Response of Chironomidae (Diptera) to DDT, Mercury, and Arsenic Legacy Pollution in Sediments of the Toce River (Northern Italy).

The Toce River (Northern Italy) is characterized by legacy contamination of dichloro-diphenyl-trichloroethane (DDT), mercury, and arsenic deriving from an industrial plant active between ca. 1915 and 1996. Chironomidae taxa assemblages and sediments were collected in 2014 and 2019 upstream and downstream of the industrial area to analyze species responses to toxic substances in a river stretch with relatively uniform natural (i.e., hydro-morphological) characteristics. A total of 32 chironomid taxa were identified. Sediment concentrations reached levels potentially toxic for benthic invertebrates: 15.7 µg kg-1 1% organic carbon for DDT, 197 µg kg-1 dry weight (d.w.) for Hg, and 55.7 mg kg-1 d.w. for As. Canonical Correspondence Analysis (CCA) revealed a predominant seasonal gradient, followed by an upstream-downstream gradient. Partial CCA indicated that 5.2% of the total variation was associated with sediment contamination. Self-Organizing Maps (SOMs) were used to represent species responses to toxicants. Most species appeared to be tolerant, e.g., Chironomus riparius, Micropsectra atrofasciata, Conchapelopia pallidula, and Polypedilum spp. Sensitivity to contaminants was observed in only a few species: Diamesa spp., Sympotthastia spinifera, and Prodiamesa olivacea to DDT; Potthastia longimanus to Hg; Odontomesa fulva and Microtendipes pedellus to As. The chironomid community was characterized in presence of contamination levels commonly observed in freshwater ecosystems.

PIT-tagging Italian spined loach (Cobitis bilineata): Methodology, survival and behavioural effects.

The Italian spined loach (Cobitis bilineata) is an elongated, small-sized (<12 cm) spined loach native to northern Italy, Slovenia and Croatia. As for loaches in general, little is known about the individual movements of this loach in nature. Passive integrated transponders (PIT-tags) are small (typically 7-32 mm), relatively cheap and allow tracking of individual fish movements and behaviour. A fundamental assumption in animal telemetry is that the performance of a tagged animal does not deviate substantially from its natural performance. Although PIT-tagged fish often display high survival and tag retention, the effect varies between species and contexts, and few studies have looked at behavioural effects of PIT-tagging. Here we demonstrate a PIT-tagging methodology for spined loaches, and compare survival, activity and provoked escape response (maximum swimming speed) between tagged and control fish. We also track tag retention in the tagged fish. Italian spined loaches tagged with 12 mm PIT-tags displayed high tag retention and no extra mortality, and no effects of tagging on activity or maximum swimming speed were observed. The tag-to-fish weight and length ratios in our study ranged from 2% to 5% and from 10% to 16%, respectively, and we conclude that PIT-tagging, within these ratios, appears suitable for Italian spined loach.

Vertical profiles of trace elements in a sediment core from the Lambro River (northern Italy): Historical trends and pollutant transport to the Adriatic Sea.

River sediments generally act as a sink for trace elements but, when resuspended, they contribute to long-term downstream transport of contamination, which may finally reach the marine environment. This study analyzed these processes in a complex aquatic system that includes a contaminated tributary, the Lambro River (Northern Italy) and its recipient and main Italian watercourse, the Po River, with the prodelta in the Adriatic Sea. The study was conducted from a historical perspective which, covering the last 50 years, examined the main driving events such as the inputs of contaminants, the construction of WWTPs and the evolution of environmental legislation. The time trend of trace element contamination was analyzed in a sediment core collected in the Lambro River and dated 1962-2011. The highest enrichments were found for Hg, Zn, Cu, Pb and Cd, which showed similar trends, with EF maxima in the '60s-'90s (172, 56, 40, 28 and 21, respectively), following industrial and urban development, and a general decreasing pattern after the late '90s. Only in the 2000s the ecological risk associated with metal contamination showed mean PEC Quotients stably below 1. The results of a literature survey on sedimentary trace elements in the Po River and the prodelta for the last 50 years were then compared to the Lambro sediment core. A significant contribution to Cu, Zn, Pb, Hg and Cd contamination was proved to derive from Lambro sediment transport. In the prodelta, increasing Ni and Cr concentrations were also evidenced, likely as a result of enhanced soil erosion in the Po basin. This study highlights the key role of WWTPs, of lower-impact industrial processes and of environmental legislation in reducing contaminant inputs. It also emphasizes the active contribution of riverine sediment-bound contamination to long-distance marine sediment quality.

Twenty-year sediment contamination trends in some tributaries of Lake Maggiore (Northern Italy): relation with anthropogenic factors.

Lake tributaries collect contaminants from the watershed, which may accumulate in lake sediments over time and may be removed through the outlets. DDx, PCB, PAH, PBDE, and trace element (Hg, As, Cd, Ni, Cu, Pb) contamination was analyzed over 2001-2018 period in sediments of the 5 main tributaries and of the outlet of Lake Maggiore (Northern Italy). Sediment cores were collected in two points of the lake, covering 1995-2017 period. Concentrations were compared to Sediment Quality Guidelines (PECs), potential sources and drivers (land use, population numbers, industrial activities, hydrology) were analyzed, and temporal trends were calculated (Mann-Kendall test). PCB, PBDE, Pb, Cd, and Hg contamination derives mainly from heavy urbanization and industry. Cu and Pb show a temporal decreasing trend in the basin, likely as result of improved wastewater treatments and change in use. A recent PAH increase in the whole lake may derive from a single point source. A legacy DDx and Hg industrial pollution is still present, due to high persistence in sediments. Values of DDx, Hg, Pb, and Cu above the PECs in lake sediments and/or in the outlet show potential risk for aquatic organisms. Results highlight the key role of tributaries in driving contamination from the watershed to the lake through sediment transport.

Methylmercury determination in freshwater biota and sediments: Static headspace GC-MS compared to direct mercury analyzer.

We developed and compared two analytical methods for determination of MeHg in freshwater biota and sediments, by: I) simplified static headspace GC-MS using internal standard (IS) isotope dilution quantification, after microwave acid digestion and aqueous phase NaBEt4 ethylation; II) Automated Mercury Analyzer, after double toluene extraction followed by back-extraction with L-cystein. The performance was evaluated by analysis of certified reference materials. For biota, mean recovery was 100 ± 2% and relative standard deviation (RSD) ≤ 6.8% for method I, and mean recovery was 98 ± 7% and RSD ≤13% for method II. For sediments, recovery of 94.5% and RSD of 8.8% were obtained with method I, and recovery of 90.3% and RSD of 9.4% with method II. Limits of detection (LOD) were 0.7 µg kg-1 and 6 µg kg-1, respectively. Both techniques were tested for MeHg analysis in freshwater invertebrates, fish and sediments, covering a large range of MeHg values (1.9-670 µg kg-1 d.w.). • Both protocols proved to be suitable for MeHg analysis in complex environmental matrices, even if, for method II, interferences in the extraction phase and limited sensitivity may hinder sediment analysis. • Passing-Bablock regression revealed a slight disproportion between methods, with line slope = 1.058 (95% CI ranging from 1.001 to 1.090).

Functional response of fish communities in a multistressed freshwater world.

Freshwater fish communities are impacted by multiple pressures, determining loss of functional diversity and redundancy. Our aim was to disentangle the roles and relevancies of different pressures in shaping fish communities in small streams of the Po plain (North Italy). Long term trend (1998-2018) of functional diversity of 31 fish communities was assessed and modeled in respect to three potential pressures: temperature increase, intensity of exotic fish invasion, and habitat quality degradation. Ecological traits mostly influenced by the pressures were also identified. Reduction of functional richness mostly due to local extinction or contraction of cold adapted predators, such as salmonids, was linked to increasing temperatures. Warming probably also led to a shift of generalist and dominant species, which became more abundant in streams hosting mixed communities of salmonids and cyprinids, and determined the increase of functional dispersion and uniqueness. Reduction of functional redundancy and increasing functional dispersion were both also related to the introduction of new ecological traits brought by expanding exotic species. Low functional overlap was found among native and exotic species, indicating that the invasion process was mainly controlled by competitive interactions and/or resource opportunism. Functional response to habitat quality was not clearly evident. In conclusion, the impact of temperature increase and exotic species on fish functional diversity was effective, idiosyncratic and mediated by the scale of analysis and by the intensity of pressures.

Independent and combined effects of egg pro- and anti-oxidants on gull chick phenotype.

Oviparous mothers transfer to their eggs components that have both independent and combined effects on offspring phenotype. The functional interaction between egg components, such as antioxidants and hormones, suggests that a change in the concentration of one component will have effects on offspring traits that depend on the concentration of other interacting components. However, the combined effects of variation in different egg components are virtually unknown. Bird eggs contain vitamin E, a major antioxidant, and also maternal corticosterone. The independent consequences of variation in the egg concentrations of these compounds for offspring phenotype are largely unknown and no study has investigated their combined effects. We manipulated the concentration of vitamin E and corticosterone in the eggs of the yellow-legged gull (Larus michahellis) by administering a physiological (2 s.d.) dose both independently and in combination. We tested for an effect on chick post-natal growth, plasma antioxidant capacity (TAC) and oxidative compounds (TOS). Separate administration of vitamin E or corticosterone caused a reduction in body mass relative to controls, whereas the combined administration of the two compounds reversed their negative effects. These results suggest that maternal egg components, such as antioxidants and steroid hormones, interact and mothers must balance their concentrations in order to achieve optimal offspring phenotype. The functional relationship between vitamin E and corticosterone is corroborated by the observation of positive covariation between these compounds.