Toxic response of aquatic organisms to guide application of artemisinin sustained-release granule algaecide

In our previous study,we prepared the granules by embedding artemisinin into alginate-chitosan using microcapsule technology.These granules can release artemisinin sustainably and have a strong inhibitory effect on the growth of both single Microcystis aeruginosa and mixed algae.To safely and effectively use artemisinin sustained-release granules to control algal blooms,the ecotoxicity was studied by assessing their acute and chronic toxicity to Daphnia magna(D.magna)and Danio rerio(D.rerio),along with their antioxidant activities.The results showed that the 48-h median effective concentration(EC50)of pure artemisinin to D.magna was 24.54 mg/L and the 96-h median lethal concentration(LC50)of pure artemisinin to D.rerio was 68.08 mg/L.Both values were classified as intermediate toxicity according to the Organization for Economic Co-operation and Development(OECD).The optimal algae inhibitory concentration of artemisinin sustained-release granules(1 g/L)had low acute toxicity to both D.magna and D.rerio.The sustained-release granules had higher chronic toxicity to D.magna than to D.rerio.Partial indices of D.magna were inhibited by granules when the concentrations were larger than 0.1 g/L.Low granule concentration had an inductive effect on antioxidant enzyme activities in D.magna and D.rerio.With the increase of the exposure concentration and time,the enzyme activity presented a trend of first increasing and then decreasing,and the overall changes were significant.The change trend and range of enzyme activity indicated that the granules could cause serious oxidative stress to D.magna and D.rerio,and the changes were consistent with the results of toxicity experimentation.

Assessing comparable bioconcentration potentials for nanoparticles in aquatic organisms via combined utilization of machine learning and toxicokinetic models

The toxicokinetic(TK)model‐derived kinetic bioconcentration factor(BCFk)provides a quantitatively comparable index to estimate the bioaccumulation potential of nanoparticles(NPs)that barely reach thermodynamic equilibrium in aquatic organisms,but experimental data are limited for various NPs.In the present study,a machine learning model was applied to offer reliable in silico predictions for the dynamic body burden of diverse NPs to derive corresponding parameters for the TK model.The developed eXtreme Gradient Boosting‐derived TK(XGB‐TK)model was applied to predict BCFk results for a broad range of metallic or carbonaceous NPs,with an appreciable prediction R2 of 0.96.The BCFk values were predicted based on a random combination of selected variable features,revealing that their bioaccumulation potential showed an overall negative correlation with NP density or organism size.By applying importance analysis and partial dependence plots,NP density and organism size were revealed to be the top essential features that impact the bioaccumulation potential.The conjunctively used XGB‐TK model enabled a prior comparison for diverse NPs and straightforward derivation on the dependency of features,which could also guide the bioaccumulation mechanism exploration and experimental condition formulation.

Significance of adverse outcome pathways in biomarker-based environmental risk assessment in aquatic organisms

In environmental risk assessments（ERA）, biomarkers have been widely used as an early warning signal of environmental contamination. However, biomarker responses have limitation due to its low relevance to adverse outcomes（e.g., fluctuations in community structure, decreases in population size, and other similar ecobiologically relevant indicators of community structure and function）. To mitigate these limitations, the concept of adverse outcome pathways（AOPs） was developed. An AOP is an analytical, sequentially progressive pathway that links a molecular initiating event（MIE） to an adverse outcome. Recently, AOPs have been recognized as a potential informational tool by which the implications of molecular biomarkers in ERA can be better understood. To demonstrate the utility of AOPs in biomarker-based ERA, here we discuss a series of three different biological repercussions caused by exposure to benzo（a）pyrene（Ba P）, silver nanoparticles（Ag NPs）, and selenium（Se）. Using mainly aquatic invertebrates and selected vertebrates as model species, we focus on the development of the AOP concept. Aquatic organisms are suitable bioindicator species whose entire lifespans can be observed over a short period; moreover, these species can be studied on the molecular and population levels.Also, interspecific differences between aquatic organisms are important to consider in an AOP framework, since these differences are an integral part of the natural environment.The development of an environmental pollutant-mediated AOP may enable a better understanding of the effects of environmental pollutants in different scenarios in the diverse community of an ecosystem.

Microplastics may reduce the fish bioaccumulation of organic pollutants

Microplastics have frequently been regarded as a threat to aquatic organisms due to their potential to enhance the accessibility of organic pollutants.However,studies of microplastics as“carriers”in the process of bioaccumulation have only been conducted on a few organic contaminants.In this study,we employed machine learning algorithms to predict the sorption capacity of 83 exogenous organic pollutants(in CCL4)on microplastics,the prediction model exhibits exceptional predictive performance,achieving R^(2) values of 0.8651 and 0.6962,RMSE values of 0.4625 and 0.1841 for the sorption coefficients Kf and n,respectively,and quantitatively estimated the contribution of microplastics to the bioaccumulation levels of organic pollutants in Gadus morhua.By considering both natural and microplastic-ingesting pathways,we demonstrated that the ingestion of microplastics containing organic pollutants facilitates the entry of organic pollutants into Gadus morhua.However,due to their robust sorption capacity,microplastics transport the organic pollutants accumulated through the natural pathway out of the fish,thereby preventing bioaccumulation.These findings elucidate the“cleaning”mechanism of microplastics concerning various organic pollutants in aquatic organisms,providing valuable insights for accurately assessing the risk of microplastics in aquatic environments.

Combined effect of microplastic and triphenyltin:Insights from the gut-brain axis

Microplastics(MPs),an emerging group of pollutants,not only have direct toxic effects on aquatic organisms but also cause combined toxicity by absorbing other pollutants.Triphenyltin(TPT),one of the most widely used organotin compounds,has adverse effects on aquatic organisms.However,little is known about the combined toxicity of MPs and TPT to aquatic organisms.To investigate the individual and combined toxicity of MPs and TPT,we selected the common carp(Cyprinus carpio)for a 42-day exposure experiment.Based on the environmental concentrations in a heavily polluted area,the experimental concentrations of MPs and TPT were set at 0.5 mg L^(−1) and 1μg L^(−1),respectively.The effects of MPs combined with TPT on the carp gut-brain axis were evaluated by detecting gut physiology and biochemical parameters,gut microbial 16S rRNA,and brain transcriptome sequencing.Our results suggest that a single TPT caused lipid metabolism disorder and a single MP induced immunosuppression in carp.When MPs were combined with TPT,the involvement of TPT amplified the immunotoxic effect induced by MPs.In this study,we also explored the gut-brain axis relationship of carp immunosuppression,providing new insights for assessing the combined toxicity of MPs and TPT.At the same time,our study provides a theoretical basis for evaluating the coexistence risk of MPs and TPT in the aquatic environment.

Historical record of effects of human activities on absolute and relative concentrations of Polycyclic aromatic hydrocarbons(PAHs) in Lake Chao,China

Polycyclic aromatic hydrocarbons（PAHs）are attracting concern because of their potential toxicity,posing serious threats to health of humans and ecosystems（Kim et al.,2013;Zhao et al.,2016）.Generally,similar to other contaminants＇behaviors（Wu et al.,2001;Zhang et al.,2007,2008;Lu et al.,2009）,PAHs result from natural organic matter and activities of humans,the latter＇s contribution usually outweighing the inputs from other sources（Fernández et al.,2000;Srogi,2007）.