Bioaccumulation and Dispersion of Uranium by Freshwater Organisms

A biodynamic model predicting copper and cadmium bioaccumulation in caddisflies: Linkages between field studies and laboratory exposures

Hydropsyche and Arctopsyche are filter-feeding caddisflies (Order: Trichoptera; Family: Hydropsychidae) that are commonly used to monitor metal exposures in rivers. While tissue residue concentrations provide important bioaccumulation data regarding metal bioavailability, they do not provide information regarding the mechanisms of uptake and loss, or exposure history. This study examined the physiological processes that control Cu and Cd uptake and loss using a biokinetic bioaccumulation model. Larvae of each taxon were experimentally exposed to either water or food enriched with stable isotopes (65Cu and 106Cd). Dissolved Cu uptake (ku) was similar between species (2.6-3.4 L-1g 1d-1), but Cd uptake was 3-fold higher in Hydropsyche than Arctopsyche (1.85 L-1g 1d-1 and 0.60 L-1g 1d-1, respectively). Cu and Cd efflux rates (ke) were relatively fast (0.14 d-1-0.24 d-1) in both species, and may explain, in part, their metal tolerance to mine-impacted rivers. Food ingestion rates (IR), assimilation efficiency (AE) of 65Cu and 106Cd from laboratory diets were also derived and used in a biodynamic model to quantify the relative contribution of dissolved and dietary exposure routes. Results from the biodynamic model were compared to tissue concentrations observed in a long-term field study and indicated that because dissolved Cu and Cd exposures accounted for less than 20% of body concentrations of either taxon, dietary exposure was the predominant metal pathway. An estimation of exposure history was determined using the model to predict steady state concentrations. Under constant exposure conditions (dissolved plus diet), steady state concentrations were reached in less than 30 days, an outcome largely influenced by rapid efflux (ke).

Effects of copper and cadmium on stream leaf decomposition: evidence from a microcosm study

We seek to understand how copper and cadmium act on leaf litter decomposition by their effects on microbial conditioning and litter fragmentation by invertebrates. In this study, we evaluated, in an integrated manner, different biological elements responsible for functioning of streams. Thus, we performed a microcosm assay with different concentrations for the two metals and their combination, evaluating their effects on fungi sporulation rate, consumption rate by shredders, and, consequently, the leaf litter decomposition rates. Sporulation rates were affected by all copper concentrations tested 10 ×  = 16 µg L-1 and 25 ×  = 40 µg L-1) but significantly reduced only at the highest concentration of cadmium (25 ×  = 22.5 µg L-1). Increased copper and cadmium concentrations reduced the consumption of leaf litter by Phylloicus at 60%. The concentrations (10 × and 25 ×) of both metals resulted in a reduction in decomposition rates. When combined, copper and cadmium negatively affected microbial conditioning, consumption by shredders, and leaf litter decomposition. Increases in concentrations of copper and cadmium directly affected organic matter decomposition in aquatic environments. Thus, the presence of a high concentration of heavy metals in aquatic environments alters the functioning of ecosystems. As trace-elements occur in a combined manner in environments, our results show that the combined effects of different metals potentiate the negative effects on ecosystem processes.

Aquatic insect accumulation of uranium at spring outflows in the Grand Canyon region as influenced by aqueous and sediment geochemistry and biological factors: implications for monitoring

Potential adverse ecological effects of expanded uranium (U) mining within the Grand Canyon region motivated studies to better understand U exposure and risk to endemic species. This study documents U exposures and analyzes geochemical and biological factors affecting U bioaccumulation at spring-fed systems within the Grand Canyon region. The principal objective was to determine if aqueous U was broadly indicative of U accumulated by insect larvae, a dominate fauna. Analyses focused on three widely distributed taxa: Argia sp. (a predatory damselfly), Culicidae (suspension feeding mosquitos), and Limnephilus sp. (a detritivorous caddisfly). The study showed that U accumulated by aquatic insects (and periphyton) generally correlated positively with total dissolved U, although correlations were strongest when based on modeled concentrations of the U-dicarbonato complex, UO₂(CO₃)₂^-2, and UO₂(OH)₂. Sediment metal concentration was a redundant indicator of U bioaccumulation. Neither insect size or U in the gut content of Limnephilus sp. substantially affected correlations between aqueous U and whole-body U concentrations. However, in Limnephilus sp., the gut and its content contained large quantities of U. Estimates of the sediment burden in the gut indicated that sediment was a minor source of U mass but contributed substantially to the total insect weight. As a result, whole-body U concentration would tend to vary inversely with the sediment burden of the gut. The correlations between aqueous U and bioaccumulated U provide an initial relational baseline against which newly acquired data could be evaluated for changes in U exposure during and after mining operations.

Phytoremediation, bioaccessibility and ecotoxicological risk assessment of arsenic in a gold mining area

The physicochemical and biological parameters of aquatic ecosystems are directly affected by mining activities, increasing the ecotoxicological risk related to exposure to contaminants and pollutants. In this study, a native and adapted floating aquatic macrophyte was used in a gold mining area as a model organism to assess the environmental risk and its potential application in bioremediation of heavy metals. The physicochemical parameters of water and sediments were evaluated, as well as the phytoremediation parameters (bioconcentration and translocation factors) of Hydrocotyle ranunculoides L. The results showed a significant bioconcentration of Cr, Pb, Cu, and Zn in the roots of the macrophyte (high BCF: As > Cu > Zn > Pb > Cr), confirming its suitability for use in rhizofiltration. Regarding arsenic bioconcentration, H. ranunculoides demonstrated a high BCF and TF > 1, indicating its phytoextraction potential, an essential requirement for plants to be used in bioremediation programs.

Assessment of metal exposure (uranium and copper) in fatty acids and carbohydrate profiles of Calamoceras marsupus larvae (Trichoptera) and Alnus glutinosa leaf litter

Physiological changes were explored in fatty acids (FA) and carbohydrate (CHO) composition in the shredder Calamoceras marsupus larvae (Trichoptera) and leaf litter (C. marsupus food) exposed to copper and uranium under natural and experimental conditions. We measured FA and CHO content in leaf litter and larvae specimens from reference and impacted streams, and exposed for 5 weeks to four realistic environmental concentrations of copper (35 μg L^-1 and 70 μg L^-1) and uranium (25 μg L^-1 and 50 μg L^-1). Regarding FA, (1) leaf litter had a reduced polyunsaturated FA (PUFA) content in metal treatments, s (14 to 33% of total FA), compared to natural conditions (≥39% of total FA). Leaf litter exposed to uranium also differed in saturated FA (SFA) composition, with lower values in natural conditions and higher values under low uranium concentrations. (2) C. marsupus had/showed low PUFA content under Cu and U exposure, particularly in high uranium concentrations. Detritivores also decreased in PUFA under exposure to both metals, particularly in high uranium concentrations. On the other hand, (1) microorganisms of the biofilm colonizing leaf litter differed in CHO composition between natural (impacted and reference) and experimental conditions, with glucose and galactose being consistently the most abundant sugars, found in different amounts under copper or uranium exposure; (2) CHO of detritivores showed similar high galactose and fucose concentrations in contaminated streams and high copper treatments, whereas low copper treatment showed distinct CHO profiles, with higher mannose, glucose, arabinose, and fucose concentrations. Our study provides evidence of metal exposure effects on FA and CHO contents at different trophic levels, which might alter the quality of food flow in trophic webs.

Contaminant fluxes across ecosystems mediated by aquatic insects

Metals and organic contaminants in aquatic systems affect the coupling of aquatic and terrestrial ecosystems through two pathways: contaminant-induced effects on insect emergence and emergence-induced contaminant transfer. Consequently, the impact of aquatic contaminants on terrestrial ecosystems can be driven by modifications in the quantity and quality of adult aquatic insects serving as prey or contaminants entering terrestrial food webs as part of the diet of terrestrial predators. Here, we provide an overview of recent advances in the field, separating metals from organic contaminants due to their differential propensity to bioaccumulate and thus their potential contribution to either of the two pathways. Finally, this review highlights the knowledge gap in the relative impact of these pathways on terrestrial insectivores.

Use of Riparian Spiders as Sentinels of Persistent and Bioavailable Chemical Contaminants in Aquatic Ecosystems: A Review

Aquatic ecosystems around the world are contaminated with a wide range of anthropogenic chemicals, including metals and organic pollutants, that originate from point and nonpoint sources. Many of these chemical contaminants have complex environmental cycles, are persistent and bioavailable, can be incorporated into aquatic food webs, and pose a threat to the health of wildlife and humans. Identifying appropriate sentinels that reflect bioavailability is critical to assessing and managing aquatic ecosystems impacted by contaminants. The objective of the present study is to review research on riparian spiders as sentinels of persistent and bioavailable chemical contaminants in aquatic ecosystems. Our review of the literature on riparian spiders as sentinels suggests that significant progress has been made during the last two decades of research. We identified 55 published studies conducted around the world in which riparian spiders (primarily of the families Tetragnathidae, Araneidae, Lycosidae, and Pisauridae) were used as sentinels of chemical contamination of lotic, lentic, and estuarine systems. For several contaminants, such as polychlorinated biphenyls (PCBs), Hg, and Se, it is now clear that riparian spiders are appropriate sentinels. However, many contaminants and factors that could impact chemical concentrations in riparian spiders have not been well characterized. Further study of riparian spiders and their potential role as sentinels is critical because it would allow for development of national-scale programs that utilize riparian spiders as sentinels to monitor chemical contaminants in aquatic ecosystems. A riparian spider sentinel program in the United States would be complementary to existing national sentinel programs, including those for fish and immature dragonflies. Environ Toxicol Chem 2022;41:499-514. © 2021 SETAC.

Aluminum at environmental concentrations affects the sperm quality of the freshwater teleost Astyanax altiparanae: An in vitro study

Aluminum (Al) is present in rivers and reservoirs in concentrations above that is allowed by regulatory agencies (e.g. 0.5 mg L^-1 Al), which can impair fish reproduction. The present study evaluated the in vitro effects on the sperm of Astyanax altiparanae upon Al exposure at different concentrations (0, 0.05, 0.1, 0.3, and 0.5 mg L^-1) with various exposure periods (50 s, 10 min, and 30 min). The following biomarkers were evaluated: membrane vitality, DNA fragmentation, morphology, kinetics (10 s and 30 s after sperm activation), and sperm mitochondrial activity. Al damages the membrane vitality of gametes at 0.3 and 0.5 mg L^-1 after 50 s of exposure. After 30 min of exposure, there was a decrease in membrane vitality at 0.1 and 0.5 mg L^-1, and the membrane vitality decreased with increased exposure time. Within 30 s after sperm activation, Al (0.3 and 0.5 mg L^-1) reduced sperm motility by more than 50% at the longest exposure time, while at 0.1 and 0.5 mg L^-1, Al exposure reduced motility over time. The average path speed (VAP; 10 s post-sperm activation) was reduced at longer exposure times at 0.05 and 0.5 mg L^-1 of Al. Increased exposure time had deleterious effects on mitochondrial activity at the highest concentrations tested. Al did not damage DNA and sperm morphology. In conclusion, Al negatively influences the sperm quality of A. altiparanae with a potential effect of exposure time and increasing concentrations.