Ecotoxicological Effects of Microplastics on Bird Embryo Development by Hatching without Eggshell

Microplastics are an emerging global pollutant type that poses a great health threat to animals due to their uptake and translocation in animal tissues ...

Chinese Academy of Sciences

University of Chinese Academy of Sciences

CaCO precipitation is one of the most common and important geochemical processes in the arid inland waters and it can be significantly affected by interaction of DOM with Ca. Effects of the drastic seasonal change of water salinity on interaction of DOM with Ca in the arid inland waters were completely unknown. In the present study, complexation of DOM with Ca in the freshwater (0.5‰ salinity) and hypersaline water (70‰ salinity) were comparatively examined by excitation-emission matrix (EEM) fluorescence quenching titration and isothermal titration calorimetry (ITC). The complexation of DOM with Ca was significantly influenced by the drastic change of salinity. The ITC complexation is exothermic at 0.5‰ salinity but turns to an endothermic process at 70‰ salinity. More energy is needed for the complex reaction between DOM and Ca under the hypersaline condition than in the fresh water. Fluorescence quenching titration indicates that DOM has stronger binding ability toward Ca in the freshwater than in the saline water, and more fractions of DOM in the freshwater are accessible to Ca than in the saline water. Ca complexation in the DOM is dominated by the tryptophan-like components at both salinities and the complexation of Ca with fulvic acid-like components is ignorable. The findings is important for understanding the aquatic geochemical processes in some lakes that seriously affected by irrigation water use in the arid zone.

Ca complexation of dissolved organic matter in arid inland lakes is significantly affected by drastic seasonal change of salinity.

Calcium carbonate (CaCO) precipitation is an important geochemical process. In the estuary zone and some arid shallow lakes, DOM (dissolved organic matter) and salinity are two frequent changing factors that may affect CaCO precipitation. The joint effect of DOM and salinity on CaCO precipitation kinetics and thermodynamics are still unclear. In this study, effects of DOM on CaCO precipitation process at 0.5‰ and 70‰ salinity were investigated by QCM (Quartz Crystal Microbalance) technique, real-time pH measurement and single-injection nanoliter ITC (isothermal titration calorimetry). The mineral crystallography was analyzed by SEM-EDS. Both DOM and salinity had inhibitory effect on CaCO precipitation. DOM had more pronounced inhibitory effect on CaCO precipitation at lower salinity. Regardless of DOM, 70‰ salinity inhibited CaCO precipitation >0.5‰ salinity. The CaCO precipitation kinetics followed the first-order kinetic model and the adhesion kinetics of the instantaneous nucleation and crystal growth stage could be well described by the exponential function. CaCO precipitation was an endothermic process and high salinity strongly hindered CaCO precipitation. The effect of DOM on the absorbed heat was significant at 0.5‰ salinity. At 70‰ salinity, regardless of the effect of DOM, CaCO precipitation rate was greatly slowed down because it needed much more heat. CaCO minerals were dominated by rhombohedral calcite while CaCO minerals were mainly shaped as spherical vaterite at 0.5‰ salinity and rhombohedral calcite at 70‰ salinity. The crystal phase changed during CaCO precipitation at 0.5‰ salinity. In conclusion, the presence of DOM had substantial impact on the micrograph of the CaCO minerals. The percentage of flawed crystals with rough surface increased significantly with increased DOM concentration.

The kinetics, thermodynamics and mineral crystallography of CaCO precipitation by dissolved organic matter and salinity.

Lakes in arid northwestern China are valuable freshwater resources that drive socioeconomic development. Environmental pollution can significantly influence the composition of microbial communities and the distribution of functional genes in lakes. This study investigated heavy metal pollution to identify possible correlations with metal resistance genes (MRGs) and bacterial community composition in water, sediment and biofilm samples from Bosten Lake and Ebi Lake in northwestern China. High levels of zinc were detected in all samples. However, the metals detected in the sediment samples of both lakes were determined to be at low risk levels according to an ecological index. The mercury resistance gene subtype merP had the greatest average abundance (4.61 × 10 copies per 16S rRNA) among all the samples, followed by merA and merC. The high abundance of merA in the pelagic zone rather than in benthic sediment suggests that the pelagic microbial community was important in mercury reduction. Proteobacteria were the main phylum found in the microbial communities in all samples. However, microbial communities in most of the water, sediment and biofilm samples had different compositions, indicating that the habitat niche plays an important role in shaping the bacterial communities in lakes. The microbial community, rather than the heavy metals, was the main driver of MRG distribution. The abundances of some bacterial genera involved in the decomposition of organic matter and the terrestrial nitrogen cycle were negatively correlated with heavy metals. This result suggests that metal pollution can adversely affect the biogeochemical processes that occur in lakes.

Bacterial community rather than metals shaping metal resistance genes in water, sediment and biofilm in lakes from arid northwestern China.

The partition of antibiotics and antibiotic resistant genes (ARGs) between the microplastics (MPs) and the surrounding water with various salinity are still unclear. In this study, we hypothesized that adsorption of antibiotics on MPs might cause a significant change of the structure of microbial communities, diversity and abundance of ARGs on MPs and this might be further affected by change of salinity. In this study, we investigated adsorption of four common antibiotics (sulfamerazine, tetracycline, chloramphenicol and tylosin) to polyethylene (PE) MPs in river, estuary and marine waters, and the differences of antibiotic resistant genes (ARGs) and bacterial communities on MPs and in the three waters. The results showed that MPs can enrich antibiotics, ARGs and microbes from the surrounding water. Elevated salinity could reduce adsorption of antibiotics to MPs and the abundance of ARGs. For example, MPs can concentrate more antibiotics and ARGs in the fresh river water than in the estuary and the marine waters. In addition, ARGs and bacterial communities on MPs at various salinity were significantly different under the pressure of four antibiotics. On MPs, sul1, sulA/folP-01, tetA, tetC, tetX and ermE increased significantly but a few new ARGs such as sulA/folP-01 and tetA appeared. The structure of the bacterial communities on MPs was different from the surrounding water since some bacteria species found on MPs were barely detected in the surrounding water while some genera on MPs vanished after exposure to antibiotics. As the antibiotics adsorbed and the ARGs on MPs decreased with the water salinity, the structure of the communities on MPs thus varied with salinity change. These findings are important to understand the effects of MPs on the transport, fate and ecological risk of antibiotics and ARGs in different aquatic environments.

Selectively enrichment of antibiotics and ARGs by microplastics in river, estuary and marine waters.

Plastic debris provides a stable substrate and novel ecological niche for microorganisms in the aquatic environment, which was referred to as "Plastisphere". Little is known about distribution patterns and responses of ecological function and structure of microbial communities in the plastisphere along rivers which usually have antibiotics pollution gradient. In this study, the differences in the community structure between the plastisphere and the planktonic bacteria, and their spatial variation of the community structure and function along a river with increased antibiotics pollution gradient was investigated at the watershed scale. The diversity of bacteria colonized on most plastic debris was higher than in surrounding water. Plastic debris could accumulate a higher abundance of some potential pathogens than surrounding water even at high antibiotics concentrations. The source tracking results showed that downstream plastisphere inherited much higher proportions of bacterial taxa from upstream than planktonic bacteria. About 92.3-99.7% of bacteria communities in downstream water were not from upstream but from the input of downstream human activities. On the contrary, high proportions of bacterial taxa in downstream plastisphere were closely connected to upstream. The plastisphere possesses higher ecological functional diversity than the planktonic bacteria. Seventy nine functional groups across plastisphere were predicted using functional annotation of prokaryotic taxa and only 65 functional groups were found in the planktonic bacteria. Plastisphere also acts as hotspot for biogeochemical cycling of nutrients such as N and S. Intensive human activities of urban and downstream agriculture and aquaculture had great effects on microbial community structure and functional groups of the Urumqi River. Pastisphere communities are much more resistant to human disturbance than planktonic bacteria. Compared to surrounding water, plastisphere increased inheritance from upstream microbial structure and function and also increased survival and propagation of pathogens in the downstream water with high concentrations of antibiotics.

Increased inheritance of structure and function of bacterial communities and pathogen propagation in plastisphere along a river with increasing antibiotics pollution gradient.

Fungi not only play important roles in biogeochemical processes but also can form biofilm on plastic debris. However, knowledge of structure composition and spatiotemporal pattern of fungal plastisphere on different kinds of plastic debris in river with specific usages, known as river functional zones, is still missing. In this study, we investigated the spatial distribution of the fungal plastisphere across a complete urban river with different functional zones (drinking, farm irrigation, aquaculture, and tail lake). Our research was performed based on both field residual plastic debris collection and a 30-day field in situ incubation experiments. Our study revealed that plastic debris enriched distinct fungal communities (including pathogenic fungi) significantly different from the surrounding water. Tracking the source of the fungi colonized on plastic debris suggested that the fungal taxa colonized on the different kinds of plastic debris were not from the surrounding water. Human activities had considerable effects on the fungal community structure on plastic debris, and the plastisphere fungal community structure strikingly varied across different river functional zones. Plastisphere may be used as an indicator for fungi biogeography and pathogenic fungi pollution in river with different functional zones. These findings are essential for ecological risk assessment and management decisions for pollution control of plastic debris and maintaining ecological health.

Distinct fungal plastisphere across different river functional zones: A watershed scale study.

The overuse of antibiotics during the medication treatment is inevitable in the extensively-applied intensive and semi-intensive aquaculture mode; the accompanied antibiotic contamination and antimicrobial resistance pose threats to the ecosystems and cause great loss to the aquaculture industry. To solve the problem, this work introduced the antibiotic-laden dietary millispheres (DMSs) with internal porous structure for the high availability, attractiveness and digestibility to fish. Two types of antibiotics with distinct solubilities - tetracycline chloride (TCH) and sulfadiazine (SDZ) were made into the DMSs, individually, which were then directly adopted in the feeding of fish. Carassius auratus was chosen as the target fish in this work. The mesocosm study demonstrate that, compared with the regular way of oral administration (feeding the mixture of antibiotics and commercial feed pellets), the DMSs could use much less (i.e. one order of magnitude lower) antibiotic dose to reach the equivalent antibiotic concentration in gastrointestine and blood. As a robust alternative, either TCH- or SDZ-laden DMSs achieved efficient drug delivery in vivo, which importantly facilitated the source reduction of antibiotics, the alleviation of antibiotic contamination in fishery and the control of antibiotic resistance especially in sediments.

Nana Xue

Xinjiang Key Laboratory of Environmental Pollution and Bioremediation,
Xinjiang Institute of Ecology and Geography,
Xinjiang Key Laboratory of Environmental Pollution and Bioremediation, Xinjiang Institute of Ecology and Geography

Chinese Academy of Sciences

Ecotoxicological Effects of Microplastics on Bird Embryo Development by Hatching without Eggshell