Restoration Of Aquatic Ecosystems Research Articles

Sustainability in Aquatic Ecosystem Restoration: Combining Classical and Remote Sensing Methods for Effective Water Quality Management

The utilization of Effective Microorganisms (EMs) for lake restoration represents a sustainable approach to enhancing water quality and rebalancing the ecology of aquatic ecosystems. The primary objective of this study was to evaluate the effects of two bioremediation treatment cycles employing EM-enriched biopreparations on water quality in the Siemiatycze lakes. Specifically, this research analyzed various parameters, including dissolved oxygen, transparency, chlorophyll-a, pH, chemical oxygen demand (COD), biochemical oxygen demand (BOD5), total phosphorus, total nitrogen, and suspended matter (SM), across eleven designated sampling locations. Additionally, this study employed remote sensing techniques, leveraging Sentinel-2 satellite imagery and the Maximum Chlorophyll Index (MCI), to detect and quantify algal blooms, with a particular focus on elevated chlorophyll-a concentrations. This comprehensive approach aimed to provide a holistic understanding of the impact of biotechnological reclamation on aquatic ecosystem restoration and sustainability. The study’s findings indicated a significant improvement in water quality in all lakes, with enhanced water clarity and oxygen profiles. Further, remote sensing studies indicated a reduction in algal blooms, particularly those with high chlorophyll-a concentrations. A considerable decrease in water eutrophication intensity was observed due to diminished nutrient concentrations. The improvements in water parameters are likely to enhance the living conditions of aquatic organisms. These results demonstrate the effectiveness of using EM-enriched biopreparations in the bioremediation of lakes, providing a sustainable approach to enhancing water quality and balancing aquatic ecosystems.

Evaluation of hydrological regime alteration and ecological flow processes in the changing environment of the Jialing River, China

Abstract Ecological flow is a key element in maintaining the biodiversity of a basin's aquatic ecosystem. This study quantifies the degree of hydrological regime alteration in the Jialing River and the contributions of various driving factors using the indicators of hydrologic alteration and range of variability approach (IHA-RVA), the river impact method (RI), and the elasticity coefficient method based on long-term hydro-meteorological data. Cross-wavelet analysis is used to reveal the periodicity and coherence of runoff and driving factors. Additionally, the improved Q90 method presents a more effective annual ecological flow process. The results show that the overall hydrological regime in the Jialing River has undergone a moderate change, with RVA and RI values of 45.02% and 0.66. Human activities contribute 54.68% to the changes in streamflow. Streamflow has an extremely significant correlation with precipitation and aridity index (Φ). Approximately 85% of the wavelet cone of influence (COI) area, tested at a 95% confidence level, falls within the region. The study also found that the ecological flow obtained through the improved Q90 method is more conducive to the healthy development of the river ecosystem in the Jialing River. These findings can provide some assistance for aquatic ecosystem restoration in the Jialing River.

Analyses of fin ray types to detect strontium markers in juvenile blunt-snout bream Megalobrama amblycephala

BackgroundRestocking by introducing hatchery-reared fish into wild habitats aids in the restoration of fishery aquatic ecosystems and reefs to increase the abundance of fish resources, restore the ecological balance of water bodies, and enhance ecosystem functioning. Accurately, rapidly, and effectively evaluating the success of restocking using chemical markers (e.g., strontium [Sr]) remains challenging for fisheries management. Consequently, for non-lethal fish sampling, hard tissues, such as fin rays, have received increasing attention as a target for marking method. However, data on the differences in marking different types of fin rays remain limited. Therefore, we exposed juvenile blunt snout bream individuals (Megalobrama amblycephala) to 0 (control group) or 800 mg/L of SrCl2·6H2O (marked group) for 5 days and transferred them into normal aerated water for post-immersion culture. We sampled their pectoral, dorsal, ventral, anal, and caudal fin rays. The Sr marks among the fin types were sampled at 0 and 20 days post-immersion and evaluated using an electron probe micro-analyzer (EPMA) for the five-day Sr/Ca ratios, along with line transect and Sr mapping analyses.ResultsSr marking signatures were observed in all fin types in the marked group, with a success rate of up to 100%. Although marking efficiency varied among the different fin ray types, the highest Sr/Ca ratios were most often detected in the dorsal fin. Cross-sectional Sr concentration maps of all fin rays sampled showed high-Sr domains in the marked group; in contrast, the entire cross-sections of the control group displayed low Sr contents, indicating successful marking efficiency.ConclusionsFin ray Sr marking is a successful method for juvenile M. amblycephala, with the advantages of non-lethality and negligible sampling injuries, facilitating the rapid and effective evaluation of Sr marking in restocking M. amblycephala.

Review on mechanism and remediation strategies of dissolved oxygen abnormal in surface water.

Dissolved oxygen (DO) is an important index to evaluate the quality of surface water environments. In recent years, anomalies in DO level have emerged as a major contributor to the decline of surface water quality. These anomalies have triggered several ecological and environmental challenges such as biodiversity loss, the degradation of water environmental quality, intensification of eutrophication, and an exacerbation of the greenhouse effect. Understanding the mechanisms underlying DO anomalies and devising targeted remediation strategies holds paramount importance in the scientific pursuit of water pollution control and aquatic ecosystem restoration. We explored and summarized the fluctuations and abnormal mechanism of DO concentration in surface water, focusing on factors like oxygen solubility, reoxygenation rates, and oxygen consumption by water bodies. We compiled a range of approaches for addressing DO anomalies, including pollution source management, artificial oxygenation, and the reconfiguration of aquatic ecosystems. Ultimately, we underscored the emerging significance of monitoring and regulating DO level in surface waters. Future research in this realm should encompass the establishment of distinct quality standards for surface water, the development of a comprehensive real-time spatial monitoring system for DO levels across watersheds, and the formulation of standardized procedures and technical norms.

A Quantitative Approach for Identifying Nitrogen Sources in Complex Yeongsan River Watershed, Republic of Korea, Based on Dual Nitrogen Isotope Ratios and Hydrological Model

Effective management of nitrate loading in complex river systems requires quantitative estimation to trace different nitrogen sources. This study aims to validate an integrated framework using soluble nitrogen isotope ratios (δ15N–NH4 and δ15N–NO3) and hydrological modeling (hydrological simulation program SPARROW) of the main stream and tributaries in the Yeongsan River to determine anthropogenic nitrogen fluxes among different land-use types in the complex river watershed. The δ15N–NH4 and δ15N–NO3 isotopic compositions varied across different land-use types (4.9 to 15.5‰ for δ15N–NH4 and −4.9 to 12.1‰ for δ15N–NO3), reflecting the different sources of nitrogen in the watershed (soil N including synthetic fertilizer N, manure N, and sewage treatment plant effluent N). We compared the soluble nitrogen isotopic compositions (δ15N–NH4 and δ15N–NO3) of the river water with various nitrogen sources (soil N, manure N, and sewage N) to assess their contribution, revealing that N from sewage treatment plant effluent as a point source was dominant during the dry season and N from forest- and soil-derived non-point sources was dominant due to intensive rainfall during the wet season. The coefficient of determination (R2) between the measured pollution load and the predicted pollution load calculated by the SPARROW model was 0.95, indicating a high correlation. In addition, the EMMA-based nitrogen contributions compared to the SPARROW-based nitrogen fluxes were similar to each other, indicating that large amounts of forest- and soil-derived N may be transported to the Yeongsan River watershed as non-point sources, along with the effect of sewage treatment plant effluent N as a point source. This study provides valuable insights for the formulation of management policies to control nitrogen inputs from point and non-point sources across different land-use types for the restoration of water quality and aquatic ecosystems in complex river systems. Given the recent escalation in human activity near aquatic environments, this framework is effective in estimating the quantitative contribution of individual anthropogenic nitrogen sources transported along riverine systems.

Environmental determinants of aquatic plant diversity differ between growth forms and range sizes

Aquatic plants are fundamental for aquatic ecosystems. Understanding variations in geographic patterns of aquatic plant diversity across growth forms is important for conservation and restoration of aquatic ecosystems. Environmental drivers, including climate, climate heterogeneity, water chemistry, habitat availability and geodiversity, could influence aquatic plant diversity and species composition across communities, yet their relative impacts remain controversial. Here, we examined geographic patterns and drivers of species richness of Chinese aquatic plants with different growth forms. We compiled distributions of 656 aquatic plant species in China at 50 × 50 km2 resolutions, and estimated richness patterns for species with different growth forms (i.e., helophyte, emergent, floating-leaved, free-drifting and submerged) and range sizes. Hierarchical partitioning analysis was employed to evaluate the independent effects of different environmental drivers on species richness. The Sørensen dissimilarity index and Multiple Matrix Regression with Randomization were used to compare the relative effects of environment and dispersal limitation on species dissimilarity between grid cells. Overall species richness was highest in northeastern and southern China, although species richness patterns varied across growth forms. Among environmental drivers examined, climate was the key determinant of the species richness of helophyte, emergent, floating-leaved and free-drifting plants, while habitat availability and water chemistry best explained the richness of submerged species. The richness of narrow-ranged species was dominated by climate, while the strongest determinant of wide-ranged species richness varied across growth forms. Our study mapped the species richness patterns of aquatic plants in China and indicated that the relationship between aquatic plant richness and environment significantly differed between growth forms and between wide-ranged and narrow-ranged species. These findings indicate the necessity of distinguishing growth forms in studies related to aquatic plants, and suggest that future climate change might threaten the distribution of narrow-ranged aquatic plants.

Quantification of agricultural best management practices impacts on sediment and phosphorous export in a small catchment in southeastern Sweden

Agricultural activities contribute to water pollution through sediments and nutrient export, negatively affecting water quality and aquatic ecosystems. However, implementing best management practices (BMPs) could help control sediments and nutrient losses from agricultural catchments. This study used the Soil Water Assessment Tool (SWAT) model to assess the effectiveness of four BMPs in reducing sediment and phosphorus export in a small agricultural catchment (33 km2) in southeastern Sweden. The SWAT model was first evaluated for its ability to simulate streamflow, sediment load, and total phosphorous load from 2005 to 2020. Then, the calibrated parameters were used to simulate the agricultural BMP scenarios by modifying relevant parameters. The model performed satisfactorily during calibration and validation for streamflow (NSE = 0.80/0.84), sediment load (NSE = 0.67/0.69), and total phosphorous load (NSE = 0.61/0.62), indicating its suitability for this study. The results demonstrate varying effects of BMP implementation on sediment and phosphorus (soluble and total) export, with no significant change in streamflow. Filter strips were highly effective in reducing sediment (−32%), soluble phosphorus (−67%), and total phosphorous (−66%) exports, followed by sedimentation ponds with −35%, −36%, and −50% reductions, respectively. Grassed waterways and no-tillage were less impactful on pollutant reduction, with grassed waterways showing a slight increase (+4%) in soluble phosphorus and no-tillage having a minimal effect on sediment (−1.3%) and total phosphorus (−0.2%) export. These findings contribute to the ongoing efforts to mitigate sediment and nutrient pollution in Swedish agricultural areas, thereby supporting the conservation and restoration of aquatic ecosystems, and enhancing sustainable agricultural practices.

Evolution Characteristics and Driving Factors of Cyanobacterial Blooms in Hulun Lake from 2018 to 2022

Algal blooms pose serious threats to water environments and the balance of aquatic ecosystems. Moreover, environmental factors may be the primary driver of bloom outbreaks. Studying the characteristics and driving factors of the evolution of cyanobacterial blooms can provide a scientific basis for the restoration of lake water environments and aquatic ecosystems. Based on the Landsat extended time series and practical ecological investigation, this study determined the bloom area and dominant species of cyanobacterial blooms in Hulun Lake, and analyzed their evolution characteristics and primary influencing factors. The results show that the area of bloom outbreak tended to decrease from 2018 to 2020, with the peak area remaining below 150 km2; in contrast, the bloom area showed an increasing trend in 2021–2022, with a maximum of 1970.55 km2 in June 2022. Pearson correlation analysis of bloom area and driving factors showed that the wind speed was the main influencing factor of bloom outbreaks. In 2022, there were five dominant species of cyanobacteria in summer and three in autumn. Redundancy analysis of the dominant species of cyanobacteria and water quality indicators showed that COD, DO, TP, WT, pH, and TN were the main influencing factors of the dominant species of cyanobacteria in summer, and COD, DO, TP, and WT were the main influencing factors in autumn. In general, cyanobacteria in Hulun Lake are sensitive to changes in wind speed and nutrient concentration. An important approach towards effectively reducing the intensity of cyanobacterial blooms in Hulun Lake and coping with the ecological risks associated with the changing environment would be to reduce external loads and regulate the ecosystem structure of the lake. In the future, while studying the law of cyanobacterial bloom outbreaks, attention should be paid to the impact of the cyanobacterial physiological status on bloom outbreaks.

Editorial: Advances in marine and freshwater monitoring to support aquatic ecosystem conservation and restoration

Editorial: Advances in marine and freshwater monitoring to support aquatic ecosystem conservation and restoration

Century-Scale Environmental Evolution of a Typical Subtropical Reservoir in the Guangdong–Hong Kong–Macao Greater Bay Area

As one of the world’s four Greater Bay Areas, the Guangdong–Hong Kong–Macao Greater Bay Area (GBA) faces many environmental challenges along with rapid economic development, causing significant degradation of aquatic ecosystems. However, there is limited knowledge on long-term environmental changes (i.e., >50 years), and restoration of the degraded aquatic ecosystems in the GBA has become increasingly difficult. This study selects a typical inland water body, the Miaotan Reservoir, from Huizhou City in the GBA, to explore long-term changes in water and the eco-environment over the past 70 years and to provide some restoration and management strategies for degrading aquatic ecosystems in the region. We collected a sediment core from the reservoir center and established an age–depth profile by integrating 210Pb and 137Cs dating. We then set up high-resolution diatom community succession stratigraphy and multiple indicators (grain size, element, geochemical and social indicators) as responses to environmental changes in the reservoir. Our results show that significant changes have occurred in the ecosystem and environment of the Miaotan Reservoir and its catchment over the past 70 years. The diatom community underwent a gradual transition from absolute dominance of the mesotrophic species Aulacoseira granulata to dominance of the eutrophic species Nicizschia gracilis, Nicizschia palea and Achanathes sp., indicating the onset of water quality degradation and ecosystem changes in the 1990s due to eutrophication. The RDA (Redundancy analysis) results demonstrate that exogenous pollutant inputs into the Miaotan Reservoir resulting from agricultural activities over the period led to serious environmental changes, e.g., toxic algal bloom and heavy metal pollution. This study enriches our understanding of long-term environmental changes in inland lakes and reservoirs in South China and provides insights into the restoration and management of aquatic ecosystems in the GBA.

Driving forces of hydrological health and multifractal response of fish habitat in regulated rivers

Climate change and anthropogenic activities are major influences on the hydrological cycle, further altering river hydrological health. However, the characteristics of the forces in driving the variations of hydrological health at long-short time scales (annual, seasonal, monthly), as well as the potential impacts of these variations on aquatic habitats, remain unclear. In this study, the flow threshold method was introduced to identify the inherent characteristics of river hydrological health degree (RHD) evolution in the upper reaches of the Yangtze River (URYR) through the extreme-point symmetric modal decomposition (ESMD) method and range of variation approach (RVA). The RHD under unregulated conditions was reconstructed to quantify the impacts of anthropogenic activities and climate change. Subsequently, a multifractal model was proposed to establish the relationship between RHD and habitat-weighted usage area (WUA) during the spawning period of the Four Famous Major Carps, aiming to analyze the response mechanisms of habitat conditions to RHD fluctuations. The results showed that the RHD in the URYR exhibited degradation characteristics, experiencing a moderate change with a value of 0.44. Climate change was identified as the dominant factor causing the annual-scale decline in RHD, with an average impact weight of 62.9%. At the annual scale, Anthropogenic activities exacerbate (−3.4), counteract (20.1), and counteract (20.5) the adverse climatic impacts at Yichang, Cuntan, and Zhutuo stations, respectively. Additionally, the effect of human activities during the flood season is slight, with the most favorable and unfavorable impacts occurring in December (50.7) at the Zhutuo station and in October (−27.2) at the Yichang station. Under the influence of driving forces, the multifractal correlation of the RHD-WUA system tended to homogenized as the time window increased, indicating the presence of potential nonlinear dependence, asymmetric fractal characteristics, and positive-to-negative persistence transitions. Therefore, modeling river health considering fish habitat cannot be limited to linear paradigms. The findings provide valuable insights for the management and restoration of aquatic ecosystems.

Eco-Engineering Technologies and Achievements of Projects for Reconstructing Landscape Water from Aquaculture Ponds in Shanghai

The post-evaluation of ecological redevelopment is a good way of describing its achievements. In this paper, eco-engineering techniques, including hydrodynamic circulation reconstruction, water purification treatment, and aquatic ecosystem restoration, along with plant harvesting management, have been applied to reconstruct landscape water from aquaculture ponds. Both sediments and water quality were sampled and tested for basic physicochemical parameters and heavy metals. The ecological redevelopment of landscape water reconstructed from aquaculture ponds was evaluated using the single and Nemero comprehensive pollution index methods. The results demonstrate that nutrients, including organic matter and organic nitrogen and their ratio to sediments, were confirmed to be in a state of moderate pollution, while the ecological risk of heavy metal pollution was relatively low. Although the concentrations of total nitrogen and total phosphorus were significantly higher than those of other indexes, ammonia nitrogen, total nitrogen and total phosphorus, all presented obvious downward trends over time, and a majority of the water samples exhibited mild-to-moderate pollution levels. In general, this study provides a set of reference values for redeveloping water ecosystems from aquaculture ponds using eco-engineering technologies.

Two centuries of changes - revision of the hydrography of the Biebrza Valley, its transformation and probable ecohydrological challenges

Human-induced changes in hydrography have led to serious changes in the hydrological and ecological condition of ecosystems, including habitat fragmentation and reduction of water in the landscape. The aim of this study was to assess the transformation of the hydrographic network in the Biebrza National Park (BbNP) over the XIX-XXI centuries and to analyze its probable ecohydrological challenges. The analysis of changes in the hydrographic network was based on a spatial comparison of hydrographic network elements on the basis of spatial sources. As a result of both natural and human-induced processes, there have been significant changes to elements of the hydrographic network of the BbNP. The length, area and sinuosity of the rivers in the BbNP area have decreased significantly in the XIX-XXI centuries, in contrast to the length of the canals dug in the XIX century - their length increased. On average, river channelization reduced channel water storage capacity by 49%. In other cases the average decrease of storage capacity of the channel was about 14%. As a result of drainage works in the XIX century, the network of drainage ditches was established in the BbNP, which was significantly extended (more than 6 times) in the XXI century. A comprehensive analysis of hydrographic changes, their causes and possible consequences is necessary to understand the dynamics of river networks. It also makes it possible to predict the future ecohydrological response of rivers to anthropogenic influences and climate change, thus helping to establish appropriate management and ecohydrological restoration of aquatic ecosystems.

Ecological network-based food web dynamic model provides an aquatic population restoration strategy

Aquatic ecosystem restoration is a crucial aspect of ecological management. However, current research tends to concentrate on single factors, such as water quality or biodiversity, rather than ecological restoration strategies based on the characteristics of an ecological network system. Due to the large number of parameters to be considered, the latter approach presents still full of challenges in practical implementation. This study introduces a food web dynamic model that can guide and facilitate aquatic ecological network restoration. The model calculates the network-based interaction relationships of species in the food web, predicting the changes in ecosystem structure and function. We test our food web model by conducting a case study. The food web considered 9 kinds of species nodes, 12 links, and 1 uncertain predator–prey interaction. Our model simulations presented a strong correlation with the measured data (R2 = 0.837). We performed sensitivity analysis on 12 parameters and also conducted link prediction analysis, which revealed that there was no predator–prey relationship between species A and N (A + N = 0). By comparing population dynamics under 3 conditions, we determined that the mass reproduction of nonnative species and the population decline of native species were both related to indirect food web interactions. Finally, we comprised 27 scenarios, including fishing and stock enhancement approaches, to predict the potential restoration effects. The results showed that the fishing approach was more effective in removing alien species when the fishing frequency was shorter. It was also found that selecting catches and releasing native or endangered species back into the environment (F4, F5, F6, and F12) was necessary. On the other hand, the stock enhancement approach was concluded to be effective in increasing the number of native species as long as the frequency of enhancement was high (per 1 year, S1, S2, and S3). However, it was found to be challenging to rely on this approach to reduce the population of nonnative species. This research will enhance the previous studies in terms of (a) including whole species interactions in the ecological network; (b) considering the influence of abiotic factors, such as water quality, terrigenous carrying capacity, shoreline substrate, and hydrological connection in our model; and (c) coupling significant parameters in ecological restoration practices. This research will provide a valuable tool for managing aquatic ecological networks and decision-making suggestions for determining restoration schemes in complex aquatic food webs.

Long-term monitoring and phenological analysis of submerged aquatic vegetation in a shallow lake using time-series imagery

Submerged aquatic vegetation (SAV) is a key functional group for the restoration of wetlands and aquatic ecosystems. It plays a vital role in the stability of ecosystem structure and function in shallow lakes and reservoirs. With Baiyangdian Lake as the research area, Landsat TM/ETM+/OLI and Sentinel-2 imagery datasets were used to explore the phenological characteristics of SAV over different time scales and construct a phenological map of the SAV groups. The long-term spatial distribution characteristics and trends of SAV from 1986 to 2021 were analyzed. The results show the following: (1) the harmonic analysis of time series (HANTS) eliminated abnormal observations and noise. Normalized difference vegetation index (NDVI) time series curves generated after HANTS accurately reflected the phenological characteristics of SAV. The early spring submerged aquatic vegetation (SAV1), such as Potamogeton crispus, entered the germination period in late February at the earliest (DOY = 53). The mature period ran from April to May, after which SAV1 began to decline gradually. The length of the growing season (LOS) was about 110 days. SAV2, which was represented by Ceratophyllum demersum, Myriophyllum verticillatum, and Potamogeton pectinatus, germinated in early April (DOY = 99). The mature period ran from July to September. The length of the growing season was 210 days. (2) The decision tree constructed based on the NDVI and modified normalized difference water index (MNDWI) identified SAV with an accuracy of 89.7%. (3) The distribution range of the SAV changed dramatically during 1986–2021. According to the area change, it can be divided into a shrinkage period, expansion period, degeneration period, and initial period of recovery. The succession trend of SAV provide a theoretical scientific basis and technical support for the ecological restoration and management of shallow lake ecosystems.

Long-term effects of Ag NPs on denitrification in sediment: Importance of Ag NPs exposure ways in aquatic ecosystems

The widespread use of silver nanoparticles (Ag NPs) inevitably leads to their increasing release into aquatic systems, with studies indicating that the mode of Ag NPs entry into water significantly affects their toxicity and ecological risks. However, there is a lack of research on the impact of different exposure ways of Ag NPs on functional bacteria in sediment. This study investigates the long-term influence of Ag NPs on denitrification process in sediments by comparing denitrifies responses to single (pulse injection of 10 mg/L) and repetitive (1 mg/L × 10 times) Ag NPs treatments over 60-day incubation. Results showed that a single exposure of 10 mg/L Ag NPs caused an obvious toxicity on activity and abundance of denitrifying bacteria on the first 30 days, reflecting by the decreased NADH amount, ETS activity, NIR and NOS activity, and nirK gene copy number, which resulted in a significant decline of denitrification rate in sediments (from 0.59 to 0.64 to 0.41–0.47 μmol15N L−1 h−1). While inhibition was mitigated with time and denitrification process recovered to the normal at the end of the experiment, the accumulated nitrate generated in the system showed that the recovery of microbial function did not mean the restoration of aquatic ecosystem after pollution. Differently, the repetitive exposure of 1 mg/L Ag NPs exhibited the evident inhibition on metabolism, abundance, and function of denitrifiers on Day 60, due to the accumulated amount of Ag NPs with the increased dosing number, indicating that the accumulated toxicity on functional microorganic community of repetitive exposure in less toxic concentration. Our study highlights the importance of Ag NPs entry pathways into aquatic ecosystem on their ecological risks, which affected dynamic responses of microbial function to Ag NPs.

High temperature frequently increases facilitation between aquatic foundation species: A global meta‐analysis of interaction experiments between angiosperms, seaweeds and bivalves

Abstract Many studies have quantified the ecological impacts of individual foundation species (FS). However, emerging data suggest that FS often co‐occur, potentially inhibiting or facilitating one another, thereby causing indirect, cascading effects on surrounding communities. Furthermore, global warming is accelerating, but little is known about how interactions between co‐occurring FS vary with temperature. Shallow aquatic sedimentary systems are often dominated by three types of FS: slower‐growing clonal angiosperms, faster‐growing solitary seaweeds and shell‐forming filter‐ and deposit‐feeding bivalves. Here, we tested the impacts of one FS on another by analyzing manipulative interaction experiments from 148 papers with a global meta‐analysis. We calculated 1942 (non‐independent) Hedges' g effect sizes, from 11,652 extracted values over performance responses, such as abundances, growth or survival of FS and their associated standard deviations and replication levels. Standard aggregation procedures generated 511 independent Hedges' g that were classified into six types of reciprocal impacts between FS. We found that (i) seaweeds had consistent negative impacts on angiosperms across performance responses, organismal sizes, experimental approaches and ecosystem types; (ii) angiosperms and bivalves generally had positive impacts on each other (e.g. positive effects of angiosperms on bivalves were consistent across organismal sizes and experimental approaches, but angiosperm effect on bivalve growth and bivalve effect on angiosperm abundance were not significant); (iii) bivalves positively affected seaweeds (particularly on growth responses); (iv) there were generally no net effects of seaweeds on bivalves (except for the positive effect on growth) or angiosperms on seaweeds (except for the positive effect on ‘other processes’) and (v) bivalve interactions with other FS were typically more positive at higher temperatures, but angiosperm‐seaweed interactions were not moderated by temperature. Synthesis. Despite variations in experimental and spatiotemporal conditions, the stronger positive interactions at higher temperatures suggest that facilitation, particularly involving bivalves, may become more important in a future warmer world. Importantly, addressing research gaps, such as the scarcity of FS interaction experiments from tropical and freshwater systems and for less studied species, as well as testing for density‐dependent effects, could better inform aquatic ecosystem conservation and restoration efforts and broaden our knowledge of FS interactions in the Anthropocene.

Response of Growth-Related Traits of Submerged Macrophytes to Light Reduction: A Meta-Analysis

Underwater light reduction is presumably becoming more frequent and intensified due to eutrophication and algal blooms, which may significantly affect submerged macrophytes’ growth. However, a comprehensive understanding of how light reduction influences growth-related traits and responses is currently lacking. Here, we compiled data from 333 records of 62 published works that used controlled experiments to explore the responses of functional traits associated with growth to light reduction. Our results indicated that light reduction significantly decreased the relative growth rate (RGR), ramet number (RM), shoot biomass (SB), root biomass (RB), soluble carbohydrates (SC), and leaf number (LN) by 38.2%, 60.0%, 59.2%, 55.4%, 30.0%, and 56.1%, respectively, but elevated the chlorophyll content (Chl) by 25.8%. Meanwhile, the responses of RGR to light reduction increased significantly with the responses of RM, SB, RB, and root-to-shoot ratio (R/S). Considering the relationships among the growth-related traits, we further found that the responses of RGR to light reduction were mainly driven by the RM rather than leaf photosynthetic capability, indicating the importance of tiller ability under low light stress. We also identified a tipping point of the response of RGR to light reduction, which might be incorporated into hydrophyte dynamic models to improve precision. Our results highlight the importance of growth-related traits, andthese traits may need to be incorporated into models to improve the prediction of distribution and area for submerged species or to provide guidance for the restoration and sustainable development of aquatic ecosystems.

Identification of the sources of different phosphorus fractions in lake sediments by oxygen isotopic composition of phosphate

Phosphorus (P) released from sediment driven by oxidation-reduction potential and enzymes can increase the concentrations of dissolved P in the overlying water, which trigger widespread algal blooms. Therefore, identification sediment P sources is critical for the management of P and restoration of eutrophic aquatic ecosystem. Sediment P fractions have been widely reported, whereas little is known regarding the source and pathway of different P fractions in eutrophic lake sediments. In this study, we applied chemical sequential extraction with oxygen isotopic compositions of phosphate (δ18OP) to identify the inorganic P (Pi) source in the sediments of Lake Dianchi, China. Results show that contents of organic P (Po), HCl-Pi, NaOH-Pi, and NaHCO3-Pi of sediment were the main P fractions compared with that of sediment H2O-Pi, which was attributed to the bioavailable difference of these P fractions. Significant difference on the equilibrium values of δ18OP (δ18OP-eq), δ18OP of sediment P fractions, and δ18OP of external P was observed, which reflected the complex transformation processes of these P fractions in sediments. Further, the values of sediment δ18ONaHCO3-Pi at some sites (17.2–22.5‰) deviated from δ18OP-eq (14.7–19.0‰), and these values fell into the values of δ18OP for external P (7.7–23.8‰), suggesting that sediment NaHCO3-Pi at these sites derived from external P. Comparison the values of sediment δ18ONaOH-Pi (14.5–24.9‰) with δ18OP-eq and δ18O of external P sources suggested that sediment NaOH-Pi was not only from external P, but also from sedimentary Po remineralization. Pi released from sediment NaOH-Pi may be responsible for the higher values of sediment δ18OHCl-Pi (15.2–20.8‰) than that of soils (13.1–15.3‰) and phosphate rock (8.9–12.6‰). Results gained from this study provided critical insights for the source and biogeochemical cycling of P across the sediment-water interface in the eutrophic lake.

Cyanobacterial Blooms Increase Functional Diversity of Metazooplankton in a Shallow Eutrophic Lake

Harmful cyanobacterial blooms disrupt aquatic ecosystem processes and biological functions. However, studies focusing on the effect of cyanobacterial blooms on the functional diversity of consumers are still insufficient. To examine the interactions of cyanobacterial blooms and the diversity and composition of metazooplankton, we investigated the variation in metazooplankton and their driven variables during the cyanobacterial bloom and non-bloom periods in 2020 and 2021 in Lake Xingkai. We found that cyanobacterial blooms reduced the metazooplankton species diversity but increased their biomass, functional dispersion, and functional evenness. Generalized additive mixed model results revealed that cyanobacteria showed different effects on metazooplankton biodiversity and functional diversity during the bloom and non-bloom periods. Variance partitioning analysis indicated that cyanobacteria, physicochemical variables, and temporal variation explained 15.93% of the variation in metazooplankton during the bloom period and 20.27% during the non-bloom periods. Notably, cyanobacteria during the bloom period explained more variations in metazooplankton composition than those during the non-bloom period. Our results suggest that cyanobacterial blooms significantly impact the functional diversity and community composition of metazooplankton. Physicochemical and spatiotemporal factors may mask the effects of cyanobacteria on metazooplankton. Our findings may improve the understanding of the dynamics and responses of metazooplankton communities to environmental changes and cyanobacterial blooms disturbances and enhance our ability to assess the effectiveness of aquatic ecosystem restoration and eutrophication management.