John Wiley & Sons, Ltd.

Modelling toxic stress by atrazine in a marine consumer‐resource system

The present study combines short‐term experiments with food chain modelling to explore long‐term effects of the herbicide atrazine on consumer‐resource dynamics in a marine intertidal ecosystem. The short‐term (28 days) lab experiments indicated that the intrinsic rate of increase (r) and carrying capacity (K) of the marine diatom Seminavis robusta decreased with increasing atrazine exposure. This decrease did not show the concave shape expected from the diatoms' lifetime productivity for the nonexposed diatoms, and single‐species toxicity data from the literature but instead was described best by a linear model. These experimentally observed atrazine‐induced decreases of r and K were used to parameterize a Rosenzweig‐MacArthur model representing a simple food chain including the tested diatom and its grazer, the harpacticoid copepod Delavalia palustris var. palustris. Stable oscillation zoo‐phytobenthos systems were produced at diatom exposures of 0, 100 and 150 µg/L atrazine. An atrazine concentration of 150 µg/L contributed to a 15% increase of the oscillation periods of both diatoms and copepods and a 52% reduction of oscillation amplitudes compared to the control situation. Although the amplitudes of copepods only increased 7% at 150 µg/L atrazine, the maximum and minimum copepod density at that concentration were reduced with 61% and 63%, respectively. The effects of atrazine on periodicity and amplitudes were robust to 20% changes in the food chain model parameters that represented allometric relationships. Our simulations suggest food chain mediated indirect effects on zoobenthos populations, indicating a reduced diatom and copepod availability throughout the year. Environ. Toxicol. Chem. © 2013 SETAC

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