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EFFECTS OF NUTRIENT PRE-EXPOSURE ON ATRAZINE TOXICITY TO VALLISNERIA AMERICANA MICHX. (WILD CELERY)
Citation:
DANTIN, D. D., R. G. BOUSTANY, M. A. LEWIS, S. J. JORDAN, R. F. MOSS, AND T. C. MICHOT. EFFECTS OF NUTRIENT PRE-EXPOSURE ON ATRAZINE TOXICITY TO VALLISNERIA AMERICANA MICHX. (WILD CELERY). ARCHIVES OF ENVIRONMENTAL CONTAMINATION AND TOXICOLOGY. Springer, New York, NY, 58(3):622-630, (2010).
Impact/Purpose:
Accelerated eutrophication is common to many freshwater and marine environments and often co-occurs with the presence of anthropogenic chemicals. However, the toxic effects of common chemical stressors such as herbicides, in the presence of elevated nutrients are not well understood for most aquatic flora, particularly the submerged aquatic vegetation (SAV). The objective of our study was to attempt to describe the presence of an interactive effect at environmentally relevant concentrations of atrazine on a common freshwater and brackish SAV that had been conditioned to varied rates of nutrient loading rates under mesocosm conditions.
Description:
The importance of aquatic plants as a valued component of coastal environments is receiving increased attention in the public policy and scientific community. Unfortunately, the fact remains that the effects of anthropogenic contaminants on both emergent (marsh) and submerged aquatic vegetation (SAV) and sea grasses remain poorly understood despite the continuing decline of aquatic plant populations. One uncertainty of interest is the risk of aquatic plants posed by an interactive effect of elevated nutrient loading in combination with low concentrations of phytotoxic compounds that, when exained singly and at environmentally relevant concentrations, does elicit a phytotoxicological response. In this study, we evaluated the effect of elevated nutrient loading rates on the toxicity environmentally relevant levels of herbicide contamination to SAV using a mesocosm design. Whole plant cores of Vallisneria americana from the St. Johns River, FL, were accliminated to "low" (1/3 of ambient), "high" (3x ambient), and "ambient" nutrient regimes based on loading rates for the St. Johns River near Palatka, FL. After four months, replicate nesocosms were exposed to a pulse dose of atrazine at 0, 11 and 110 ug 1-1 nominal concentrations. AT 0-hour pre-exposure of 24, 48, and 96-hour post-exposure measurement periods, pulse amplitude modulated (PAM) fluorometry was used to measure the rate of chlorophyll fluorescence activity in V. americana tissue. Significant reductions in electron transport rate (ETR) were observed at each nutrient condition following exposure to 110 ug 1-1 atrazine. The ETR reductions were also greater with higher nutrient loading. Significant differences were also observed at 11 ug 1-1 atrazine, but only in combination with high nutrient loading. These observations are notable since 11 ug 1-1 atrazine is less than the proposed national water quality criterion of 17 ug 1-1. The results of the study indicate the importance of nutrient-contaminant interactions and the value of chlorophyll fluorescence as a rapid and reliable technique for measuring phytotoxicity. The potential for interative effects of high nutrient loading and low (i.e. below criteria) concentrations of phytotoxic compounds on aquatic macrophytes should be considered when assessing risk to the aquatic environment.