether this population was a morph of a previously known Lampsilin species or if they were worthy of being treated as an evolutionarily significant unit (ESU) or an undescribed species. In addition, I expanded the known phylogeny of Lampsilin by including three species (Lampsilis fasciola, Lampsilis hydiana, Ligumia subrostrata) not included in previous phylogenies. Genetic analysis involved sequencing cytochrome c oxidase subunit 1 (COI) and 16s ribosomal RNA (rrnL) genes and producing maximum likelihood trees with bootstrap values for each gene individually and combined. Genetic results showed that an population from an isolated pond (named Junk Pond in this study) were closely related to members of the genus Ligumia (pondmussels), with Ligumia subrostrata being their closest relative. Morphologically, these Junk Pond mussels were noticeably different from other Ligumia species, so genetic and morphometric data was used to try and characterize this population of mussels from Junk Pond. The genetic distance between these two groups, measured using K2P distance method, were like the distances of other known sister species within Lampsilini. Morphometric analysis involved landmark and semi-landmark analyses to quantify the differences of the internal and external shapes of the shell, respectively, and determine differences that could be species defining characteristics. Landmark analysis results showed that Ligumia subrostrata and the Junk Pond mussels had similar internal valve structures though semi-landmark results showed differences among all groups including L. subrostrata and the Junk Pond mussels. I determined that this isolated population, due to its geographic isolation, genetic differences, variant shell morphology, and limited population size, should be treated as an ESU. The expanded Lampsilin tree showed a few differences involving Ligumia nasuta that did not support a previously published tree. Many other relationships within this phylogeny agreed with previously published works. The isolated population of the Junk Pond mussels are worthy of future research using more genetic data, such as COI, and morphometric work involving other Lampsilin members in order to conclude whether this group are worthy of being recognized as an undescribed species.

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This project evaluated the feasibility of salvaging zebra mussel-infested freshwater mussels from their native habitat by determining 1) how zebra mussel infestation affects unionid feeding and body condition, 2) how starvation in quarantine affects body condition of unionids, and 3) what feeding regime maintain unionid condition in quarantine. The effects of zebra mussel infestation on two mussel species were evaluated through glycogen analyses of mantle tissue and gut content analysis. Specimens of Amblema p. plicata (Say, 1817) and Quadrula p. pustulosa (I. Lea, 1831), collected from a heavily infested reach of the Ohio River in 1996, had significantly lower (p<0.05) glycogen levels than specimens collected from a low-infestation reach upstream. In 1996 and 1997, heavily infested Amblema p. plicata and Quadrula p. pustulosa had significantly less (p<0.01) organic matter and fewer algal cells in their guts than lightly infested specimens. In addition, gut contents of individual A. p. plicata contained significantly less (p<0.05) organic matter and fewer algal cells than the combined gut contents of all zebra mussels (18-33 mm in length) attached to their shells. Gut analyses also revealed significant diet overlap between native unionids and infesting zebra mussels. Thus, competitive interactions or interference by zebra mussels likely reduced unionid ingestion and consequently reduced glycogen stores. During quarantine, unionids salvaged from a lightly infested area and starved for 30 days had glycogen levels that declined dramatically. After 30 days without supplemental feeding, mean glycogen levels of A. p. plicata declined 85%, and mean glycogen levels of Q. p. pustulosa declined 70%. Thus, feeding of unionids is necessary to maintain their condition during lengthy quarantine. To determine the best feeding regime for unionids in quarantine, assimilation efficiencies and carbon budgets were established for the rainbow mussel, Villosa iris (Lea, 1829), using radio-labelled cultures of Neochloris oleoabundans (Chantanachat and Bold 1962) at three cell concentrations. Assimilation efficiencies for Villosa iris at 100,000cells/ml, 10,000 cells/ml, and 1,000 cells/ml were similar (45-56%); however, regardless of these similarities, assimilation efficiencies from this study indicate that Neochloris oleoabundans is readily assimilated (~50% AE) by Villosa iris . In addition, total assimilation was maximized at 100,000cells/ml, which indicates that Villosa iris has the greatest amount of energy available for growth, reproduction, and maintenance of condition in captivity at this cell concentration. During a second quarantine experiment, specimens were provided with 100,000cells/ml of N. oleoabundans twice per day. Initial mean glycogen levels for Amblema p. plicata (9.4 + 2.4 mg/g) and Quadrula p. pustulosa collected from ORM 175.5 in July 1997 were not significantly different (p>0.3) than the mean glycogen levels of A. p. plicata and Q. p. pustulosa collected from the same site in July 1996. Glycogen stores of unionids entering quarantine, therefore, were similar in both the starvation and controlled feeding experiments. After 7, 14, and 30 days of controlled feeding in quarantine, mean glycogen levels of A. p. plicata and Q. p. pustulosa did not change significantly (p>0.1). Thus, quarantine protocol for salvaged native mussels should include the feeding of algae to captive specimens to sustain glycogen levels prior to relocation. / Master of Science

This research was divided into four objectives for assessing the impacts of coal mining on ecosystem health. The first objective was to provide an ecotoxicological assessment in the upper Clinch River using standard bioassessment techniques. Analysis of sediments and interstitial water (porewater) indicate higher concentrations of trace metals in samples from sites located above both a power plant (CRP) and Dumps Creek mining influences. The furthest sampling site located near Pounding Mill, Virginia (CR-PM) had higher concentrations of aluminum (2,250.9 mg/kg), copper (5.9 mg/kg) and iron (12,322.6 mg/kg) compared to samples collected directly below the Dumps Creek confluence (site CR-2). Similar results were obtained from bioaccumulation in-situ tests with the Asian clam (Corbicula fluminea) in 2009. Aluminum (7.81 mg/kg), Fe (48.25 mg/kg) and Zn (7.69 mg/kg) were accumulated in higher concentrations at CR-PM site than CR-2. However, the site located below the CRP effluent discharges (CR-3L) on the left bank had substantially higher concentrations of Al (14.19 mg/kg), Cu (6.78 mg/kg), Fe (88.78 mg/kg) and Zn (7.75 mg/kg) than both CR-PM and samples collected directly opposite of this site at CR-3R. To further understand the potential impact active mining on the Clinch River, a more comprehensive ecotoxicological evaluation was conducting in the Dumps Creek subwatershed. Field bioassessments determined that biological impairment occurred directly below a deep mine discharge (CBP 001), which was characterized by a distinct hydrogen sulfide odor. Total abundance and richness of benthic macroinvertebrates decreased to 3.5-20 and 1.25-2.3, respectively at DC-1 Dn. The discharge also caused the proliferation of a sulfur-oxidizing bacterium, Thiothrix nivea. During continuous discharge of the effluent, the bacteria was observed coating all surfaces at DC-1 Dn and may also contribute to an Fe-encrusted biofilm observed on in-situ clams at downstream site, DC-2 Dn. Toxicity tests with mining effluents indicate some potential toxicity of the 001 discharge, but this was variable between test organisms. Selecting the most appropriate test species for sediment and water column assays has been a primary goal for ecotoxicologists. Standard test organisms and established test guidelines exist, but US EPA recommended species may not be the most sensitive organisms to anthropogenic inputs. Therefore, Chapter Three and Four addressed the use of mayflies in routine laboratory testing. Preliminary results of toxicity tests with the mayfly, Isonychia sp. (Ephemeroptera) suggested that Isonychia were moderately sensitive to NaCl after 96-hr with an average LC50 value of 3.10 g NaCl/L. When exposed to a coal-mine processed effluent, Isonychia generated LC50 values that ranged from 13 to 39% effluent and were more sensitive to the effluent than Ceriodaphnia dubia. Based on results of the feasibility study in presented in Chapter Four, field collected organisms appear to be too unpredictable in test responses and therefore, such tests would be unreliable as stand-alone indicators of effluent toxicity. / Ph. D.

No description available.

No description available.