Browsing by Subject "Estuaries"
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Item Mission-Aransas NERR Ecosystem Based Management Tool Demonstration Project : An Integrated Approach to Land Use Planning in Aransas County(The University of Texas Marine Science Institute, 2011-11-18) Madden, Kiersten; Morehead, SallyItem Responses of continuous-series estuarine microecosystems to point-source input variations(1970) Cooper, David C. (David Clayton), 1943-; Copeland, B. J., 1936-A group of six continuous-series microecosystems were constructed to simulate hydrological factors of estuarine regions. Exchange and retention characteristics were adjusted to closely model the hydrological conditions of Trinity Bay, Texas. The responses of the microecosystems to quantitative and qualitative changes in freshwater input were investigated. Due to fundamental similarities of all living systems, these responses might be especially representative of those which would occur in Trinity Bay if subjected to similar conditions; actual testing of this conjecture was logistically and operationally infeasible. Magnitudes of primary production and community respiration in the freshwater portions of the microecosystems were dependent on both quantity and quality of freshwater input. Magnitudes of primary production and community respiration in the saltwater portions of the microecosystems were virtually independent of the quantity and quality of freshwater input. The metabolism of the freshwater portions of the microecosystems was heterotrophic under conditions of 60 day freshwater retention time and autotrophic under conditions of infinite freshwater retention time. Addition of an industrial effluent to the freshwater inputs resulted in extensive shifts towards metabolic heterotrophy by the more freshwater portions of the microecosystems. The metabolism of the saltwater cell positions was heterotrophic under all conditions of freshwater input. The communities of the freshwater portions of the microecosystems adapted to a dependency on allochthanous materials input for production and respiratory maintenance. The retardation of freshwater input resulted in larger portions of the nutrient pool within the systems being tied up in living components. The addition of industrial effluent increased the maintenance requirements of the communities. The retardation of freshwater input acted as an environmental stress on the freshwater portions of the microecosystems. Magnitudes of production and respiration were significantly lower, and zooplankton standing crops and species diversity decreased significantly. The addition of industrial effluent produced the same effects. There was a synergistic effect of reduced freshwater input and effluent loading on the freshwater portions of the microecosystems when the stresses were applied simultaneously. The effect of one of the stresses on the receiving systems rendered the communities more succeptible to the imposition of the secondary stress. The organismal composition of the microecosystems was qualitatively similar but quantitatively dissimilar to the organismal composition of Trinity Bay. Periphytonic flora gradually attained the dominant producer status, and were the successional aftermath of planktonic floral dominance. Additional studies indicated that: low level grazing by herbivores enhanced the primary productivity of the periphytonic flora; CO[2] enrichment enhanced primary production only in the freshwater portions of the microecosystems; and rates of production, respiration, and zooplankton standing crop magnitudes were largely independent of long term acclimation temperaturesItem Watershed export events and ecosystem responses in the Mission-Aransas National Estuarine Research Reserve(2009-08) Mooney, Rae Frances, 1982-; McClelland, James W.; Dunton, Kenneth H.; Maidment, David R.River export has a strong influence on the productivity of coastal waters. During storm events, rivers deliver disproportionate amounts of nutrients and organic matter to estuaries. Anthropogenic changes to the land use/cover (LULC) and water use also have a strong influence on the export of nutrients and organic matter to estuaries. This study specifically addressed the following questions: 1) How does river water chemistry vary across LULC patterns in the Mission and Aransas river watersheds? 2) How do fluxes of water, nutrients, and organic matter in the rivers vary between base flow and storm flow? 3) How do variations in nutrient/organic matter concentrations and stable isotope ratios of particulate organic matter (POM) in Copano Bay relate to river inputs? Water was collected from the Mission and Aransas rivers and Copano Bay from July, 2007 through November, 2008 and analyzed for concentrations of nitrate, ammonium, soluble reactive phosphorus (SRP), dissolved organic nitrogen, dissolved organic carbon, particulate organic nitrogen, particulate organic carbon (POC), and the stable C and N isotope ratios of the POM. The first half of the study period captured relatively wet conditions and the second half was relatively dry compared to long term climatology. Riverine export was calculated using the USGS LOADEST model. The percentage of annual constituent export during storms in 2007 was much greater than in 2008. Concentration-discharge relationships for inorganic nutrients varied between rivers, but concentrations were much higher in the Aransas River due to waste water contributions. Organic matter concentrations increased with flow in both rivers, but POM concentrations in the Aransas River were two fold higher due to large percentages of cultivated crop land. Values of [delta]¹³C-POC show a shift from autochthonous to allochthonous organic matter during storm events. Following storm events in Copano Bay, increases and quick draw down of nitrate and ammonium concentrations coupled with increases and slow draw down of SRP illustrate nitrogen limitation. Organic matter concentrations remained elevated for ~9 months following storm events. The [delta]¹³C-POC data show that increased concentrations were specifically related to increased autochthonous production. Linkages between LULC and nutrient loading to coastal waters are widely recognized, but patterns of nutrient delivery (i.e. timing, duration, and magnitude of watershed export) are often not considered. This study demonstrates the importance of sampling during storm events and defining system-specific discharge-concentration relationships for accurate watershed export estimation. This study also shows that storm inputs can support increased production for extended periods after events. Consideration of nutrient delivery patterns in addition to more traditional studies of LULC effects would support more effective management of coastal ecosystems in the future.