This study investigates the chronology of copper (Cu) contamination and its stable isotopes within an emblematic Brazilian mangrove impacted by multiple urban and industrial Cu sources, deforestation, and eutrophication. In particular, it tests Cu isotopes as tracers of anthropogenic inputs into an anthropized watershed impacted by multiple sources. To do so, we used multi-isotopic approaches (δ65Cu, δ13C, and δ15N), elemental analyses (Al, Ca, Fe, P, Cu, C, and N), and selective and sequential extractions in a210Pb-dated sediment core. This geochemical "toolbox" allowed identifying two main stages of Cu evolution in the sediment core. In the first stage, before 1965, Cu isotope fingerprints responded to landscape changes, indicating a shift from marine to geogenic dominance due to the remobilization and erosion of terrestrial materials. In the second stage, after 1965, the sediment geochemical profile showed increased Cu total concentrations with a higher bioavailability (as reflected by sequential extraction data) accompanying changes in Cu isotope signatures towards anthropogenic values. The findings evidence that local industrial sources, possibly combined with diffuse urban sources, export Cu into downstream mangroves with a distinguishable isotope signature compared to natural values. This study demonstrates the applicability of Cu isotopes as new environmental forensic tools to trace anthropogenic sources in mangrove sediments. Incorporated into a robust geochemical toolbox that combines inorganic and organic proxies for sedimentary materials, this new tool provides a comprehensive understanding of Cu dynamics in mangrove ecosystems, shedding light on the historical and current sources of Cu.

International audience | In the Algerian Sahara, non-renewable groundwater resources estimated at 5 billion m3 thus constitute the indispensable support for irrigation. In the Berriane region in the north of Ghardaïa region (center of Algerian Sahara), an agricultural perimeter called Oued El Bir (300 ha in total) was officially created in 2013 downstream a wastewater treatment plant. A “frontier settlement” that proves the high value placed on this resource.As part of Massire project financed by IFAD (2018-2024), the objective of our study was to analyze the water reuse practices in this Berriane arid region, i.e. to study the importance of the institutional management of the treated wastewater reuse on the one hand. And on the other hand to show that the malfunctioning of the wastewater treatment plants can lead to many side effects such as the infiltration of raw sewage into the groundwater, illicit untreated wastewater irrigation and a slowdown in the development of the agricultural perimeter. Our research methodology is founded, firstly, on interviews with the local stakeholders (about 20 surveys with farmers and local institutions) and, secondly, on isotopic, chemical and biological water analyses that will be carried out soon to validate the hypothesis of infiltration of wastewater into the aquifer. In addition, to address the institutional opposition and issues relating to the technical sustainability of water reuse in the region, we implemented a water reuse demonstrator. The choice of location and equipment was determined in concertation with local stakeholders. The decentralized treatment process is based on a septic tank and a fixed bacterial filter (Advanced Enviro Septic) with 10 m3/day capacity. The treated wastewaters are used to irrigate a 1 ha surface of the new oasis area. As part of our study, we are investigating the sanitary and agronomic safety of this new treatment process for water reuse in the arid context.

Anthropogenic pollutants are near-ubiquitous in aquatic systems. Aquatic animals such as fishes are subject to physiological stress induced by pollution present in aquatic systems, which can translate to changes in behaviour. Key adaptive behaviours such as shoaling and schooling may be subject to change as a result of physiological or metabolic stress or neurosensory impacts of pollution. This can result in fitness and ecological impacts such as increased predation risk and reduced foraging success. Here, we conducted a systematic metanalysis of the existing literature, comprising 165 studies, on the effects of anthropogenic pollution on sociability and group cohesion in fish species. Both organic (number of studies = 92, posterior mean (PM) = -0.483, p < 0.001) and inorganic (n = 24, PM = -0.697, p < 0.05) chemical pollutants, as well as light exposure (n = 21, PM = -3.176, p < 0.01) were found to reduce sociability. These pollutants did not reduce group cohesion, indicating that effects may be masked in group settings, though fewer studies were carried out on group cohesion and this is a key area for future research. Mixtures of chemical pollutants (n = 16) were found to reduce cohesion (PM = -45.42, p < 0.01), but increase sociability (PM = 46.00, p < 0.01). Evidence was found that fish may behaviourally acclimate to two forms of pollutant, namely mixed chemical pollutants (PM = -0.693, p < 0.05) and noise exposure (n = 22, PM = -4.059, p < 0.05). While aquatic systems are often subject to pollution from multiple sources and of multiple types, very few studies investigated the effects of multiple stressors concurrently. This review identifies trends in the existing literature, and highlights areas where further research is required in order to understand the behavioural and ecological impacts of anthropogenic pollutants in aquatic systems.

Small pelagics are small fish species often schooling that mainly feed on planktonic organisms and are foraging species of larger animals. These species have experienced important declines in their wild populations during the last decades. For instance, the decrease of the European sardine (Sardina pilchardus) body condition has had a detrimental impact on its landings, leaving their commercial fishing unprofitable in some Mediterranean areas. The causes for this decline are not clearly established but seems to be mainly related to changes with planktonic communities inducing a switch in their foraging behaviour from particulate-feeding to filter-feeding. Moreover, it has been highlighted that sardines ingest plastic fibres throughout their natural spatial distribution, suggesting this additional pollution as a possible new threat affecting their populations’ health. In this study we developped an experimental setup allowing us to maintain wild fish in captive controlled conditions in order to test the possible factors affecting plastic fibres ingestion in sardines. We demonstrate that sardines ingest fibres from water, and the amount of fibres ingested is highly impacted by their feeding behaviour. Sardines feeding by filtration ingest less food but more plastic fibres (mean = 4.95 fibres / ind; SD = 3.43), compared to sardines that feed by particulate-feeding (mean = 0.6 fibres / ind; SD = 1.04). Moreover, a decrease in sardine body condition factor was detected for filter-feeding individuals, mostly linked to the lower amount of food they ingested rather than to the fibre ingestion itself. Nonetheless, higher water temperature seems to accelerate the pattern of fibre expulsion in filter-feeding sardines. Alltogether, it is suggested that plastic fibres pollution and phytoplanctonic changes under global change, might synergistically act at disturbing the health of this species in wild populations.

The behavior, and history of lead (Pb) contamination in the ecosystem of the Loire estuary was examined using elemental concentrations and Pb isotope data in water, sediment, bivalves, shrimps, and fish. In the estuary and in the surrounding coastal area, Pb concentrations in water and sediment decreased compared to concentrations determined in the 1980s, with concentrations ranging from 15.8 to 65.7 mg kg−1 in the surface sediment, 0.04–0.26 nM in the water column, and 48.0–77.9 mg kg−1 in suspended particles. Pb biomonitoring using blue mussels collected by the French Mussel Watch Program over the last 40 years showed a concentration decrease from 3.8 to 0.8 mg kg−1. A similar trend is observed in an estuarine sediment core. Changes in accompanying Pb isotope compositions strongly suggest a binary mixing process between Pb derived from terrigenous material and anthropogenic sources. Thus, environmental regulations restricting the release of lead into the environment contribute to a decrease in estuarine levels of this pollutant, which occurs on a decadal time scale.

Polycyclic aromatic hydrocarbons (PAHs) are one of the most common groups of pollutants that have toxic and carcinogenic effects. Black alder trees (Alnus glutinosa L.) have been used to remediate contaminated soils from industrial pollutants and heavy metals; however, their usefulness for PAH remediation is unclear. In this study, we examined the response of seedlings from four alder half-sib families (genetic groups sharing the same mother but different fathers) to exposure to four PAHs—phenanthrene, pyrene, naphthalene, and fluoranthene—each at three concentrations. Plant growth parameters were evaluated, and concentration of secondary metabolites and antioxidant activity were measured. The results of the morphological parameters showed that in general, higher PAH concentrations had a more negative effect on tree vitality than lower concentrations (shoot growth reduction by up to 76%). Each half-sib family also exhibited distinct responses in total phenol content (TPC) when exposed to varying concentrations of pollutants, with reductions in TPC ranging from 4 to 52% across different genetic lineages. Enzyme activity also varied between families, pollutants, and their concentrations; for example, while phenanthrene generally increased glutathione S-transferase (GST) activity in the 13–99-1K and 38–61-7K half-sib families, it unexpectedly decreased GST levels by 23% and 29% in the seedlings of the 26–133-6K and 41–65-7K families, respectively, emphasizing the nuanced and divergent enzymatic responses observed in this study. Further secondary metabolite and antioxidant activity analysis revealed distinct variations in the way PAHs impact the defense mechanism of alder seedlings from different genetic groups—prioritizing either enzymatic or non-enzymatic systems. To sum up, analyzing the varying effects of PAHs on distinct half-sib families of alders can prove advantageous in identifying the most efficient black alder genetic families for phytoremediation purposes.

International audience | Although coastal ecosystems are naturally submitted to temporal variations of salinity, salinization has been increasing over time threatening coastal biodiversity. Species that exploit such habitats can thus be exposed to brackish water at different life stages. However, the impacts of variations of salinity on wildlife remain poorly understood. This is particularly true for coastal amphibians, due to the strong dependency of early life stages (embryos and larvae) on aquatic environments. In order to investigate the effect of salinity during egg laying and embryonic and larval development of coastal amphibians, we used a full-factorial design to expose reproductive adults, eggs, and larvae of coastal spined toads (Bufo spinosus) to fresh (0 g.l⁻¹) or brackish water (4 g.l⁻¹). At egg laying, we evaluated parental investment in reproduction. During embryonic and larval development, we assessed effects on survival, development, and growth. We highlighted strong effects of environmental salinity on reproduction (reduced egg laying time, marginally reduced egg size, and reduced investment in reproduction). Responses to salinity were highly dependent on the developmental stages of exposure (stronger effects when individuals were exposed during embryonic development). These effects carried over when exposure occurred at egg laying or during embryonic development, highlighting the importance of the environmental conditions during early life on ontogenetic trajectories. We also highlighted partial compensation when individuals were transferred back to freshwater. Whether the magnitude of these responses can allow coastal biodiversity to overcome the observed detrimental effects of salinization remain to be assessed.

International audience | The placing of plant protection products (PPPs) on the market in the European Union is governed by numerous regulations. These regulations are among the most stringent in the world, however they have been the subject of criticisms especially because of the decline in biodiversity. The objectives of this work were to review (1) the functioning and actors involved in the PPP framework processes, (2) the construction of the environmental risk assessment focused on biodiversity, and (3) the suggested ways to respond to the identified limits. Both literature from social sciences and ecotoxicology were examined. Despite the protective nature of the European regulation on PPPs, the very imperfect consideration of biodiversity in the evaluation process was underlined. The main limits are the multiplicity of applicable rules, the routinization of the evaluation procedures, the lack of consideration of social data, and the lack of independence of the evaluation. Strengths of the regulation are the decision to integrate a systemic approach in the evaluation of PPPs, the development of modeling tools, and the phytopharmacovigilance systems. The avenues for improvement concern the realism of the risk assessment (species used, cocktail effects…), a greater transparency and independence in the conduct of evaluations, and the opening of the evaluation and decision-making processes to actors such as beekeepers or NGOs. Truly interdisciplinary reflections crossing the functioning of the living world, its alteration by PPPs, and how these elements question the users of PPPs would allow to specify social actions, public policies, and their regulation to better protect biodiversity.

Watersheds and estuaries are impacted by multiple anthropogenic stressors that affect their biodiversity and functioning. Assessing their ecological quality has consequently remained challenging for scientists and stakeholders. In this paper, we propose a multidisciplinary approach to identify the stressors in seven small French estuaries located in agricultural watersheds. We collected data from landscape (geography, hydrobiology) to estuary (pollutant chemistry) and fish individual scales (environmental signatures, proteomics). This integrative approach focused on the whole hydrosystems, from river basins to estuaries. To characterize each watershed, we attempted to determine the land use considering geographic indicators (agricultural and urbanised surfaces) and landscape patterns (hedges density and riparian vegetation). Juveniles of European flounder (Platichthys flesus) were captured in September, after an average residence of five summer months in the estuary. Analyses of water, sediments and biota allowed to determine the concentrations of dissolved inorganic nitrogen species, pesticides and trace elements in the systems. Environmental signatures were also measured in flounder tissues. These environmental parameters were used to establish a typology of the watersheds. Furthermore, data from proteomics on fish liver were combined with environmental signatures to determine the responses of fish to stressors in their environments. Differential protein abundances highlighted a dysregulation related to the detoxification of xenobiotics (mainly pesticides) in agricultural watersheds, characterized by intensive cereal and vegetable crops and high livestock. Omics also revealed a dysregulation of proteins associated with the response to hypoxia and heat stress in some estuaries. Furthermore, we highlighted a dysregulation of proteins involved in urea cycle, immunity and metabolism of fatty acids in several systems. Finally, the combination of environmental and molecular signatures appears to be a relevant method to identify the major stressors operating within hydrosystems.

In order to reduce the contamination of marine ecosystems by plastic materials, the scientific community is engaged in the development of biodegradable substitutes for conventional plastics. While certain candidates have been successfully tested in coastal marine environments, the degradation process in deep-sea environments remains poorly understood. This study examined the degradation of two industrial biopolyesters, a poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and a polybutylene-succinate (PBS), in two deep marine environments of the Middle and Eastern Atlantic, at depths of 780 and 1740 m, as well as under laboratory conditions under hydrostatic pressure and without micro-organisms. The findings reveal a considerable biodeterioration of PHBV and a pronounced influence of flax fibre reinforcement on the degradation mechanisms. Conversely, PBS exhibits minimal to no indications of degradation. Additionally, the results confirm that biotic factors are the primary determinants of the degradation processes, with no degradation observed under abiotic conditions.