Browsing by Subject "Eutrophication"
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Item Determination of algae growth potential in natural environment(Texas Tech University, 1974-05) Maqsood, Syed AzharNot availableItem Effects of Nutrient Additions on Three Coastal Salt Marsh Plants Found in Sunset Cove, Texas(2012-02-14) Rulon, LeslieEutrophication, particularly due to nitrogen (N) and phosphorus (P) input, has been massively altered by anthropogenic activities. Thus it is important to understand the impact on salt marsh plants; however studies on salt marsh plants within Galveston Bay, Texas are limited. In this study, the effects of repeated nutrient additions in monospecific plots of Spartina alterniflora, Batis maritima? and Salicornia virginica as well as mixed plots of B. maritima and S. virginica were studied over 15 months. Results showed that nutrient loading led to an increase in height, biomass, growth rate and percent nitrogen (N) within all three species studied, but were species specific more than dose dependent. Nitrogen content in leaves had a positive correlation with P content in leaves but a negative correlation with carbon (C) content. Nutrient loading lead to a significant increase in total chlorophyll in the fertilized plots of S. alterniflora and S. virginica one month into the study. Nutrient addition to two succulent species, B. maritima and S. virginica in mixed plots did not reveal a distinct superior competitor within the 15 month study in terms of growth and nutrient use efficiencies; however using the maximum growth rates of the monospecific plots, the Monod model was used to determine which species would dominate at high nutrient loads. Based on height data S. alterniflora would dominate, while B. maritima would dominate according to the Monod model based on biomass.Item Extractable soil phosphorus, correlation with P forms in soil runoff, and relationships with the Texas p index as a nutrient management tool for cafos(Texas A&M University, 2006-08-16) Jacoby, Freddy J.Phosphorus (P) inputs into water reservoirs are the primary cause for accelerated eutrophication affecting water quality. Attempts are underway to regulate inputs originating from concentrated animal feeding operations (CAFOs). The purpose of this research was to relate runoff dissolved (DP) and total P (TP) losses to site-specific characteristics from plots in CAFOs and compare them to their corresponding risk assessment using the Texas Phosphorus Index (PI). Initial studies showed that soil test P (STP) methods used in Texas by inductively coupled plasma were highly reproducible regardless of manure source or application rate. However, NH4OAc-EDTA extraction efficiency was increased with respect to other methods as soil conditions became less acidic, probably due to dissolution of the greater portion of Ca-bound P resulting in STP values that could be three times greater than those of Mehlich III for the same soil. Surface application of dairy manure to high pH soils were positively correlated to STP at various soil-sampling depths down to 15 cm. First order linear relationships between STP values and DP concentrations in runoff were statistically significant for extraction methods and sampling depths but were different among different soils under neutral to calcareous conditions. Attempts to reproduce this relationship on fields that received periodic applications of manure or effluent with various incubation periods failed, although there was a single highly significant relationship between STP and runoff DP for different soils when soil conditions were acid ( pH<6.5) with various sampling depths. Analyses of NH4OAc-EDTA extractable soil elements showed Mg was significantly correlated to DP concentration across various management and soils, indicating that Mg-bound P is a major component controlling P release into runoff. Use of the Texas PI reflected vegetation type closely, with grass-covered sites averaging the lowest risk rating, and having the lowest DP and TP losses, while conversely tilled sites had the highest. However, overall relationship was poor when estimates for erosion rates were used due to experimental design limitations. Use of measured erosion rates for plots and inclusion of extractable Mg improved correlations between PI rating to DP and TP losses, with r2 ranging from 0.60 to 0.87.Item Quantifying the role of agriculture and urbanization in the nitrogen cycle across Texas(2012-05) Meyer, Lisa Helper; Yang, Zong-liang; Dickinson, Robert E.; Breecker, Daniel O.Over-enrichment of nutrients in coastal waters has been a growing problem as population growth has enhanced agricultural and industrial processes. Enhanced nitrogen (N) fluxes from land to coast continue to be the result of over fertilization and pollution deposition. This over-enrichment of nutrients has led to eutrophication and hypoxic conditions in coastal environments. This study was conducted along the Gulf of Mexico, through the state of Texas, in order to quantify all agricultural and industrial sources of N in a region which contains a large precipitation gradient, three major metropolitan areas, and one of the top livestock industries in the United States. Nitrogen inputs from fertilizer, livestock, crop fixation, and oxidized deposition from both dry and wet atmospheric processes were quantified and compiled into a Texas Anthropogenic N Budget (TX-ANB). In addition, comparisons and regional enhancements were made to the Net Anthropogenic Nitrogen Input dataset (NANI toolbox), which is a national dataset developed at Cornell University by Hong et al. [2011]. These enhancements ultimately will help understand the full pathways of anthropogenic influences on coastal systems in a regional setting. All three datasets (NANI, NANI Regional, and TX-ANB) indicate agriculture to be the primary contributor to the N cycle in Texas, with TX-ANB showing 38% of inputs from fertilizer, 37% of inputs from livestock, and 2% of inputs from legumes. N input due to atmospheric deposition of oxidized N clearly highlights urban areas, indicating a strong influence of urbanization on the N cycle due to anthropogenic impacts; 23% of N input in Texas is the result of deposition of oxidized N. Quantification of inputs spatially indicates a strong enhancement of N from human influence in the coastal plain where nutrient export is heightened by major storm events. This enhancement of N along a coastal drainage area will likely have a negative impact on downstream environments.Item Wastewater Discharge, Nutrient Loading, and Dissolved Oxygen Dynamics in a Shallow Texas Bay(2014-05-07) Schroer, Lee AllenIn Oso Bay, a wastewater treatment plant acts as a source of eutrophication and may have measureable impact on the health of the bay. The objectives of this study were to create a model for modeling dissolved oxygen concentrations over time and to determine if eutrophication caused by the wastewater treatment plant is harmful to the bay. Continuous monitoring of environmental variables was carried out at 6 stations in Oso Bay over a 9-month period beginning in February and ending in December of 2013. Variables measured were water temperature (oC), pH, salinity (ppt), conductivity (mS), depth (meters), turbidity (nephilometric turbidity units), dissolved oxygen in both % saturation and concentration (mg/L), and chlorophyll-? concentration (?g/L). Grab samples of chlorophyll concentration (?g/L), total suspended solids (mg/L), and nutrient concentrations (?M) were also taken throughout the sampling period. Nutrients of interest were phosphate (PO_(4)), silicates (SiO_(4)), ammonium (NH_(4)), and nitrate+/-nitrite (NO_(x)). Hypoxia was observed at each of the stations in the bay and fluctuated on a diel cycle. Temperature, salinity, and temporal variability were significant factors in explaining the variance in dissolved oxygen concentrations (P < .0001) and were used to model dissolved oxygen variance (R^(2) = .7810). It is likely that the respiratory patterns of phytoplankton and bacteria also influence dissolved oxygen concentrations in Oso Bay, and that this is an indirect result of the discharge from the wastewater treatment plant.Item 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.