Analysis of Pesticide Runoff From Mid-Texas Estuaries and Risk Assessment Implications for Marine Phytoplankton

Abstract

During 1993, estuarine surface water samples were collected from the mid-Texas coast (Corpus Christi to Port Lavaca, TX). Agricultural watershed areas as well as tidal creeks immediately downstream were chosen as sampling sites along with adjoining bay sampling stations. Collections were made throughout the growing season (February to October 1993) before and after periods of significant (> 1.25 cm) rainfall. All samples were initially screened for the presence of pesticides using enzyme-linked immunosorbent assay (ELISA) test kits (EnviroGard) for triazine herbicides and carbamate insecticides. All samples were extracted and then analyzed using gas chromatography (GC) for quantification of atrazine. Only samples testing positive for carbamate insecticides via ELISA were further extracted for GC analysis to quantify aldicarb and carbofuran. Additionally, laboratory toxicity tests using phytoplankton were examined from published, peer-reviewed literature and compared with the atrazine field levels found in Texas. Results of ELISA screening indicated the presence of triazine herbicides in nearly all samples (>93%). GC analysis further confirmed the presence of atrazine concentrations ranging from <0.01-62.5 microg/L. Screening tests also found detectable levels of carbamate insecticides (aldicarb and carbofuran) that were also confirmed and quantified by GC. Comparison of measured concentrations of atrazine compared with published toxicity tests results indicated that there was a potential environmental risk for marine/estuarine phytoplankton in surface waters of Texas estuaries, particularly when the chronic nature of atrazine exposure is considered.

Stressor‐induced biodiversity gradients: revisiting biodiversity–ecosystem functioning relationships

“…In the case of toxic chemicals however, such extensive biodiversity loss is unlikely to happen. Realistic biodiversity loss most often only affects a fraction of the existing species pool, resulting in alterations of evenness rather than richness (Pennington et al , Hillebrand and Matthiessen ), even at chemical concentrations well above environmental concentrations, as represented by the highest atrazine concentrations in our study (Pennington et al ). Evenness alterations induced by atrazine were less severe than those in the richness‐based random assembly approach, which in this case overestimated the biodiversity loss induced by chemical stress.…”

Toxicity of atrazine to the estuarine phytoplankter Pavlova sp. (Prymnesiophyceae): Increased sensitivity after long‐term, low‐level population exposure

“…Regardless of the long‐term exposure scenario (with or without recovery), concerns arise, especially when there are noted field sites [9,10] that are continuously contaminated by atrazine. For example, pesticide input from agricultural areas to adjacent estuarine areas typically occurs in a pulsed, episodic, and occasionally highly concentrated fashion with low‐level pesticide concentrations remaining in surface waters between the pulsed events [9]. It is conceivable that aquatic microalgal communities may never have the chance to fully recover from atrazine exposure and may incur increased sensitivity over time; thus, recovery scenarios may be a moot point for some areas.…”

“…In the United States, the annual agricultural use of atrazine is estimated at over 4,200 metric tons (1982) of active ingredient [7] in coastal counties and 34,000 to 37,000 metric tons (1997) of active ingredient nationally [8]. Two studies [9,10] have shown that atrazine residues persist in surface waters for months and even years because of this high usage. Pennington et al [9] found that 96% of surface water samples from mid‐Texas, USA, estuaries contained detectable levels of atrazine (January‐October 1993), averaging approximately 4.0 μg/L.…”

“…Two studies [9,10] have shown that atrazine residues persist in surface waters for months and even years because of this high usage. Pennington et al [9] found that 96% of surface water samples from mid‐Texas, USA, estuaries contained detectable levels of atrazine (January‐October 1993), averaging approximately 4.0 μg/L. Similarly, Clark et al [10] found that 97% of samples from the Mississippi River at Baton Rouge, Louisiana, USA, collected from 1991 through 1997 had detectable levels of atrazine ranging from <0.05 to 4.0 μg/L with a median value of approximately 0.5 μg/L.…”

Cumulative effect of low and high atrazine concentrations on Arabidopsis thaliana plants

“…The highest detected residual amounts reach 1mg/kg soil [4]. Usually, in the agricultural areas this herbicide can be detected in 1-100 µ g per kg soil or liter water [3,[5][6][7]. On the other hand, it was reported that in some plants the same atrazine concentrations exhibit cytokinin-like properties [8].…”