Biological responses of the polychaete Hediste diversicolor (O.F.Müller, 1776) to inorganic mercury exposure: A multimarker approach.

Mercury (Hg) is a global priority pollutant given its relevance in terms of environmental damage and threat to human health. Its ecotoxicity was tested using the benthic keystone species Hediste diversicolor as target species. After 10 days of exposure to different levels of inorganic Hg (10 and 50 µg L-1), bioaccumulation and a wide range of biological responses were evaluated at different biological levels, including biomarkers of exposure, neurotoxicity, oxidative stress, genotoxicity and cytochemistry. In controlled laboratory conditions, Hg was taken up by H. diversicolor in a dose-response manner and caused a range of biological responses, including oxidative stress (GSTs, GPx, GSH-2GSSG, and TOSCA), neurotoxicity (AChE), and cellular damages at the membrane level (LFs, NLs, Ca2+-ATPase); however, it did not cause significant DNA damage or mortality. This study confirms the capability of H. diversicolor to tolerate high levels of metals and clarifies the mechanisms underlying the damage caused by waterborne Hg and the defense mechanisms, activated in this species. In particular, detoxification of the inorganic form of Hg in this species was found to be strongly related to glutathione expression and several antioxidant enzymes of the antioxidant system. This process also efficiently minimized negative effects on DNA and prevented death, but was not sufficient to avoid neurotoxicity and some cellular damages, mainly at the intestinal level.

Temporal evolution of the environmental quality of the Vallona Lagoon (Northern Mediterranean, Adriatic Sea).

Guidance Document 25/2010, suggests sediment and biota are the most suitable matrices for the trend monitoring purpose, because they integrate the pollution over time and space. So, from 2005 to 2014, the sediment and biota concentrations of heavy metals (As, Cd, Cr, Hg, Ni, Pb) were analysed in the Vallona Lagoon (northern Adriatic Sea, Italy), widely used for intensive and extensive bivalve farming. The contamination levels in sediment and biota were compared with Environmental Quality Standard (EQS) and threshold levels (TL) for human health. The results identified critical issues related to Cd in sediment samples as well as to Hg and Pb in biota which were not only ascribable to the physiological and seasonal variability of organisms. The Cr and Ni levels in sediment were higher than the EQS. However, the concentration increases at biota stations close to sites where EQS excesses were observed in sediment were not verified.

Toxicity evaluation of diethylene glycol and its combined effects with produced waters of off-shore gas platforms in the Adriatic Sea (Italy): bioassays with marine/estuarine species.

Diethylene glycol (DEG) is commonly used to dehydrate natural gas in off-shore extraction plants and to prevent formation of gas hydrates. It may be released into the sea accidentally or in discharged produced waters (PWs). PWs samples from off-shore gas platforms in the Adriatic Sea (Italy) have been used in this study. The objectives of the study were: a) to evaluate the toxicity of DEG for marine organisms; b) to evaluate if a high DEG content in PWs may alter their toxicity; c) to verify whether the DEG threshold concentration established by the Italian legislation (3.5 g/l) for PWs discharged at sea is safe for marine environment. Ten different species (Vibrio fischeri, Phaeodactylum tricornutum, Dunaliella tertiolecta, Brachionus plicatilis, Artemia franciscana, Tigropus fulvus, Mytilus galloprovincialis, Crassostrea gigas, Tapes philippinarum and Dicentrarchus labrax) have been exposed to DEG; four of these species were also exposed to PWs in combination with DEG. The results showed that: a) DEG is not toxic at levels normally detected in Adriatic PWs; b) DEG in combination with PW showed mainly additive or synergistic effects; c) short-term bioassays showed that the DEG limit of 3.5 g/l could be acceptable.

An ecotoxicological protocol with caged mussels, Mytilus galloprovincialis, for monitoring the impact of an offshore platform in the Adriatic Sea.

An ecotoxicological protocol with caged mussels, Mytilus galloprovincialis, was developed to evaluate the potential impact of an offshore gas platform in the central Adriatic Sea. Reference organisms were collected on a seasonal basis from an unpolluted site and transplanted for four weeks in both the sampling area and to the investigated platform. Chemical analyses of trace metals in mussel tissues were integrated with a multi-biomarker approach for the early detection of biological responses at several cellular targets. Induction of metallothioneins, peroxisomal proliferation and activity of acetylcholinesterase were measured as markers for specific classes of chemicals. Special attention was given to oxyradical metabolism and appearance of oxidative-mediated toxicity to reveal a more general onset of cellular disturbance. In addition to individual antioxidants (superoxide dismutase, catalase, glutathione S-transferases, glutathione reductase, Se-dependent and Se-independent glutathione peroxidases, and levels of total glutathione), the total oxyradical scavenging capacity (TOSC) allowed a quantification of the overall capability to neutralize specific forms of intracellular reactive oxygen species (ROS; i.e. peroxyl and hydroxyl radicals). Cellular damages were evaluated as lysosomal destabilization (membrane stability, accumulation of lipofuscin and neutral lipids), lipid peroxidation products (malondialdehyde) and DNA integrity (strand breaks and micronuclei); the air survival test was finally applied to evaluate the overall physiological condition of mussels. Concentration of trace metals (As, Ba, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Zn) revealed only limited variations in transplanted mussels during various experimental periods and such changes appeared partly related to natural fluctuations. Among biological responses, variations of antioxidants and lysosomal stability were confirmed as sensitive early warning signals for biological disturbance of both natural and anthropogenic origin. The presented protocol with caged mussels allowed marked biological effects caused by the investigated platform to be excluded, and represented a useful approach that is easy to extend for monitoring the impact of offshore activities in the Adriatic sea.

Application of biomarkers for assessing the biological impact of dredged materials in the Mediterranean: the relationship between antioxidant responses and susceptibility to oxidative stress in the red mullet (Mullus barbatus).

In the period 1997-2000, approximately 1,800,000 m3 of material dredged from the Port of Leghorn was discharged into a sea dumping site located 14 miles from the coast. The red mullet (Mullus barbatus) was used as a bioindicator species for monitoring the biological impact of these discharges on a geographical and temporal scale. Organisms were sampled over three years (1998-2000) at different stations and several biomarkers, both of exposure and effect, were analyzed. Bioavailability of specific classes of pollutants was evaluated by analyzing levels of metallothioneins, the activity of cytochrome P450 1A (CYPIA) and of glutathione S-transferases. Among biomarkers of effect, special attention was paid to the balance between prooxidant challenge and antioxidant defenses, and to the appearance of damage caused by oxidative stress. The analyses of the main components of the antioxidant system included superoxide dismutase, catalase, glutathione peroxidases, glutathione reductase, glyoxalase I and II, and total glutathione. These data were integrated with the measurement of total oxyradical scavenging capacity (TOSC) as an indication of the overall biological resistance to toxicity of different forms of oxyradicals (peroxyl radicals, hydroxyl radicals and peroxynitrite). Results indicated a biological impact in organisms sampled near the disposal site; the impact was particularly evident during 1999 and mainly related to organic chemicals such as PAH. Exposure to these pollutants also caused variations in the levels and activity of several antioxidants. The analysis of TOSC, however, revealed that the overall capacity of specific tissues of organisms to absorb various oxidants was not seriously compromised when challenged with increased prooxidant pressures. Variations of single antioxidants were useful in revealing early warning "biological responses", while integration with TOSC analyses indicated if such changes also reflect a more integrated and functional "biological effect" with possible consequences at the organisms level. The red mullet appears to be a useful sentinel species for a biomarker approach to monitoring impact caused by dredged materials.