Robert Kröger

The smallmouth buffalo Ictiobus bubalus is a native benthivore to floodplain lakes in the Yazoo River Basin, USA. Based on evidence from other benthivorous fish studies we hypothesized high biomasses of I. bubalus contribute to poor water quality conditions. We tested this hypothesis in shallow (I. bubalus at high and moderate biomasses significantly (p I. bubalus on water clarity may have considerable ecological implications in natural habitats such as shallow floodplain lakes.

Low-grade weirs are controlled surface drainage management structures that are being advocated for improving water quality of downstream ecosystems within agricultural landscapes. Low-grade weirs are small controlled drainage structures that are placed in series in an agricultural drainage ditch to create biogeochemical conditions for enhanced nutrient retention but also to slow runoff velocities and encourage sedimentation. This study evaluated eight low-grade weirs for sediment and P accumulation in agricultural drainage ditches 1 yr after installation. On average, sediment (weir: 54 ± 25cm; reference: 13 ± 7 cm; P ≤ 0.001) and water (weir: 9 ± 7cm; reference: 1.16 ± 2 cm; P ≤ 0.05) depth was greater upstream of weirs when compared within ditch references sites. There were no significant differences in total P concentrations of sediments or between any P fractions between 1-yr-old weirs and their respective references. Bioavailability ratios of P (i.e., the ratio of potentially bioavailable to nonbioavailable P fractions) were also found to be similar between weir and reference sites. Based on these results, weirs increase the hydrological capacity of drainage ditches and significantly retain more sediment and P within the drainage ditch within 1 yr of construction. Future research will examine temporal changes in weir sediments and associated P concentrations to aid our understanding of how maintenance of weirs should occur to maximize physical and chemical characteristics for greatest sediment and P retention. Copyright © 2013. . Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Large tracts of lowlands have been drained to expand extensive agriculture into areas that were historically categorized as wasteland. This expansion in agriculture necessarily coincided with changes in ecosystem structure, biodiversity, and nutrient cycling. These changes have impacted not only the landscapes in which they occurred, but also larger water bodies receiving runoff from drained land. New approaches must append current efforts toward land conservation and restoration, as the continuing impacts to receiving waters is an issue of major environmental concern. One of these approaches is agricultural drainage management. This article reviews how this approach differs from traditional conservation efforts, the specific practices of drainage management and the current state of knowledge on the ecology of drainage ditches. A bottom-up approach is utilized, examining the effects of stochastic hydrology and anthropogenic disturbance on primary production and diversity of primary producers, with special regard given to how management can affect establishment of macrophytes and how macrophytes in agricultural landscapes alter their environment in ways that can serve to mitigate non-point source pollution and promote biodiversity in receiving waters.

Agricultural runoff carries high nutrient loads to receiving waters, contributing to eutrophication. Managed wetlands can be used in integrated management efforts to intercept nutrients before they e...

BACKGROUND: Pesticide application is common in agriculture and often results in applied pesticides entering adjacent aquatic systems. This study seasonally analyzed a suite of 17 current‐ and past‐use pesticides in both drainage waters and sediments to evaluate the prevalence of pesticides in drainage ditches across the Lower Mississippi Alluvial Valley (LMAV). RESULTS: There were significantly higher concentrations ( P < 0.05) of current‐use than past‐use pesticides; however, there were consistently high numbers of detections of past‐use pesticides in sediments. Sediment pesticide concentrations were an order of magnitude higher (150–1035 µg kg ⁻¹ ) than water samples (6–20.9 µg L ⁻¹ ). Overall, 87% of all samples analyzed for current‐ and past‐use pesticides were non‐detects. p , p ′‐DDT was detected in 47.5% of all drainage waters and sediments sampled. There were significant correlations (0.372 ≥ r ² ≤0.935) between detected current‐use water and sediment concentrations, but no significant correlations between past‐use water and sediment concentrations. CONCLUSION: Overall, there was a high percentage (87%) of sediment and water samples that did not contain detectable concentrations above the lower limit of analytical detection for each respective pesticide. This lack of pesticide prevalence highlights the improved conditions in aquatic systems adjacent to agriculture and a potential decrease in toxicity associated with pesticides in agricultural landscapes in the LMAV. Copyright © 2011 Society of Chemical Industry

Fipronil, a phenyl‐pyrazole insecticide, is often used in rice (Oryza sativa L.) production agriculture, with elevated runoff concentrations and loads having potential toxicological effects on downstream aquatic environments. This study evaluated two species of aquatic plants—broadleaf cattail (Typha latifolia L.) and powdery alligator‐flag (Thalia dealbata Fraser ex Roscoe)—placed in series against a nonvegetated mesocosm in reducing concentrations and loads of fipronil, and associated metabolites. Vegetation type and hydrological condition (inundated vs. dry) were treatment effects used for comparison. The vegetated mesocosms significantly reduced higher loads and concentrations of fipronil, fipronil sulfone, and sulfide in both inundated and dry hydrological conditions over nonvegetated mesocosms. Under inundation conditions, vegetated mesocosms reduced >50% of influent fipronil concentrations and between 60 and 70% of fipronil loads, which was significantly higher than the dry conditions (10–32% concentration and load). These results show that agricultural management strategies using ephemeral aquatic zones, such as drainage ditches, can be optimized to couple chemical applications with vegetation presence and hydrology to facilitate the reduction in chemical waste loads entering downstream aquatic ecosystems. Such reduction is critical for use with fipronil, where negative impacts have been demonstrated with several nontarget species.