Assessment of Different Contaminants in Freshwater: Origin, Fate and Ecological Impact

Living on the edge – An overview of invertebrates from groundwater habitats prone to extreme environmental conditions

Groundwater ecosystems from cold polar and circumpolar regions, hot springs, as well as those developed in salt, gypsum or in volcanic rocks are one of the environments considered to exhibit extreme environmental conditions such as low (below 0°C) or high (over 45°C) temperatures, hypersaline waters, or with elevated content of toxic gases like hydrogen sulfide or methane. They represent the “unseen ecosystem beneath our feet” and are inhabited by a large diversity of organisms, persisting and flourishing under severe environmental conditions that are usually hostile to the majority of organisms. These types of groundwater ecosystems are remarkable “evolutionary hotspots” that witnessed the adaptive radiation of morphologically and ecologically diverse species, whereas the organisms living here are good models to understand the evolutionary processes and historical factors involved in speciation and adaptation to severe environmental conditions. Here, we provide an overview of the groundwater invertebrates living in continental groundwater habitats prone to extreme environmental conditions in one or more physico-chemical parameters. Invertebrates are represented by a wide variety of taxonomic groups, however dominated by crustaceans that show specific adaptations mostly metabolic, physiologic, and behavioral. Symbiotic associations among bacteria and invertebrates are also discussed enlightening this biological interaction as a potential adaptation of different groundwater invertebrates to cope with severe environmental conditions. Given the high pressures that anthropogenic activities pose on groundwater habitats worldwide, we predict that several of these highly specialized organisms will be prone to extinction in the near future. Finally, we highlight the knowledge gaps and future research approaches in these particular groundwater ecosystems by using integrative-omic studies besides the molecular approach to shed light on genetic variation and phenotypic plasticity at species and populational levels.

GRAPHICAL ABSTRACT

Polystyrene microplastics increase Pb bioaccumulation and health damage in the Chinese mitten crab Eriocheir sinensis

Microplastics may be potential vectors for environmental contaminants such as heavy metals in the aquatic ecosystem due to their highly hydrophobic surfaces and fugacity property. To investigate the combined effects of microplastics with Pb, we exposed juvenile Chinese mitten crabs Eriocheir sinensis to different Pb concentrations (0, 5 and 50 μg/L) combined with microplastics (0 and 400 μg/L) for 21 days to determine the Pb bioaccumulation, oxidative stress, lipid anabolism, and histopathology of hepatopancreas. In general, the results showed that compared to single Pb exposure, the combination of MPs and Pb significantly increased the bioaccumulation of Pb, activities/content of antioxidant biomarkers and lipid metabolism enzymes, and liver injury parameters in crabs, indicating MPs are potential vector of heavy metals and co-exposure exerts more severe effects on crabs. This study provides the insights into the oxidative defense and preliminary lipid anabolism of economic crustaceans in response to combined stress of Pb and MPs.

Low-Cost Goethite Nanorods for As (III) and Se (VI) Removal from Water

Arsenite (As(III)) and Selenate (Se(VI)) are universally touted as extremely toxic oxyanions in natural and industrial water systems. Thus, the production of low-cost adsorbents that are scalable and toxic-free is of great importance today. In this work, a large-scale goethite nanorods (α-FeOOH NRs) is synthesized using a modified rapid hydrolysis method. The obtained powder is characterized using different multidisciplinary techniques. Accordingly, the results showed uniform and straight nanorods (length ~400 nm and diameter ~40 nm) resembling cigar-like morphology while the structure is confirmed to be of orthorhombic α-FeOOH phase. The potential application of this material to adsorb As (III) and Se (VI) ions in water is explored. In particular, for initial adsorbate concentrations (~500 µg/L), the removal efficiencies are found exceptional with α-FeOOH doses of 0.33 g/L and ~0.5 g/L for As (III) and Se (VI), respectively. Attractively, the adsorption capacities were estimated using trusted isotherms and then experimentally verified at ultimately high concentrations. Besides, a pH-controlled adsorption study showed that a pH of 5–8 is a favored range for higher ionic uptake, which meets the World Health Organization (WHO) benchmarks of drinking water. To conclude, the α-FeOOH NRs are potential adsorbent for the sustainable removal of toxin ions in water systems.