Location: Water Quality and Ecology Research2014 Annual Report
1a. Objectives (from AD-416):
Objective 1. Develop and evaluate farm and land management practices that reduce erosion, conserve soil, improve water quality, and protect ecological resources. Sub-objective 1a. Quantify the effects of conservation practices on runoff water quality and soil resources in Beasley Lake Conservation Effects Assessment Project (CEAP) watershed. Sub-objective 1b. Assess the influence of conservation practices on ecology and agricultural contaminant fate and transport in alluvial plain landscapes. Objective 2. Characterize and/or quantify the structure, function, and key processes of ecosystems in agricultural settings. Sub-objective 2a. Evaluate how nutrients, pesticides, and sediments interact with watershed hydrology to influence mechanisms regulating water quality and aquatic ecosystem structure and function in agricultural watersheds. Sub-objective 2b. Examine effects of water flow, climate-change-induced drought, and agricultural nutrient contaminants on stream microbial productivity and nutrient processing. Sub-objective 2c. Examine associations between fish species composition, hydrologic connectivity, and hypoxia in agricultural watersheds. Objective 3. Integrated assessment of the effects of agriculture on ecosystem services for watershed-scale endpoints. Sub-objective 3a. Develop integrated remote sensing tools to better evaluate wetlands and riparian buffers. Sub-objective 3b. Develop agricultural conservation strategies to adapt to climate change. Sub-objective 3c. Develop integrated modeling tools to assess the effectiveness of conservation practices that enhance ecosystem services at multiple scales. Objective 4. As part of the Long-Term Agro-ecosystem Research (LTAR) network, and in concert with similar long-term, land-based research infrastructure in Lower Mississippi River Basin (LMRB), use the Beasley Lake Experimental Watershed to improve the observational capabilities and data accessibility of the LTAR network, to support research to sustain or enhance agricultural production and environmental quality in humid environments characteristic of the LMRB, as per the LTAR site responsibilities and other information outlined in the 2012 USDA Long- LTAR Network Request for Information (RFI) to which the location successfully responded, and the LTAR Shared Research Strategy, a living document that serves as a roadmap for LTAR implementation. Participation in the LTAR network includes research and data management in support of the ARS GRACEnet and/or Livestock GRACEnet projects.
1b. Approach (from AD-416):
Long-term viability of U.S. agriculture depends upon implementation of management strategies that address goals of environmental sustainability and economic viability. Despite significant financial investment in conservation practices and water quality protection over recent decades, water quality issues remain unsolved in many agricultural landscapes. Off-site and downstream impacts of agricultural water pollution continue to raise concerns, most notably marine dead zones linked to excess nitrogen (N) and phosphorus (P). Biodiversity continues to decline due to water quality and habitat degradation. Future influences on environmental quality include synergistic effects of climate change, biofuel production, increased human population and exotic species. To address issues of water quality and watershed ecosystem function, investigations will pursue complementary approaches that consider the entire landscape, from upland fields to receiving water bodies. First, farm and land management technologies that reduce erosion, pesticide, and nutrient losses, conserve and improve soil, and protect ecological resources will be assessed. Second, studies will be conducted to improve understanding of structure, function, and key processes of aquatic systems, guiding better management of these systems and providing a scientific basis for regulatory agencies to establish water quality criteria. Third, investigations will develop and assess technology for improving water quality and ecosystem function in agriculturally impacted aquatic systems. Fourth, investigations will assemble and use long-term databases to develop and further enhance computer models for quantifying effects of conservation measures on agricultural watershed ecosystem services. This plan calls for experiments to be conducted across a range of spatial scales from the laboratory bench to the watershed.
3. Progress Report:
Long-term (1996-present) assessments in Conservation Effects Assessment Program (CEAP) Beasley Lake Watershed continue to demonstrate that a combination of management practices such as vegetative buffers, Conservation Reserve Program, and sediment basins contribute to: • Clearer lake water: Lower turbidity, higher secchi visibility, reduced total solids 65%, with improvements observed most strongly during the spring season. • Lower concentrations of total phosphorus and nitrate in lake water: Decreased over 50% during the study period. • Healthier lake conditions: Long-term nutrient, algae, and water clarity trends indicate Beasley Lake has shifted from a hyper-eutrophic to a more eutrophic condition. A project assessing ecosystem health of three Mississippi-Delta Bayou Watersheds since 2010 is continued and has demonstrated: • Shallow, low gradient, low-flow streams (bayous) are susceptible to land-use changes (crops and riparian acreage) causing seasonal excess sediment and nutrient loads and chronic low dissolved oxygen (hypoxia). • Bayou ecology is driven by seasonal combinations of light limitation (sediment), hyper-eutrophication (excess nutrients), and hydrology (water depth and flow). • Bayou algae have adapted to light limited, high nutrient, shallow conditions while fish populations and diversity are poor (low) under these conditions. • Nutrient-rich (hyper-eutrophic) lakes and bayous are used by farmers for irrigation, so hydrology (depth and flow) and water quality varies with growing season. A long-term study assessing runoff as influenced by field and edge-of-field management practices in corn showed reduction in off-site loss of sediment and nutrients associated with sediment, but loss of soluble nutrients and organic carbon were not significantly reduced. A new phase of the study will begin in fall 2014 with the integration of conservation and irrigation scheduling technologies in soybean to address water quantity and quality issues related to aquifer depletion. Studies utilize artificial stream mesocosms at the University of Mississippi Field Station to simulate agricultural streams. These experiments are showing: • Organic carbon inputs exacerbate dissolved oxygen minimums under no-flow and drought conditions while increasing the processing time of dissolved organic carbon. • Nitrogen and phosphorus inputs (eutrophication) followed by organic carbon inputs caused 12-18 hour hypoxic to anoxic conditions with and without flow. • Fish exposed to higher sediment concentrations gained more weight than fish in clear water. The hypothesis is that either sediments stimulate algae to supplement fish diet or that higher sediment improves swimming efficiency in certain fishes. Several research projects assess edge-of-field conservation practices such as ditch, buffer, and wetland management. These studies demonstrated that vegetation, in combination with weirs, reduced drainage flow, thus reducing sediment and chemical loss from ditch systems. Also, a water-level controlled natural wetland was effective in trapping sediment and chemicals, thus buffering negative ecological effects of chemicals. USDA Annualized AGricultural Non-Point Source (AnnAGNPS) pollutant loading model development and calibration continues. The modeling research demonstrated that utilizing buffers 5-40 m wide can filter up to 72-100% of sediment entering a buffer, although buffer efficacy is significantly reduced (to 3%) when concentrated flow (e.g., gullies) passes through buffers. Work is progressing to improve the riparian buffer component of the model with respect to water quality. A field experiment is conducted to test the hypothesis that long-term applications of glyphosate to both resistant and non-resistant corn under reduced and conventional tillage management impact soil characteristics and nutrient uptake. Preliminary results demonstrated no discernable differences in nutrient uptake or in soil and root rhizosphere microbial community structure and activity (based on genomics and exoenzymes) between the transgenic and non-transgenic corn cultivars. A new study was implemented to assess the efficacy of a tailwater recovery system to conserve water and improve water quality. Another new study was begun in collaboration with other ARS locations to assess the effects of flue-gas desulfurization gypsum and vegetative buffers on phosphorus runoff loss from corn. Involvement and leadership in the ARS Long-Term AgroEcosystem Research (LTAR) project was begun. Plans to develop and coordinate LTAR research in the Lower Mississippi River Basin are ongoing.
1. Multiple combined best management practices (BMPs) reduce sediments and increase lake water clarity. As ARS scientists in Oxford, MS, continue to try to improve water quality through the use of agricultural BMPs, there is a need to better understand how effective these BMPs are within an entire watershed. To address this, water quality measurements of water clarity, total suspended sediment and total dissolved solids were collected in Beasley Lake, a Conservation Evaluation Assessment Program watershed in the Mississippi Delta from 1996 to 2009. Results showed how a variety of BMPs in the watershed changed lake water quality. BMPs put in place from 1997-2006 included within-field, edge-of-field, and Conservation Reserve Program (CRP) practices. Over the 14 years that lake water quality was studied, the lake had clearer water, less suspended sediments, and lower dissolved solids coinciding with the amount of BMPs put in place and these changes were seen most strongly during spring. The study showed that BMPs put in place improved lake water quality and will help make a healthy, sustainable lake. These results are of interest to regulatory and other agencies and farming stakeholders by providing additional information to improve and sustain lake and flood plain water quality and overall environmental quality using conservation practices.
2. Conservation practices improve water quality of Oxbow Lake and show potential for improving fisheries. Lakes in the Mississippi Delta are often contaminated with sediment and fertilizers from agricultural runoff, and these contaminants may ultimately be harmful to fish. ARS scientists in Oxford, MS, applied a series of conservation management practices in Beasley lake watershed with the goal of reducing sediment and nutrients entering the lake via agricultural runoff. Application of these practices reduced sediment and nutrients and improved water clarity and plankton populations. Fish populations increased early in the study as water quality improved. However, catch and release fishing practices resulted in an overabundance of larger and older fish, thus reducing overall catch. This study shows that improved water quality is possible through the use of conservation practices, but management of the sport fishery is crucial for maintaining a balanced lake ecosystem.
3. Ecological studies point to hidden contaminants. Success of any aquatic restoration project is based on the assumptions that 1. physical features can be manipulated in such a way as to improve habitat, water quality or both, and 2. that there is nothing inherent about the site that would prevent the project from succeeding. ARS scientists in Oxford, MS, conducted toxicological tests of sediment and fish on several oxbow lakes and surrounding rivers in and near the Mississippi Delta and found that some of the potential restoration sites contained contaminants that might inhibit successful recovery of the aquatic resources. The ecological data from this site indicated some type of impairment of its designated use of supporting fish and wildlife. While contaminants were found, further investigation is necessary to identify a specific stressor. This work shows the importance of conducting ecological analysis before selecting sites for restoration projects.
4. Constructed wetlands trap nutrients and pesticides. Because agricultural runoff can have significant impacts on rivers, lakes, and streams, a study was conducted to better understand the efficacy of constructed wetlands in trapping nutrients and pesticides in runoff from agricultural fields. ARS scientists in Oxford, MS, measured the ability of a constructed wetland to trap different combinations of nutrients and pesticides to determine whether the system could be used as a management tool for processing contaminants. The study showed the wetland was better in trapping nutrients without pesticides, potentially preventing them from moving downstream to a water body. These results are of interest to regulatory and other agencies and farming stakeholders by providing additional information to improve and sustain lake and flood plain water quality and overall environmental quality using conservation practices.
5. Constructed wetlands help to protect aquatic ecology. While agricultural best management practices can improve water quality, there is a need to demonstrate such improvements protect and enhance aquatic ecology. ARS scientists in Oxford, MS, examined how well a constructed wetland could decrease the effects of a variety of mixtures of agricultural contaminants on algae and an aquatic invertebrate animal, Hyalella azteca. The study showed algae increased when only nutrients like nitrogen and phosphorus were present, while decreasing at some distances from application points when pesticides or mixtures of nutrients and pesticides were present. Animal survival in wetland water decreased up to 20 meters from application points within the first two days after adding pesticides or mixtures of nutrients and pesticides. Animal survival in wetland soil was not affected by agricultural contamination but animal growth was temporarily inhibited after contamination with nutrient and pesticide mixtures. The study showed that constructed wetlands are effective at buffering the effects of agricultural contaminant mixtures of nutrients and pesticides. These results are of interest to regulatory and other agencies and the pesticide industry by providing information to improve and sustain water quality and overall environmental quality using constructed wetlands as an effective conservation practice.
6. Riparian corridors are important habitats for small mammals within agricultural watersheds. Expanding agriculture and stream channelization has reduced quality of riparian habitats within agricultural watersheds. In northwestern Mississippi, steep and enlarged streambanks caused by channel incision frequently result in gully erosion that migrates through the riparian zone and into agricultural fields. Installation of erosion control structures (drop pipes) at the riparian zone - agricultural field interface stops gully erosion and establishes animal habitat. ARS scientists in Oxford, MS, assessed small mammals (i.e., mice, shrews, voles) within riparian habitats created by drop pipe installation. Small mammal diversity and abundance was greatest when drop pipe installation resulted in riparian habitats greater than 1,000 square meters, greater than 21 percent coverage of woody vegetation, greater than 1.8 meters tall, and water pool volumes greater than 41 cubic meters. These results suggest that modifying the installation design for drop pipes to improve its effectiveness in creating riparian habitats will increase the ecological benefits resulting from this conservation practice.
7. Mixtures of plants offer year-round nutrient mitigation in ditches. Excessive nutrients entering rivers and lakes cause significant damage to plants and animals in aquatic receiving systems. Conservation practices are needed to help reduce nutrient runoff into water bodies. ARS scientists in Oxford, MS, evaluated three aquatic plant species for their ability to remove nutrients from runoff water during both summer and winter months. Results demonstrated one particular plant was able to remove more nitrate in summer than winter, while a different plant removed more phosphorus in winter than summer. This suggests a mixture of plants within the drainage ditches is most beneficial for year-round maximum nutrient processing. Results from this study will benefit farmers, landowners, conservationists, and regulators.
8. Low-grade weirs improve nutrient reduction. Agricultural drainage ditches are now being used as best management practices to help clean up farm runoff containing pesticides and nutrients. In order for ditches to process these chemicals, water needs to be retained in the systems for increased periods of time. ARS scientists in Oxford, MS, assessed the ability of low-grade weirs and slotted risers to decrease nutrient concentrations leaving drainage ditches. The final outcome determined that a significant declines in nutrient loads (67-98%) could be achieved in controlled-drainage systems when compared to control ditches with no controlled drainage. The important balance in ditches is to allow for drainage, while still giving the system maximum opportunity for ecological processes to break down or remove potentially harmful runoff chemicals. When weirs are placed in drainage ditches, water is held at levels that are ecologically beneficial, while still allowing sufficient drainage to occur.
9. Sediment and plant bacteria help degrade pesticides. Bacteria have been shown to play a valuable role in degrading pesticides in the environment. However, little work has been done with bacteria present in sediment and plants commonly found in vegetated agricultural drainage ditches. ARS scientists in Oxford, MS, in collaboration with scientists from the University of Mississippi, mimicked rhizosphere properties of the soft rush, a common aquatic plant, by building a single-stage gradostat reactor. Bacterial isolates, collected from plant rhizospheres in the field, were amended with the pyrethroid insecticide lambda-cyhalothrin. Specific isolates were capable of degrading the pesticide, emphasizing the importance of microbial activity in pesticide mitigation practices. This research will help scientists understand what specific aquatic plants more positively influence pesticide degradation in ditches and wetlands.
10. Hydrology and nitrogen levels affect plants used for phytoremediation. The use of plants to clean up contaminants (phytoremediation) is growing in popularity among farmers and conservationists. Using vegetated drainage ditches is an economical and environmentally sound way to help alleviate contaminants associated with agricultural runoff. However, little research has examined the plant physiological responses, including nutrient uptake, when exposed to variable flooding regimes. ARS scientists in Oxford, MS, in collaboration with researchers from the University of Memphis, exposed rice cutgrass to various flooding and nitrogen concentrations and then quantified the allocation of nutrients and biomass to plant components. Results from this study indicated that rice cutgrass, a common drainage ditch species, can affect nutrient and other elemental concentrations in runoff water through trapping and allocation of materials to plant leaves, stems, and roots. This information will be of benefit to farmers, conservationists and landowners committed to improving ecosystem health.
11. Common ditch plants capable of cleaning pesticides from water. Agricultural runoff containing pesticides can damage fish, invertebrates, and other aquatic organisms following storm or irrigation runoff events. One proposed management practice is the use of vegetated agricultural drainage ditches to intercept agricultural runoff and filter out the pesticides. ARS scientists in Oxford, MS, evaluated three common types of plants found in ditches to see how well they could reduce the amount of pesticides travelling in storm water. The plant rice cutgrass was the most effective at decreasing concentrations and loads of the two insecticides and one herbicide tested. Cattails and bur-reeds were slightly less effective, but still valuable in reducing pesticides in water. These results are important for conservation planners and farmers interested in reducing the amount of pesticides leaving agricultural fields following runoff.
12. Ditches may be either sources or sinks for phosphorus runoff. Drainage ditches are important agricultural landscape features that transport excess water from crops into receiving aquatic systems. ARS scientists in Oxford, MS, conducted a study of agricultural ditches in four states to determine the presence of phosphorus in both water and sediment. Drainage ditches may serve as sinks for phosphorus-laden agricultural runoff, but they may also serve as sources, depending on the chemical makeup of the ditch sediment. Results indicated that ditch sediments sampled in the Lower Mississippi Alluvial Plain had the capacity to adsorb phosphorus (serve as a sink). However, sediment binding energy was not strong enough to actually attract phosphorus to the sediment. This research will assist in phosphorus management within aquatic systems such as drainage ditches within the agricultural landscape, as well as enhance phosphorus mitigation strategies at the source, prior to runoff.
13. Soil phosphorus saturation due to heavy fertilization accelerates pollution. Farmers can use fertilizers containing phosphorus to boost yields, but elevated phosphorus levels in streams and lakes are detrimental to water quality. Links between the amount of fertilizer applied to a watershed and the amount of phosphorus subsequently lost from the land ("loads") are poorly understood. ARS scientists from Oxford, MS, working with colleagues from the US EPA and the USDA-NRCS, used Annualized AGricultural Non-Point Source (AnnAGNPS) model computer simulations of an Ohio watershed to quantify the extent to which long-term high fertilization rates accentuate phosphorus loads leaving the watershed. This dramatic change in load indicates that a "critical point in soil phosphorus levels may exist beyond which phosphorus load increases dramatically. This finding is directly applicable by agencies and land managers implementing plans that include nutrient management practices and guidelines for agricultural watersheds.
14. Hydrologic transport of Salmonella may be greater than that of Escherichia coli (E. coli). Irrigation is often used to help incorporate soil-applied herbicide into the soil. When manure is also broadcast as a fertilizer in these systems, the irrigation to incorporate herbicide may facilitate manure loss in surface runoff. An ARS scientist in Oxford, MS, in collaboration with other ARS scientists, designed a rainfall simulation experiment to determine the effect of irrigation on quantities of manure bacteria in storm water runoff from agricultural fields managed as either conventional tillage or no-tillage. Results of this experiment indicated that total runoff from the conventional tillage system was 3-times greater than that from the no-tillage system. However, quantities of E. coli and Salmonella in runoff from the two tillage practices were not different. Recovery of Salmonella in runoff was more than ten thousand times greater than recovery of E. coli. This disparity in recovery between these two fecal bacteria provides evidence that E. coli, as a standard indicator of pathogen contamination, may not be effective at indicating risk to public health. This is important information for state and federal environmental protection agencies and managers of watersheds impacted by agriculture.
15. Reservoirs impact downstream fish communities due to changes in hydrology. Understanding relationships between changes in stream flow and ecological measures is critical to mitigating impacts of altered hydrology in rivers. An ARS scientist in Oxford, MS, in collaboration with scientists from the USGS Fish and Wildlife Cooperative Research Unit in Ithaca, NY, assessed impacts of reservoirs on riverine fish communities using long-term datasets spanning pre- and post-dam periods from two different rivers in Oklahoma. Hydrology in the stream with more upstream storage behind dams was substantially altered and exhibited larger changes in fish communities. However, species associated with lake environments increased within fish communities in both systems. These results indicate that downstream fish communities do respond to high levels of hydrologic alteration associated with dams on rivers, but other factors may also influence shifts in fish communities. These findings help water resource managers establish stream flows below reservoirs that limit impacts to ecological communities while meeting human demands for water storage and flood control.
16. Genetic markers distinguish sources of fecal pollution between cows and calves. Manure from cattle production is a source of water pollution. Calves are prone to infections from pathogenic microorganisms that also infect humans, so it is important to be able to determine if surface water pollution is from calves on dairies in agricultural watersheds. An ARS scientist in Oxford, MS, in collaboration with USEPA scientists used genetic markers to distinguish sources of fecal pollution between cows and calves. Research demonstrated that the microbial composition of calf manure was distinct from its mother until it was weaned. These results are important for state and federal environmental protection agencies and managers of watersheds impacted by dairies and cow-calf operations.
17. Phosphorus enrichment impacts stream communities at low concentrations. Water resource managers seek quantitative nutrient criteria that are protective of freshwater environments. An ARS scientist in Oxford, MS, collaborated with researchers from Baylor and Texas A&M Universities to sample algae and fish from 38 central Texas streams to identify minimum amounts of nutrient enrichment that result in big changes in freshwater communities. Results indicated that water concentrations for total phosphorus should not exceed 21 parts per billion in order to prevent negative shifts in the nutrient chemistry and species composition of algae, as well as significant declines in sensitive fish species. These changes can be interpreted as threshold responses to nutrient enrichment and are being considered as management criteria for preventing degradation of high quality streams associated with phosphorus enrichment in Texas.
18. Gypsum applications reduce fecal bacterial contamination. Flue gas desulfurized gypsum is a byproduct of coal burning electric power generating facilities that has potential agronomic value as a soil amendment. An ARS scientist in Oxford, MS, in collaboration with other ARS scientists, conducted rainfall simulations to determine whether gypsum application will decrease off-field movement of fecal bacteria associated with manure applications in runoff. Salmonella was detected in the poultry litter applied in 2009, but not in 2011, and was not detected in any of the runoff samples. No differences between treatments were observed in 2009. In 2011, the highest rate of gypsum significantly decreased the load of Escherichia coli in runoff. Applications of gypsum may be considered a management practice to reduce microbial contamination of surface waters from manure applications to agricultural fields.
19. Applications of gypsum conserve soil plant nutrients. Gypsum produced as a by-product in power plants during the process of cleaning the exhaust fumes of sulfur dioxide gas (referred to as flue gas desulfurization gypsum (FGDG)) can be a useful soil amendment. An ARS scientist in Oxford, MS, in collaboration with other ARS scientists conducted a study to determine the effects of gypsum and broiler litter on runoff losses of nitrogen, phosphorus, calcium and magnesium losses in hay fields. Adding gypsum to broiler litter treated soil reduced nitrate and phosphorus levels in runoff by more than 75%. However, adding gypsum increased both calcium and magnesium levels in runoff. These results serve as useful gauges for developing best management practices using gypsum to ameliorate water quality concerns in agriculture.
20. Manure-borne pathogens were detected in surface waters in the Satilla River watershed. A byproduct of large-scale broiler chicken production is large quantities of broiler litter, which can be a source of the bacterial pathogens. An ARS scientist in Oxford, MS, in collaboration with other ARS scientists and scientists at the University of Georgia, sampled sites within the Satilla River watershed to determine potential relationships between animal agriculture and the presence of Salmonella and Campylobacter in surface waters. Samples were analyzed for the presence of various bacterial pathogens. When compared with samples collected from a watershed without broiler production, scientists determined that Salmonella and Campylobacter detection frequencies were positively associated with the number of poultry houses in a watershed. These results are important for state and federal environmental protection agencies and managers of watersheds impacted by broiler chicken production.
21. Sample storage time and temperature affect nutrient analyses. Water quality, especially with regard to eutrophication and hypoxia, are of great interest to the public at large. Although most researchers generally agree on proper methods for analysis of nutrients in water samples, some discrepancies still exist with regard to methods of sample storage. Additionally, remote locations used for sampling do not always lend themselves to newly emphasized quality assurance protocols. ARS scientists in Oxford, MS, examined differences in nutrient concentrations from samples stored using four different methods prior to analysis. Results indicated that freezer storage led to more variation than analyzing samples immediately, analyzing after 24 hours at ambient temperature, or analysis after refrigerating for 7 days. While immediate analysis is always recommended, this research also demonstrated that limited storage time under controlled conditions does not adversely affect data obtained from analysis of water samples. This research is important to help field researchers and laboratories adhering to quality control standards better understand the changes in nutrient concentrations which may occur in different temperature and holding time scenarios.
22. Microbial identification methods evaluated for consistency. The standard method used to determine fecal contamination of recreational water supplies is the membrane filter technique. This method provides an estimate of fecal coliforms, of which a certain number of positive colonies must be further examined for identification. The public sometimes assumes that positive fecal coliform samples equate to Escherichia coli contamination, which is not always the case. ARS scientists in Oxford, MS, in collaboration with researchers at the University of Mississippi examined the various methods used to identify the genus of positive M-FC colonies to demonstrate the importance of choosing methods that provide color changes, rather than identifying a specific color for positive results. This research is important to the regulatory community as it continues to refine acceptable methods for water quality protection for both human and ecosystem health.
Lizotte Jr, R.E., Locke, M.A., Testa III, S. 2014. Influence of varying nutrient and pesticide mixtures on abatement efficiency using a vegetated free water surface constructed wetland mesocosm. Chemistry and Ecology. 30(3):280-294.
Moore, M.T., Locke, M.A. 2013. Effect of storage method and associated holding time on nitrogen and phosphorus concentrations in surface water samples. Bulletin of Environmental Contamination and Toxicology. 91:493-498.
Knight, S.S., Rebich, R.A., Locke, M.A., Smith, Jr., S. 2012. Effects of agricultural conservation practices on oxbow lake watersheds in the Mississippi River alluvial plain. Soil and Water Research. 8(3):113-123.
Knight, S.S., Lizotte Jr, R.E., Shields Jr, F.D. 2014. Effects of contaminated sediments on a backwater restoration project in the Mississippi River Delta. Journal International Environmental Application and Science. 9(2):231-237.
Yuan, Y., Bingner, R.L., Locke, M.A., Stafford, J., Theurer, F.D. 2011. Assessing long term impact of phosphorus fertilization on phosphorus loadings using AnnAGNPS. International Journal of Environmental Research and Public Health. 8(6):2181-2199.
Taylor, J.M., King, R.S., Pease, A.A., Winemiller, K.O. 2014. Nonlinear response of stream ecosystem structure to low-level phosphorus enrichment. Freshwater Biology. 59(5)969-984.
Taylor, J.M., Seiheimer, T.S., Fisher, W.L. 2014. Downstream fish assemblage response to river impoundment varies with degree of hydrologic alteration. Hydrobiologia. 728:23-39.
Jenkins, M., Truman, C.C., Franklin, D.H., Potter, T.L., Bosch, D.D., Strickland, T.C., Nuti, C. 2014. Fecal bacterial losses in runoff from conventional and no-till pearl millet fertilized with broiler litter. Agricultural Water Management. 134:38-41.
Shanks, O.C., Kelty, C.A., Peed, L., Sivaganesan, M., Mooney, T., Jenkins, M. 2014. Age-related shifts in the density and distribution of genetic marker water quality indicators in cow and calf feces. Applied and Environmental Microbiology. 80:1588-1594.
Schomberg, H.H., Fisher, D.S., Reeves, D.W., Endale, D.M., Raper, R.L., Jayaratne, K., Gamble, G.R., Jenkins, M. 2014. Grazing winter rye cover crop in a cotton no-till system: yield and economics. Agronomy Journal. 106:1041-1050. DOI:10.2134/agronj13.0434.
Lizotte Jr, R.E., Testa III, S., Locke, M.A., Steinriede Jr, R.W. 2013. Responses of phytoplankton and Hyalella azteca to agrichemical mixtures in a constructed wetland mesocosms. Archives of Environmental Contamination and Toxicology. 65:474-485.
Moore, M.T., Tyler, H.L., Locke, M.A. 2013. Aqueous pesticide mitigation efficiency of Typha Latifolia (L.), Leersia Oryzoides (L.) SW., and Sparganium Americanum Nutt. Chemosphere. 92:1307-1313.
Kroger, R., Moore, M.T. 2011. Phosphorus dynamics within agricultural drainage ditches in the lower Mississippi Alluvial Valley. Ecological Engineering. 37:1905-1909.
Peacock, T.J., Mikell, A.T., Moore, M.T., Smith, S. 2014. Application of a redox gradostat reactor for assessing rhizosphere microorganism activity on lambda-cyhalothrin. Bulletin of Environmental Contamination and Toxicology. 92:347-351.
Kroger, R., Moore, M.T., Farris, J.L., Gopolan, M. 2011. Evidence for the use of low-grade weirs in drainage ditches to improve nutrient reductions from agriculture. Water, Air, and Soil Pollution. 221:223-234.
Smiley, P.C., Cooper, C.M. 2013. Small mammal habitat use within restored riparian habitats adjacent to channelized streams in Mississippi. Journal of Environmental Protection. 4:1280-1291. DOI:10.4236/jep.2013.411149.
Knight, S.S., Cullum, R.F. 2014. Effects of conservation practices on fisheries management. Journal of Agriculture and Biodiversity Research. 3(1):1-8.
Moore, M.T., Kroger, R., Locke, M.A., Tyler, H.L., Cooper, C.M. 2013. Seasonal and interspecific nutrient mitigation comparisons of three emergent aquatic macrophytes. Bioremediation Journal. 17(3):147-158.
Koontz, M.B., Koontz, J., Pezeshki, S.R., Moore, M.T. 2013. Nutrient and growth responses of Leersia oryzoides, rice cutgrass, to varying degrees of soil saturation and water nitrogen concentration. Journal of Plant Nutrition. 36(14):2236-2258.
Shields Jr, F.D., Alonso, C.V. 2012. Assessment of flow forces on large wood in rivers. Water Resources Research. 48(4):1-16.
Vereen, E., Lowrance, R.R., Jenkins, M., Adams, P., Rajeev, S., Lipp, E.K. 2013. Landscape and seasonal factors influence salmonella and campylobacter prevalence in a rural mixed use watershed. Water Research. 47:6075-6085.
Jenkins, M., Schomberg, H.H., Endale, D.M., Franklin, D.H., Fisher, D. 2013. Hydrologic transport of fecal bacteria attenuated by flue gas desulfurization gypsum. Journal of Environmental Quality. doi: 10.2134/jeq2012.0132.
Endale, D.M., Schomberg, H.H., Fisher, D.S., Franklin, D.H., Jenkins, M. 2013. Flue gas desulfurization gypsum: Implication for runoff and nutrient losses associated with broiler litter use on pastures on Ultisols. Journal of Environmental Quality. doi: 10.2134/jeq2012.0259.
Fielo, M., Mikell, Jr, A.T., Moore, M.T., Cooper, C.M. 2014. Variability in the characterization of total coliforms, fecal coliforms, and escherichia coli in recreational water supplies of North Mississippi, USA. Bulletin of Environmental Contamination and Toxicology. 93(2):133-137.