Behavioural and biochemical alterations in gammarids as induced by chronic metallic exposures (Cd, Cu and Pb): Implications for freshwater biomonitoring

Acute and chronic toxicity of rare earth elements-enriched sediments from a prospective mining area: Effects on life history traits, behavioural and physiological responses of Gammarus fossarum (Crustacea Amphipoda)

Rare earth elements (REE) have an essential role and growing importance in the world's economy. They are attracting interest from society, policymakers, and scientists. The rapidly growing global demand for REE in several strategic industrial and agricultural sectors led many countries to consider the (re)-opening of mining activities for REE extraction. Hence, their increasing use led to the disruption of their biogeochemical cycles with anthropic abnormalities already observed in aquatic ecosystems. Nonetheless, REE remain less studied, and their mechanisms of toxicity actions are not fully understood. As amphipods, Gammarus fossarum represent an important part of the aquatic macroinvertebrate assemblage and are generally used in ecotoxicological studies for their high ecological relevance. However, their use for the study of REE effects has been rather limited so far. The current study aims to assess the potential effects of two naturally REE-enriched sediments (N2 and B4) on G. fossarum. Effects on life history traits, behavioural and physiological responses have been evaluated. Exposing G. fossarum males for 72h to sediments N2 and B4 led to a decrease in haemolymph osmolality and locomotion while an increase in ventilatory activity was observed. Exposing G. fossarum pre-copula pairs with females at the same reproductive stage to the naturally REE-enriched sediments, for one moult cycle duration (∼30 days) showed that sediment B4 led to i) a significant uptake of REE, ii) a significant decrease in the proportion of females with oocytes and iii) a significant reduction in the total number of juveniles. The physicochemical analyses of sediments showed that B4 contains the highest amount of REE with a higher proportion of light REE. The present study gives the first insights into the potential toxicity of REE on G. fossarum as they may have deleterious effects on G. fossarum population's dynamics, which may alter the functioning of aquatic ecosystems.

Toxic effects of trace metal(loid) mixtures on aquatic organisms

The co-occurrence of metal (loid)s in realistic aquatic environments necessitates the evaluation of their combined effects. However, the generality of the additive effect hypothesis is contentious, particularly due to metal(loid)-metal(loid) interactions. The absence of systematic evaluation approaches restricts our ability to draw overall conclusions and make reliable predictions. In this study, we reviewed 1473 effect sizes from 38 publications, and classified all responses into seven main categories (from molecular to individual levels) according to their toxicological significance. Our meta-analysis revealed that metal(loid) mixtures had significant effects on aquatic organisms (33 %, 95 % CI 28 %-39 %, P < 0.05), along with significant response heterogeneity (Qt = 690,319.62, P < 0.0001; I2 = 99.95 %). Concurrently, we developed a Random Forest machine learning model to predict adverse effects and identify key variables. These two methods demonstrated that the toxicity of metal(loid) mixtures is primarily linked to the choice of toxicity endpoints, and the characteristics of metal(loid) mixtures. Our findings underscore the potential of combining meta-analysis with machine learning, a more systematic approach, to enhance the understanding and prediction of the adverse effects of metal(loid) mixtures, and they offer guidance for risk assessment and policy-making in complex environmental scenarios.

Individual and combined impact of microplastics and lead acetate on the freshwater shrimp (Caridina fossarum): Biochemical effects and physiological responses

Microplastics and heavy metals pollution is recognised as a major problem affecting aquatic ecosystems. For this reason, this study aims to assess the toxicity of different concentrations of polyethylene microplastics (PE-MPs) (0.0, 500, and 1000 μg L-1) with a mean size of 15-25 μm and lead acetate Pb(C2H3O2)2 (0.0, 2.5, and 5 mg L-1), both individually and in combination, through the exposure of the freshwater grass shrimp, Caridinia fossarum for 15 days, focusing on microplastic interaction with co-occurring contaminants. After being exposed to both contaminants, either individually or in combination, significant alterations in numerous biochemical markers were observed. Specifically, exposure to lead acetate alone resulted in significant changes across ALP, AST, ALT, LDH, GGT, and BChE enzyme activity levels indicating hepatotoxicity and neurotoxicity. Also, Pb exposure led to alterations in total antioxidant capacity, MDA, total lipids, and glycogen contents, signalling the onset of oxidative stress. Exposure to PE-MPs alone led to changes in ALP, LDH, GGT, and BChE enzyme levels, and in MDA, total lipids, and glycogen samples' contents. Remarkably, the study observed increased bioaccumulation of lead acetate in samples treated with the combination, emphasizing the synergistic impact of PE-MPs on the toxicity of lead acetate. This synergy was also evident in AST and ALT enzyme activity levels and MDA contents. This underscores the necessity for measures to address both microplastic pollution and heavy metal contamination, taking into account the synergistic behaviour of MPs in the presence of concurrent contaminants.

Current Status of Omics in Biological Quality Elements for Freshwater Biomonitoring

Freshwater ecosystems have been experiencing various forms of threats, mainly since the last century. The severity of this adverse scenario presents unprecedented challenges to human health, water supply, agriculture, forestry, ecological systems, and biodiversity, among other areas. Despite the progress made in various biomonitoring techniques tailored to specific countries and biotic communities, significant constraints exist, particularly in assessing and quantifying biodiversity and its interplay with detrimental factors. Incorporating modern techniques into biomonitoring methodologies presents a challenging topic with multiple perspectives and assertions. This review aims to present a comprehensive overview of the contemporary advancements in freshwater biomonitoring, specifically by utilizing omics methodologies such as genomics, metagenomics, transcriptomics, proteomics, metabolomics, and multi-omics. The present study aims to elucidate the rationale behind the imperative need for modernization in this field. This will be achieved by presenting case studies, examining the diverse range of organisms that have been studied, and evaluating the potential benefits and drawbacks associated with the utilization of these methodologies. The utilization of advanced high-throughput bioinformatics techniques represents a sophisticated approach that necessitates a significant departure from the conventional practices of contemporary freshwater biomonitoring. The significant contributions of omics techniques in the context of biological quality elements (BQEs) and their interpretations in ecological problems are crucial for biomonitoring programs. Such contributions are primarily attributed to the previously overlooked identification of interactions between different levels of biological organization and their responses, isolated and combined, to specific critical conditions.

Heavy metals and metalloid in aquatic invertebrates: A review of single/mixed forms, combination with other pollutants, and environmental factors

Heavy metals (HMs) and metalloid occur naturally and are found throughout the Earth's crust but they are discharged into aquatic environments at high concentrations by human activities, increasing heavy metal pollution. HMs can bioaccumulate in higher organisms through the food web and consequently affect humans. In an aquatic environment, various HMs mixtures can be present. Furthermore, HMs adsorb on other environmental pollutants, such as microplastics and persistent organic pollutants, causing a synergistic or antagonistic effect on aquatic organisms. Therefore, to understand the biological and physiological effects of HMs on aquatic organisms, it is important to evaluate the effects of exposure to combinations of complex HM mixtures and/or pollutants and other environmental factors. Aquatic invertebrates occupy an important niche in the aquatic food chain as the main energy link between higher and lower organisms. The distribution of heavy metals and the resulting toxic effects in aquatic invertebrates have been extensively studied, but few reports have dealt with the relationship between HMs, pollutants, and environmental factors in biological systems with regard to biological availability and toxicity. This review describes the overall properties of individual HM and their effects on aquatic invertebrates and comprehensively reviews physiological and biochemical endpoints in aquatic invertebrates depending on interactions among HMs, other pollutants, and environmental factors.

Screening potential toxicity of currently used herbicides in the freshwater amphipod Gammarus fossarum based on multi-level biomarker responses to field-realistic exposures

Herbicides are widely used to control weeds and maximize crop growth. Because of agricultural runoff, these chemicals are potentially hazardous to aquatic wildlife. However, their ecotoxicity and resulting disturbance in individual performance remain scarcely documented in freshwater crustaceans. This study aimed to screen the potential toxicity of currently used herbicides in the ecosystem engineer Gammarus fossarum using multi-level biomarkers. In microcosms, gammarids were exposed for 72 h to 12 herbicides individually (quinmerac, mesotrione, bentazone, isoproturon, chlortoluron, metazachlor, chloridazone, diflufenican, flufenacet, aclonifen, prosulfocarb and metolachlor) at a field-realistic concentration (i.e. 10 μg/L). The sublethal effects were assessed by monitoring several biochemical, physiological and behavioural traits. In exposed gammarids, alterations in behavioural activities were observed, i.e. increased locomotion and respiration as a general trend. Moreover, biochemical biomarkers suggested herbicide-dependent disruptions in moulting, antioxidant responses and cell integrity. Integrating multi-metric variations through statistical analyses allowed us to identify herbicide clusters likely to trigger common sets of biological responses. Depressed antioxidant defence at the cell level and impaired respiration at the individual level were the predominant toxic effects of herbicides, related to their hydrophobic feature. Furthermore, establishing relationships between sublethal alterations in gammarids and acute lethality or chronic toxicity values defined for regulatory purposes supports the relevance of these alterations as early warnings of toxicity. Our findings demonstrate that currently used herbicides have unexpected toxicological effects in a non-target wild animal, with possible long-term alterations in population dynamics and associated ecological functions, which constitute promising diagnostic tools for risk assessment in agricultural areas.

Individual performances and biochemical pathways as altered by field-realistic exposures of current-use fungicides and their mixtures in a non-target species, Gammarus fossarum

Persistent fungicides, which are widely applied to agricultural soils to protect crops, are frequently detected in freshwaters because of hydraulic transfer, possibly resulting in unintentional adverse effects on wildlife. However, the ecotoxicity of fungicides in aquatic species remains scarcely assessed at environmentally relevant concentrations, and there is scant information available on their combined effects. This study aims at investigating multi-level changes elicited by two currently used fungicides, boscalid and tebuconazole, in the amphipod Gammarus fossarum. In microcosms, gammarids were exposed for 72 h to fungicides tested individually or in binary mixture at 0.01, 0.1 and 1.0 μg/L to monitor individual performances (locomotion, respiration and amplexus formation) and biochemical parameters (involved in energy metabolism, growth, moulting and cell stress). This range of exposure concentrations was field-realistic and largely lower than local environmental quality standards for the protection of aquatic wildlife. Overall, results showed that single and combined exposures altered the mobility and respiratory activity of individuals. At the cellular level, boscalid inhibited energy-based biomarkers whereas tebuconazole led to cytotoxicity associated with reduced antioxidant defences. In binary mixtures, the biochemical responses were mainly driven by the presence of boscalid. Multi-variable analyses, integrating individual alterations and cellular impairments alike, confirmed the relevance of the multi-level approach in forecasting the toxicity of fungicides and their mixtures towards other aquatic species. This study demonstrates dose-related sublethal effects of fungicides on multiple functional traits in an ecosystem engineer under realistic exposure scenarios, highlighting the harmful signs of these toxicants. Such sublethal alterations could thus constitute reliable tools for the early diagnosis of the organisms' health and the ecological status of agriculturally impacted hydrosystems.

Inorganic mercury effects on biomarker gene expressions of a freshwater amphipod at two temperatures

Mercury (Hg) is a global contaminant resulting of both natural processes and human activities. In aquatic environments, studies conducted on vertebrates highlighted changes of gene expression or activity of antitoxic and oxidative enzymes. However, although Hg is a highly toxic compound in aquatic environments, only a few studies have evaluated the lethal and sublethal effects of inorganic Hg on Gammarus sp. Therefore, this study aimed at evaluating the effects of inorganic Hg (HgCl₂) on the expression of 17 genes involved in crucial biological functions or mechanisms for organisms, namely respiration, osmoregulation, apoptosis, immune and endocrine system, and antioxidative and antitoxic defence systems. The study was performed in males of the freshwater amphipod Gammarus pulex exposed to two environmentally relevant concentrations (50 and 500 ng/L) at two temperature regime fluctuations (16 °C and 20 °C +/-2 °C) for 7 and 21 days. Results showed that G. pulex mortality was dependent on Hg concentration and temperature; the higher the concentration and temperature, the higher the mortality rate. In addition, the Integrated Biomarker Response emphasized that HgCl₂ toxicity was dependent on the concentration, time and temperature of exposure. Overall, antioxidant and antitoxic defences, as well as the endocrine and immune systems, were the biological functions most impacted by Hg exposure (based on the concentration, duration, and temperature tested). Conversely, osmoregulation was the least affected biological function. The results also demonstrated a possible adaptation of G. pulex after 21 days at 500 ng/L, regardless of the exposure temperature. This study allowed us to show that Hg deregulates many crucial biological functions after a short exposure, but that during a long exposure, an adaptation phenomenon could occur, regardless of temperature.