Location: Water Quality and Ecology Research2013 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 integrataed 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.
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:
Effectiveness of farm and land management practices were assessed. Assembly of a comprehensive data set for Beasley Lake Watershed, a Conservation Effects Assessment Program (CEAP) watershed, is ongoing. Monitoring of lake water quality and fish populations, evaluation of runoff water quality from Conservation Reserve Program and buffer areas, and a two-cell sediment basin, continues. Watershed data includes soils, cropping patterns, cultural practices, topography, climate, water quality, ecology, and Light Detection and Ranging (LiDAR). These data are being input on the Sustaining the Earth's Watersheds: Agricultural Research Data System (STEWARDS) data base. Several small- to large-scale field experiments are being conducted to assess the effectiveness of a range of conservation practices. Effects of conservation tillage, nutrient, cover crop, and edge-of-field buffers on runoff water quality and changes in soil characteristics are assessed in a long-term row crop corn study. In another study, long-term (6 years) effects of transgenic corn and glyphosate application on soil characteristics are evaluated. Constructed wetlands, with and without rice, are being used to study the effectiveness of rice plants in trapping and processing nutrients and pesticides associated with a simulated storm runoff. A study is being implemented to evaluate the effectiveness of tailwater-recovery systems in improving runoff water quality through contaminant sequestering and processing. Characterizing ecosystem processes in agricultural watersheds was conducted. A comprehensive data set is being assembled for three low-flow agricultural stream watersheds. Monitoring of stream water quality, hydrology, land-use, microbial activity, fish populations, and aquatic invertebrate populations initiated in 2011 continues. Large-scale and small-scale experiments were conducted to assess ecological processes such as nutrient limitation and light limitation effects on algal growth and productivity. A large-scale experiment assessing organic matter processing rates is ongoing. Several small scale experiments are being conducted in artificial streams to assess microbial activity and ecosystem productivity with increased nutrient (carbon and nitrogen) and variable flow or drought conditions as well as examine the effects of suspended sediment from Mississippi Delta on fathead minnows. Watershed assessment of agricultural ecosystem services was conducted. Techniques are being developed to use LiDAR and remotely sensed riparian buffer vegetation data that will be integrated with AnnAGNPS to model changes in water quality. Climate data are being assembled to produce models of different climate conditions and possible effects of climate changes on water quality in Beasley Lake Watershed. Modeling simulations are being conducted with AnnAGNPS using data from large watershed-scale and smaller field-scale experiments assessing the effectiveness of conservation practices on water quality.
1. Models help guide wetland placement in agricultural watersheds to reduce nutrients. The wide installation of nutrient removal wetlands in tile drained watersheds of the Midwest may represent the best opportunity to reduce nitrate loads in the Mississippi River Basin and mitigate Gulf of Mexico hypoxia with a single conservation practice. However suitable locations to place wetlands must be identified, along with their potential impact on nutrient load reductions at the watershed scale, to implement this approach. In this study, ARS scientists in Oxford, MS, and Ames, IA, used results of an aerial laser altimetry survey to develop a detailed topographic map of a Hydrologic Unit Code (HUC-12) (16,000 acre) watershed in Illinois. We applied a conservative set of criteria, modified from a wetlands program in Iowa, to identify eleven sites that could readily be converted to wetlands with minimal loss of productive cropland. These wetlands could intercept and treat tile drainage from 30% of the watershed. A modeling exercise showed that these wetlands could reduce nitrate loads from the watershed by as much as 16%. However load reductions among the wetland locations varied considerably, depending on watershed-to-wetland area ratios, land use in the upslope area, and nitrate loads generated under that land use. These issues will need to be considered by policy makers interested in developing incentive structures that encourage wetlands, including the establishment of nutrient trading schemes.
2. Conservation practices improve soil quality. Conservation practices are an increasingly important component of sustainable management systems, and information about their influence on soil characteristics is needed. ARS scientists in Oxford, MS, conducted a six-year cotton field study in the Mississippi Delta, USA, to assess long-term changes in soil as influenced by conservation tillage (no-tillage and minimum tillage) and cover crop (rye and balansa clover versus no cover). Overall improvement in soil quality over time was observed for both conservation tillage practices and both cover crop practices. Both cover crops and no-tillage increased soil chemical properties such as total carbon, total nitrogen, and soil enzyme activity. Cover crop also resulted in soil structural improvements, including stability of soil aggregates. Moderate tillage slightly increased populations of reniform nematodes and earthworms, but neither was affected by cover crop. Implications for farmers are that, given parity in crop production, any of the combination of tillage and cover crop management practices should provide environmental benefits.
3. Agricultural management practices reduce phosphorus loss. Agricultural management practices have been studied for reducing nonpoint source pollution and improving water quality. The Mississippi Delta (flood plain of Mississippi River) is an important agricultural region of the United States, and high phosphorus (P) loss from the region has been an environmental concern because of potential water quality problems in streams and lakes. Therefore, the overall objectives of this study were to identify factors that affect P losses from agricultural fields in two Mississippi Delta watersheds to improve the understanding of P losses and assess whether management practices might mitigate these losses. The paper presents results of rainfall, runoff, orthophosphorus (ortho-P), total phosphorus (TP) and sediment collected from three agricultural fields mainly in cotton production in Mississippi Delta watersheds. Agricultural management practices during the study period also were recorded. ARS scientists in Oxford, MS, found that application of P in the fall resulted in more ortho-P losses, likely because high rainfall usually occurred in the winter months soon after P application. However, tillage associated with planting and incorporating applied P in spring may have resulted in more TP loss in sediment. These results indicate that applying P fertilizer in the spring may be recommended to reduce potential ortho-P loss during the dormant season; in addition, conservation practices may reduce potential TP loss associated with soil loss.
4. Drainage ditches contain microbes that degrade herbicides. 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. While the physical and chemical processes involved in this management practice are being understood better, little advancement in the biological understanding of these systems, especially in terms of microbial activity, has been made. Soil samples were collected from agricultural fields and ditches by ARS scientists in Oxford, MS, and were spiked with the herbicide atrazine. Following a 28 day incubation experiment, in addition to molecular analysis of the soil, it was determined that specific genes responsible for degrading atrazine were present. These genes increased the rate of atrazine degradation as opposed to degradation in a non-agricultural soil. These results are important for conservation planners and farmers interested in reducing the amount of atrazine leaving agricultural fields following runoff.
5. Watershed-wide Conservation practices reduce the risk of pesticides to aquatic organisms. ARS scientists in Oxford, MS, examined pesticide contamination in lake surface water and their potential risk to aquatic animals and algae in relation to conservation and cropping practices within the watershed of an oxbow lake in the Mississippi Delta from 2000 to 2009. We looked for thirteen pesticides in lake surface water. During the ten-year study period, crops changed from mostly cotton in 2000-2001 to mostly soybean in 2002-2004, 2006, 2008, and 2009 with mostly milo and corn in 2007. Conservation practices such as reduced tillage began in 2001 and Conservation Reserve Program enrollment began in 2003 with planting of cottonwood trees. Over the ten-year study period, risk to lake aquatic animals and algae was greatest in 2000-2002, lowest in 2005-2006, and low in 2007-2009. Overall, lake water pesticide contamination decreased annually until 2005-2006 and increased again in 2007-2009 due, in part, to changes in crops from reduced tillage soybeans to conventional-till milo and corn in 2007. These results are of interest to regulatory and other agencies and the pesticide industry by providing additional information to improve and sustain lake and flood plain water quality and overall environmental quality using conservation practices.
6. Drainage ditch vegetation reduces phosphorus. Best management practices are needed to help reduce the potential harmful effects of nutrients in agricultural runoff before they contribute to downstream eutrophication. Management practices such as constructed wetlands and vegetated ditches rely on plants to help mitigate nutrients from the runoff water. ARS scientists in Oxford, MS, examined three plant species common to wetland and ditch habitats and found they were able to reduce the amount of phosphate in runoff water significantly following a simulated storm event. This research is critical in order to afford better design and community composition of vegetated aquatic systems that serve to filter out nutrients in storm runoff.
7. Agricultural swine management practices reduce risk of parasitic infection. Since the parasite Cryptosporidium (crypto for short) was the cause of several large-scale outbreaks of diarrhea and in some cases death in humans, it has become a public health concern. Other than sewage treatment facilities, the source of this parasite in the environment is animal agriculture. Researchers have shown, for example, that waste lagoons of large-scale swine operations can be a source of crypto. They have also shown that a small percent of the total amount of crypto observed in a lagoon may be infectious. This surviving fraction of crypto is an indication that crypto dies-off occurs in waste lagoons. Waste from the lagoon is periodically applied to spray fields as irrigation water and plant nutrients. The waste from a lagoon can also contaminate surface waters with crypto during rain storms. To better understand how long crypto associated with swine operations can survive in a lagoon and spray field, USDA-ARS scientists at J. Phil Campbell, Sr., Natural Resource Conservation Center in Watkinsville, GA, and scientists at Cornell University in Ithaca, NY, performed experiments to determine the time it takes for 99% of live crypto to die-off in a swine lagoon and spray field of a large-scale swine operation in Georgia. Results of their study indicated that the time it takes to kill 99% of crypto in the lagoon was 13 weeks in the summer and 20 weeks in fall and winter. In contrast to die-off in the waste lagoon, it took 38 weeks for Cryptosporidium to reach 99% die-off. This study demonstrated that the waste lagoon/spray field system of swine waste management was effective at reducing the numbers of this infectious pathogen and the likelihood of their contaminating surface waters and threatening public health. This study will be of interest to state and federal environmental protection agencies.
8. Increasing water quantity (flooding) improves water quality. ARS scientists in Oxford, MS, measured the effects of a late summer artificial flooding event on water quality in a river floodplain backwater (severed meander bend) along the Coldwater River in Tunica, County, Mississippi, USA. Flooding affected water temperature, oxygen, acidity, nutrients, and algae. Flooding stabilized and improved overall water quality for aquatic plants and animals and can be used to restore river floodplain backwater habitats. These findings are of interest to land managers and scientists interested in riverine aquatic ecosystem restoration and management.
9. River backwater fish habitat and water quality rehabilitated using weirs. Aquatic habitats within lowland river floodplains are extremely productive and valuable, but are adversely impacted by intensive agriculture. ARS scientists in Oxford, MS, sampled hydrology, water quality and fish from five sites representing different habitats along the Coldwater River in the Mississippi Delta for four years. The types of fish and the water quality found in these sites were indicative of degraded conditions, with high levels of turbidity and water temperature and low dissolved oxygen. Since habitat conditions were tightly linked to water depth and pollution of inflowing runoff, one large backwater site was rehabilitated by building a weir to increase water depth and divert runoff. This measure was partially effective, but the rehabilitated backwater continued to experience periods of low dissolved oxygen during hot, dry weather. These findings are useful to others interested in protecting and managing floodplains to conserve ecosystem services.
10. Improved understanding of agricultural pollution provides better predictability of ecological effects. Agricultural runoff from fields simultaneously introduces many different pollutants into aquatic ecosystems. It is not clear how aquatic microorganisms respond to mixtures of pollutants, as many pollutants act antagonistically on organism development. When introduced individually, some pollutants such as nutrients can increase growth, and some such as herbicides can decreae growth. ARS scientists in Oxford, MS, recorded how atrazine reduced algal growth and nutrients stimulated algal growth in laboratory chambers. Mixtures generally had an intermediate influence on algae, as one pollutant did not completely override the effect of the other. In the wetland, nutrients and atrazine contributed to algal changes, but other pollutants, specifically total suspended solids, were more influential. The type of wetland algal response (stimulation or inhibition) was inconsistent with distance from the runoff input site and often changed between adjacent sampling sites. Pollutant relationships with algae were complex, with atrazine correlated with increased algal biomass and nutrients correlated with decreased biomass. Overall, algal biomass was affected more than functional aspects such as primary productivity and nutrient uptake rates. Multiple pollutants in complex mixtures can change the influence of individual pollutants like nutrients and atrazine on algae. Knowing species composition and system hydrology, in addition to runoff chemical characteristics, can enable better predictions of periphyton responses to agricultural runoff. These results are of interest to regulatory and other agencies and the pesticide industry by providing additional information to improve and sustain river, stream and lake water quality and overall environmental quality through improved understanding and predictability of effects of complex pollutant mixtures.
11. River channelization reduces fish habitat. Straightening of a river channel can cause bank erosion that results in wide, shallow river with very little aquatic habitat. ARS scientists in Oxford, MS, sampled fish using electroshocking gear and hoop nets to evaluate the impact of stream bank erosion and loss of habitat resulting from channelization on fish communities. This research shows what when a river is channelized the loss of habitat results in a river that can only support very small fishes. This information may be useful in making comparison of damaged riverine ecosystems and assist managers in determining impairment and success in meeting Total Maximum Daily Load (TMDL) goals.
12. Wetlands help reduce the ecological impacts of pestcides. Wetlands are sometimes used to lessen possible ecological impacts from agriculture. ARS scientists in Oxford, MS, examined the pesticide effects on an aquatic invertebrate animal, Hyalella azteca, in sediment from a managed wetland after an artificially produced agricultural runoff event. We examined the ability of this managed wetland to decrease the ecological effects of three pesticides, atrazine, S-metolachlor, and permethrin, occurring in wetland sediment on this aquatic invertebrate animal. The study showed that the managed wetland was effective at decreasing the effects of pesticides moving into sediment after an agricultural runoff on aquatic animals during average rainfall events. Our results are of interest to regulatory and other agencies and the pesticide industry by providing additional information to improve and sustain river, stream and lake sediment quality and overall environmental quality using constructed wetlands as an effective conservation practice.
13. Flood control levee borrow pits improve river fish habitat. To protect crops from flooding, earthen flood control levees are often constructed along streams in floodplain landscapes such as the Mississippi Delta, isolating natural areas from periodic flooding on which they depend. Lost ecosystem services due to levee construction may be partially recovered by using floodplain soils excavated from pits on the waterside of the levee so that the pits provide floodplain lake habitats after levee construction. The value of such borrow pits along large rivers is well established, but little information is available regarding borrow pits along smaller streams. Six borrow pits along Abiaca Creek in north central Mississippi were studied by ARS scientists in Oxford, MS, for two years. Sport fish populations were of highest quality in the larger pits with sinuous shorelines, periodic hydrologic connection to the stream, and greatest water clarity. These findings may be used to design and manage flood control levee projects.
Murdock, J.N., Shields Jr, F.D., Lizotte Jr, R.E. 2013. Periphyton responses to nutrient and atrazine mixtures introduced through agricultural runoff. Ecotoxicology. 22(2):215-230.