Lake Restoration Projects Research Articles

Anatomical hooking location and bleeding occurrence in northern pike (Esox lucius) caught in recreational catch-and-release angling in a lake with reduced prey fish availability

Catch-and-release (C&R) is a common practice in recreational angling for northern pike (Esox lucius), whereby the angler releases the fish back into the water after capture with the expectation that it will survive with negligible stress and physical injuries. This may not always be the case, as hooking in critical anatomical locations, such as gills, esophagus, and stomach, increases the frequency of bleeding at the hook wound and has been recognized as a key determinant of post-release mortality in pike. Several factors (e.g. bait type and size, hook characteristics, and fish length) can influence the risk of hooking in critical locations, and the fish’s willingness to strike the fishing lure/bait may largely depend on previous feeding history and associated motivation to feed. In this respect, food deprivation and greater feeding motivation can be expected to result in an intensified response and more forceful attacks on fishing lures/baits, which could increase the risk of hooking injuries in sensitive tissues, as the fish may ingest the hook more deeply. Here, we assess the hooking location and bleeding occurrence in pike caught on soft plastic shads and baitfish in a shallow eutrophic lake. The prey fish density of this lake, primarily common roach (Rutilus rutilus), has been substantially reduced by seining as part of a lake restoration project. Experimental angling sessions took place at the end of 2020 and 2022, approximately 1–2 months and 25–26 months after the initial reduction in prey fish density, respectively. Removal of roach from the lake was also done regularly by seining after the angling sessions in 2020. Pike angled in 2022 had significantly lower body condition than individuals caught in 2020, indicating that mass removal of roach from the lake resulted in food shortage. The risk of hooking in critical locations (herein defined as hooking in gills and back of mouth) was not associated to angling year, body condition, or length of the pike. However, across the two angling years, the incidence of hooking in critical locations was higher for soft plastic shads compared to baitfish (24.2% versus 7.4%). Pike caught on soft plastic shads also bled more frequently than individuals caught on baitfish (19.7% versus 6.2%), most likely due to the fact that hooking in the gills almost exclusively occurred with soft plastic shads. Bleeding propensity was also not related to angling year, body condition, or fish length. Hence, the present study found no evidence that long-term reductions in food availability and resulting declines in body condition influence how pike strike and ingest fishing lures/baits, at least not in a manner that increases the risk of hooking injuries in sensitive locations. Instead, bait type seems to play the largest role for the observed bleeding patterns. We recommend that future studies investigate the potential effects of C&R angling on the post-release survival of pike with reduced body condition due to limited food availability.

Monitoring and Effect Evaluation of an Ecological Restoration Project Using Multi-Source Remote Sensing: A Case Study of Wuliangsuhai Watershed in China

Quantitative assessment of the effectiveness of ecological restoration provides timely feedback on restoration efforts, and helps to accurately understand the extent of restoration, while providing scientific support for optimizing restoration programs. In recent decades, the Wuliangsuhai watershed in China’s Inner Mongolia Autonomous Region has been affected by anthropogenic activities, resulting in an increasingly unbalanced ecological environment. In order to curb environmental degradation, the local government implemented the “mountain, water, forest, field, lake and grass ecological protection and restoration project of the Wuliangsuhai watershed” from 2018 to 2020. The project has been completed and there is an urgent need for remote sensing monitoring to aid in performance evaluation. We took the ecological protection and restoration area of the Wuliangsuhai watershed in China as the research object, applied multi-source remote sensing imagery and auxiliary data such as meteorology and geographic basic data, extracted information of each evaluation index before and after the implementation of this project, and used the entropy value method to determine the index weights to comprehensively evaluate the ecological restoration effect. The results showed that after the implementation of the ecological restoration project, the vegetation coverage was further improved, the effectiveness of desert management was obvious, soil and water conservation capacity was strengthened, the ecosystem became more stable, and the areas with good environment were mostly located in the central and eastern parts. A total of 37.86% of the areas had obvious ecological restoration effects, and all indicators were further improved. Among the main treatment areas, the restoration effect of the Wuliangsuhai water ecological restoration and biodiversity conservation area was the best. The restoration effect will be further accentuated over time. This study provides a scientific reference for the further management of the ecological environment in the watershed and can provide a reference for the evaluation of the ecological restoration effect in similar areas in the future.

区域生态保护修复碳汇潜力评估方法与应用——基于第一批山水林田湖草生态保护修复工程的研究

PDF HTML阅读 XML下载 导出引用 引用提醒 区域生态保护修复碳汇潜力评估方法与应用——基于第一批山水林田湖草生态保护修复工程的研究 DOI: 10.5846/stxb202202220422 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家重点研发计划专项(2019YFC0507804) Methodology and application of carbon sink potential assessment for regional ecological conservation and restoration: Based on the research of the first batch of pilots for ecological protection and restoration project of mountains-rivers-forests-farmlands-lakes-grasslands system Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:山水林田湖草生态保护修复工程是生态系统恢复的有效措施,借助生态保护与修复提升生态系统固碳潜力,无疑是土地利用碳减排的新路径。基于山水林田湖草沙综合整治视角,从生态系统的格局和质量两个方面评估了第一批山水林田湖草生态保护修复工程的实施效果,并借助InVEST模型定量化地分析了工程实施前后的生态系统碳汇能力。结果如下:(1)山水林田湖草生态保护修复试点工程加速了各类生态系统间的相互转化,主要表现为城镇生态系统的增加、农田生态系统的减少;工程区植被覆盖度整体提高,NDVI值平均水平不断上升、高值区逐步扩大,劣质、低质生态系统改造成果显著,陆地生态系统质量有效提升。(2)试点区生态系统碳汇能力和潜力得到有效改善,工程累积增加碳汇面积22.68%,其中工程实施前期增加碳汇面积18.06%,中后期增加面积4.62%;工程实施后2018年碳汇总量增加32.74 Tg,2020年碳汇总量增加31.28 Tg,年均碳汇潜力的提升约1.24%;工程在增加生态系统质与量、碳汇潜力的巩固与提升上具有显著成效。分析结果表明,生态保护修复是实现"双碳"目标的必然选项,这也是生态保护修复在实现"双碳"目标中的基本定位。 Abstract:The ecological protection and restoration project of mountains-rivers-forests-farmlands-lakes-grasslands system is an effective measure for ecosystem restoration. Enhancing the carbon sequestration potential of ecosystems with the help of ecological protection and restoration is undoubtedly a new path for land use carbon reduction. Based on the perspective of comprehensive improvement of mountains-rivers-forests-farmlands-lakes-grasslands system, this paper evaluates the implementation effect of the first batch of landscape, forest, field, lake and grass ecological protection and restoration projects from two aspects of ecosystem pattern and quality, and quantitatively analyzes the ecosystem carbon sink capacity before and after the project implementation with the help of InVEST model. The results are as follows: (1) the pilot project of ecological protection and restoration of mountains-rivers-forests-farmlands-lakes-grasslands system accelerated the mutual transformation of various ecosystems, mainly manifested in the increase of urban ecosystems and the decrease of farmland ecosystems. The overall vegetation cover in the pilot area has increased and the average NDVI value has been rising. The high value area has been gradually expanded, the transformation of poor quality and low quality ecosystems has achieved remarkable results, and the quality of terrestrial ecosystems has effectively improved. (2) The carbon sink capacity and potential of the ecosystem in the pilot area has been effectively improved. The project has increased the carbon sink area by 22.68% cumulatively, including 18.06% in the early stage of the project implementation and 4.62% in the middle and late stages. The total carbon sink increased by 32.74 Tg in 2018 and 31.28 Tg in 2020 after the project implementation, with an increase of 1.24% in the average annual carbon sink potential. The project has significant effectiveness in increasing the quality and quantity of the ecosystem and consolidating and improving the carbon sink potential. The analysis results show that ecological protection and restoration is an inevitable option to achieve the "double carbon" target, which is also its basic position in achieving the "double carbon" target. 参考文献 相似文献 引证文献

Urbanization promotes specific bacteria in freshwater microbiomes including potential pathogens

Freshwater ecosystems are characterized by complex and highly dynamic microbial communities that are strongly structured by their local environment and biota. Accelerating urbanization and growing city populations detrimentally alter freshwater environments. To determine differences in freshwater microbial communities associated with urbanization, full-length 16S rRNA gene PacBio sequencing was performed in a case study from surface waters and sediments from a wastewater treatment plant, urban and rural lakes in the Berlin-Brandenburg region, Northeast Germany. Water samples exhibited highly habitat specific bacterial communities with multiple genera showing clear urban signatures. We identified potentially harmful bacterial groups associated with environmental parameters specific to urban habitats such as Alistipes, Escherichia/Shigella, Rickettsia and Streptococcus. We demonstrate that urbanization alters natural microbial communities in lakes and, via simultaneous warming and eutrophication and creates favourable conditions that promote specific bacterial genera including potential pathogens. Our findings are evidence to suggest an increased potential for long-term health risk in urbanized waterbodies, at a time of rapidly expanding global urbanization. The results highlight the urgency for undertaking mitigation measures such as targeted lake restoration projects and sustainable water management efforts.

Impacts of sediment resuspension on phytoplankton biomass production and trophic transfer: Implications for shallow lake restoration

Wind-induced sediment resuspension in shallow lakes may enhance nutrient availability while reducing light availability for phytoplankton growth, thereby affecting the entire food-web. Lake restoration projects that reduce wind-induced resuspension are expected to enhance trophic transfer efficiencies, thereby improving food-web structure and functioning. Yet, reduced resuspension may also lead to lower nutrient concentrations in the water column, promote benthic algae development, reduce phytoplankton biomass production and thereby reduce secondary production by zooplankton. Lake Markermeer is a shallow delta lake in The Netherlands subject to wind-induced sediment resuspension. Restoration project Marker Wadden consists of newly built islands aiming to reduce sediment resuspension and promote higher trophic levels. Here, we tested the effects of reduced sediment resuspension on phytoplankton biomass build-up, benthic algae development, and zooplankton abundances at different temperatures in a 14-day indoor microcosm experiment. We used Marker Wadden sediment with three resuspension intensities combined with three temperatures, to also test effects of higher temperatures in shallow sheltered waters. Reduced sediment resuspension decreased nutrient concentrations and phytoplankton biomass build-up, while increasing light availability and enhancing benthic algae biomass development. Reduced sediment resuspension furthermore increased zooplankton biomass. Enhanced sediment resuspension and higher temperatures synergistically interacted, maintaining a high level of inorganic suspended solids. Our experimental results are in line with long-term seasonal observations from Lake Markermeer. Our findings demonstrate that for shallow lakes suffering from wind effects, measures such as Marker Wadden aimed at reducing sediment resuspension can be effective in restoring secondary production and supporting higher trophic levels.

Holocene lake phosphorus species and primary producers reflect catchment processes in a small, temperate lake

AbstractThis paleolimnological study aims to investigate how natural processes and anthropogenic land‐use changes have affected sedimentary phosphorus (P) forms and primary producers in a small, temperate lake (Lake Fuglsø, Denmark) throughout the Holocene. Our multi‐proxy approach uses pollen, X‐ray fluorescence scanning, carbon (C) and nitrogen contents and stable isotopes, sequential P extraction, 31P nuclear magnetic resonance spectroscopy, pigments, diatoms, and plant macrofossils from a 14C‐dated sediment record. We found three periods of human impact: (1) low disturbance from domestic grazing during the early/mid Neolithic (~3600 to ~2600 BC), (2) higher disturbance because of animal husbandry and some grain cultivation during the Late Bronze and Pre‐Roman Iron Age (~800 BC to AD ~100), and (3) strong disturbance caused by domestic grazing, intensified crop cultivation and, in particular, by retting of fiber plants during the Middle Ages and Renaissance (AD ~1000 to ~1700). Cultural eutrophication during the latter phase caused unprecedented changes in the lake, including altered species composition, high production, and strongly accelerated sediment accumulation rates. Generally, catchment deforestation was related to elevated proportions of metal (iron, aluminum, calcium)‐bound P forms in the sediment, while high tree cover correlated with elevated proportions of P forms associated with organic material (“organic” P, humic‐bound P, refractory organic P) and loosely bound P. During phases with forest in the catchment, silicon (Si) inputs to the lake were insufficient and diatom frustules were mostly absent in the sediments. In contrast, diatoms thrived in the lake when the landscape was open and erosional Si influx was high. This study is the first to show long‐term (~eight millennia) and recurring Si limitation of diatoms, a finding that may explain the absence of diatoms in sediment records of other sites too. In summary, human land‐use with preceding deforestation accelerated the transport of nutrients and elements from the terrestrial to the aquatic environment, leading to substantial and irreversible changes in Lake Fuglsø. Our study is a good example of the tight links between catchment processes and lake status, indicating that catchment dynamics should be considered in lake restoration projects, particularly for lowland lakes with high catchment : lake area ratios.

Restoring shallow lakes impaired by eutrophication: Approaches, outcomes, and challenges

Shallow lake ecosystems are widely impaired by eutrophication. Lake restoration projects frequently fail or are only partially successful, reflecting that environmental managers face difficult challenges in addressing this complex problem. Key uncertainties relate to selecting appropriate methods and predicting the resulting response trajectory, that is, “what should be done, how much improvement should be expected, and how long will it take?” This review critically evaluates approaches applied to address eutrophication in shallow lakes. A set of shallow lake restoration case studies from across the globe, involving moderate to high effort monitoring, was evaluated to determine common features and to identify advantages/disadvantages and drivers of successful restoration projects. Approaches are broadly grouped into four categories: 1) external nutrient load reductions, 2) internal nutrient load reductions, 3) biomanipulation, and 4) hydrological manipulations. Case studies highlight that external load reduction is an essential component of successful restoration, although supplementary measures can support restoration goals. To inform planning and help set realistic expectations, the following key challenges to the restoration of shallow lakes were identified: 1) insufficient reductions in external nutrient loads, 2) biogeochemical lags, 3) resistance of a stable, algal-dominated state due to hysteresis in the turbidity–nutrient load relationship, 4) delayed macrophyte reestablishment, 5) climate change, 6) need for lake-specific approaches, and 7) social and political shortcomings. Managing these challenges is crucial to the success of shallow lake restoration projects.

Effects of plant size on the growth of the submersed macrophyte Vallisneria spinulosa S.Z.Yan at different light intensities: implications for lake restoration

The growth and reproduction of plants are highly size-dependent and markedly affected by light intensity. Vallisneria spinulosa S.Z.Yan is a common submersed macrophyte and is widely used in current lake restoration projects. The size of plants to be used to get optimal restoration results is not known, however, and may vary with water clarity. In this study, the effects of different plant sizes (large, medium and small, i.e. approximately 2.40 g, 1.01 g and 0.27 g per plant) on the growth and reproduction of V. spinulosa were tested under three light intensities (high, medium, low, i.e. 25%, 6% and 1% of full sunlight, respectively). Both plant size and light intensity were found to be of great significance for plant growth and reproduction. The relative growth rate (RGR) of biomass was higher for small than for large plants at both high and low light, while the absolute growth rate (AGR) of biomass was higher for large-sized plants at medium and high light intensity. Asexual reproduction of V. spinulosa was positively correlated with plant size and more affected by plant size than by light intensity, while sexual reproduction was most affected by light intensity. RGR and AGR of plant height were highest for medium-sized plants at moderate light intensity. Therefore, the size of submersed macrophytes should be considered when using this species in connection with lake restoration. Verification of our results under field conditions is needed, though, before firm conclusions can be reached about the optimal plant size of V. spinulosa to be used in lake restoration as also other factors like, e.g. periphyton shading and wave actions may play a role.

Valuation of Ecosystem Services from an Important Wetland of Nepal: A Study from Begnas Watershed System

Determining the economic value of wetlands is essential while creating sustainable wetland development plans and market-based ecological protection strategies. This paper studies the value of Begnas Watershed System by assessing the economic values of its selective ecosystem servicees. We conducted household surveys, multiple focus group discussions, stakeholder consultation, indepth interviews and used a combination of market and non-market based valuation methods like market price method, travel cost method, revealved price method, contingent valuation method, and benefit transfer method to determine the value of ecosystem services of the Begnas Watershed System. This study discovered that the economic benefit generated from the wetland was worth US 3.91 million per year, equivalent to US 650.67 per household and US$ 799.79 per hectare. The direct non-consumptive (recreational) service was the most beneficial service holding about 85% of the total value. This research study concludes that the Begnas Watershed System is economically beneficial for the local communities living in or close to the watershed and is worth the investment in lake restoration projects. This results from this study will serve as an important tool for policymakers and stakeholders during the formulation of management plans for the wetland's sustainability.

Detection and density of breeding marsh birds in Iowa wetlands.

Accounting for imperfect detection is an important process when obtaining estimates of density or abundance for breeding birds, and this is particularly true when researchers are monitoring birds to assess the success of restored wetlands. Due to the dramatic decline in areal cover and habitat quality, wetland restoration in the Prairie Pothole Region (PPR) is critically important to breeding birds. The Shallow Lakes Restoration Project (SLRP), a partnership between the Iowa Department of Natural Resources and Ducks Unlimited, Inc., aims to restore degraded shallow lakes throughout the Iowa PPR. We conducted unlimited-radius point counts with call-broadcast surveys for breeding marsh birds at 30 shallow lakes in various stages of restoration in 2016 and 2017. Our goals were to assess the impact of covariates on detection probability and estimate density of these species at non-restored, younger (1-5 years since restoration), and older (6-11 years since restoration) restorations. Detection probability ranged between 0.07 ± 0.009 (SE) for Red-winged Blackbird and 0.40 ± 0.09 (SE) for Common Yellowthroat. Percent cattail had a positive quadratic effect on detection probability for four species, with detection decreasing sharply as percent cattail increased and increasing slightly with 100% cattail cover. Wind speed negatively influenced the detection probability of Pied-billed Grebes but had a negative quadratic effect on the detection probability of Marsh Wrens. Both restored shallow lakes had greater densities of breeding Pied-billed Grebes, Marsh Wrens, and Yellow-headed Blackbirds than non-restored shallow lakes, but there was no significant difference between younger and older restorations. Including both habitat and environmental covariates on models for detection probability can improve the precision of estimates for density and should be considered when assessing bird populations pre- and post-restoration of shallow lakes.

Relationships between breeding waterbird abundance, diversity, and clear water status after the restoration of two shallow nutrient‐rich Danish lakes

Abstract Breeding waterbird communities have suffered globally from the effects of anthropogenic changes in water quality (especially nutrient enrichment) in recent decades, but few studies have demonstrated the positive effects of restorative actions. Annual breeding waterbird surveys in the period 1977–2005 at two restored southern Danish lake basins (combining nutrient load reduction and biomanipulation) showed an up to five‐fold increase in abundance, and considerable changes in species richness and diversity, following restoration to clear water status in both lakes. Parallel surveys at a third lake, which retained clear water quality throughout, offering a form of natural ‘control', showed no such changes over the same time period. Consistent relationships between breeding waterbird abundance, species richness, and diversity with measures of water clarity (Secchi disc depth, chlorophyll a, and suspended matter) suggest that water clarity mainly drives the relationship; inverse relationships between these measures and total nitrogen and phosphorus were less consistent than for water clarity. The results suggest that an improvement in water clarity plays a key role in restoring breeding waterbird communities and suggest that breeding waterbirds can be indicators of the success of lake restoration projects, but more studies are needed to confirm their wider utility under a variety of conditions.

Lake recovery from eutrophication: Quantitative response of trophic states to anthropogenic influences

Lake eutrophication is a serious environmental problem worldwide, caused by both natural processes and anthropogenic influences. For effective lake eutrophication management, a variety of models have been designed to investigate the complex interrelationship between physical, chemical and biological factors and processes in lakes. However, these models are inconvenient for predictions of lake eutrophication in practical application. To date, very few studies have focused on lake eutrophication in terms of anthropogenic influences (such as sewage emissions and agricultural practices), which are more readily regulated than natural processes. Effective lake eutrophication prediction models should base primarily on facile controlled or predictable indicators. Therefore, to meet this requirement, we designed simple predictive models to determine the interrelationship between the trophic states of lakes and nutrient inputs, which is a direct measurement to characterize anthropogenic influences. Lake Taihu (China) was used as a representative eutrophic water body to assess the accuracy of the proposed predictive models. Firstly, to comprehensively understand the role of nutrient input indicators (NIIs) during eutrophication, Pearson correlation coefficient analysis was conducted on 7 NIIs and 38 types of algae. Secondly, based on the NIIs identified with high correlation coefficients, we modified three commonly used growth models (Gompertz, logistic and Richards) to describe the lake's trophic state. A particle swarm optimization algorithm (PSOA) was used to optimize model variables. Results showed that the mean absolute percentage errors of the optimized Gompertz, logistic and the Richards models were 2.95%, 2.88% and 2.17%, respectively. Finally, these optimized models were used to predict lake eutrophication under several different nutrient input scenarios. Two adjustment scenarios revealed remarkably satisfied trophic states (including roughly oligotrophic and even ultra-oligotrophic) by the 2030s. Our results show that these established models are a simple way to support lake restoration projects by setting realistic and effective targets.

Impacts of Shallow Lake Restoration on Vegetation and Breeding Birds in Iowa

The Shallow Lakes Restoration Project aims to restore eutrophic shallow lakes throughout the Iowa Prairie Pothole Region (PPR). We compared the vegetation taxa richness and frequency of taxa in three vegetation groups surveyed in 2016 and 2017 across non-restored sites, younger restorations, and older restorations. We also assessed the impact of these groups on numbers of breeding marsh birds. Restored wetlands had between 2.7 (95% CI 2.3, 3.2) and 4.7 (95% CI 3.9, 5.5) more species than non-restored sites among the three vegetation groups. Typha sp. was the most abundant emergent species. Lemna minor and Ceratophyllum demersum were the most abundant floating-leaved and submersed species, respectively. The frequency of submersed aquatic vegetation increased with years since restoration, while floating-leaved vegetation and Typha sp. peaked at 7 years post-restoration. The frequency of Typha sp. positively influenced Marsh Wrens and Yellow-headed Blackbirds. Water depth negatively affected Marsh Wrens, but water depth positively influenced Yellow-headed Blackbirds. Floating-leaved vegetation positively affected Virginia Rails, while water depth had a negative effect on this species. Our results indicate that after about 7 years further management of the vegetation and water levels may need to occur and should include maintaining appropriate conditions for breeding marsh birds.

Environmental impacts and sustainability of low-value roach fish when used as food

One of the major global environmental challenges is the overuse of nutrients and related eutrophication problems. Specifically in Finland, the roach fish population is rapidly increasing in eutrophic water systems. Currently roach fish does not have economic value, and it is mainly composted despite the fact that it could provide a direct protein source for human needs. This paper assumes that new business could be established by removing roach fish from eutrophic water systems and using them as a protein source for human consumption. Removing roach fish directly removes nutrients and indirectly impacts the vicious cycle of eutrophication. This paper assesses different environmental sustainability perspectives of roach fish removal and utilization. It also aims to present different environmental impacts on the planetary boundary framework. The research is carried out using life cycle assessment methodology.Based on the results, the use of roach fish as a protein source would help in returning to a safe operational zone in biochemical flows. Phosphorous removal with roach fish is 5.8 (1.9–10.3) g kg−1 while nitrogen removal is 28.4 (26.4–30.4) g kg−1. However, the production has also climate change impacts which are 2.9–5.2 kgCO2eq kg−1 roach protein. Nevertheless, the climate change impacts are 12–57 times lower than positive impacts on eutrophication.Different environmental impacts are assessed regarding whether or not they help to avoid crossing planetary boundaries. Roach fish should be marketed especially for green consumers, and creating new markets for roach fish could also help in eutrophic lake restoration projects. Additionally, new business could be created from nutrient offsetting by roach fish removal.Roach removal from eutrophic water systems and use as food helps in returning to a safe operational zone in biochemical flows and the positive impacts are far greater than the negative impacts on climate change from fishing and fish processing.

Management and time preferences for lakes restoration in Brazil

As in many developing countries, the eutrophication of lakes has become one of the most severe environmental problems in Brazil. We implemented a choice experiment to investigate local preferences for the restoration of five lakes in the city of Campos dos Goytacazes, Brazil. This study focuses on two attributes of the proposed environmental project: 1) the delay in reaching the targeted level of water quality and 2) the institution that would manage the lakes restoration project. Choice responses are analyzed using a mixed logit model to control for potential heterogeneity among respondents. Results show that the willingness to pay for lakes restoration decays with restoration time in a non-linear fashion. Findings also indicate that respondents would prefer an interinstitutional, non-governmental committee over the municipal government to manage the lakes restoration project.

Investigation on the eco-toxicity of lake sediments with the addition of drinking water treatment residuals

Drinking water treatment residuals (WTRs) have a potential to realize eutrophication control objectives by reducing the internal phosphorus (P) load of lake sediments. Information regarding the ecological risk of dewatered WTR reuse in aquatic environments is generally lacking, however. In this study, we analyzed the eco-toxicity of leachates from sediments with or without dewatered WTRs toward algae Chlorella vulgaris via algal growth inhibition testing with algal cell density, chlorophyll content, malondialdehyde content, antioxidant enzyme superoxide dismutase activity, and subcellular structure indices. The results suggested that leachates from sediments unanimously inhibited algal growth, with or without the addition of different WTR doses (10% or 50% of the sediment in dry weight) at different pH values (8–9), as well as from sediments treated for different durations (10 or 180days). The inhibition was primarily the result of P deficiency in the leachates owing to WTR P adsorption, however, our results suggest that the dewatered WTRs were considered as a favorable potential material for internal P loading control in lake restoration projects, as it shows acceptably low risk toward aquatic plants.

Nitrous oxide emission from infralittoral zone and pelagic zone in a shallow lake: Implications for whole lake flux estimation and lake restoration

We measured nitrous oxide (N2O) emission from the infralittoral zone and pelagic zone in a shallow lake on the Tibetan Plateau during the growing season of 2009, prior to the lake restoration project aiming to raise the lake water by 0.5–1m. Mean flux rates of N2O were 0.054±0.094mg N2Om−2h−1 and 0.009±0.072mg N2Om−2h−1 from infralittoral zone and pelagic zone respectively. Submerged plant biomass index (SPBI) (R=0.43, P<0.01, n=16), nitrate content in surface sediment (R=0.22, P<0.05, n=16) and surface sediment temperature (R=0.79, P=0.000, n=16) were found to significantly correlated to the spatial pattern of N2O flux. Nitrates loading gradient across (sub) zones along with the enhancing effect of plant on nitrate removal were thought to be responsible for this spatial pattern of N2O flux, while temperature act as a regulator on denitrification. Infralittoral zone had the greatest relative contribution (62.2%) of N2O emission to the whole lake budget among various (sub) zones, indicating infralittoral zone a vital component of N2O emission from shallow lakes. As the consequence of the lake restoration project, the response of N2O flux to the raised water depth might vary from different (sub) zones, therefore further study should be conducted so as to have a better understanding on the effect of restoration project on the overall N2O flux from the lake.

Invasive Crayfish Threaten the Development of Submerged Macrophytes in Lake Restoration

Submerged macrophytes enhance water transparency and aquatic biodiversity in shallow water ecosystems. Therefore, the return of submerged macrophytes is the target of many lake restoration projects. However, at present, north-western European aquatic ecosystems are increasingly invaded by omnivorous exotic crayfish. We hypothesize that invasive crayfish pose a novel constraint on the regeneration of submerged macrophytes in restored lakes and may jeopardize restoration efforts. We experimentally investigated whether the invasive crayfish (Procambarus clarkii Girard) affects submerged macrophyte development in a Dutch peat lake where these crayfish are expanding rapidly. Seemingly favourable abiotic conditions for macrophyte growth existed in two 0.5 ha lake enclosures, which provided shelter and reduced turbidity, and in one lake enclosure iron was added to reduce internal nutrient loading, but macrophytes did not emerge. We transplanted three submerged macrophyte species in a full factorial exclosure experiment, where we separated the effect of crayfish from large vertebrates using different mesh sizes combined with a caging treatment stocked with crayfish only. The three transplanted macrophytes grew rapidly when protected from grazing in both lake enclosures, demonstrating that abiotic conditions for growth were suitable. Crayfish strongly reduced biomass and survival of all three macrophyte species while waterfowl and fish had no additive effects. Gut contents showed that crayfish were mostly carnivorous, but also consumed macrophytes. We show that P. clarkii strongly inhibit macrophyte development once favourable abiotic conditions for macrophyte growth are restored. Therefore, expansion of invasive crayfish poses a novel threat to the restoration of shallow water bodies in north-western Europe. Prevention of introduction and spread of crayfish is urgent, as management of invasive crayfish populations is very difficult.

Restoring macrophyte diversity in shallow temperate lakes: biotic versus abiotic constraints

Although many lake restoration projects have led to decreased nutrient loads and increased water transparency, the establishment or expansion of macrophytes does not immediately follow the improved abiotic conditions and it is often unclear whether vegetation with high macrophyte diversity will return. We provide an overview of the potential bottlenecks for restoration of submerged macrophyte vegetation with a high biodiversity and focus on the biotic factors, including the availability of propagules, herbivory, plant competition and the role of remnant populations. We found that the potential for restoration in many lakes is large when clear water conditions are met, even though the macrophyte community composition of the early 1900s, the start of human-induced large-scale eutrophication in Northwestern Europe, could not be restored. However, emerging charophytes and species rich vegetation are often lost due to competition with eutrophic species. Disturbances such as herbivory can limit dominance by eutrophic species and improve macrophyte diversity. We conclude that it is imperative to study the role of propagule availability more closely as well as the biotic interactions including herbivory and plant competition. After abiotic conditions are met, these will further determine macrophyte diversity and define what exactly can be restored and what not.

An Ecosystem Model for Exploring Lake Restoration Effects on Fish Communities and Fisheries in Florida

Developing quantitative ecosystem–scale expectations of habitat restoration projects and examining trade‐offs associated with alternative approaches has been a challenge for restoration ecology. Many of the largest freshwater lake restoration projects have occurred in Florida to remediate degradation to vegetated littoral habitats resulting from stabilized water levels, but effects across lake food‐webs have not been assessed. We developed an ecosystem model using Ecopath with Ecosim and Ecospace for a generalized large, eutrophic Florida Lake to explore how simulated restoration activities could influence fish communities with emphasis on sport fish abundance. We modeled three habitat restoration scenarios: (1) “no control,” (2) a “10‐year control” that restored littoral habitat every 10 years, and (3) a “combined control” scenario that restored littoral habitat every 10 years with maintenance controls between 10‐year periods. Our “combined control” scenario provided the largest long‐term habitat restoration benefits for sport fish abundance and the fisheries they support. In Ecospace, we simulated a littoral habitat restoration project that reduced lake‐wide tussock coverage from 30 to 15%. Ecospace predicted positive benefits to sport fish and fisheries following the restoration simulation and highlighted the importance of habitat edge effects, spatial design of habitat restoration projects, and sampling designs for evaluating restoration projects.