Browsing by Subject "salinity"
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Item Algal biofuels : the effect of salinity and pH on growth and lipid content of algae(2009-08) Gutierrez, Cesar Carlos; Marshall, Jill Ann; Sathasivan, Kanagasabapathi; Mehdy, Mona Cynthia, 1955-Supplies of nonrenewable fossil fuels are becoming more limited even as they continue to contribute to pollution and economic concerns. Alternative sources of energy must be developed that help minimize these problems. One potential source of energy is the production of biofuels from algae. Here we evaluate algae found in South Texas brackish water ponds used for aquaculture of fish as a possible source of biofuels. In particular, we examine the effects of salinity and pH on the growth and lipid content of the algae. Samples of algae from the ponds exhibited high levels of growth and lipid production at a salinity of 9 ppt and pH 7. These conditions are similar to the natural conditions of the ponds, indicating that they may be a good source of algal biofuels.Item Impacts of Natural Salt Pollution on Water Supply Capabilities of River/Reservoir Systems(2011-08-08) Lee, Chi HunSalinity is a major determinant of where and how water resources are used worldwide. Natural salt pollution severely constrains the beneficial use of large amounts of water in Texas and neighboring states. High salinity loads in several major river/reservoir systems, including the Brazos River, originate largely from salt seeps and springs in isolated areas of the upper river basins located in the Permian Basin geologic region. Research objectives were (1) to improve salinity simulation capabilities of the Water Rights Analysis Package (WRAP) modeling system, and (2) to develop a better understanding of the occurrence, transport, and impacts of salinity in the Brazos River and Lakes Possum Kingdom, Granbury, and Whitney. Water volume budgets and total dissolved solids load budgets were developed for five river reaches covering 405 miles of the upper Brazos River. Methodologies were developed for creating and applying WRAP salinity input datasets. The WRAP modeling system was expanded and applied to the entire Brazos River Basin to investigate alternative modeling premises and impacts of salinity and salinity control measures on water supply capabilities. Water and salinity budget analyses of the Brazos River system based primarily on measured stream flow, reservoir storage, and total dissolved solids data compiled by the U.S. Geological Survey were performed to explore the characteristics of flow and storage volumes and salinity loads and concentrations in the river/reservoir system. WRAP salinity input datasets were developed based on results from the salinity budget study. One dataset was designed and applied specifically for testing salinity routing methods and calibrating salinity routing parameters. A second complete basin salinity dataset was developed and applied to simulate the Brazos River Basin for alternative management strategies. The results of the simulations demonstrate, for example, that previously proposed salt control impoundments can significantly reduce salinity loads and concentrations in the three reservoirs and at all locations on the Brazos River from the impoundments downstream to the Gulf of Mexico. The WRAP salinity simulation features are designed to provide flexibility in combining water quantity simulation datasets from the Texas Water Availability Modeling System or other sources, which may be very complex, with available salinity data which varies in extent and format between different river basins. The modeling capabilities demonstrated by the Brazos River Basin study can be applied in other river basins as well.Item Mating behaviour, epibiotic growth, and the effect of salinity on grooming activity in the hermaphroditic shrimp Lysmata wurdemanni(Texas A&M University, 2004-09-30) Giri, TuhinMany species of caridean shrimp are protandrous hermaphrodites, maturing initially as males but developing into females as they age and grow. A unique sexual system was recently discovered in the peppermint shrimp, Lysmata wurdemanni. In this species, individuals are initially male, but become simultaneous functional hermaphrodites over time. As in most caridean shrimp, L. wurdemanni can mate as a male during the intermoult period, but can reproduce through female function for only a short period after moulting. Ecdysis does not occur en masse in this species, and thus the operational sex ratio found in populations of L. wurdemanni is extremely male-biased. Sexual selection theory suggests that these conditions will result in increased competition for access to mates. Evolutionary pressures should therefore have selected for mechanisms that permit individuals to quickly identify and locate potential mating partners. L. wurdemanni were exposed to chemical stimuli collected from recently moulted conspecifics of varying reproductive condition. Test animals were able to distinguish among the different conditions, and physically manipulated only the plastic nozzle used to pump solutions collected from shrimp with ovaries filled with vitellogenic oocytes. It was subsequently hypothesized that methyl farnesoate, a hormone associated with ovarian maturation in crustaceans, might be a key component of sex pheromones used by L. wurdemanni. However, a series of methyl farnesoate concentrations did not elicit responses, indicating this species does not use this hormone alone when determining reproductive condition. Reproductive behaviour in L. wurdemanni was observed to differ both before and after copulation, as well as with increasing population density. Intermoult individuals were more likely to approach, follow and remain in the vicinity of a near-moult shrimp before mating could occur, and under high density conditions. The near-moult shrimp approached conspecifics only under low density conditions, and performed rapid escape behaviours only after copulation had occurred. The unusual occurrence of epibiota upon L. wurdemanni was described, and the location, size and age of barnacles quantified. The effect of salinity upon grooming activities was tested. Results indicated that carapace grooming was depressed at low salinities, and could account for the considerable epibiota found in this region.Item Relationship of salinity and depth to the water table on Tamarix spp. (Saltcedar) growth and water use.(Texas A&M University, 2004-09-30) Schmidt, Kurtiss MichaelSaltcedar is an invasive shrub that has moved into western United States riparian areas and is continuing to spread. Saltcedar is a phreatophyte that can utilize a saturated water table for moisture once established and is also highly tolerant of saline soil and water conditions. Literature has indicated that depth to the water table and salinity have a significant effect on growth and water use by saltcedar. Several studies were initiated to help develop a simulation model of saltcedar growth and water use based on the EPIC9200 simulation model. A study was initiated at the USDA-ARS Blackland Research Center Temple, Texas in the summer of 2002 to better understand the effects of water table depth and salinity on (1) saltcedar above and below ground biomass, root distribution, leaf area and (2) water use. Five different salinity levels (ranging from 0 ppm to 7500 ppm) and three different water table depths (0.5m, 1.0m, and 1.75m) were studied. Results indicated that increasing depth to the water table decreased saltcedar water use and growth. For the 0.5m water table depth, saltcedar water use during the 2002 growing season averaged 92.7 ml d-1 while the 1.75m depth averaged 56.6 ml d-1. Both root and shoot growth were depressed by increasing water table depth. Salinity had no effect on saltcedar growth or water use except at the 1250 ppm level, which used 110 ml of H2O d-1. This salinity had the highest water use indicating that this may be near the ecological optimum level of salinity for saltcedar. A predictive equation was developed for saltcedar water use using climatic data for that day, the previous day's climatic data, water table depth and salinity that included: previous day total amount of solar radiation, water table depth, previous day average wind speed, salinity, previous day total precipitation, previous day average vapor pressure, minimum relative humidity, previous day average wind direction, and maximum air temperature. Data from the field study and a potential growth study were integrated into the model. The model was parameterized for the Pecos River near Mentone, Texas. Predicted saltcedar water use was slightly lower than results reported by White et al. 2003.Item Response of Benthic Microalgal Community Composition at East Beach, Galveston Bay, Texas to Changes in Salinity and Nutrients(2010-07-14) Lee, Alyce R.Benthic microalgal community composition on an ephemerally submerged sandflat at East Beach, Galveston Island, Texas was studied to determine the spatial and temporal variability of total biomass and community composition and its responses to experimental manipulations of two environmental factors (salinity and nutrients). Four field studies were conducted between August 2004 and February 2005. The community consisted of two major algal groups, diatoms, and cyanobacteria with two less abundant groups, green algae, and phototrophic bacteria. Spatial variability showed that patch sizes of 12 - 25 m were detected over larger scales with smaller scale (cm) patches of approximately 28 - 201 cm^-2 contained within the larger patches. The second study examined the spatio-temporal variability of BMA over a 21-month period in a 1,000 m^2 area. Sampling location and date explained a significant amount of the variability in the abundances of algal groups, which were positively correlated with the water content of the sediments and negatively correlated with temperature (sediment and water). All of the algal groups showed a seasonal pattern with higher abundances measured in the winter months and lower abundances found during the summer. BMA biomass (100 mg Chl a m^-2 or greater) maxima occurred at temperatures less than 22 degrees C and sediment water content greater than 15% (g water g sediment^-1). BMA response to different salinities and nutrient (N+P) amended sediments was assessed in four bioassays conducted over a 6-month period (Aug. 2004, Oct. 2004, Dec. 2004, and Feb. 2005). In the salinity study, the treatments that were either 100% or partially diluted with deionized water had the lowest BMA biomass over all. Chlorophyll a and fucoxanthin were significantly affected by salinity with higher abundances found in salinities that averaged 15 with a preference for salinities greater than 22. Chlorophyll b was affected by salinity with higher abundances measured in the treatments with lowest salinity (DL and DI); and was affected by the time of year. This would suggest that this algal group prefers an environment with salinity less than 2 but can easily adapt to environments with higher salinities. BMA abundances were not significantly affected by the nutrient amended sediment, but were significantly affected by stations with higher water content, and during the cooler months (Dec. 2004 and Feb. 2005).Item Soil and Plant Responses to Lipid-Extracted Algae(2014-08-25) Lewis, KatieAlthough algae is much more productive per area of cultivation compared to first-generation biofuel feedstocks, algae production may not be economically sustainable without high value coproducts. One of many possible coproducts may be algae residue following lipid extraction that might be used as a soil amendment for agricultural production. The overall objective of this series of experiments was to determine the feasibility and management strategies required to best utilize lipid-extracted algae (LEA) as an organic fertilizer and soil conditioner. Effects of LEA on nutrient availability, soil C storage, aggregate stability, soil acidity and salinity, greenhouse gas (GHG) loss, changes in soil microbial activity and community composition, and forage growth were assessed. Soil organic C (SOC) measured 392-d after amending soil with 1.5 and 3.0% LEA for a microcosm incubation was increased by approximately 0.2 and 0.3% OC, respectively, compared to the control. Approximately 10% of added LEA-C was mineralized and lost as CO2 compared with 15% of added wheat straw-C. Lipid-extracted algae enhanced aggregate formation and soil SOC storage in microaggregates at 0-15 cm depth over a 12-month field incubation with greater mean weight diameter by 12 months and approximately 42 and 66% of total SOC from 1.5 and 3.0% LEA treatments, respectively. With glass house and field studies, nutrient availability was enhanced with LEA amendments; however, LEA applied at a 30% rate decreased seedling emergence of foxtail millet (Setariaitalica) and salt-tolerant ryegrass (Lolium multiflorum), and thus, herbage mass (HM) and nutrient uptake were also decreased. Soil amended with 1.5% a LEA, however, increased HM of peal millet (Pennisetum glaucum), salt-tolerant ryegrass, and a sorghum-sudangrass hydrid [(Sorghum bicolor (L.) Moench ? Sorghum Sudanese (P.)]. Soil LEA-application should be a significant source of organic nutrients for microbial transformation and usage and plant uptake, and thus, may reduce inputs of inorganic fertilizer. The potential for LEA amendments enhancing aggregate formation, and consequently soil C storage, was indicated by mean weight diameter and SOC within macro- and microaggregates increasing over time. Lipid-extracted algae application may be a means of mitigating SOC losses due to agricultural production, and also, maintaining or improving soil structure and quality. However, problems with excess soil salinity, sodicity, and nutrients may occur at high LEA addition rates.Item Soil Salinity Abatement Following Hurricane Ike(2012-10-19) Mueller, RyanIn September 2008 Hurricane Ike hit the Texas Gulf Coast with a force stronger than the category 2 storm at which it was rated. With a 3.8 m (12.5 ft) storm surge, the agricultural industry in the area was devastated. The goal of this research was to determine the length of time required to reduce the salt levels brought by the storm surge to near pre-hurricane levels. To do this, four sets of samples were taken across two years and analyzed for salinity using the saturated paste extract method. The initial salt levels in November 2008 had an electrical conductivity (ECe) of the inundated soils as high as 26.7 dS/m. Fifty-four percent of the soils sampled in the 0-15 cm horizons and 9% in the 15-30 cm horizons of the edge area had an ECe >= 4 dS/m. In the surge area 79% of the soils sampled in the 0-15 cm horizons and 30% in the 15-30 cm horizons had an ECe >= 4 dS/m. In April 2009, 38% of the soils sampled in the 0-15 cm horizons and 13% in the 15-30 cm horizons of the edge area had an ECe >= 4 dS/m. In the surge area 71% of the soils sampled in the 0-15 cm horizons and 39% in the 15-30 cm horizons had an ECe >= 4 dS/m. By December 2009, none of the soils sampled in the edge area had an ECe >= 4 dS/m. In the surge area 21% of the soils sampled in the 0-15 cm horizons and 33% in the 15-30 cm horizons had an ECe >= 4 dS/m. By October 2010, all soils sampled had leached sufficient salts to be classified as non-saline to very slightly saline soils. Utilizing the November 2008 data set, 28 random samples were selected for exchangeable Na percent (ESP) in order to develop the ESP-SAR (Na adsorption ratio) predictive equation, ESP= 1.19(SAR)^0.82. The SAR-ESP relationship is statistically significant (95% confidence level), with a correlation coefficient of 0.964 (df=26).Item The conjunctive use of saline irrigation water on deficit-irrigated cotton(Texas A&M University, 2005-02-17) Henggeler, Joseph CharlesCotton (Gossypium hirsutum) is able to survive relatively large levels of both water and salinity stress. The objective of this study was to evaluate cotton lint production and soil salinization under a conjunctive use strategy using saline water at deficit levels. A three-year experiment applying irrigation at deficit amounts on cotton was conducted in Pecos, Texas on a Hoban silty clay loam. Treatments were four irrigation water qualities, conjunctively applied. Initial irrigation was with water having an electrical conductivity (ECIW) of 4.5 dSm-1, representing about one-third of the total amount of water applied. Thereafter, treatments were applied using water of varying ECIW, e.g., 1.5, 4.5, 9.0, and 15.0 dSm-1 for all subsequent irrigations. Total irrigation plus rain was approximately two-thirds of full water requirements. Lint yields for the three years averaged 1050, 1008, 809, and 794 kg ha-1, respectively, and treatment levels did not decline over time. However, the soil salinity levels of the three more saline treatments increased throughout the test period. Yields declined due to salinity prior to reaching the published threshold value (Maas and Hoffman, 1977) of ECe = 7.7 dSm-1. Under the deficit conditions of two-thirds of the full water requirements, the threshold level was lowered to 4.5 dSm-1. The overall yield loss that resulted from limiting water by one-third was three times > than the yield loss from even the highest salinity treatment. Relative lint yield was reduced 3% for each dSm-1 of ECIW. The pre-dawn and solar-noon leaf water potential values decreased at a rate of 0.026 and 0.042 MPa per dS m-1 of the ECIW, respectively. Study conclusions were that yields within treatments remained stable for three years. However, the increase of salinity in the soil profile indicated that long-term viability of using highly saline water conjunctively is impractical under deficit irrigation conditions. In the short-term, however, saline water of up to 15.0 dS m-1 can be used at mid-season under deficit conditions on Hoban silty clay loam soil to secure 75% of the yield level obtained by using high quality water if a pre-plant irrigation of medium quality water is first applied.Item Using Trends and Geochemical Analysis to Assess Salinity Sources along the Pecos River, Texas(2012-07-16) Hoff, AaronIncreasing salinity has been a growing concern for users of waters from the Pecos River and the reservoirs it feeds in the Texas portion of the River's watershed. Irrigation water diverted from the river in the northern reach of this watershed is often only suitable for a limited number of crops, reducing harvesting options for local farmers. In the south, the Pecos feeds into the International Amistad Reservoir along the border with Mexico. During the 1990s, total dissolved solids concentrations in the reservoir rose as much as 10 mg/L per year and often approached the drinking water standard for potable water (1000 mg/L). Since this time, control efforts have focused on reducing the river's salinity, requiring the identification of salt sources. Hydrologic trend analysis and geochemical identification methods were used to determine these sources for the reach of the river between Red Bluff Reservoir and Brotherton Ranch. Between Red Bluff Reservoir and Coyanosa, flow diversions remove much of the flow that carries the salts, resulting in decreased salt loads, but also making the river more sensitive to evapotranspirative concentration. This sensitivity is evident in the river between Coyanosa and Girvin, where salinity begins to increase to the highest levels within the study area. However, salt loads increase here as well, indicating external salt sources as a contributor. The most substantial increase in bromide ions and the Br-/Cl- ratio appears between Grandfalls and Imperial, although no conclusion could be drawn regarding the identity of the source. The ratio continues to increase up to Girvin, where it appears that evapotranspirative concentration again has a significant effect. Here, several points drifted to the right of the groundwater mixing zones, plotting at values that were uncharacteristic of these sources.