The coastal wetlands at Aransas National Wildlife Refuge near Austwell, Texas, support the last migrating population of whooping cranes during the winter months (October through April). With a population currently at 216 individuals, these are the rarest cranes in the world. The wetlands in which they winter are a part of the San Antonio Bay system, a bay that receives constant fresh water flow from the Guadalupe River. Currently there is a plan for using water diverted from the Guadalupe River just before it enters San Antonio Bay as a water supply for the greater San Antonio metropolitan area located 200 km to the northwest. The Guadalupe River delivers nutrients and sediment into the estuary along with fresh water. Because of the importance of sediment within a tidal wetland ecosystem, it is imperative to understand the sediment budget and underlying forces that drive it if one is to ultimately grasp how this ecosystem functions. To document natural and anthropogenic factors exerting control over sediment movement in this system, three sites on tidal creeks near the boundary between marsh and bay were chosen. The Gulf Intracoastal Waterwayparallels the marsh edge. Over six, non-consecutive weeks water level and velocity were automatically monitored in the tidal creeks. Automated water samplers extracted water samples that were analyzed for suspended sediment. In addition, bedload traps were deployed in one creek to monitor sediment movement along the channel bottom. Inflow exceeded outflow during the study. As a result there was a net influx of suspended sediments into the marsh. Bedload material also moves with current direction, and it appears to move in response to barge induced outflow currents. Barges passing on the Gulf Intracoastal Waterway exert influence on water level, flow direction, and velocity within tidal creeks. Natural factors such as winds, tides, and freshwater input from upland runoff or river discharge also impact suspended and bedload sediments.

Biogeographic patterns across a landscape are developed by the interplay of environmental processes operating at different spatial and temporal scales. This research investigated dynamics of salt marsh vegetation on the Skallingen salt marsh in Denmark responding to environmental variations at large, medium, and fine scales along both spatial and temporal spectrums. At the broad scale, this research addressed the importance of wind-induced rise of the sea surface in such biogeographic changes. A new hypothetical chain was suggested: recent trends in the North Atlantic Oscillation index toward its positive phase have led to increased storminess and wind tides on the ocean surface, resulting in increased frequency, duration, and magnitude of submergence and, hence, waterlogging of marsh soils and plants, which has retarded ecological succession. At the mid-scale, spatial patterns of vegetation and environmental factors were examined across tidal creeks. Sites closer to tidal creeks, compared to marsh interiors, were characterized by the dominance of later-successional species, higher bulk density, and lower nutrient contents and electrical conductivity. This finding implies that locations near creeks have experienced a better drainage condition than the inner marshes, which eventually facilitated the establishment of later-successional plants that are intolerant to physical stress. At the micro-scale, this research examined how the extent and mode of facilitation and competition vary for different combinations of plant species along physical gradients. Both positive and negative relationships were spatially manifested to a greater degree on the low marsh than on the mid marsh. This insight extends our current knowledge of scale-dependent interactions beyond pioneer zones to higher zones. On the low marsh, different types of bivariate point pattern (i.e., clustered, random, and regular) were observed for different combinations of species even at similar spatial scales. This finding implies that it is difficult to generalize at which scales competition and facilitation occur. To conclude, this research stresses the need for a holistic approach in future investigations of salt marsh biogeography. For example, based on results of this current research, it would be meaningful to develop a comprehensive simulation model that incorporates salt marsh ecology, geomorphology, and hydrology observed across scales.

To assess the potential influence of coastal development on the quality of estuarine habitat for nekton, we characterized land use and the intensity of land development surrounding small tidal tributaries of Tampa Bay. Based on this characterization, we classified tributaries as undeveloped, industrial, urban or man-made (i.e., mosquito-control ditches). Over one-third (37%) of tributaries were determined to be heavily developed, while fewer than one-third (28%) remain relatively undeveloped. We then examined the nekton community from eleven tributaries in watersheds representing the defined land-use classes. Whereas mean nekton density and species richness were both independent of land use, nekton-community structure differed between non-urban (i.e., undeveloped, industrial, ditches) and urban tributaries. In urban tributaries, the community was skewed towards high densities of poeciliid fishes while typically dominant estuarine taxa were in low abundance or nearly absent. Densities of economically important taxa in urban creeks were also only half that observed in most non-urban creeks, but were similar to those observed in mosquito ditches. Furthermore, six of nine common taxa were found to be in relatively poor condition (6-22% smaller in mass), or were rarely collected, in urban creeks. Reproductive output was reduced for both sailfin mollies (i.e., fecundity) and grass shrimp (i.e., very low densities and few ovigerous females) in urban tributaries. Canonical correspondence analysis differentiated non-urban and urban tributaries based on greater impervious surface, less natural mangrove shoreline, higher frequency of hypoxia and lower, more variable salinities in urban tributaries. These characteristics explained 48% of the variation in nekton data, including the high densities of poeciliid fishes, greater energy reserves in sailfin mollies and low densities of several common nekton and economically important taxa from urban creeks. Our results suggest that urban development in coastal areas has the potential to alter the quality of habitat for nekton in small tidal tributaries as reflected by variation in nekton metrics between urban and non-urban tributaries. To further evaluate the link between coastal development fish-habitat quality, we examined the relationship between landscape development intensity (LDI) and the body condition of juvenile sailfin mollies (Poecilia latipinna), a dominant forage fish in tidal tributaries. Morphometric condition, measured as least-square mean dry weight, did not differ statistically among tributaries (P = 0.85). In contrast, biochemical condition, measured as the concentration of triacylglycerol (TAG), the predominant storage lipid, was significantly different among tributaries (P < 0.0001). LDI explained less of the observed variation in TAG content (R2 = 0.18, P = 0.11) than long-term mean salinity (R2 = 0.81, P < 0.0001), which also tended to be lower in more intensively developed watersheds. We hypothesized that urban land use, characterized by considerably greater impervious surface than undeveloped lands, contributed to altered watershed hydrology, high freshwater runoff and low salinities in urbanized creeks. Together these factors appear to foster conditions conducive to lower energetic cost of osmoregulation in urban creeks, and development of a benthic microalgal community of greater nutritional value than the food resources available in non-urban tributaries. To our knowledge, this is one of the first studies to relate urbanization to the condition of resident fishes. While not directly related to coastal urbanization, the level of predation risk within a habitat is a direct measure of habitat quality that could be reflected by the reproductive strategy of potential prey. To evaluate the use of reproductive metrics of fish-habitat quality, we examined reproduction in P. latipinna from eleven tidal tributaries. Our results revealed a gradient along which females produced many, small offspring at one extreme (mean=42 offspring, 17 mg each) and fewer, larger offspring at the other (24 offspring, 29 mg each). Reproductive allotment ranged from 14.9 - 21.5% maternal biomass. Based on our observation of divergent reproductive strategies, we experimentally tested the null hypothesis of no difference in predation risk among tributaries using a novel quantitative approach to estimate predation. We predicted greater risk in tributaries where mollies produced many, small offspring. Tethering confirmed increasing risk from 16.2 ± 5.3% SE to 54.7 ± 3.6% fish lost h-1 across sites in agreement with observed variation in reproduction. Predation was unexpectedly higher than predicted at one of the four sites suggesting that additional factors (e.g., food) had influenced reproduction there. Our results provide insight into the well-studied concept of predator-mediated variation in prey reproduction by quantitatively demonstrating differential risk for mollies exhibiting divergent reproductive strategies. While the observed range of variation in reproductive traits was consistent with previous studies reporting strong predator effects, higher than expected predation in one case may suggest that the prey response does not follow a continuous trajectory of incremental change with increasing predation risk, but may be better defined as a threshold beyond which a significant shift in reproductive strategy occurs.

Made available in DSpace on 2016-06-02T19:28:58Z (GMT). No. of bitstreams: 1 TeseAS.pdf: 2981431 bytes, checksum: 5aa43d392871f5fb8a0ab8af1836259a (MD5) Previous issue date: 2006-06-02 / Universidade Federal de Sao Carlos / Studies related to the quality of the water in coastal environments as bays, estuaries and tidal creeks are important due to the high productivity and intense influence of anthropic activities in these areas. This study aims the physical, chemical and microbiological characterization of diverse tidal creeks along Paraná coast. We analized seasonal variations in four tidal creeks and differences among rainy and dry periods in two tidal creeks. The cellular density of the pico, nano and microplanktonic fractions in different trophic conditions, differentiating the auto and heterotrofic compartments were performed. The temperature, salinity, pH, alkalinity, CO2, dissolved oxygen, nitrite, nitrate, ammonium, phosphate, silicate, suspended matter, particulate organic and humic matter, total chlorophyll, total coliforms and Escherichia coli were analyzed. The pico- and the nanoplankton were analyzed by direct counting under epifluorescence microscopy, while the microphytoplankton and the protozooplankton were through the Utermöhl method. In relation to the physico-chemical and biological characteristics the Perequê tidal creek exhibited larger saline intrusion, and in the Olho d´Água tidal creek was detected great amount of discharged domestic effluents. Among the pico- and nanoplanktonic fractions prevailed the heterotrophic compartment, in both phases. On the other hand, the abundance of the phytoplankton prevailed under the protozooplankton in the microplanktonic fraction along the whole study. Differences between dry and rainy periods were confirmed. In the rainy period was observed in the two tidal creeks an increase in nitrite, suspended matter, organic particulate matter and picoplankton and a reduction of nitrate, chlorophyll, nanoplankton (auto- and heterotrophic) and of the autotrophic microplankton. Increase of phosphate, ammonium and humic substances were only observed in Barranco tidal creek and of dissolved oxygen and E. coli in Olho d´Água. These results show that in periods of high pluviosity elevated amounts of nutrients are exported by the tidal creeks to the adjacent internal continental shelf. It was not possible to define a pattern for none of the variables in relation to the tide and to the day and night periods. / xi Estudos relacionados com a qualidade da água em ambientes costeiros como baías, estuários e gamboas são importantes por serem regiões de alta produtividade e influenciadas por atividades antrópicas. Neste estudo foram avaliadas variáveis físicoquímicas e biológicas em diversas gamboas ao longo da costa do Estado do Paraná. Foram analisadas variações sazonais em quatro gamboas e diferenças entre períodos secos e de alta pluviosidade em duas das gamboas. A densidade celular das frações pico, nano e microplanctônicas, em diferentes condições tróficas e diferenciando os compartimentos auto e heterotróficos, foi avaliada. Foi realizada a análise de temperatura, salinidade, pH, alcalinidade, dióxido de carbono, oxigênio dissolvido, nitrito, nitrato, amônio, fosfato, silicato, material particulado em suspensão, matéria orgânica particulada, substâncias húmicas, clorofila total, coliformes totais e de Escherichia coli. O pico e o nanoplâncton foram analisados por contagem direta em epifluorescência, enquanto que o microfitoplâncton e o protozooplâncton foram determinados pelo método de Utermöhl. Em relação às características fisico-químicas e biológicas, foi detectada uma maior intrusão salina na Gamboa Perequê e a Gamboa Olho d´Água se diferenciou por causa da grande quantidade de efluentes domésticos que recebe. Entre as frações pico e nanoplanctônicas predominou o compartimento heterotrófico, em ambas as fases. Prevaleceu à abundância do fitoplâncton sob o protozooplâncton na fração microplânctonica ao longo de todo o estudo. No estudo sazonal confirmaram-se as diferenças entre os períodos seco e chuvoso. No período chuvoso foi observado aumento de nitrito, material particulado em suspensão, matéria orgânica particulada e picoplâncton e redução de nitrato, clorofila, nanoplâncton (auto e heterotrófico) e do microplâncton autotrófico nas duas gamboas. Foram observados aumento de fosfato, amônio e substâncias húmicas na Gamboa Barranco e de oxigênio dissolvido e E. coli na Gamboa Olho d´Água. Estes resultados mostram que em períodos de alta pluviosidade são exportadas pelas gamboas quantidades mais elevadas de nutrientes para a plataforma continental interna adjacente. Em relação à maré e aos períodos diurno e noturno, não foi possível definir um padrão para as diferentes variáveis analisadas. Palavas-chave: gamboa, picoplâncton, nanoplâncton, fitoplâncton, protozooplâncton, maré, estado trófico.