Evaluation of the effects of pesticides resulting from trophic transfer in freshwater feed chain consisting of two species (Chlorella vulgaris and daphnia magna)

While pesticides directly affect all organisms in the area where they are applied, although at different levels, they can accumulate in the exposed organisms, turn into more toxic metabolites as biotransform, and/or be transferred from one organism to another through interactions and food chain. In this study, the effects of food chain exposure to a glyphosate-based herbicide (GBH) and a trifloxystrobin-based fungicide (TBF) on Daphnia magna were evaluated using biochemical and morphological markers. In the study, Chlorella vulgaris, an alga representing the producers level of freshwater ecosystems, and Daphnia magna, representing the primary consumers level, were selected as the test organism. Lethality, height, width, and spin lengths of exposed D. magna individuals were determined both in studies to determine the mean lethal concentration (LC50) and in studies evaluating the effects of different environments (non-fed and mixed feed and fed with Chlorella) on pesticide toxicity. In addition, glutathione S-transferase, glutathione reductase, catalase (CAT), carboxylesterase, acetylcholinesterase activities, and reduced glutathione levels were measured in D. magna adults exposed to pesticides in different environments. 48 hour LC50 values of GBH and TBF for D. magna were determined as 253.1 mg/L and 20.7 µg/L, respectively. When the effects of different environments on pesticide toxicity were evaluated, it was found that lethality increased in relation to concentration for both GBH and TBF in studies. Similarly, both pesticides caused an increase in CAT activity. The increase in lethality and CAT activity together is thought to be a mechanism to combat oxidative stress. On the other hand, for both pesticides, the CAT activity showed less increase in the groups fed with Chlorella, similar to lethality, and it can be concluded that feeding with Chlorella reduced the oxidative stress and toxic effect.