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Despite decades of management and regulation, global freshwater resources remain imperiled. Management has had mixed success in restoring degraded lakes and has few mechanisms for stopping the decline of high-quality systems. Too often, lake managers play catch-up by addressing stressors only after damage occurs or has become entrenched, or make decisions without acquiring sufficient information about how a lake might respond to proposed management actions. As a tool to address these management challenges, we propose the MoReCo (Monitoring, Restoring/Protecting, Community Engagement) lake management framework. The framework centers around community engagement, and we outline engagement mechanisms in the context of lake management. The framework includes 2 loops: a monitoring loop to detect emerging stressors, and a restoring/protecting loop to address stressors that are causing or may cause lake degradation. The MoReCo framework builds on the strengths of existing natural resource management frameworks and was developed to address the unique challenges associated with lake management and protection, as well as those resulting from climate change. Specifically, it can address multiple stressors concurrently, which makes it simultaneously suitable for ameliorating stressors while also protecting lake ecosystems. The MoReCo framework is an interactive and multidirectional process in which management occurs even when no stressor is apparent, and it incorporates explicit benchmarks for evaluating management actions and determining whether additional measures should be taken. This novel lake management framework is suitable to address any stressors that may threaten a lake ecosystem, and we present it here as a resource for those who manage freshwater resources.

13 februari 2023, Contains fulltext : 290585.pdf (Publisher’s version ) (Open Access)

Progressively more community initiatives have been undertaken over last decades to monitor water quality. Biological data collected by volunteers has been used for biodiversity and water quality studies. Despite the many citizen science projects collecting and using macroinvertebrates, the number of scientific peer-reviewed publications that use this data, remains limited. In 2018, a citizen science project on biological water quality assessment was launched in the Netherlands. In this project, volunteers collect macroinvertebrates from a nearby waterbody, identify and count the number of specimens, and register the catch through a web portal to instantaneously receive a water quality score based on their data. Water quality monitoring in the Netherlands is traditionally the field of professionals working at water authorities. Here, we compare the data from the citizen science project with the data gathered by professionals. We evaluate information regarding type and distribution of sampled waterbodies and sampling period, and compare general patterns in both datasets with respect to collected animals and calculated water quality scores. The results show that volunteers and professionals seldomly sample the same waterbody, that there is some overlap in sampling period, and that volunteers more frequently sampled urban waters and smaller waterbodies. The citizen science project is thus yielding data about understudied waters and this spatial and temporal complementarity is useful. The character and thoroughness of the assessments by volunteers and professionals are likely to differentiate. Volunteers collected significantly lower numbers of animals per sample and fewer animals from soft sediments like worms and more mobile individuals from the open water column such as boatsmen and beetles. Due to the lack of simultaneous observations at various locations by volunteers and professionals, a direct comparison of water quality scores is impossible. However, the obtai

Globally the number of relatively deep, isolated lakes is increasing because of sand, gravel, or clay excavation activities. The major excavation areas are located within the delta of rivers, and thus the deep freshwater ecosystems formed upon excavation, called quarry lakes, are unique to the landscape. They are embedded in a landscape comprised of shallow, naturally formed lakes. Given that quarry lakes are by definition novel ecosystems, water managers face difficulties in optimally managing them to deliver ecosystem services using existing frameworks designed for natural ecosystems. All lakes in delta areas are subject to similar pressures such as urbanization and eutrophication, leading to shifts in biodiversity and ecosystem functioning, and ultimately changing the ecosystem services the systems can provide. We propose a framework to enable water managers to assess the provision of ecosystem services by quarry lakes based on their ecological quality. For each ecosystem service we determined threshold values of ecological quality based on available scientific literature, an extensive field survey of 51 quarry lakes in the Netherlands, or expert knowledge. To illustrate the usefulness of our approach, we applied our framework to a lake before and after a rehabilitation focused on improving the nutrient status of the waterbody. Assessing ecosystem services under varying levels of ecological health is important to initiate action from legislators, managers, and communities.

Harmful algal blooms are symptomatic of eutrophication and lead to deterioration of water quality and ecosystem services. Extreme climatic events could enhance eutrophication resulting in more severe nuisance algal blooms, while they also may hamper current restoration efforts aimed to reduce nutrient loads. Evaluation of restoration measures on their efficacy under climate change is essential for effective water management. We conducted a two-month mesocosm experiment in a hypertrophic urban canal focussing on the reduction of sediment phosphorus (P)-release. We tested the efficacy of four interventions, measuring phytoplankton biomass, nutrients in water and sediment. The measures included sediment dredging, water column aeration and application of P-sorbents (lanthanum-modified bentonite - Phoslock® and iron-lime sludge, a by-product from drinking water production). An extreme heatwave (with the highest daily maximum air temperature up to 40.7 °C) was recorded in the middle of our experiment. This extreme heatwave was used for the evaluation of heatwave-induced impacts. Dredging and lanthanum modified bentonite exhibited the largest efficacy in reducing phytoplankton and cyanobacteria biomass and improving water clarity, followed by iron-lime sludge, whereas aeration did not show an effect. The heatwave negatively impacted all four measures, with increased nutrient releases and consequently increased phytoplankton biomass and decreased water clarity compared to the pre-heatwave phase. We propose a conceptual model suggesting that the heatwave locks nutrients within the biological P loop, which is the exchange between labile P and organic P, while the P fraction in the chemical P loop will be decreased. As a consequence, the efficacy of chemical agents targeting P-reduction by chemical binding will be hampered by heatwaves. Our study indicates that current restoration measures might be challenged in a future with more frequent and intense heatwaves.

Ecological thresholds are useful indicators for water quality managers to define limits to nutrient pollution. A common approach to estimating ecological thresholds is using critical nutrient loads. Critical nutrient loads are typically defined as the loads at which the phytoplankton chlorophyll-a exceeds a certain concentration. However, national policies, such as in China, use chemical indicators (nitrogen and phosphorus concentrations) rather than ecological indicators (phytoplankton chlorophyll-a) to assess water quality. In this study, we uniquely define the critical nutrient loads based on maximum allowable nutrient concentrations for lake Baiyangdian. We assess whether current and future nutrient loads in this lake comply with the Chinese Water Quality standards. To this end, we link two models (MARINA-Lakes and PCLake+). The PCLake+ model was applied to estimate the critical nutrient loads related to ecological thresholds for total nitrogen, total phosphorus and chlorophyll-a. The current (i.e., 2012) and future (i.e., 2050) nutrient loads were derived from the water quality MARINA-Lakes model. Nitrogen loads exceeded the nitrogen threshold in 2012. Phosphorus loads were below all ecological thresholds in 2012. Ecological thresholds are exceeded in 2050 with limited environmental policies, and urbanization may increase nutrient loads above the ecological thresholds in 2050. Recycling and reallocating animal manure is needed to avoid future water pollution in Lake Baiyangdian. Our study highlights the need for effective policies for clean water based on policy-relevant indicators.

Parasites are generally considered the most commonly occurring type of consumers, yet their biomass and population dynamics are rarely quantified at community level. Here, we used 12 years of weekly or fortnightly monitoring data (518 time points) to determine the occurrence of chytrids, fungal parasites of phytoplankton, to assess their seasonality and long-term (seasonally-detrended) dynamics in the pelagic plankton community of a temperate, eutrophic, and polymictic lake. Chytrid infections were observed in c. 75% of all samples with recurrent infections in multiple host taxa. Infection prevalence was highest in spring, but infections occurred throughout the entire year with an average of 2.3 host taxa infected per time point (ranging from 0 to 10 host taxa) and an average infection prevalence of 2.78% (ranging from 0% to 47.35%). Infected host biomass equalled that of the carnivorous zooplankton and decreased over time, while infection prevalence remained unchanged. Seasonal infection prevalence increased with phytoplankton biomass, but decreased with increasing temperature and phosphorus concentrations, reflecting that peak prevalence occurred in spring when temperature and phosphorus concentrations were relatively low. In contrast, seasonally-detrended prevalence increased with temperature, but decreased with increasing phosphorus concentrations. Chytrids are a common component of the pelagic plankton community with sizeable biomass and removing an—at times—substantial proportion of the primary production, challenging the long-standing underrepresentation of parasites in ecological studies. Chytrids responded differentially to seasonal variation and long-term trends in host density, water temperature and nutrient availability, highlighting the need to disentangle seasonal signals from long-term changes.

Water quality improvement to avoid excessive phytoplankton blooms often requires eutrophication management where both phosphorus (P) and nitrogen (N) play a role. While empirical eutrophication studies and ecological resource competition theory both provide insight into phytoplankton abundance in response to nutrient loading, they are not seamlessly linked in the current state of eutrophication research. We argue that understanding species competition for multiple nutrients and light in natural phytoplankton communities is key to assessing phytoplankton abundance under changing nutrient supply. Here we present GPLake-S, a mechanistic model rooted in ecological resource competition theory, which has only eight parameters and can predict chlorophyll-a to nutrient relationships for phytoplankton communities under N, P, N+P colimitation and light limitation. GPLake-S offers a simple mechanistic tool to make first estimates of chlorophyll-a levels and nutrient thresholds for generic lake properties, accounting for variation in N:P ratio preferences of phytoplankton species. This makes the model supportive of water management and policy.

Nutrients are essential resources for food production but are used inefficiently, and thereby they pollute inland and coastal waters and are lost into the oceans. Nutrient conservation by retention and consecutive reuse would prevent nutrient losses to the atmosphere and downstream ecosystems. We present Smart Nutrient Retention Networks (SNRNs) as a novel management approach to achieve nutrient conservation across networks of connected waterbodies through strategic water quality management. To present the key features of SNRNs, we review existing knowledge of nutrient retention processes in inland waters, water quality management options for nutrient conservation, and nutrient retention models to develop SNRNs. We argue that successful nutrient conservation, even at a local level, through SNRN management strategies requires clearly formulated goals and catchment-wide system understanding. Waterbody characteristics, such as hydraulic residence time and the presence of macrophytes, shape local nutrient retention with potential network-wide cascading effects of improved water quality and are therefore key targets of SNRN management strategies. Nutrient retention models that include the self-reinforcing feedback loop of ecological water quality, nutrient retention, and nutrient loading in networks of inland waters in relation to management options can support the development of SNRNs. We conclude that SNRNs can contribute to sustainable use of nutrients in human food production.

Volunteers have become more and more involved in monitoring the quality of the environment in which they live. Traditionally, water quality monitoring is the field of professionals at water authorities, however, community initiatives have been undertaken to monitor abiotic conditions in waterbodies. To date, biological water quality assessment based on data collected by volunteers remains scarce. A citizen science project on biological water quality assessment was launched in the Netherlands in 2018. In this project, volunteers collect macroinvertebrates from in a nearby waterbody, identify and count the number of specimens, and register their catch through a web portal to instantaneously receive a water quality score based on their data. This study compares the data from the volunteers with the data from professionals focussing on type of sampled waterbody, sampling period, observed animals and water quality. The analyses show that volunteers and professionals seldomly sample the same waterbody, that there is some overlap in sampling period, and that volunteers more frequently sampled smaller water bodies and more urban waters. The citizen science project is thus yielding useful spatially and temporally complementarity data. The assessments by volunteers and professionals likely differ in character and thoroughness. Volunteers collected significantly lower numbers of animals per sample and fewer animals from soft sediments but more mobile individuals from the open water column. As a result, the water quality scores between volunteers and professionals differ. To bridge these differences, new tools and processes may need to be developed to further increase the value of monitoring biological water quality by volunteers for professionals.

Beschermde gebieden waarin menselijke invloed beperkt wordt vormen sinds lang de hoeksteen van natuurbescherming. Deze aanpak heeft de biodiversiteitscrisis echter niet kunnen voorkomen. Daarbij wordt met deze aanpak het beeld gecreëerd dat alleen datgene dat binnen deze beschermde gebieden leeft natuur is. Natuur laat zich echter niet begrenzen, en de menselijke invloed daarop evenmin. In ditessay werken we daarom een gebiedsdekkende en mens-inclusieve visie op natuurbescherming uit tot een nieuwe benadering voor nationale parken: Nationaal Park 3.0.