The progressive increase of marine macro-litter on the bottom of the Mediterranean Sea is an urgent problem that needs accurate information and guidance to identify those areas most at risk of accumulation. In the absence of dedicated monitoring programs, an important source of opportunistic data is fishery-independent monitoring campaigns of demersal resources. These data have long been used but not yet extensively. In this paper, MEDiterranean International Trawl Survey (MEDITS) data was supplemented with 18 layers of information related to major environmental (e.g. depth, sea water and wind velocity, sea waves) and anthropogenic (e.g. river inputs, shipping lanes, urban areas and ports, fishing effort) forcings that influence seafloor macro-litter distribution. The Random Forest (RF), a machine learning approach, was applied to: i) model the distribution of several litter categories at a high spatial resolution (i.e. 1 km2); ii) identify major accumulation hot spots and their temporal trends. Results indicate that RF is a very effective approach to model the distribution of marine macro-litter and provides a consistent picture of the heterogeneous distribution of different macro-litter categories. The most critical situation in the study area was observed in the north-eastern part of the western basin. In addition, the combined analysis of weight and density data identified a tendency for lighter items to accumulate in areas (such as the northern part of the Tyrrhenian Sea) with more stagnant currents. This approach, based on georeferenced information widely available in public databases, seems a natural candidate to be applied in other basins as a support and complement tool to field monitoring activities and strategies for protection and remediation of the most impacted areas.

High altitude (alpine) lakes are efficient sentinels of environmental processes, including local pollution and long-range atmospheric transfer, because these lakes are highly vulnerable to ongoing climate changes and increasing anthropogenic pressure. Towards improving the knowledge of trace element geochemistry in the water column of alpine lakes, we assessed 64 physico-chemical parameters, including macro- and micronutrients, major and trace element concentrations in the water column of 18 lakes in the Pyrenees, located along the border between France and Spain. Lake depth, morphology, retention time and watershed rock lithology did not exhibit sizable impact on major and trace element concentrations in the water column. However, acidic (pH = 4.7 ± 0.2) lakes were distinctly different from circumneutral lakes (pH = 6.8 ± 0.5) as they exhibited >10 times higher concentrations of SO42− and trace metals (Fe, Mn, Zn, Cd, Pb, Co, Ni, Be, Al, Ga and REEs). While some of these elements clearly mark the presence of sulphide-rich minerals within the watershed (Fe, Zn, Cd and Pb), the increased mobility of lithogenic elements (Be, Al, Ga and REEs) in acidic lakes may reflect the leaching of these elements from silicate dust derived from atmospheric deposits or surrounding granites. At the same time, compared to circumneutral lakes, acidic lake water displayed lower concentrations of dissolved oxyanions (As, Mo, V, B and W) and elevated SO42− concentrations. The latter could lead to efficient Ba removal from the water column. The exploitation of metal ores within the watershed of three lakes clearly impacted high Zn and Cd concentrations observed in their water column, despite two of these lakes not being acidic. We conclude that local impacts have a greater effect on the water column than long-range atmospheric inputs and that dissolved trace element concentration measurements can be used for revealing sulphide-rich minerals or acid mine drainage within the lakes’ watershed.

International audience

A Correction to this article was published on 30 January 2024 https://doi.org/10.1007/s11356-024-32246-9 | International audience | The widespread use of copper-based pesticides, while effective in controlling plant diseases, has been identified as a major source of copper contamination in soils. This raises concerns about potential adverse effects on earthworms, key players in soil health and ecosystem function. To inform sustainable pesticide practices, this study aimed to establish copper toxicity thresholds for earthworm avoidance in agricultural soils impacted by copper-based pesticides. We collected 40 topsoil samples (0-5 cm) from orchards and vineyards in the O'Higgins Region of central Chile, and 10 additional soils under native vegetation as background references. A standardized avoidance bioassay using Eisenia fetida assessed the impact of copper-based pesticides on the soils. Total copper concentrations ranged between 23 and 566 mg kg -1 , with observed toxic effects on earthworms in certain soils. The effective concentration at 50% (EC 50 ) for total soil copper, determined by Eisenia fetida's avoidance response, was 240 mg kg -1 , with a 95% confidence interval of 193-341 mg kg -1 . We further compared our EC 50 values with existing data from agricultural soils impacted by mining activities. Interestingly, the results revealed a remarkable similarity between the thresholds for earthworm avoidance, regardless of the source of copper contamination. This observation underscores the universality of copper toxicity in agricultural ecosystems and its potential impact on soil biota. This study provides novel insights into copper toxicity thresholds for earthworms in real-world, pesticide-contaminated soils.

International audience | Our study focused on the removal of pollutants from combined sewer overflow (CSO) using aerated vertical flow wetlands (VFW). Over a 7-months period, a pilot was fed with variable inlet concentrations and hydraulic loading rates of 0.5, 1.0, and 1.5 m3.m-2. Two aeration strategies were tested, intermittent aeration and continuous aeration, and their results were compared. Online measurement of NH4-N and NO3-N helps to balance nitrogen oxidation processes during a feeding event. The average removal rates of TSS, COD, dissolved COD (CODs), and NH4-N were always above 74%. Despite continuous aeration had showed higher oxygen concentration, the percentage of untreated NH4-N leaving the filter was similar in both aeration strategies. Additionally, higher NO3-N outflow loads during continuous aeration may be explained by temperature effect. Ongoing tests aim to reach a better comprehension on nitrogen conversion processes.

Rare Earth Elements (REE) and several trace elements abundances in mussel's shells collected along the St. Lawrence River, the Estuary, and the Gulf of St. Lawrence (EGSL) reveal coherent chemical variations, with a sharp contrast between freshwater and seawater bivalves. In freshwater mussel's shells, Rare Earth Elements and Y (REY) patterns are rather flat. Their Mn and Ba concentrations are higher than those of EGSL mussel shells, which are much richer in Sr. Shale-normalized REY abundances in mussel's shells from the EGSL show positive anomalies in La and Y and well-marked negative anomalies in Ce, reflecting those of seawater. Prince Edward Island shells show light REE depletion relative to PAAS, positive La and Y anomalies, and negative Ce anomalies. Our data confirm the lack of detectable Gd pollution in the St. Lawrence River and in the EGSL, as well as Pb pollution at the mouth of the Saguenay Fjord and near Rimouski.

Staphylococcus is a significant food safety hazard. The marine environment serves as a source of food for humans and is subject to various human-induced discharges, which may contain Staphylococcus strains associated with antimicrobial resistance (AMR). The aim of this study was to assess the occurrence and geographical distribution of AMR Staphylococcus isolates in seawater and whiting (Merlangius merlangus) samples collected from the English Channel and the North Sea. We isolated and identified 238 Staphylococcus strains, including 12 coagulase-positive (CoPs) and 226 coagulase-negative (CoNs) strains. All CoPs isolates exhibited resistance to at least one of the 16 antibiotics tested. Among the CoNs strains, 52% demonstrated resistance to at least one antibiotic, and 7 isolates were classified as multi-drug resistant (MDR). In these MDR strains, we identified AMR genes that confirmed the resistance phenotype, as well as other AMR genes, such as quaternary ammonium resistance. One CoNS strain carried 9 AMR genes, including both antibiotic and biocide resistance genes. By mapping the AMR phenotypes, we demonstrated that rivers had a local influence, particularly near the English coast, on the occurrence of AMR Staphylococcus. The analysis of marine environmental parameters revealed that turbidity and phosphate concentration were implicated in the occurrence of AMR Staphylococcus. Our findings underscore the crucial role of wild whiting and seawater in the dissemination of AMR Staphylococcus within the marine environment, thereby posing a risk to human health.

International audience | The abiotic transformations of quinolones and tetracyclines facilitated by redox-active minerals has been studied extensively, however limited information is available regarding the antimicrobial activity and toxicity of their resultant transformation products. In this study, we first investigated the mechanisms underlying the transformation of two commonly used antibiotics, ciprofloxacin (CIP) and tetracycline (TC), by the ubiquitous redox soil mineral, birnessite (MnO2). Subsequently, we evaluated the impact of these transformation products on both the growth and activity of the environmental denitrifier Pseudomonas veronii. Following the reaction with birnessite, four transformation products for CIP and five for TC were identified. Remarkably, the antibacterial activity of both CIP and TC was lost upon the formation of transformation products during their interaction with birnessite. This loss of antimicrobial efficacy was associated with specific chemical transformations, such as the opening of the piperazine ring for CIP and hydroxylation and demethylation for TC. Interestingly, denitrifying activity, quantified in terms of nitrate reduction rates, remained unaffected by both CIP and TC at low concentrations that did not impact bacterial growth. However, under certain conditions, specifically at low concentrations of CIP, the second step of denitrification-nitrite reduction-was hindered, leading to the accumulation of nitrite. Our findings highlight that the transformation products induced by the mineral-mediated reactions of CIP or TC lose the initial antibacterial activity observed in the parent compounds. This research contributes valuable insights into the intricate interplay between antibiotics, redox-active minerals, and microbial activity in environmental systems.

Green tides occurrence has increased in coral reefs, yet few reference values have been documented to support bloom management in these ecosystems. Here, we took advantage of recent Ulva green tides that occurred in New Caledonia to (i) identify the elements limiting the growth of Ulva spp. during these blooms; and (ii) validate the use of isotopic markers for identifying sources of nutrients that generated blooms. N/P ratios highlighted a stronger limitation of algae by phosphorus than by nitrogen on sites under oceanic influence, while the proportions of N and P were optimal for algal growth at sites where green tides occurred. Macroalgae highly exposed to sewage water was characterized by higher δ15N than macroalgae collected in areas exposed to synthetic inorganic fertilizers. From these results, we established a new set of threshold values for using δ15N in Ulva species as an indicator of nitrogen source type in coral reefs.

The transport of non-indigenous species in ship's ballast water represents a threat to marine biodiversity. This study is the first on marine bioinvasion in Sub-Saharan Africa. The Port of Douala (PoD), located in the Gulf of Guinea, is experiencing increasing maritime traffic, hence the importance of preventing biological invasions. PoD received ballast water from 41 ports and 20 ecoregions during the study period (2018–2021). We used a biological invasion model and showed that ships from the ports of Antwerp, Durban, Dar es Salaam, Pointe-Noire (Southern Gulf of Guinea) and Dakar (Sahelian Upwelling), with their associated ecoregions present a major invasion risk. Treating ballast water from these ships to IMO D-2 standards could reduce their probability of biological invasion by 97.18, 98.43, 98.80, 98.77 and 98.84 %, respectively. Climate change may also mitigate the risk of biological invasion, particularly for ships in the North Sea ecoregion from the port of Antwerp.