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Previous studies suggested the suitability of the brackish-water serpulid (Ficopomatus enigmaticus) to be used as model organism for both marine and brackish waters monitoring, by the performance of sperm toxicity and larval development assays. The present study focused on larval development after the exposure of two F. enigmaticus populations (Mediterranean and Atlantic, collected in Italy and Portugal, respectively) to different trace elements (copper, mercury, arsenic, cadmium, and lead) at different concentrations. Results of larval development assays were presented as the percentage of abnormal developed larvae. The effect, measured in terms of EC 50 for all toxicants tested, showed that mercury was the most toxic metal for larvae of both populations. Specifically, the tested trace elements may be racked in the following order from the highest to the lowest toxicity: Mediterranean: mercury > copper > lead > arsenic > cadmium; Atlantic: mercury > copper > cadmium > arsenic > lead. Responses of both populations were similar for arsenic. Lead was the least toxic element for the Atlantic population, while cadmium showed the least toxicity for the Mediterranean population. These preliminary results demonstrate the sensitivity and suitability of the organisms to be used in ecotoxicological bioassays and monitoring protocols. Moreover, chemical analyses on soft tissues and calcareous tubes of collected test organisms and their sampling site water were performed, to identify and quantify the concentration of the tested trace elements in these 3 matrices. Populations exhibited less sensitivity to a certain element together with a relevantly higher concentration of the same element in soft tissues. This may indicate a certain resistance to particular contaminant toxic effects by organisms that tend to accumulate the same toxicant. This highlights the potential correlation between wild-caught test organisms' responses and a deep characterization of the sampling site to identify putative abnormalities or differences in model organism response during bioassay execution., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Ocean acidification events are recognized as important drivers of change in biological systems. Particularly, the impacts of acidification are more severe in estuarine systems than in surface ocean due to their shallowness, low buffering capacity, low salinity and high organic matter from land drainage. Moreover, because they are transitional areas, estuaries can be seriously impacted by a vast number of anthropogenic activities and in the last decades, carbon nanomaterials (CNMs) are considered as emerging contaminants in these ecosystems. Considering all these evidences, chronic experiment was carried out, trying to understand the possible alteration on the chemical behaviour of two different CNMs (functionalized and pristine) in predicted climate change scenarios and consequently, how these alterations could modify the sensitivity of one the most common marine and estuarine organisms (the polychaeta Hediste diversicolor) assessing a set of biomarkers related to polychaetes oxidative status as well as the metabolic performance and neurotoxicity. Our results demonstrated that all enzymes worked together to counteract seawater acidification and CNMs, however oxidative stress in the exposed polychaetes to both CNMs, especially under ocean acidification conditions, was enhanced. In fact, although the antioxidant enzymes tried to cope as compensatory response of cellular defense systems against oxidative stress, the synergistic interactive effects of pH and functionalized CNMs indicated that acidified pH significantly increased the oxidative damage (in terms of lipid peroxidation) in the cotaminated organisms. Different responses were observed in organisms submitted to pristine CNMs under pH control, where the lipid peroxidation did not increase along with the increasing exposure concentrations. The present results further demonstrated neurotoxicity caused by both CNMs, especially noticeable at acidified conditions. The mechanism of enhanced toxicity could be attributed to slighter aggregation and more suspended NMs in acidified seawater (as demonstrated by the DLS analysis). Therefore, ocean acidification may cause a higher risk of CNMs to marine ecosystems., (Copyright © 2019 Elsevier B.V. All rights reserved.)