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<p>Research into the age, growth, and reproductive characteristics of chondrichthyan fishes has increased substantially over the past couple of decades. This study set out to estimate age deepsea skate, <i>Bathyraja abyssicola</i> using vertebral centra and caudal thorns, estimate length at age, and determine length at maturity. Sixty-three specimens of <i>B. abyssicola</i> (n=29 males; n=34 females) were taken on National Marine Fisheries Service bottom trawl surveys between 2001 and 2012. Information derived and structures collected from these samples included sex, maturity class, total length, caudal thorns and, vertebrae. Ageing methods attempted include histology and gross sectioning (vertebral centra) and surface staining (caudal thorns). Moderate success with centra sectioned using the histological method allowed some inference to be made into life history characteristics. Deepsea skates appear to have slow average growth (26 mm yr^-1 &plusmn;5.41, 95% c.i.) and mature at a large size (males: TL₅₀ = 1175.4 mm, females: TL₅₀ = 1267.3 mm). Band pair counts were not validated as true ages. Males from which growth bands could be enumerated were smaller (<i>n</i> = 10, x&macr; = 718 mm, SD = 209 mm) on average than that for females (n = 7, x&macr;=990 mm, SD = 319 mm). This study provides the first attempt to assess <i>abyssicola</i> age, growth rate, and sexual maturity traits; information needed for informed skate management.</p>

<p> Though humans have over a century of experience with catastrophic marine and terrestrial oil spills, response plans and cleanup techniques are still active areas of research and development. This work evaluated the oil degradation potential and changes in the microbial community following nutrient additions in polluted marine sediment and desert soil. </p><p> Biostimulation experiments on Alaskan beach sediment still contaminated by the <i>Exxon Valdez</i> tanker oil spill demonstrated that ambient air and hydrogen peroxide both serve as suitable sources of oxygen to stimulate aerobic microbial degradation of the oil. The addition of oxygen to the oil-contaminated sediment stimulated the growth of Proteobacteria, which made up 77-92% of the population in the presence of ambient oxygen and 76-88% with hydrogen peroxide. These experiments also revealed that sediment samples collected from a non-contaminated portion of the beach also contained a large fraction of microbial species that are known oil degraders. A phytoremediation experiment using mesquite trees in motor-oil-contaminated desert soil indicated that the use of compost as a soil amendment enhanced oil degradation, while biochar hindered degradation activity.</p>

<p> Global change is driving chemistry, climate, and atmospheric composition to new regimes over the coming century, threatening attainment of air quality standards globally. The models used to quantify future air quality changes are often plagued with large surface ozone biases, hindering efforts to directly compare models with observations and to accurately quantify future changes. Studies of air quality extremes often rely on point-based measurements and an absolute threshold exceedance; consequently, they neither capture the large-scale, spatially coherent structures of the worst pollution episodes nor compare directly with models&rsquo; grid cell averages. This dissertation develops novel statistical approaches to commensurately compare observations and models with a specific focus on extreme pollution episodes.</p><p> The first of four studies led by the doctoral candidate develops a generalizable interpolation algorithm that converts irregularly spaced ozone measurements from surface networks in North America and Europe into maps of grid cell averaged ozone, allowing direct comparison with a global model. Air quality extreme (AQX) events are defined locally as statistical extremes of the ozone climatology and are found to predominantly occur in clustered, coherent, multiday episodes with spatial extents of more than 1,000 km. Additionally, the University of California, Irvine Chemistry Transport Model (UCI CTM) demonstrates skill in hindcasting the observed extreme episodes, thus identifying a new diagnostic to test global chemistry-climate models. The second study evaluates the ability of the UCI CTM and a suite of models from the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP) to simulate the observed, present-day surface ozone climatology over North America and Europe. The tests span temporal scales from diurnal to multi-year variability and on statistics from median geographic patterns to the timing and size of AQX episodes. We also identified and corrected an error in the UCI CTM diurnal cycle. The third study uses the ACCMIP models to quantify the effect of future climate change on surface ozone. The fourth study extends the methods to characterize the co-occurrence of surface ozone, particulate matter, and temperature extremes, providing further diagnostics for model evaluation and enabling an investigation of the multi-stressor impacts of poor air quality and heat waves.</p>

<p>Marine mammals exploit the efficiency of sound propagation in the marine environment for essential activities like communication and navigation. For this reason, passive acoustics has particularly high potential for marine mammal studies, especially those aimed at population management and conservation. Despite the rapid realization of this potential through a growing number of studies, much crucial information remains unknown or poorly understood. This research attempts to address two key knowledge gaps, using the well-studied bottlenose dolphin (Tursiops truncatus) as a model species, and underwater acoustic recordings collected on four fixed autonomous sensors deployed at multiple locations in Sarasota Bay, Florida, between September 2012 and August 2013. Underwater noise can hinder dolphin communication. The ability of these animals to overcome this obstacle was examined using recorded noise and dolphin whistles. I found that bottlenose dolphins are able to compensate for increased noise in their environment using a wide range of strategies employed in a singular fashion or in various combinations, depending on the frequency content of the noise, noise source, and time of day. These strategies include modifying whistle frequency characteristics, increasing whistle duration, and increasing whistle redundancy. Recordings were also used to evaluate the performance of six recently developed passive acoustic abundance estimation methods, by comparing their results to the true abundance of animals, obtained via a census conducted within the same area and time period. The methods employed were broadly divided into two categories – those involving direct counts of animals, and those involving counts of cues (signature whistles). The animal-based methods were traditional capture-recapture, spatially explicit capture-recapture (SECR), and an approach that blends the “snapshot” method and mark-recapture distance sampling, referred to here as (SMRDS). The cue-based methods were conventional distance sampling (CDS), an acoustic modeling approach involving the use of the passive sonar equation, and SECR. In the latter approach, detection probability was modelled as a function of sound transmission loss, rather than the Euclidean distance typically used. Of these methods, while SMRDS produced the most accurate estimate, SECR demonstrated the greatest potential for broad applicability to other species and locations, with minimal to no auxiliary data, such as distance from sound source to detector(s), which is often difficult to obtain. This was especially true when this method was compared to traditional capture-recapture results, which greatly underestimated abundance, despite attempts to account for major unmodelled heterogeneity. Furthermore, the incorporation of non-Euclidean distance significantly improved model accuracy. The acoustic modelling approach performed similarly to CDS, but both methods also strongly underestimated abundance. In particular, CDS proved to be inefficient. This approach requires at least 3 sensors for localization at a single point. It was also difficult to obtain accurate distances, and the sample size was greatly reduced by the failure to detect some whistles on all three recorders. As a result, this approach is not recommended for marine mammal abundance estimation when few recorders are available, or in high sound attenuation environments with relatively low sample sizes. It is hoped that these results lead to more informed management decisions, and therefore, more effective species conservation.</p> / Dissertation

<p>Terrestrial ecosystems, occupying more than 25% of the Earth's surface, can serve as</p><p>`biological valves' in regulating the anthropogenic emissions of atmospheric aerosol</p><p>particles and greenhouse gases (GHGs) as responses to their surrounding environments.</p><p>While the signicance of quantifying the exchange rates of GHGs and atmospheric</p><p>aerosol particles between the terrestrial biosphere and the atmosphere is</p><p>hardly questioned in many scientic elds, the progress in improving model predictability,</p><p>data interpretation or the combination of the two remains impeded by</p><p>the lack of precise framework elucidating their dynamic transport processes over a</p><p>wide range of spatiotemporal scales. The diculty in developing prognostic modeling</p><p>tools to quantify the source or sink strength of these atmospheric substances</p><p>can be further magnied by the fact that the climate system is also sensitive to the</p><p>feedback from terrestrial ecosystems forming the so-called `feedback cycle'. Hence,</p><p>the emergent need is to reduce uncertainties when assessing this complex and dynamic</p><p>feedback cycle that is necessary to support the decisions of mitigation and</p><p>adaptation policies associated with human activities (e.g., anthropogenic emission</p><p>controls and land use managements) under current and future climate regimes.</p><p>With the goal to improve the predictions for the biosphere-atmosphere exchange</p><p>of biologically active gases and atmospheric aerosol particles, the main focus of this</p><p>dissertation is on revising and up-scaling the biotic and abiotic transport processes</p><p>from leaf to canopy scales. The validity of previous modeling studies in determining</p><p>iv</p><p>the exchange rate of gases and particles is evaluated with detailed descriptions of their</p><p>limitations. Mechanistic-based modeling approaches along with empirical studies</p><p>across dierent scales are employed to rene the mathematical descriptions of surface</p><p>conductance responsible for gas and particle exchanges as commonly adopted by all</p><p>operational models. Specically, how variation in horizontal leaf area density within</p><p>the vegetated medium, leaf size and leaf microroughness impact the aerodynamic attributes</p><p>and thereby the ultrane particle collection eciency at the leaf/branch scale</p><p>is explored using wind tunnel experiments with interpretations by a porous media</p><p>model and a scaling analysis. A multi-layered and size-resolved second-order closure</p><p>model combined with particle </p><p>uxes and concentration measurements within and</p><p>above a forest is used to explore the particle transport processes within the canopy</p><p>sub-layer and the partitioning of particle deposition onto canopy medium and forest</p><p>oor. For gases, a modeling framework accounting for the leaf-level boundary layer</p><p>eects on the stomatal pathway for gas exchange is proposed and combined with sap</p><p>ux measurements in a wind tunnel to assess how leaf-level transpiration varies with</p><p>increasing wind speed. How exogenous environmental conditions and endogenous</p><p>soil-root-stem-leaf hydraulic and eco-physiological properties impact the above- and</p><p>below-ground water dynamics in the soil-plant system and shape plant responses</p><p>to droughts is assessed by a porous media model that accommodates the transient</p><p>water </p><p>ow within the plant vascular system and is coupled with the aforementioned</p><p>leaf-level gas exchange model and soil-root interaction model. It should be noted</p><p>that tackling all aspects of potential issues causing uncertainties in forecasting the</p><p>feedback cycle between terrestrial ecosystem and the climate is unrealistic in a single</p><p>dissertation but further research questions and opportunities based on the foundation</p><p>derived from this dissertation are also brie</p><p>y discussed.</p> / Dissertation