Despite growing concern about the occurrence of microplastics in aquatic ecosystems there is only rudimentary understanding of the pathways through which any adverse effects might occur. Here, we assess the effects of polystyrene microplastics (PS-MPs; <70 μm) on a common and widespread algal species, Chlorella sorokiniana. We used laboratory exposure to test the hypothesis that the lipids and fatty acids (FAs) are important molecules in the response reactions of algae to this pollutant. Cultivation with PS-MPs systematically reduced the concentration of essential linoleic acid (ALA, C18:3n-3) in C. sorokiniana, concomitantly increasing oleic acid (C18:1n-9). Among the storage triacylglycerols, palmitoleic and oleic acids increased at the expenses of two essential fatty acids, linoleic (LIN, C18:2n-6) and ALA, while PS-MPs had even more pronounced effects on the fatty acid and hydrocarbon composition of waxes and steryl esters. The FA composition of two major chloroplast galactolipids, monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG), were affected implying changes in the conformational structure of photosynthetic complexes in ways that can impair the photosynthesis. These data reveal how exposure to polystyrene microplastics can modify the concentrations of lipid molecules that are important intrinsically in cell membranes, and hence the lipid bilayers that could form an important barrier between algal cellular compartments and plastics in the aquatic environment. Changes in lipid synthesis and fatty acid composition in algae could also have repercussions for food quality, growth and stressor resistance in primary consumers. We advocate further studies of microplastics effects on the lipid composition of primary producers, and of their potential propagation through aquatic food webs.

The active use of solid fossil fuels (coal) in the production of heat and electricity has led to significant pollution, climate change, environmental degradation, and an increase in morbidity and mortality. Many countries (in particular, European ones, China, Japan, the USA, Canada, etc.) have launched programs for using plant and agricultural raw materials to produce heat and electricity by burning them instead of or together with traditional fuels. It is a promising solution to produce slurry fuels, based on a mixture of coal processing, oil refining and agricultural waste. This paper presents the results of experimental research into the formation and assessment of the most hazardous emissions (sulfur and nitrogen oxides) from the combustion of promising coal slurry fuels with straw, sunflower and algae additives, i.e. the most common agricultural waste. A comparative analysis has been carried out to identify the differences in the concentrations of sulfur and nitrogen oxides from the combustion of typical coal, coal processing waste, as well as fuel slurries with and without plant additives. It has been shown that the concentration of sulfur and nitrogen oxides can be reduced by 62–87% and 12–57%, respectively, when using small masses of plant additives (no more than 10 wt%) and maintaining high combustion heat of the slurry fuel. However, the use of algae and straw in the slurry composition can increase the HCl emissions, which requires extra measures to fight corrosion. A generalizing criterion of slurry fuel vs. coal efficiency has been formulated to illustrate significant benefits of adding plant solid waste to coal-water slurries containing petrochemicals. Straw and sunflower waste (10 wt%) were found to be the best additives to reduce the air pollutant emissions.

Metalaxyl is a broad-spectrum chiral fungicide that used for the protection of plants, however extensive use of metalaxyl resulted in serious environmental problems. Thus, a study on the detoxification mechanism in algae/cyanobacteria and their ability for phycoremediation is highly recommended. Here, we investigated the physiological and biochemical responses of two cyanobacterial species; Anabaena laxa and Nostoc muscorum to R-metalaxyl toxicity as well as their ability as phycoremediators. Two different levels of R-metalaxyl, at mild (10 mg/L) and high dose (25 mg/L), were applied for one-week. We found that A. laxa absorbed and accumulated more intracellular R-metalaxyl compared to N. muscorum. R-metalaxyl, which triggered a dose-based reduction in cell growth, photosynthetic pigment content, and photosynthetic key enzymes’ activities i.e., phosphoenolpyruvate carboxylase (PEPC) and ribulose‒1,5‒bisphosphate carboxylase/oxygenase (RuBisCo). These decreases were significantly less pronounced in A. laxa. On the other hand, R-metalaxyl significantly induced oxidative damage markers, e.g., H₂O₂ levels, lipid peroxidation (MDA), protein oxidation and NADPH oxidase activity. However, these increases were also lower in A. laxa compared to N. muscorum. To alleviate R-metalaxyl toxicity, A. laxa induced the polyphenols, flavonoids, tocopherols and glutathione (GSH) levels as well as peroxidase (POX), glutathione peroxidase (GPX), glutathione reductase (GR) and glutathione-s-transferase (GST) enzyme activities. On the contrary, the significant induction of antioxidants in N. muscorum was restricted to ascorbate, catalase (CAT) and ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR) enzyme activities. Although A. laxa accumulated more R-metalaxyl, it experienced less stress due to subsequent induction of antioxidants. Therefore, A. laxa may be a promising R-metalaxyl phycoremediator. Our results provided basic data for understanding the ecotoxicology of R-metalaxyl contamination in aquatic habitats and the toxicity indices among cyanobacteria.

The effects of microplastics pollution on the marine ecosystem have aroused attention. Copepod grazing stimulates dimethylsulfide (DMS) release from dimethylsulfoniopropionate (DMSP) in phytoplankton, but the effect of microplastics exposure on DMS and DMSP production during copepod feeding has not yet been revealed. Here, we investigated the effects of polyethylene (PE) and polyamide-nylon 6 (PA 6) microplastics on ecotoxicity and DMS/DMSP production in the copepod Tigriopus japonicus. The microplastics had detrimental effects on feeding, egestion, reproduction, survival, and DMS and DMSP production in T. japonicus and presented significant dose-response relationships. The 24 h-EC50 for ingestion rates (IRs) of female T. japonicus exposed to PE and PA 6 were 57.6 and 58.9 mg L⁻¹, respectively. In comparison, the body size of the copepods was not significantly affected by the microplastics during one generation of culture. Ingesting fluorescently labeled microplastics confirmed that microplastics were ingested by T. japonicus and adhered to the organs of the body surface. T. japonicus grazing promoted DMS release originating from degradation of DMSP in algal cells. Grazing-activated DMS production decreased because of reduced IR in the presence of microplastics. These results provide new insight into the biogeochemical cycle of sulfur during feeding in copepods exposed to microplastics.

Excessive nitrogen (N) losses from food production and consumption have resulted in noticeable environmental impacts, e.g., air pollution and climate change, saturation of soil N, and water eutrophication. In the present study, a rural-scale N flow model was constructed in Quzhou county, Hebei province to investigate the characteristics of the N flux, N use efficiency (NUE), and N loss and their driving factors in the food production and consumption system during 1997–2017. Our results show that the N fluxes of the crop-production subsystem (CPS), the livestock-breeding subsystem (LBS), and the household-consumption subsystem (HCS) all followed an upward trend. During 1997–2017, the N losses from the system were high (51.38%), and the CPS was a major source. When the N fertilizer application level was optimal (403–475 kg N ha⁻¹), the NUE in the CPS (NUEc) decreased sharply, resulting in a higher N cost than that observed at larger scales. For the LBS, the NUE of animal feed (NUEa) was high (46.37%); however, the waste utilization rate of the HCS was below 30%. The chemical fertilizer application level, feed input, animal-food demand, and livestock manure application level were closely related to the environmental N losses. Due to the lack of reasonable N treatment and utilization methods, the increasing N losses are expected to have a large future impact on environmental issues such as haze, soil acidification, and frequent algal blooms. Therefore, adjusting N management in the processes of food production and consumption is of great significance to the improvement of global NUE and reduction of environmental pollution.

In shallow eutrophic lakes, metal remobilization is closely related to the resuspension and eutrophication. An improved understanding of metal dynamics by biogeochemical processes is essential for effective management strategies. We measured concentrations of nine metals (Cr, Cu, Zn, Ni, Pb, Fe, Al, Mg, and Mn) in water and sediments during seven periods from 2014 to 2018 in northern Lake Taihu, to investigate the metal pollution status, spatial distributions, mineral constituents, and their interactions with P. Moreover, an automatic weather station and online multi-sensor systems were used to measure meteorological and physicochemical parameters. Combining these measurements, we analyzed the controlling factors of metal dynamics. Shallow and eutrophic northern Lake Taihu presents more serious metal pollution in sediments than the average of lakes in Jiangsu Province. We found chronic and acute toxicity levels of dissolved Pb and Zn (respectively), compared with US-EPA “National Recommended Water Quality Criteria”. Suspended particles and sediment have been polluted in different degrees from uncontaminated to extremely contaminated according to German pollution grade by LAWA (Bund/Länder-Arbeitsgemeinschaft Wasser). Polluted particles might pose a risk due to high resuspension rate and intense algal activity in shallow eutrophic lakes. Suspended particles have similar mineral constituents to sediments and increased with increasing wind velocity. Al, Fe, Mg, and Mn in the sediment were rarely affected by anthropogenic pollution according to the geoaccumulation index. Among them, Mn dynamics is very likely associated with algae. Micronutrient uptake by algal will affect the migration of metals and intensifies their remobilization. Intensive pollution of most particulate metals were in the industrialized and down-wind area, where algae form mats and decompose. Moreover, algal decomposition induced low-oxygen might stimulate the release of metals from sediment. Improving the eutrophication status, dredging sediment, and salvaging cyanobacteria biomass are possible ways to remove or reduce metal contaminations.

As an important part of extracellular secondary metabolites, extracellular polymeric substances (EPS) can play a significant role in protecting cells from the threat of exogenous substances, including nanoparticles (NPs). However, the regulation mechanisms of EPS secretion under NPs exposure remain largely unknown. This study investigated the signaling pathways and molecular responses related to EPS secretion of algae (Chlorella pyrenoidosa) upon the exposures to anatase and rutile TiO₂ NPs (nTiO₂-A and nTiO₂-R, respectively) at two similar toxic (20% and 50% of algal growth inhibition) concentrations. The results showed that EPS responded to nTiO₂ stress via excess secretion and compositional variation, and nTiO₂-A induced more EPS secretion than nTiO₂-R at similar toxicity concentrations. The up-regulation of the Ca²⁺ signaling pathway might play a greater role in promoting EPS secretion under nTiO₂-R exposure compared with nTiO₂-A exposure, while the significantly increased intracellular ROS could mainly account for the increased EPS secretion under nTiO₂-A exposure. The up-regulated genes related to biological synthesis and protein metabolism and the enhanced biosynthetic metabolism might be the direct causes of the increased EPS secretion. The increased ROS could have a greater effect on the amino acid metabolism and related genes upon the exposure to nTiO₂-A than nTiO₂-R to induce more EPS secretion. More serious membrane damage caused by nTiO₂-R than nTiO₂-A would affect the intracellular inositol phospholipid metabolism more severely, while the inositol phospholipid pathway and Ca²⁺ signaling pathway might agree and communicate with each other inherently to regulate EPS secretion upon nTiO₂-R exposure. The findings address the regulation mechanisms of algal EPS secretion under nTiO₂ exposure and provide new insights into algal bio-responses to nTiO₂ exposure.

Large benthic foraminifers (LBFs) are significant contributors to coral island formation in the Pacific Ocean. In recent years, the population of LBFs has decreased because of the increase in anthropogenic influences, such as wastewater (WW) discharge. To implement efficient mitigation measures, pollution tolerance in LBFs should be understood. However, the effects of WW on LBFs and their symbionts have not yet been demonstrated. This study examined the changes in the photosynthetic efficiency (Y[II]) of Calcarina gaudichaudii and Baculogypsina sphaerulata in response to WW by using a pulse-amplitude-modulation fluorometer. These LBFs were exposed to WW with different dilution levels for 22 days. The Y(II) values of the LBFs were found to deteriorate within 1–2 days. However, the Y(II) values both deteriorated and were enhanced in the experiments, thus indicating that WW contains both harmful and beneficial components. Baculogypsina sphaerulata showed an earlier response and greater sensitivity to WW and a higher epibiont infestation than C. gaudichaudii. This result can be attributed to the differences in the physiological and morphological responses of distinct LBFs. A sequencing analysis of 18S rDNA confirmed that the dominant eukaryotic symbionts in the two LBFs studied were Ochrophyta and Labyrinthulomycetes. These eukaryotic symbionts were released and attached as epibionts onto LBFs that were exposed to WW, thus leading to an increase in inactive LBFs. The Shannon–Weaver and Simpson diversity indices revealed that eukaryotic symbiont communities decreased in biodiversity after exposure to WW because of the abundance of algal symbionts. On the basis of these results, we conclude that WW, even with 10,000 × dilution, causes a decrease in active LBF populations owing to the release of eukaryotic symbionts, the decrease in biodiversity, and the infestation of epibionts even though Y(II) is temporarily enhanced. These responses are more significant in B. sphaerulata than in C. gaudichaudii.

Information on the occurrence and trophodynamics of per- and polyfluoroalkyl substances (PFASs) in the Antarctic region is limited. We investigated the occurrence of PFASs in an ecosystem in the Fildes Peninsula at King George Island and Ardley Island, Antarctica. The profiles, spatial distribution, and trophic transfer behavior of PFASs were further studied. ∑PFASs ranged from 0.50 ± 38.0 ng/g dw (dry weight) in algae to 4.97 ± 1.17 ng/g dw in Neogastropoda (Ngas), which was lower than those in the low- and mid-latitude regions and even Arctic regions. Perfluorobutyric acid (PFBA) was predominant with detection frequencies above 50% in all types of samples, and the relative contribution of PFBA ranged from 22% to 57% in the biota samples. The biomagnification factors of PFBA, perfluoroheptanoate (PFHpA), perfluorohexane sulfonate (PFHxS), and perfluorooctane sulfonate (PFOS) between Archaeogastropoda (Agas) and Ngas were 0.67 ± 0.54, 0.77 ± 0.38, 1.04 ± 1.56, 3.30 ± 4.07, and 1.61 ± 0.89, respectively. The trophic magnification factors of PFHxS and PFOS were 2.09 and 2.92, respectively, which indicated that they could be biomagnified through the food chain. Considering the increasing production and uncertain toxicological risks of emerging PFASs and the sensitive ecosystems in Antarctic regions, more attention should be paid, especially for the short-chain ones in the Antarctic region.

The complexation with extracellular polymeric substances (EPS) greatly reduces the toxicity of heavy metals towards organisms in the environment. However, the molecular mechanism of EPS−metal complexation remains unclear owing to the limitation of precise analysis for key fractions and functionalities in EPS that associate with metals. Herein, we explored the EPS−Cd (II) complexation by fluorescence excitation emission matrix coupled with parallel factor (EEM−PARAFAC), two-dimensional Fourier transform infrared correlation spectroscopy (2D-FTIR−COS) and X-ray photoelectron spectroscopy (XPS), attempting to explain the mechanisms of EPS in alleviating Cd (II) toxicity toward a green alga Chlorella vulgaris (C. vulgaris). When the algal EPS were removed, the cell internalizations of Cd (II), growth inhibition rate and chlorophyll autofluorescence increased, but the surface adsorption and esterase activities decreased, indicating that the sorption of Cd (II) by EPS was crucial in alleviating the algal toxicity. Moreover, the complexation with proteins in EPS controlled the sorption of Cd (II) to algal EPS, resulting in the chemical static quenching of the proteins fluorescence by 47.69 ± 2.37%. Additionally, the complexing capability of the main functionalities, COO⁻ and C–OH in proteins with Cd (II) was stronger than that of C–O(H) and C–O–C in polysaccharides or C–OH in the humus-related substances. Oxygen atom in protein carboxyl C–O might be the key site of EPS−Cd (II) complexation, supported by the modified Ryan−Weber complexation model and the obvious shift of oxygen valence-electron signal. These findings provide deep insights into understanding the interaction of EPS with heavy metals in aquatic environment.