The extensive oil exploration has led to a series of environmental issues worldwide, over the years. In the last decades, great attention has been paid to the impact of oil refinery wastewaters and discharged effluents, which are released to the environment as gases, particles, sludge, and liquid effluents. They thus represent potential sources of petrochemical pollution, which can have many deleterious effects such as a reduction in marine diversity and ecosystem function. In environmental biomonitoring programmes, marine mussels have been routinely used as bioindicator species because of their propensity to bioaccumulate toxic compounds and their tolerance towards a wide range of environmental conditions. With the aim of recovering an ecosystem disturbed by petrochemical pollution, within the national project PRIN 2010-2011 (prot. 2010ARBLT7_001/008) bioremediation technologies were applied as water and sediment recovery strategies. Specifically, controlled mesocosm-scale experiments were conducted to measure the effects on mussels Mytilus galloprovincialis of different remediation actions on petrochemical-polluted waters and sediments collected from a contaminated area in Augusta (eastern Sicily, Italy). Both for water and sediments, three different environmental conditions were simulated: a control area (W, white group), a petrochemical polluted area (B, black group), and a polluted area subjected to remediation actions (G, grey group). Mussels were exposed to each condition for 15 days, and then the biological effects of biotechnological actions for the potential recovery of petrochemical contamination were evaluated by a multi-biomarkers approach, including histology, metabolomics, immunohistochemistry, and enzymatic investigations. Mussel gills, mainly involved in nutrient uptake and gas exchange, were chosen as target organs. In respect to the white group, the gills of mussels from the black mesocosms, both for water and sediments, displayed marked morphological alterations with intense hemocytic infiltration. Protonic nuclear magnetic resonance (1H NMR)-based metabolomics, which has shown considerable potential as a powerful tool for environmental monitoring studies, was also herein applied on mussel gills. 1H NMR-based metabolomics, associated with chemiometrics analyses, highlighted changes in metabolites involved in different metabolic pathways, i.e. cellular defense, osmoregulation, energy metabolism, and neurotransmission. Alterations in serotoninergic (i.e. serotonin, 5-HT, and its receptor, 5-HT3R) and cholinergic (i.e. acetylcholinesterase, AChE, and acetylcholintransferase, ChAT) systems were observed in mussel gills from the black group by immunohistochemical investigation, as well as supported by enzymatic analysis of AChE activity and metabolomics, which revealed changes in some neurotransmitters. Conversely, in the grey mesocosms, after applying the same battery of biomarkers and methodological approaches, it was possible to observe a general recovery trend in mussel gills. Overall, the application of environmental metabolomics, in conjunction with a multi-biomarker panel, results effective in assessing the environmental influences of petrochemical pollutants on the health of aquatic organisms. Moreover, findings from this study demonstrated that the remediation actions herein applied on petrochemical-polluted waters and sediments might be able to recover an ecosystem impacted by petrochemical pollution, and may be useful to develop a sustainable waste management.
3b. Life below water
