Distribution characteristics of microplastics and corresponding feeding habits of the dominant shrimps in the rivers of Chongming Island.

There is increasing global concern regarding microplastics. Rivers play a key role in the transportation and storage of microplastics on the Earth's surface. Here, we aimed to investigate the spatial-temporal variations in the distribution of microplastics in water as well as in the dominant species of the macrobenthic fauna Exopalaemon modestus and Macrobrachium nipponense in the river system of Chongming Island by setting up 16 fixed sampling sites. We found that the abundance of microplastics in the water of the rivers on the Chongming Island was 0.48 ± 0.10 n/L. There was no significant difference among different reaches. The abundance of microplastics in the major rivers was significantly higher in summer than in the other seasons. Detection rates of microplastics in Exopalaemon modestus and Macrobrachium nipponense were 50.12 % and 64.58 %, with mean abundances of 1.92 ± 0.52 n/g and 1.49 ± 0.30 n/g, respectively. The composition characteristics of the microplastics in shrimps were affected by the microplastics in the aquatic environment. The microplastic content in the shrimps and water were linearly correlated in terms of the same characteristics (shape, color, and polymer). Shrimps showed a stronger feeding preference {Target Group Index (TGI) > 1} for microplastics with fibrous shapes, transparent and green colors, rayon (RA) and polyethylene (PE) polymers, and relatively small sizes (<400 µm). These results indicate that shrimps prefer to consume microplastics that have similar appearance to their prey. Their benthic dwelling habits may limit their feeding space to the bottom of the water, which in turn leads to an increase in the feeding probability on microplastics of greater densities (e.g., RA). The catabolism of microplastics in shrimps may lead to an overestimation of their feeding preference for smaller sizes. Further controlled experiments should be carried out to obtain deeper insights into the preferences of shrimp for microplastics.

Does differential phosphorus processing by plankton influence the ecological state of shallow lakes?

Shallow lakes have a tendency to settle into turbid or clear-water states, the latter having lower concentrations of total phosphorus (TP). However, how P-cycling is affected by and perhaps contributes to maintaining the different states is not well understood, in part because quantifying the processes involved by traditional methods is difficult. To elucidate these processes, we conducted experiments using 32P-PO4 as a tracer on samples collected from the unrestored, unvegetated sections of Huizhou West Lake where turbid water prevails as well as the restored, clear-water, macrophyte-rich waters of the lake. We measured PO4 uptake rates, 32P-PO4 accumulation by various plankton size-fractions (picoplankton (0.2-2 µm), nanoplankton (2-20 µm) and microplankton (>20 µm)) as well as release rates of 32P-PO4 by labelled plankton. Our results revealed slow PO4 uptake in the turbid state due to low PO4 concentration, slow recycling of the high particulate P, and high levels of particulate 32P which may allow for continuous high growth and biomass of phytoplankton. In contrast, in the clear water state, the uptake of PO4 was rapid due to a higher PO4 concentration, the recycling rates of particulate 32P were high and the levels of particulate 32P were low, potentially constraining the phytoplankton growth. A greater proportion of particulate 32P was in the microplankton fraction in clear waters, suggesting that grazing by microplankton may play an important role in the rapid P recycling in clear-waters. Our results provide some evidence for a reinforcement of the turbid conditions (low recycling rate) when the lake is in a turbid state and vice versa when in the clear water state. The results add new knowledge to the understanding of P cycling in shallow lakes and illustrate the utility of using P-kinetics in contrasting states in plankton communities.

Occurrence and distribution of PAHs and microbial communities in nearshore sediments of the Knysna Estuary, South Africa.

This study investigated the polycyclic aromatic hydrocarbons (PAHs) occurrence, and their impact on the microbial community and PAH-degrading genera and genes in the Knysna Estuary of South Africa. The results reveal that the estuary exhibits low PAH levels (114.1-356.0 ng g-1). Ignavibacteriae and Deferribacteres, as well as Proteobacteria and Bacteroidetes, are keystone phyla. Among measured environmental factors, total organic carbon (TOC), nutrients such as nitrite and nitrate, metals as Al, Cr, Cu, Ni, Pb and Zn, and environmental properties (pH and salinity) are primary contributors to structuring the bacterial community assemblage. The abundance of alpha subunit genes of the PAH-ring hydroxylating dioxygenases (PAH-RHDα) of Gram-negative bacteria lies in the range of (2.0-4.2) × 105 copies g-1, while that of Gram-positive bacteria ranges from 3.0 × 105 to 1.3 × 107 copies g-1. The PAH-degrading bacteria account for up to 0.1% of the bacterial community and respond mainly to nitrate, TOC and salinity, while PAHs at low concentration are not significant influencing factors. PAH degraders such as Xanthomonadales, Pseudomonas, and Mycobacterium, which play a central role in PAH-metabolization coupled with other biogeochemical processes (e.g. iron cycling), may contribute to maintaining a healthy estuarine ecosystem. These results are important for developing appropriate utilization and protection strategies for pristine estuaries worldwide.

Variation in microplastics composition at small spatial and temporal scales in a tidal flat of the Yangtze Estuary, China.

Microplastics are small, degrade slowly, and easily persist in the water column because they are close to neutrally buoyant. Understanding the distribution of microplastics is fundamental to evaluating the ecological risks that they cause and to identifying ways to control microplastics pollution. Most of the existing research on the distribution of microplastics in the coastal zone has focused on large spatial and temporal scales. To build on past work, we investigated variation in microplastics in a tidal flat of the Yangtze Estuary on small spatial (sediment depth, mudflat vs. vegetation zone) and temporal (fortnightly and semidiurnal) scales. Microplastics were more abundant in surface (0-2 cm) sediments during neap versus spring tide cycles, likely indicating increased deposition during periods with calm waters and increased suspension when water was more turbulent, but did not vary at greater depths in the sediment. Individual microplastics particles were also larger during neap versus spring tide periods. In contrast to the variation between spring and neap tide periods, we found no variation in the abundance of microplastics on the semidiurnal scale. Microplastics were also more abundant in the transect in the vegetation than at slightly lower elevations in the adjacent mudflat. Across all samples, the abundance of microplastics was negatively correlated with the strength of hydrological processes such as submergence time and flow velocity. Our results showed that sampling of microplastics in the intertidal environment needs to consider variation among spring and neap tide cycles, and also among different intertidal habitats that may differ only slightly in elevation. We encourage coupling sampling with direct measures of hydrological processes so that variation in microplastics abundance and size can be rigorously linked to hydrological processes.

The synthesis of Zr-metal-organic framework functionalized magnetic graphene nanocomposites as an adsorbent for fast determination of multi-pesticide residues in tobacco samples.

In this paper, a simple and reliable method has been established to determine the residues of nine pesticides in tobacco by using GC-MS coupled with magnetic solid phase extraction. A novel magnetic Zr-MOF nanocomposite based on graphene was synthesized, and characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FT-IR), Raman spectroscopy and N2 adsorption-desorption measurements. The prepared material has the advantage of large surface area (178 m2/g), good magnetic response and high thermal stability, which is shown to be suited for the fast enrichment of multi-pesticides in tobacco matrix. The extraction conditions including amount of adsorbent, adsorption time, eluting solvent as well as desorption time were investigated. The whole process of pretreatment is accomplished within 10 min. This method shows low limit of detection, wide linear range and good reproducibility (relative standard deviations <12.7%), satisfactory recoveries were obtained, ranging from 57.9% to 126.3% for tobacco samples.

Microplastics and mesoplastics in fish from coastal and fresh waters of China.

Plastic pollution is a growing global concern. In the present study, we investigated plastic pollution in 21 species of sea fish and 6 species of freshwater fish from China. All of the species were found to ingest micro- or mesoplastics. The average abundance of microplastics varied from 1.1 to 7.2 items by individual and 0.2-17.2 items by gram. The average abundance of mesoplastics varied from 0.2 to 3.0 items by individual and 0.1-3.9 items by gram. Microplastics were abundant in 26 species, accounting for 55.9-92.3% of the total number of plastics items in each species. Thamnaconus septentrionalis contained the highest abundance of microplastics (7.2 items/individual). The average abundance of plastics in sea benthopelagic fishes was significantly higher than in freshwater benthopelagic fishes by items/individual. The plastics were dominanted by fiber in shape, transparent in color and cellophane in composition. The proportion of plastics in the stomach to the intestines showed great variation in different species, ranging from 0.5 to 1.9 by items/individual. The stomach of Harpodon nehereus and intestines of Pampus cinereus contained the highest number of plastics, (3.3) and (2.7), respectively, by items/individual. Our results suggested that plastic pollution was widespread in the investigated fish species and showed higher abundance in comparison with worldwide studies. The ingestion of plastics in fish was closely related to the habitat and gastrointestinal tract structure. We highly recommend that the entire gastrointestinal tract and digestion process be used in future investigations of plastic pollution in fish.

Effects of sulfamethazine on denitrification and the associated N2O release in estuarine and coastal sediments.

Denitrification is an important pathway of nitrogen removal and nitrous oxide (N2O) production in estuarine and coastal ecosystems, and plays a significant role in counteracting aquatic eutrophication induced by excessive nitrogen loads. Estuarine and coastal environments also suffer from increasing antibiotic contamination because of the growing production and usage of antibiotics. In this study, sediment slurry incubation experiments were conducted to determine the influence of sulfamethazine (SMT, a sulphonamide antibiotic) on denitrification and the associated N2O production. Genes important for denitrification and antibiotic resistance were quantified to investigate the microbial physiological mechanisms underlying SMT's effects on denitrification. SMT was observed to significantly inhibit denitrification rates, but increasing concentrations of SMT enhanced N2O release rates. The negative exponential relationships between denitrifying gene abundances and SMT concentrations showed that SMT reduced denitrification rates by restricting the growth of denitrifying bacteria, although the presence of the antibiotic resistance gene was detected during the incubation period. These results imply that the wide occurrence of residual antibiotics in estuarine and coastal ecosystems may influence eutrophication control, greenhouse effects, and atmospheric ozone depletion by inhibiting denitrification and stimulating the release of N2O.

[Effect of temperature on the eubacteria associated with marine sponge Pachychalina sp].

UNLABELLED: Temperature is important factor affecting the bacterial diversity. OBJECTIVE: In order to disclose the effect of temperature on the diversity of microorganisms. METHODS: The diversity of microorganisms associated with the sponge Pachychilina sp. at 16 degrees C and 30 degrees C of the seawater in the Gulf of Zhanjiang was examined by a restriction fragment length analysis termed ARDRA (amplified rDNA restriction analysis) and 16S rRNA-encoding DNA (rDNA) sequence analysis. The computer-aided clustering was performed after separate restriction analysis with enzymes Hae III. RESULTS: By this method, 100 cloned 16S rDNA fragments were clustered into a total of 34 different groups at 16 degrees C and 32 different groups at 30 degrees C. Hae III ARDRA patterns showed different among eubacteria living at different temperature degree, whereas the whole communities of eubacteria were not changed distinctly. Screening 60 clones by sequence analysis suggested vast majority of eubacteria related to alpha, gamma, delta subclasses of the class Proteobacteria, some related to sulfur bacteria, desulfobacter, and hydrocarbon utilizing bacteria, minority belonging to actinomyceten at 16 degrees C and 30 degrees C. Alpha subclass of the class Proteobacteria were the predominant bacteria at 30 degrees C, and gamma-Proteobacteria were predominant bacteria at 16 degrees C, additionally sulfur bacteria and desulfobacter were mainly attributed to chilly-enduring bacteria. Sequence analysis of clones with an identical ARDRA pattern confirmed that members of an ARDRA group were closely related to each other.

[Seasonal and semi-lunar changes in fish community structure in low salinity intertidal area of Yangtze estuary].

Based on the survey of the fishes in low salinity intertidal area of the Yangtze estuary from spring (May) 2006 to winter (February) 2007, the seasonal and semi-lunar changes of fish species and abundances were analyzed. A total of 53 fish species were collected, most of which belonged to Cyprinidae, followed by Gobiidae, and few of other families. The fish species and average abundance were higher in spring, summer, and autumn than in winter and lower in low tides than in high tides in four seasons. Shannon-Weaver (H') value had a greater fluctuation in a tidal cycle, and was appreciably lower in low tides than in high tides. The fish species and abundance were clustered into two groups, i. e., that of winter, and of the other seasons. As for the whole year, the abundance had the highest positive correlation with water temperature, then with tide height, and lowest with water salinity.

THIS ARTICLE HAS BEEN RETRACTED Exergy as an ecological application used in the recovery process of benthic communities.

Exergy, the thermodynamic function that represents the distance of an open system from equilibrium, is proposed as an ecological indicator for summarizing the complex dynamics occurring in a disturbed community during its recovery processes. These complex dynamics can be difficult to capture by using classical indices. In this study, we sampled macrobenthos using the BACI scheme (before versus after; control versus impact) in tidal wetlands of west Chongming Island, China, an area that has been disturbed by ecological engineering measures. Exergy storage is estimated for benthic communities. The control area is proposed as dynamic reference for estimating local exergy storage of the benthic community. Three different methods were used for estimating exergy on the basis of coefficients: (a) taken for taxa groups; (b) estimated from coding genes given for broad taxonomic groups; and (c) estimated from genome size taken as close as possible to the taxonomic level of the species, providing a basis for inferring similarities. We found a decrease of local exergy content in the disturbed area 9 days after the disturbance. Subsequently, the reference exergy of the benthic community increased (i.e. in the surrounding control area) in accordance with the proposed hypothesis regarding the dynamics of exergy storage during a system's development. Estimates of local exergy arrived at using the three methods provided comparable results. Based on this, we then discuss the feasibility of using the more readily available genome size data for estimating exergy. This result may have important implications for broader application of this indicator to biological systems. Moreover, the adjacent control samples seem to represent an appropriate dynamic reference for estimating the local exergy of disturbed communities. We found that exergy was a useful indicator that integrates the processes underlying the recovery of the benthic community after disturbance.