Assessing the Chronic Environmental Risk of Graphene Oxide Using a Multimarker Approach Across Three Trophic Levels of the Aquatic Ecosystem

With the rapid increase in the synthesis and application of graphene oxide (GO), questions have emerged about its inadvertent entry into aquatic habitats and the ecological consequences associated with such exposure While several studies have addressed the acute effects of GO, knowledge on its chronic impacts across multiple trophic levels remains limited. In this study, we assessed the chronic toxicity of a well-characterized GO product using model organisms representing three trophic levels: the bioluminescent marine bacterium <i>Aliivibrio fischeri,</i> unicellular green algae (<i>Chlamydomonas reinhardtii</i>, <i>Chlorella vulgaris</i>, <i>Desmodesmus subspicatus</i>), the cyanobacterium <i>Synechococcus elongatus</i>, and the freshwater cladoceran <i>Daphnia magna</i>. Endpoints included bioluminescence inhibition in bacteria, growth inhibition in photosynthetic primary producers, and reproduction and refined physiological parameters (heart rate, feeding activity) in <i>D. magna</i>. Our results demonstrated clear concentration-dependent chronic effects of GO, with <i>A. fischeri</i>, the applied photosynthetic primary producers and <i>D. magna</i> exhibiting significant inhibition of bioluminescence, growth, delayed onset of reproduction, and reduced fitness parameters, respectively. Based on the collected data, a comprehensive ecotoxicological risk assessment was carried out, revealing that pristine GO may pose negligible hazard to aquatic ecosystems under environmentally relevant exposure scenarios. The outcomes clearly demonstrate the relevance of incorporating chronic and multi-trophic effects when evaluating the ecological risks of emerging nanomaterials such as GO.