Multi-level Toxicity Assessment of Different Emerging Contaminants Towards Aquatic and Terrestrial Model Organisms

In recent years, emerging contaminants have attracted the attention of scientific community because of their occurrence and potential hazard towards natural ecosystems. Among emerging contaminants, three major classes of molecules can be identified: pharmaceuticals and personal care products (PPCPs), illicit drugs and microplastics (MPs). After anthropic use, these contaminants enter the environment through several routes, such as the sewage systems or direct input, resulting in a widespread contamination of atmosphere, water, soil and biota. Although the presence of these molecules is well-known, there is still a dearth of information regarding their potential negative effects induced towards aquatic and terrestrial non-target organisms. The majority of the studies on this topic have focused on the investigation of effects at low levels of the biological hierarchy, while limited attention has been addressed to the higher ones, such as individual, population or community level. Whilst PPCPs toxicity has been investigated for more than two decades, only in recent years ecotoxicologist focused their attention on the presence and the potential effects of illicit drugs and microplastics. Thus, the aim of this project was to investigate the effects induced by the exposure to different illicit drugs and microplastics. As in environment these contaminants could interact with a wide range of organisms, resulting in species-specific differential effects at different levels of biological organization, their effects have been investigated on six different model organisms, representative for freshwaters (Daphnia magna and Xenopus laevis), marine (Mytilus gallopovincialis, Ruditapes philippinarum and Paracentrotus lividus) and soil (Achatina reticulata) ecosystems. To reach the goal of the project, a multi-level approach based on the application of assays at sub-individual (i.e., biochemical biomarkers), tissue (i.e., histological analysis), individual (i.e., mortality, growth rate and/or swimming behavior) and, when possible, population level (i.e., reproduction) was used. Regarding illicit drugs, different experiments were planned to evaluate the effects induced by the exposure to the two most used and environmentally detected illicit stimulants, cocaine (COC) and methamphetamine (METH), to the freshwater cladoceran Daphnia magna. Moreover, considering that illicit drugs occur in aquatic ecosystems as complex mixtures, an additional experiment was planned to evaluate independent and combined effects induced by the exposure to cocaine and its main metabolite benzoylecgonine (BE), towards the Mediterranean mussel Mytilus galloprovincialis. The exposure to environmentally relevant concentrations of COC and METH induced a modulation of the oxidative status, as well as a molecule-specific effect on swimming behavior and reproduction, in D. magna. Similarly, the exposure to COC and BE, both independently and in mixture, induced an alteration of the oxidative status of Mediterranean mussels. These data suggested that illicit drugs might represent a threat for both freshwaters and marine non-target organisms. Regarding microplastics, the attention was focused on two polymers, polystyrene (PS) and polyethylene terephthalate (PET), having different chemico-physical features and environmental fate. In fact, because of its low density, PS tends to float in the water column, while in contrast high-density PET sinks and accumulates to sediments. For this reason, the administration of PS or PET MPs allowed to investigate the toxicity towards organisms with different feeding strategies and ecological role in ecosystems. The effects of regular PS-MPs were evaluated towards two freshwater organisms, namely the cladoceran Daphnia magna and the amphibian Xenopus laevis, Moreover, considering that in environment irregular shaped MPs are most common than regular ones, three experiment were planned to investigate the effects of irregular shaped PET-MPs towards two marineorganisms, the Manila clam Ruditapes philippinatum and the sea urchin Paracentrotus lividus, and a soil organism, the giant snail Achatina reticulata. The results obtained in these experiments showed that MPs were efficiently ingested by all the tested organisms, but no or limited adverse effects occurred, depending on the considered model organism. In conclusion, illicit drugs and microplastics can induce different species-specific adverse effects towards aquatic and terrestrial organisms. Moreover, the project pointed out the usefulness of using a multi-level approach to deeply study the toxicity of emerging pollutants. The integration of information coming from sub-individual and higher levels of the biological hierarchy can allow to shed a light on the propagation of the effects and to explore the complexity of contaminant-induced toxicity. Lastly, the use of different model organisms with different life-history traits and ecological role can allow to explore species-specific differences generated by the exposure to contaminants and to assess the risk of a specific class of contaminations towards the whole ecosystem.