Importance of salinity on regulating the environmental fate and bioaccumulation of lithium in the Yangtze River Estuary

The demand of lithium (Li) has increased rapidly in recent decades under carbon neutrality strategies, but the environmental fate and potential risks of Li in aquatic ecosystem are barely known. This study conducted a comprehensive field survey in the Yangtze River Estuary (YRE) and the adjacent East China Sea (ECS), to investigate the spatial distribution of dissolved Li and bioaccumulation of Li in the coastal food web. The dissolved Li increased with salinity (from 7.39 to 189 μg L-1), controlled by the conservative mixing of Li-enriched seawater and Li-poor riverine water. Negative correlation was observed between Li content and stable nitrogen isotope in the coastal biota, indicating bio-diminish of Li in the food web. Furthermore, the Li contents in muscle tissues were significantly higher in bivalves (as filter-feeders; mean: 0.75 ± 0.41 μg g-1) than in fish (as predator; mean: 0.10 ± 0.05 μg g-1) and other biota species, indicating that dissolved uptake might be the major exposure pathway for Li. Importantly, it was noticed that the bioaccumulation factors (BAFs) in fish muscle varied greatly (from 0.17 to 5.82), showing lower BAFs for fish inhabiting in marine and benthic regions (with higher salinity and higher dissolved Li concentration). Such inhibition effects of salinity on Li bioaccumulation could not be explained by the modulation of salinity on Li speciation, but highly attributed to the inhibition of high salinity on the dissolved uptake of Li, which was associated with the co-transportation of Li and Na. Our results illuminate the importance of salinity on regulation the spatial variations of dissolved Li and Li bioaccumulation in the YRE and the adjacent ECS, which could help the understanding of Li biogeochemical cycling and potential risks in estuarine and coastal regions.

Lithium: A review on concentrations and impacts in marine and coastal systems

The Lithium (Li) industry has been expanding worldwide, over the last decades, and projections expect an increasing demand for its production in the coming years. It has been identified as an emerging pollutant and it occurs widely in aquatic environments, raising concern about its effects on ecosystems. Besides the increasing research on this topic, there is still limited understanding and discussion on the marine and coastal implications of Li occurrence. The present review aims to fill these knowledge gaps by analysing the literature concerning Li occurrence and its effects on marine and coastal ecosystems, including transition areas. Since 1960, the number of publications has increased, especially over the last decade, and available information has reported Li in water and sediments of these areas, while few studies investigated Li in tissues of biota. Among all the studied ecosystems, Chile reported one of the highest Li concentrations. Regarding the adverse effects of Li in aquatic organisms, Bacillariophyceae, Scyphozoa, Bivalvia, Gastropoda, Cephalopoda, Polychaeta, Malacostraca, Echinoidea and Actinopteri were the studied taxonomic classes, and development inhibition, malformations, cellular and metabolic alterations, and behaviour changes were some of the observed impacts. This review might be particularly important in the mitigation of Li pollution as well as in the implementation of new directives and thresholds, as it highlights the impacts of Li and the urgent need to address new solutions and alternatives, meeting the Agenda 2030 for sustainable development.

Effects of the herbicide Irgarol 1051 on the transcriptome of hermatypic coral Acropora tenuis and its symbiotic dinoflagellates

Coral reefs face multiple threats, including climate change, agricultural runoff, shipping activities, coastal development, and chemical pollutants. Irgarol 1051, a PSII herbicide, has been used as an antifouling booster since the previously used antibiofouling agent tributyltin (TBT) was banned worldwide. Although the mechanisms through which elevated temperatures cause coral bleaching have been reported, it remains unclear how PSII herbicides cause bleaching. Thus, in this study, we investigated the transcriptomes of Acropora tenuis and its symbiotic dinoflagellates by RNA-sequencing (RNA-Seq) to elucidate the molecular mechanisms underlying Irgarol-induced bleaching. Coral exposure to 10 μg/L Irgarol for 7 d affected coral body colour, specifically by an increase in their red, green, and blue (RGB) values; however, no such effect was observed in corals exposed to 1 μg/L Irgarol. RNA-Seq revealed the differentially expressed genes (DEGs) in corals and symbiotic dinoflagellates following Irgarol exposure. Coral DEGs encoded green fluorescent protein, blue-light-sensing photoreceptor (cryptochrome), chromoprotein, caspase 8, and nuclear receptors; DEGs in symbiotic dinoflagellates encoded light-harvesting proteins, photosystem II proteins, and heat shock proteins (i.e. HSP70 and HSP90), and ubiquitin. Bioinformatic analyses revealed that both Irgarol treatments disrupted various gene ontology terms, pathways, and protein interaction networks; these are different in corals (e.g. oxidative phosphorylation, metabolic pathway, transforming growth factor-β signalling pathway, adherens junction, and apoptosis) and symbiotic dinoflagellates (e.g. protein processing in endoplasmic reticulum, carbon fixation in photosynthetic organisms, metabolic pathway, and photosynthesis). Our data suggest that Irgarol disrupts the expression of various coral genes, thereby affecting various gene ontology terms, pathways, and protein interaction networks. Our study provides new insights into the potential molecular mechanisms underlying the bleaching effect of PSII herbicides, such as Irgarol, on corals and symbiotic dinoflagellates.

Potential mechanisms underlying embryonic developmental toxicity caused by benzo[a]pyrene in Japanese medaka (Oryzias latipes)

Polycyclic aromatic hydrocarbons (PAHs), such as benzo[a]pyrene (BaP), are widely distributed in air, water, and sediments; however, limited data are available regarding their potential adverse effects on the early life stages of fish. In this study, we evaluated the embryonic teratogenicity and developmental toxicity of BaP in Japanese medaka (Oryzias latipes) using a nanosecond pulsed electric field (nsPEF) technique and predicted their molecular mechanisms via transcriptome analysis. The gas chromatography/mass spectrometry analyses revealed that the BaP was efficiently incorporated into the embryos by nsPEF treatment. The embryos incorporating BaP presented typical teratogenic and developmental effects, such as cardiovascular abnormalities, developmental abnormalities, and curvature of backbone. DNA microarray analysis revealed several unique upregulated genes, such as those involved in cardiovascular diseases, various cellular processes, and neural development. Furthermore, the gene set enrichment and network analyses found several genes and hub proteins involved in the developmental effects of BaP on the embryos. These findings suggest a potential mechanism of teratogenicity and developmental toxicity caused by exposure to BaP. The nsPEF and transcriptome analyses in combination can be effective for evaluating the potential effects of chemical substances on medaka embryos.