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Nile tilapia is a highly invasive fish species, deliberately introduced into many lakes and reservoirs worldwide, sometimes resulting in significant ecosystem alterations. A short-term mesocosm experiment with and without Nile tilapia (Oreochromis niloticus) was designed to test the hypotheses that the presence of tilapia may affect phytoplankton community structure, increase nutrients availability in water column and deteriorate water quality. Nutrients, total suspended solids (TSS) and biomass of phytoplankton in different size classes (as Chl a) were measured. We found that tilapia increased the total nitrogen (TN), total dissolved nitrogen (TDN), NH4 + and TSS concentrations, deteriorating the water quality. In addition, under tilapia presence, the biomass of phytoplankton, as well as that of micro- and nano-phytoplankton, increased leading to a change in the structure of the phytoplankton assemblage. Moreover, a reduction in the biomass of periphyton was observed. Omnivorous tilapia is often dominant in tropical and subtropical waters, and removal of this fish may represent an effective management tool to improve the water quality.

The evolution of the shoals and vegetation plays an important role in maintaining the stability of the river regime and the estuarine ecosystem. However, the interaction between the evolution of shoals and vegetation dynamic has rarely been reported. In this study, we determined the interaction between the shoal and vegetation evolution of Jiuduansha in the Changjiang River Estuary in the last 30 years. We did this through the collection and summarization of the existing data of the regional hydrological processes, wading engineering, and vegetation, and combined it with the analysis of nautical charts and remote sensing images. During the past 30 years, the expansion of the shoals within the 0 m isobath in Jiuduansha was obvious, with an increase of 176.5%, while the expansion of the shoals within the 5 m isobath was relatively slow. The regional hydrological characteristics in the Jiuduansha area changed dramatically, especially the sediment discharges. The area of vegetation in Jiuduansha increased from 9.1 km2 in 1990 to 65.68 km2 in 2015, while the variations in the different vegetation types were different. The best combination of environmental factors with a significant correlation on the shoals within the 0 m isobath is the area of Spartina alterniflora and Phragmites australis. The evolution of Jiuduansha shoals was significantly affected by the variations in hydrological characteristics. Meanwhile, on a long-term scale, the expansion of the shoals could promote the regional vegetation expansions due to the suitable elevation and environmental conditions it provides. The interaction between the shoal and vegetation evolution varied in the different vegetation types and different elevations. In the future, long-term monitoring and detailed data are needed to the systematical analysis of the interaction between the hydrological processes and the evolution of the shoal and vegetation.

Urban green spaces are among the relatively few places to connect with nature in cities and represent locations where city dwellers can experience a variety of critical ecosystem services. As urbanization increases, deepening our understanding of the connections between city dwellers and the natural environment has become critical. In this study, we investigated the social values for ecosystem services by demonstrating an approach that combines a visitor-employed photography (VEP) method with the Social Values for Ecosystem Services (SolVES) mapping tool and applying this method to an urban wetland park. As a result, a quantified value index (VI) informs managers of the type and extent of urban ecosystem services (UESs) acknowledged by the public. Social values for each UES and environmental variable are delineated in a quantitative and spatially explicit manner. These outcomes could help planners and managers target specific areas in need of construction or improvement. Notably, public perceptions in this study are derived from photographs taken by invited park visitors. Real-time and on-site visiting experiences tend to be more effective and robust than recalling points of interest after visiting and manually marking them on maps via questionnaires. All the data used in this study are likely available in other green spaces. This approach can be generally extended to UES assessments elsewhere.

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.

Muddy coasts downdrift of large river mouths trap fine-grained sediments supplied from these rivers and have provided important settlement sites for prehistoric people, although the evolutionary history of such environments has not been well described. In this study, we integrate multi-proxy analyses (lithology, particle size, sedimentary structure, bioturbation, microfossil, and AMS 14C) on two new sediment cores (CC and ZF) from the Ningbo Plain, southeast of Hangzhou Bay, east China, with results from previous studies to explore the early to mid-Holocene sedimentary history of the palaeo-Ningbo Bay in response to post-glacial sea-level rise. The results show that the early to mid-Holocene stratigraphy in core CC was characterized by a muddy embayment succession before 7.3 cal kyr B.P. and an aggradational tidal flat to coastal marsh succession after that time. Rapid sediment accumulation occurred before ca. 7.7 cal kyr B.P. and at 7.3–7.2 cal kyr B.P., whereas periods of reduced sediment supply are recorded between 7.7 and 7.3 cal kyr B.P. and after 7.2 cal kyr B.P. At site ZF, in contrast, only sediments of coastal freshwater marsh overlay the last glacial stiff muds after ca. 7.5 cal kyr B.P. We suggest that the sheltered embayment favoured trapping of the fine-grained sediments during the early to mid-Holocene, while geometric changes of the bay in response to a phase of accelerated sea-level rise at ca. 7.7 cal kyr B.P. resulted in a reduced sedimentation rate and increased tidal energy. Abundant, large, and diverse (0.5–1.0 cm wide, 5–24 cm long) vertical burrows are present in core CC during 8.9–7.9 cal kyr B.P. and the trace fossils declined abruptly at 7.9 cal kyr B.P. We suggest this may have been induced by the exploitation of seafood by Neolithic people settled in the sheltered embayment, as supported by archaeological remains found at the Neolithic site. Rapid progradation of tidal flats and coastal marsh occurred since ca. 7.2 cal kyr B.P. in the palaeo-bay, which may reflect a response to a stable sea level after that time. The development of a thick early to mid-Holocene sediment sequence in the palaeo-Ningbo Bay and its relationship to sea-level changes indicate that such muddy embayments downdrift of large river mouths should be considered important in reconstructing the Holocene depositional system of the adjacent coast.

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.

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.

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

Common carp (Cyprinus carpio) have been introduced into aquatic systems across the world, where their benthivorous feeding behavior has resulted in serious water quality problems. A 12-week mesocosm experiment was set up to test the hypotheses that common carp increase water column nutrient levels and decrease water clarity in aquatic ecosystems dominated by submerged plants. Further, we tested whether the effect of common carp on macrophytes depended on the species of plants. Relative to the controls, the presence of carp decreased water clarity by increasing total suspended solids (TSS) and light attenuation. However, levels of total nitrogen (TN) and total phosphorus (TP) in the water column were reduced. No significant change in phytoplankton biomass (measured as chlorophylla) and the biomass ofHydrilla verticillatawas observed between common carp treatment mesocosms and controls, but the common carp did reduce the biomass of the submerged macrophyteVallisneria denseserrulata. We conclude that removal of common carp is likely to improve water clarity in aquatic ecosystems dominated by submerged plants primarily by decreasing TSS and that the effect of common carp on macrophytes is stronger for the meadow formingVallisneriathan for the canopy formingHydrilla.

We analyzed the effects of various levels of sediment-slurry addition on the restoration of the macroinvertebrate community and its related habitat (i.e., sediment and vegetation) 7 years after application to a subsided Louisiana salt marsh affected by sudden marsh dieback. Moderate sediment additions restored macroinvertebrate species richness, diversity, density, and total biomass to levels equivalent to those in reference marshes, although individual species and taxa had variable recovery depending on treatment-level. Total aboveground plant biomass and live Spartina alterniflora biomass, stem density and height were equivalent to those in reference marshes. In contrast, total belowground biomass had not yet reached equivalency with reference marshes. Although moderate sediment application created conditions that were ecologically equivalent with reference marshes for most macroinvertebrate and plant variables, degraded areas that received high sediment addition had impaired recovery across all metrics, even 7 years after sediment application. Thus, when sediment-slurries are applied to proper elevations, the macroinvertebrate community, as well as aboveground marsh vegetation, can recover to reference conditions. However, too much sediment impairs recovery. Consequently, greater consideration must be given to establishing suitable post-construction marsh elevations to insure successful ecosystem restoration.

Based on the fishing net surveying data about anguillid elver of the Yangtze estuary collected in 2006 and historical data from previous research of the region, this study was focused on analyzing the fishing effort and catch variations of the elver, revealing the effects on fishery resources caused by elver fishing activities. It was found that the elver fishing activities took place in the tidal area of the Yangtze estuary from January to April. The yearly elver catch in 2000–2006 was 3 times greater than that in the 1970s–1980s. The catch per unit effort (CPUE) (ind./net/day) of the elver had some characteristics of temporal variation. It was higher in spring tide periods than that in neap tide periods, and the CPUE in February and March was 3–4 times greater than that in January. Twenty-eight fish species, 6 shrimp species, 2 crab species and 8 other invertebrates were found in the by-catch of the eel nets. Among the fishes, shrimps and crabs, the individual proportion of fishes is the highest, and they are mostly juveniles or small-size fishes, while the shrimps and crabs also make up a certain proportion. Most of the individuals in the by-catch were juveniles and were dead when they were harvested. It was proven that the activity of elver fishing has a great negative effect on regional fishery resources, though it has brought great commercial benefit. Relevant management and conversation should be reinforced.

Over the course of a year, we conducted a study on future restoration work in the Sanyang wetland, a degraded permanent river wetland that is close to the center of Wenzhou city, China. Our main objective was to plan the restoration by using both structural indices and a valuation of the wetland's ecosystem services, thereby linking the science to human welfare. Based on field surveys and research into the history of the study area, we calculated both the potential and current values of the main ecosystem services. The results showed that the potential value at the Sanyang wetland was 55,332 yuan ha −1 yr −1 , while the current value was only 5807 yuan ha −1 yr −1 . In other words, 89.5% of the service value needs to be restored for the wetland to reach its potential value. We recommend that the service provided by the wetland's ability to purify the environment needs to be the top priority in restoration. In addition, water and sediment quality should also be greatly improved.

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.

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.

Temperature is important factor affecting the bacterial diversity.In order to disclose the effect of temperature on the diversity of microorganisms.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.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.