Reducing cardiometabolic risk in adults with a low socioeconomic position: protocol of the Supreme Nudge parallel cluster-randomised controlled supermarket trial

This erratum describes changes made in our previously published study protocol [1], as the occurrence of the COVID-19 pandemic has led to insurmountable challenges in feasibility to maintain the original design. The planned start of participant recruitment for the trial coincided with the first COVID-19 lockdown in the Netherlands starting March 16 2020. As a result, the start of the study was postponed by 11 months. The continued/renewed lockdown hampered face-to-face contact and thus some planned physical measurements. These circumstances required adaptation to remote data collection methods, revision of recruitment goals and of the primary study outcomes, and inclusion of additional study sites to secure adequate participant inclusion rates. Therefore, below we present the revised methodology of the Supreme Nudge parallel cluster-randomised controlled supermarket trial. All changes made to the original protocol were reviewed and approved by the Medical Ethics Review Committee of VU University Medical Center (reference number: 2019.334) prior to implementation

Effect of Temperature on Oxygen Profiles and Denitrification Rates in Freshwater Sediments

Vegetated ditches and wetlands are important sites for nutrient removal in agricultural catchments. About half of the influx of inorganic nitrogen can be removed from these ecosystems by denitrification. Previous studies have shown that denitrification in aquatic ecosystems is strongly temperature dependent, resulting from temperature-dependent oxygen availability. Here, we study short-term temperature effects on sediment oxygen demand (SOD) and the maximum depth of oxygen penetration into the sediment (Z), in relation to overall denitrification rates. We set up sixteen wetland microcosms at four different temperatures (11–25 °C), in which we determined SOD and Z from sediment oxygen microprofiles. Denitrification rates were measured using 15N-labeling, analysed by membrane inlet mass spectrometry. Temperature strongly affected sediment oxygen dynamics. SOD exponentially rose with temperature, ranging from 0.37 to 1.53 g m−2 d−1 (Q10 = 2.4). Correspondingly, warming led to shallower oxygen penetration into the sediment, ranging from 4.12 to 2.08 mm. Denitrification rates increased with warming (Q10 = 2.6), ranging from 8.4 to 86 μmol N m−2 h−1. The results of this short-term experiment confirm the potential increase of denitrification with rising temperature, promoted by lower oxygen availability in the top layer of the sediment, which supports the understanding of denitrification variability in freshwaters

Modeling nutrients in Lake Dianchi (China) and its watershed

Lake Dianchi suffered from severe eutrophication for decades. Past efforts to reduce the eutrophication were not very effective. The objective of this study is to improve our understanding of nitrogen (N) and phosphorus (P) loadings and to analyze to what extent they exceed critical nutrient loadings of Lake Dianchi. To this end, we applied the nutrient MARINA model and the ecosystem model PCLake. Results show that river export of dissolved N and P was high in 2012. About 6 209 ton of total dissolved N (TDN) was exported to the lake (i.e. 23.6 kg ha−1), of which more than two-thirds in the form of dissolved inorganic N. For total dissolved P, this export was about 413 ton (i.e. 1.6 kg ha−1), of which 75% dissolved inorganic P. Urban sewage is a major source of nutrients in rivers in the northern sub-basins. In southern sub-basins, agriculture is an important source of both N and P, while P mining and processing is a major source of dissolved inorganic P. Nutrient inputs to the lake are particularly high from urbanization sub-basins draining into the northern part of the lake (Caohai). Critical nutrient loadings for the northern part of the lake (Caohai) are 0.34 mg P m−2d−1 (3.06 mg N m−2d−1) and for the southern part (Waihai) 0.38 mg P m−2d−1 (3.42 mg N m−2d−1). Actual loadings exceed the critical nutrient loadings by 82 times and 17 times of Caohai and Waihai, respectively. Our study illustrates how linking MARINA with PCLake helped to quantify the causes of lake eutrophication and to identify critical loadings for N and P in the lake. Our study can assist local authorities to formulate management options to reduce nutrient pollution in Lake Dianchi in the future.</p

How Regime Shifts in Connected Aquatic Ecosystems Are Affected by the Typical Downstream Increase of Water Flow

All over the world freshwater ecosystems like ponds, ditches and lakes suffer from nutrient-driven regime shifts from submerged plants to dominance by algae or free-floating plants. Although freshwaters are often connected and part of a network, most of our current knowledge on regime shifts comes from studies of isolated ecosystems. The few studies that have assessed the spatial manifestation of regime shifts overlooked the hydrological fact that the water flow through connected waters typically increases in the downstream direction. Here, we use a complex ecosystem model to show that this increase in flow does not lead to spatial differences in ecosystem state. We support these findings with a simple, analytically tractable, nutrient retention model on connected waterbodies. The model shows that all bodies have the same nutrient concentration despite spatial gradients in the flow of water as well as nutrients carried by the water. As a consequence, each connected waterbody is equally vulnerable to a regime shift, implying a regime shift to be system-wide. Furthermore, it appeared that each connected waterbody behaves the same as an isolated waterbody, implying that the vast body of theory on isolated systems, like alternative stable states theory, can still be useful for connected systems. Although these findings are violated when there is heterogeneity in lateral runoff or waterbody characteristics—leading to spatial differences in ecosystem state and therefore to differences in the vulnerability to a regime shift—they show that the typical downstream build-up of water flow does not necessarily lead to differences in ecological state, and thereby provide a basic concept to better understand the ecology of connected freshwaters

Comparing critical source areas for the sediment and nutrients of calibrated and uncalibrated models in a plateau watershed in southwest China

Controlling non-point source pollution is often difficult and costly. Therefore, focusing on areas that contribute the most, so-called critical source areas (CSAs), can have economic and ecological benefits. CSAs are often determined using a modelling approach, yet it has proved difficult to calibrate the models in regions with limited data availability. Since identifying CSAs is based on the relative contributions of sub-basins to the total load, it has been suggested that uncalibrated models could be used to identify CSAs to overcome data scarcity issues. Here, we use the SWAT model to study the extent to which an uncalibrated model can be applied to determine CSAs. We classify and rank sub-basins to identify CSAs for sediment, total nitrogen (TN), and total phosphorus (TP) in the Fengyu River Watershed (China) with and without model calibration. The results show high similarity (81%–93%) between the identified sediment and TP CSA number and locations before and after calibration both on the yearly and seasonal scale. For TN alone, the results show moderate similarity on the yearly scale (73%). This may be because, in our study area, TN is determined more by groundwater flow after calibration than by surface water flow. We conclude that CSA identification with the uncalibrated model for TP is always good because its CSA number and locations changed least, and for sediment, it is generally satisfactory. The use of the uncalibrated model for TN is acceptable, as its CSA locations did not change after calibration; however, the TN CSA number changed by over 60% compared to the figures before calibration on both yearly and seasonal scales. Therefore, we advise using an uncalibrated model to identify CSAs for TN only if water yield composition changes are expected to be limited. This study shows that CSAs can be identified based on relative loading estimates with uncalibrated models in data-deficient regions

Smart Nutrient Retention Networks : a novel approach for nutrient conservation through water quality management

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.</p

Towards a global model for wetlands ecosystem services

Wetlands play an important role in the provision of important ecosystem services like the provision of clean water to the world, adaptation to climate change, and support for biodiversity; although they are sometimes also associated with adverse climate effects. Wetlands are, however, currently grossly underrepresented in global environmental models. In this paper, we explore the required functionality of a generic model of the effects of climate and land-use changes on wetlands ecosystem services worldwide. We briefly review existing models to identify elements which can be combined to compile a generic wetland model. The proposed global wetland model should be integrated into and receive data from existing hydrology and climate models. Wetland delineation can be based on local hydrological and topographical conditions and verified with global wetland databases. We conclude that an integrated approach combining hydrology, biogeochemistry and vegetation for wetlands is not available yet, however, useful building blocks exist that can be combined

Towards a global model for wetlands ecosystem services

Wetlands play an important role in the provision of important ecosystem services like the provision of clean water to the world, adaptation to climate change, and support for biodiversity; although they are sometimes also associated with adverse climate effects. Wetlands are, however, currently grossly underrepresented in global environmental models. In this paper, we explore the required functionality of a generic model of the effects of climate and land-use changes on wetlands ecosystem services worldwide. We briefly review existing models to identify elements which can be combined to compile a generic wetland model. The proposed global wetland model should be integrated into and receive data from existing hydrology and climate models. Wetland delineation can be based on local hydrological and topographical conditions and verified with global wetland databases. We conclude that an integrated approach combining hydrology, biogeochemistry and vegetation for wetlands is not available yet, however, useful building blocks exist that can be combined

Mowing Submerged Macrophytes in Shallow Lakes with Alternative Stable States : Battling the Good Guys?

Submerged macrophytes play an important role in maintaining good water quality in shallow lakes. Yet extensive stands easily interfere with various services provided by these lakes, and harvesting is increasingly applied as a management measure. Because shallow lakes may possess alternative stable states over a wide range of environmental conditions, designing a successful mowing strategy is challenging, given the important role of macrophytes in stabilizing the clear water state. In this study, the integrated ecosystem model PCLake is used to explore the consequences of mowing, in terms of reducing nuisance and ecosystem stability, for a wide range of external nutrient loadings, mowing intensities and timings. Elodea is used as a model species. Additionally, we use PCLake to estimate how much phosphorus is removed with the harvested biomass, and evaluate the long-term effect of harvesting. Our model indicates that mowing can temporarily reduce nuisance caused by submerged plants in the first weeks after cutting, particularly when external nutrient loading is fairly low. The risk of instigating a regime shift can be tempered by mowing halfway the growing season when the resilience of the system is highest, as our model showed. Up to half of the phosphorus entering the system can potentially be removed along with the harvested biomass. As a result, prolonged mowing can prevent an oligo—to mesotrophic lake from becoming eutrophic to a certain extent, as our model shows that the critical nutrient loading, where the lake shifts to the turbid phytoplankton-dominated state, can be slightly increased

Mowing Submerged Macrophytes in Shallow Lakes with Alternative Stable States : Battling the Good Guys?

Submerged macrophytes play an important role in maintaining good water quality in shallow lakes. Yet extensive stands easily interfere with various services provided by these lakes, and harvesting is increasingly applied as a management measure. Because shallow lakes may possess alternative stable states over a wide range of environmental conditions, designing a successful mowing strategy is challenging, given the important role of macrophytes in stabilizing the clear water state. In this study, the integrated ecosystem model PCLake is used to explore the consequences of mowing, in terms of reducing nuisance and ecosystem stability, for a wide range of external nutrient loadings, mowing intensities and timings. Elodea is used as a model species. Additionally, we use PCLake to estimate how much phosphorus is removed with the harvested biomass, and evaluate the long-term effect of harvesting. Our model indicates that mowing can temporarily reduce nuisance caused by submerged plants in the first weeks after cutting, particularly when external nutrient loading is fairly low. The risk of instigating a regime shift can be tempered by mowing halfway the growing season when the resilience of the system is highest, as our model showed. Up to half of the phosphorus entering the system can potentially be removed along with the harvested biomass. As a result, prolonged mowing can prevent an oligo—to mesotrophic lake from becoming eutrophic to a certain extent, as our model shows that the critical nutrient loading, where the lake shifts to the turbid phytoplankton-dominated state, can be slightly increased