Assessment of risk reduction strategies for the management of agricultural nonpoint source pesticide runoff in estuarine ecosystems

Abstract

Agricultural nonpoint source (NPS) runoff may result in significant discharges of pesticides, suspended sediments, and fertilizers into estuarine habitats adjacent to agricultural areas or downstream from agricultural watersheds. Exposure of estuarine fin fish and shellfish to toxic levels of pesticides may occur, resulting in significant declines in field populations. Integrated pest management (IPM), best management practices (BMP), and retention ponds (RP) are risk management tools that have been proposed to reduce the contaminant risk from agricultural NPS runoff into estuarine ecosystems. Field studies were conducted at three sites within coastal estuarine ecosystems of South Carolina (SC) from 1985 to 1990 that varied in terms of the amount and degree of risk reduction strategies employed. An intensively managed (IPM, BMP, and RP) agricultural treatment site (TRT) was studied for pesticide runoff impacts. From 1985 to 1987, there were minimal (some IPM and BMP) management activities at TRT, but from 1988 to 1990, TRT was managed using an intensive risk reduction strategy. A second unmanaged agricultural growing area, Kiawah (KWA), was also studied and compared with TRT in terms of pesticide runoff and the resulting impacts on grass shrimp (Palaemonetes pugio) and mummichogs (Fundulus heteroclitus). A third, non-agricultural, reference site (CTL) was used for comparing results from the managed and unmanaged agricultural sites. In situ toxicity tests and field samples of the grass shrimp populations were conducted at each site and compared in terms of survival and the effectiveness of current risk reduction strategies. Significant runoff of insecticides (azinphosmethyl, endosulfan, and fenvalerate) along with several fish kills were observed at TRT prior to the implementation of rigorous risk reduction methods. A significant reduction of in stream pesticide concentrations (up to 90%) was observed at TRT following the implementation of strict NPS runoff controls, which greatly reduced impacts on estuarine fish and shellfish. At the unmanaged KWA, continued impacts due to the runoff of these insecticides were observed, along with several fish kills. Additional monitoring indicated that gravid female grass shrimp populations from KWA had elevated levels of P-glycoprotein (P-gp), a multidrug resistance protein, which may transport various pesticides across cellular membranes. Comparison of field results with laboratory toxicity tests established that pesticide exposure was the primary cause of observed field impacts at each site. These findings clearly indicate the value of an integrated risk reduction strategy (BMP, IPM, and RP) for minimizing impacts from NPS agricultural pesticide runoff.

Mitigation of agricultural nonpoint-source pesticide pollution in artificial wetland ecosystems

“…A parallel study using laboratory testing with amphipod (Hyalella azteca) indicated that 44 m of vegetated and 111 m of nonvegetated wetland would reduce the mortality to \5% (Schulz et al 2003c). The implementation of retention ponds in agricultural watersheds was examined by Scott et al (1999) as one strategy to reduce the amount and toxicity of runoffrelated insecticide pollution discharging into estuaries. However, wetland sizes and retention rates are not further detailed.…”

Novel Indicators of Anthropogenic Influence on Marine and Coastal Ecosystems

“…Additionally, alteration of the landscape often increases rates of sedimentation (Crossland et al, 2005;Syvitski et al, 2005;Syvitski and Milliman, 2007) that can smother sessile species or reduce their viability by altering light levels. Agricultural activities and sewage effluent lead to eutrophication in these systems (Scott et al, 1999;Costanzo et al, 2001;Rabalais et al, 2009Rabalais et al, , 2010, and shoreline hardening and other physical alterations can disrupt coastal ecosystems (Rice, 2006;Jackson et al, 2008;Morley et al, 2012). All of these insults collectively alter and destroy biogenic habitats occurring in marine coastal regions (Duarte et al, 2008(Duarte et al, , 2013McLeod et al, 2011;Fourqurean et al, 2012;Watanabe and Kuwae, 2015).…”

Effects of Endosulfan (Thiodan 35 EC®) on Meiofauna Community Through a Microcosm Approach

“…In the "sediment situation", many toxicants may not be bioavailable to meiofauna (Coull & Chandler, 1992) due to their toxicities may be reduced by several factors such as chelation, complexation, or by binding to organic ligands and colloidal aggregations on the sediment surface (Giere, 2009). On one hand, Scott et al (1999) determined a LC50 of 1.01 µg.L -1 for the estuarine grass shrimp Paleomonetes pugio by field and laboratory bioassays due to gravid female grass shrimp populations have elevated levels of P-glycoprotein (P-gp), a multidrug resistance protein, which may transport various pesticides across cellular membranes. On the other hand, Leonard et al (2001) determined a 10-d no observed effect using 42 µg.kg -1 sediment-associated endosulfan for the epibenthic mayfly Jappa kutera.…”