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<p> As a result of human activities, the level of CO₂ in the Earth&rsquo;s atmosphere has increased by nearly 40% since the industrial revolution. The rate of green house gas emission is accelerating, with current trends exceeding those predicted by &ldquo;worst case&rdquo; global climate change scenarios. The chemistry of the ocean is fundamentally changing as a result of increasing atmospheric CO₂, which dissolves in seawater, making it more acidic, a process referred to as ocean acidification (OA). A rapidly expanding body of science is now being generated to understand the impact of this global environmental change. To date, most studies evaluating OA effects have centered on simplified laboratory analyses that expose single populations to short-term treatments in order to quantify responses of individuals. These designs offer a limited assessment of the degree to which phenotypic plasticity and local adaptation might influence the response of populations to OA. </p><p> To address these questions, I carried out studies on members of Phylum Bryozoa, a species-rich clade of calcified colonial marine invertebrates distributed throughout the global ocean. Bryozoans were selected as a model system for this work because the clade exhibits a broad array of growth and calcification strategies, and because of the relative paucity of data regarding their expected response to future acidification. In addition, bryozoans can be subdivided into genetically identical replicate clones, which can then be assigned to separate treatments, allowing variation across treatments to be uniquely partitioned into the variance components of statistical models. In order to culture bryozoans for comparative experiments, I designed and constructed a new flow-through OA system at the Bodega Marine Laboratory, capable of finely manipulating both the temperature and carbonate chemistry of seawater, allowing for controlled laboratory experiments of long duration. </p><p> In Chapter 1, I performed a comparative 9-month laboratory experiment examining the effects of ocean acidification on the native Californian bryozoan <i> Celleporella cornuta. C. cornuta</i> was sampled from two regions of coastline that experience different oceanographic conditions associated with variation in the intensity of coastal upwelling. Under different CO₂ treatments, the biology of this bryozoan was observed to be remarkably plastic. Colonies raised under high CO₂ grew more quickly, invested less in reproduction, and produced skeletons that were lighter compared to genetically identical clones raised under current atmospheric values. Bryozoans held in high CO₂ conditions reduced their investment in skeletal carbonate, changed the Mg/Ca ratio of skeletal walls and increased the expression of organic coverings that may serve a protective function. Differences between populations in growth, reproductive investment, and the frequency of organic covering production were consistent with adaptive responses to persistent variation in local oceanographic conditions. </p><p> In Chapter 2, I tested whether skeletal mineralogy can vary plastically in some invertebrates using the cosmopolitan bryozoan <i>Membranipora tuberculata</i> as a model. In a 6-month laboratory experiment, I cultured genetic clones of <i>M. tuberculata</i> under a factorial design with varying food availability, temperature, and dissolved CO₂ concentrations. Elevated food availability increased growth in colonies while cold temperatures and high CO₂ induced degeneration of colony zooids. However, colonies were able to maintain equivalent growth efficiencies under cold, high CO₂ conditions, suggesting a compensatory tradeoff whereby colonies increase the degeneration of older zooids under adverse conditions, redirecting this energy to the maintenance of growth. Elevated food and cold temperatures also decreased Mg concentrations in skeletal material, and this skeletal material dissolved less readily under high CO₂ conditions. This suggests that these factors interact synergistically to affect dissolution potential in this and other species. </p><p> Finally, in Chapter 3, I explore stable isotope values for &delta;¹⁸O and &delta;¹³C in the calcium carbonate structures of the bryozoan <i>Membranipora tuberculata</i>. I tested whether this species accurately records both temperature and pH variability during periods of coastal upwelling by analyzing &delta;¹⁸O and &delta;¹³C in colonies grown in the field and in controlled laboratory cultures. Field-grown colonies were out planted next to a Durafet^&reg; pH sensor, which provided a high-resolution record of the temperature and pH conditions these colonies experienced. &delta;¹³C was found to negatively co-vary with pH in both laboratory and field growth, and calculated field temperatures derived from laboratory &delta;¹⁸O temperature calibrations aligned with the records from the pH sensor. &delta;¹⁸O_c values were more depleted under low pH in laboratory trials, which stands in contrast to patterns observed in other taxa. This may indicate that <i>Membranipora</i> utilizes bicarbonate ion (HCO₃^-) in its calcification pathway, and could help explain why many bryozoan species appear to exhibit enhanced growth under high CO₂ conditions. (Abstract shortened by ProQuest.)</p>

<p> Given the current mass extinction crisis and continued fragmentation of resources worldwide, the outlook is dire for global biodiversity. Rising global temperature, sea levels, and storm frequency all create environmental conditions that can drive change in species abundance and distribution across a landscape. Those species reliant upon a single type of habitat and resource for survival, termed "specialists", are particularly vulnerable to change due to their inability to utilize a variety of resources well. As a result, specialism is now considered one of the dominant factors determining extinction of species. In this dissertation I explore the effects of disturbance on habitat specialist birds in tidal marshes of the northeastern United States. This ecosystem is important due to the significant ecosystem services it provides to humans, and supports several specialist species including the saltmarsh sparrow (<i>Ammodramus caudacutus</i>). I examine this specialist bird community across scales of space, time, and ecological organization to A) evaluate the impacts of disturbance on tidal marsh communities and B) provide findings and management recommendations for long-term maintenance and conservation of coastal marsh ecosystems, specifically as they pertain to salt-marsh specialist birds. In Chapter 1 I introduce my study system and give background for the current conservation status of tidal marsh birds. In Chapter 2 I generate population trends in the five species particularly specialized to tidal marsh using a database of historical records, and explore potential drivers for population change through local and regional habitat disturbance. In Chapter 3 I expand upon patterns in Chapter 2 ad quantify life history strategy in marsh birds across a gradient of habitat specialization to explore how this metric explains species persistence in tidal marshes. In Chapter 4 I test several theoretical hypotheses from disturbance ecology empirically using traditional and novel community metrics. Finally, in Chapter 5 I respond to research needs identified in Chapter 4 to develop a method for quantification of high-marsh habitat using remote sensing methods. I hope the findings presented here contribute towards understanding of the mechanisms driving biodiversity patterns on our planet and help inform conservation priorities within the changing tidal marsh landscapes.</p>

Canada is one of the wealthiest and most technologically advanced countries in the world. Yet, it fails to maintain an effective and comprehensive system for responding to weather-related hazards. The adverse socio-economic impacts of extreme weather are sufficiently serious to make climate change a threat to humanity. Weather events have lingering effects on peoples’ financial stability, particularly in low-income households. The goal of this thesis is to illuminate the nature of the legal, economic and social challenges posed by extreme weather. Thus, I present a comprehensive study of the Canadian institutional responses to these disasters. / Graduate

<p>Blue carbon systems (mangroves, salt marshes, and seagrass beds) sequester large amounts of carbon via primary productivity and sedimentation. Sequestered carbon can be respired back to the atmosphere, buried for long time periods, or exported (&ldquo;outwelled&rdquo;) to adjacent ecosystems. This study estimates the total outwelling of dissolved organic carbon (DOC) from the Neponset Salt Marsh (Boston, Massachusetts) as well as the major plant and sediment processes contributing to the overall flux. The total export was quantified via high-resolution <i> in situ</i> chromophoric dissolved organic matter (CDOM) measurements as a proxy for DOC using 12 years of transect data. Seasonal trends, alternate sources of fresh water, and long-term trends in DOC export will be discussed. To characterize the percentage of this flux attributable to marsh vegetation, the effects of sunlight, anoxia, plant species, biomass type, and microbes on plant leaching were studied using incubations of above- and belowground biomass over four seasons. Seasonal comparisons led to the &ldquo;Fall Dump&rdquo; hypothesis in which higher DOC concentrations are leached during the fall when marsh plants senesce for winter. In summing seasonal fluxes from vegetation, approximately 46% of the total DOC export from the marsh may be attributed to leaching from the three dominant plant species in the Neponset Salt Marsh. The influence of seasonality and climate change (e.g., drought) on both overland flow and deep sediment pore water leaching were also investigated. Depending on season and marsh condition, overland flow and sediment pore water leaching combined could contribute 8&ndash;16% of the total export from the marsh. Finally, the influence of natural sunlight irradiation and microbes on the release of dissolved organic matter (DOM) from resuspended surface sediments was studied and approximately 11&ndash;22% of the total export could be attributable to this flux. Approximately 49 mol C m^&minus;2 yr^&minus;1 are outwelled from the Neponset Salt Marsh and, using net primary productivity estimates from the literature, 16 &plusmn; 12 mol C m^&minus;2 yr^&minus;1 are buried in the Neponset Salt Marsh. </p>

The thesis concerns the analysis and interpretation of data from satellite borne radar altimeters over ice covered ocean surfaces. The applications of radar altimetry are described in detail and consider monitoring global climate change, the role that sea ice plays in the climate system, operational applications and the extension of high precision surface elevation measurements into areas of sea ice. The general nature of sea ice cover is discussed and a list of requirements for sea ice monitoring is provided and the capability of different satellite sensors to satisfy needs is examined. The operation of satellite borne altimeter over non-ocean surfaces is discussed in detail. Theories of radar backscatter over sea ice are described and are used to predict the radar altimeter response to different types of sea ice cover. Methods employed for analysis of altimeter data over sea ice are also described. Data from the Seasat altimeter is examined on a regional and global scale and compared with sea ice climatology. Data from the Geosat altimeter is compared with co-incident imagery from the Advanced Very High Resolution Radiometer and also from airborne Synthetic Aperture Radar. Correlations are observed between the altimeter data and imagery for the ice edge position, zones within the ice cover, new ice and leads, vast floes and the fast ice boundary. An analysis of data collected by the Geosat altimeter over a period of more than two years is used to derive seasonal and inter-annual variations in the total Antarctic sea ice extent. In addition the retrieval of high accuracy elevation measurements over sea ice areas is carried out. These data are used to produce improved maps of sea surface topography over icecovered ocean and provide evidence of the ability of the altimeter to determine sea ice freeboard directly. In addition the changing freeboard of two giant Antarctic tabular icebergs, as measured by the Geosat altimeter, is presented. As a summary the achievements are reviewed and suggestions are made towards directions for further work on present data sets and for future data from the ERS-1 satellite.

No description available.