<p> The South Texas Banks are a mesophotic coral ecosystem (30-150m deep). Understanding the community structure, biodiversity and, geographic connectivity of the South Texas Banks is essential with increasing threats from climate change, ocean acidification, invasive species, and pollution. In this study, a remotely operated vehicle (ROV) was used to examine the fish communities at five of the South Texas Banks: Big Adam, Hospital, Mysterious, North Hospital, and Southern. Reef fish were identified to the lowest possible taxon and enumerated from ROV transect video footage. A total of 3,838 demersal and pelagic fishes were recorded representing 61 species in 22 families including invasive <i>Pterois volitans. Bodianus pulchellus, Holocentrus adscensionis, Priacanthus arenatus,</i> and the Gobiidae family were the only fishes observed at all five banks. Habitat suitability models were created that highlight the rich biodiversity found on the South Texas Bank, which will warrant for future research and conservation efforts.</p>

<p> The impacts of a 20,993 L diesel and gasoline spill on the benthic macroinvertebrate (BMI) and diatom communities in Cold Creek and the Santa Ana River (below its confluence with Cold Creek) were assessed by comparing species richness, diversity and compositions between fuel-impacted and reference sites. BMIs and diatoms were sampled four times (13&ndash;26 months after the spill) in sites located upstream from the spill (reference) and in sites located 0.5, 1.3, 2.7 and 3.0 km downstream from the spill (impact). BMI communities up to 2.7 km below the spill and in Cold Creek had (1) lower species richness and diversity for at least 25 months after the spill and (2) dissimilar species compositions for up to 26 months after the spill when compared to the reference site. Diatom communities up to 2.7 km below the spill and in Cold Creek had (1) similar or higher species richness and diversity when compared to the reference site and (2) dissimilar species compositions when compared to the reference site for the entirety of the study. BMI and diatom communities located 3.0 km below the spill and in the Santa Ana River had similar species richness, diversity and compositions when compared to the reference site. These results provide evidence that the fuel spill had an impact on the BMI and diatom communities in Cold Creek and that these communities are still changing.</p>

The purpose of this study was to develop an efficient method for the concentration of specific volatile taste and odor compounds produced by a selected aquatic actinomycete. A second purpose was to isolate and identify the specific taste and odor compound present in the highest concentration.

There were two purposes of this investigation: the first was to develop a method for studying spore germination, hyphal growth and mycelial development of the aquatic actinomycetes under the microscope so that the life cycle of this organism could be continuously followed. The second purpose was to determine the rate of carbon utilization from various types of nutritional sources, and to correlate this with the colony development and spore formation.

The objective of this study was to elucidate the nature and extent of drift by the aquatic insect populations of the Brazos River, Texas.

<p> Though land conversion and flow alteration have heavily impacted the Sacramento River riparian ecosystem, restoration opportunities still exist in the hydrogeomorphically active Middle Reach. This study of riparian forest succession focused on six dominant riparian tree species to explore relative establishment timing and the potential impacts of altered flow regimes. We utilized tree inventory data and increment cores collected from riparian forest stands to establish a temporal chronosequence of floodplain surfaces and associated tree ages and colonization timing. Tree age calculations incorporated raw ring counts and sampling error simulations. Results were then used to construct species-specific, diameterage models and predict age distributions for all inventoried trees. Cottonwood&rsquo;s colonization window was longer than expected (up to 95 years after floodplain creation), whereas box elder and walnuts established on floodplains &lt;50 years old. This study lays the groundwork for future research into the health and development of the Middle Reach riparian forest.</p>

<p> Information on the movement of migratory demersal fishes such as Pacific halibut, Pacific cod, and sablefish is needed for management of these valuable fisheries in Alaska, yet available methods such as conventional tagging are too coarse to provide detailed information on migration characteristics. In this dissertation, I present methods for characterizing seasonal and annual demersal fish movement at multiple scales in space and time using electronic archival and acoustic tags. In Chapter 1, acoustic telemetry and the Net Squared Displacement statistic were used to identify and characterize small-scale movement of adult female Pacific halibut during summer foraging in a Marine Protected Area (MPA). The dominant movement pattern was home range behavior at spatial scales of less than 1 km, but a more dispersive behavioral state was also observed. In Chapter 2, Pop-up Satellite Archival Tags (PSATs) and acoustic tags were deployed on adult female Pacific halibut to determine annual movement patterns relative to MPA boundaries. Based on observations of summer home range behavior, high rates of year-round MPA residency, migration timing that largely coincided with winter commercial fisheries closures, and the demonstrated ability of migratory fish to return to previously occupied summer foraging areas, the MPA is likely to be effective for protecting both resident and migrant Pacific halibut brood stock year-round. In Chapter 3, I adapted a Hidden Markov Model (HMM) originally developed for geolocation of Atlantic cod in the North Sea for use on demersal fishes in Alaska, where maximum daily depth is the most informative and reliable geolocation variable. Because depth is considerably more heterogeneous in many regions of Alaska compared to the North Sea, I used simulated trajectories to determine that the degree of bathymetry heterogeneity affected model performance for different combinations of likelihood specification methods and model grid sizes. In Chapter 4, I added a new geolocation variable, geomagnetic data, to the HMM in a small-scale case study. The results suggest that the addition of geomagnetic data could increase model performance over depth alone, but more research is needed to continue validation of the method over larger areas in Alaska. In general, the HMM is a flexible tool for characterizing movement at multiple spatial scales and its use is likely to enrich our knowledge about migratory demersal fish movement in Alaska. The methods developed in this dissertation can provide valuable insights into demersal fish spatial dynamics that will benefit fisheries management activities such as stock delineation, stock assessment, and design of space-time closures. </p><p>

<p> Natural and sexual selection shape animal communication signals according to the demands of social context and the environment, which results in enormous variation in signal properties. My dissertation uses the electrocommunication signals of South American weakly electric knifefish to compare signal structure across several closely related species, with particular emphasis on signals that are extreme or unusual. Weakly electric fish continuously generate an electric field using an electric organ discharge (EOD). During short-range social interactions, fish produce chirps by rapidly and transiently increasing EOD frequency. I used recordings with playbacks of conspecific signals and hormone manipulation to characterize the sexually dimorphic chirp duration of <i>Parapteronotus hasemani</i>, a species of electric fish with high-frequency, long-duration chirps and huge variation in male morphology. I also described signaling behavior in <i>Distocyclus conirostris </i>, a species of electric fish with a low-frequency EOD and an unusual asymmetrical behavioral response to &ldquo;jamming&rdquo; created when EODs of similar frequencies interact. Next, I compared across species to examine how signal properties (EODs and chirping) interact to influence each other&rsquo;s detection and evolution. Certain signal parameters such as chirp frequency modulation and EOD frequency difference have substantial effects on chirp conspicuousness. Contrary to expectations, there was little support for a strict co-evolution in which a species&rsquo; chirps are most conspicuous on their own EOD waveforms. Thus, although EOD properties influence chirp conspicuousness, other factors such as the social or physical environment also likely shape chirp structure. Additionally, I show that EOD waveform may differ in perceptibility based on the EOD waveform complexity of the interacting fish. I consider how chirp conspicuousness could drive the evolution of sexually dimorphic chirps (such as those produced by <i>P. hasemani</i>), and I raise questions about whether low-frequency EODs (such as those produced by <i>D. conirostris</i>) contain sufficient information for fish to detect conspecific EOD frequencies using the neural mechanisms described in fish with high-frequency EODs. Taken together, these results show how the properties of multi-component signals shape each other and impact signal detectability. Finally, my dissertation concludes with a description of an innovative approach to teaching scientific communication skills in a highly structured undergraduate introductory biology lab.</p>

Created wetlands are often limited in soil organic matter, usually a long-term product of ecosystem succession. Although many studies have tested the effect of adding organic material to these systems, few if any, have quantified the effect of various loadings of organic matter in created wetlands. The goal of this study was to determine how vegetation composition, standing crop biomass, woody vegetation development, and ecosystem gas exchange varied in a created freshwater wetland along a gradient of soil organic carbon (0 to 336 Mg ha-1 loading rates). Plot surface elevation varied positively with OM loadings, suggesting that inundation/aeration may modify OM effects. Soil nutrients (C, N, C:N, and P) also positively correlated with loading rate. Vegetation measurements suggested an overall similarity of plant assemblage composition and biomass regardless of loading rate, and a slight increase in tree size with loading rate. Gross primary production and net ecosystem exchange were weakly positively and negatively correlated with loading rate, respectively. Respiration was strongly positively correlated with loading rate, and was likely the controlling factor of CO2 gas flux among treatments. Soil nutrient values and vegetation composition, as well as ecosystem gas flux balance appear to be the best parameters upon which to base an organic matter loading rate decision. In this study, adding an organic matter amendment between LR 2 (56 Mg ha-1) and 3 (112 Mg ha-1) seems most appropriate, and may provide a “jumpstart” for the created non-tidal wetlands while also minimizing changes in surface elevation due to the added bulk material.

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