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With rising population growth, there is a need for increased food production. With rising temperatures and more frequent droughts due to climate change, it becomes more challenging to keep up with this increased demand for food. Therefore, a change in land use and management is needed in which enhanced silicate weathering (ESW) can play an important role. Weathering of silicate rocks has been regulating the atmospheric CO2 concentrations for over decades, but with the rise in atmospheric CO2, the natural weathering is too slow. Grinding the silicate rocks into a fine powder and spread it over for example agricultural fields will increase the reactive surface area and hence, the amount of CO2 that is stored in soils. The application of silicate minerals to soils can enhance plant growth by multiple processes, for example by counteracting soil acidification and by the release of plant nutrients. In this way, ESW can be used on agricultural fields without competing for land like other carbon capture techniques (e.g. Bio-Energy with carbon capture and storage). This study investigates the use of olivine (a fast-weathering Mg-rich silicate mineral) as a fertilizer in agriculture using a full-factorial mesocosm experiment. Barley and wheat were grown under two different rain regimes (daily rain vs weekly rain) and with application of two different grain sizes of olivine (p80 = 1020 µm and p80 = 43.5 µm). Our results showed increased plant growth and biomass with olivine addition, albeit only for fine olivine. However, this was not translated in an increase in yield of wheat and barley. Besides changes in biomass, we found significant differences in plant nutrient concentrations. As expected, Mg concentration increased significantly. However, BSi and Ca concentrations decreased with fine olivine application. Nitrogen in grains was also increased in the fine olivine treatment. In contrast to fine olivine, coarse olivine addition had almost no influence on nutrients. Ca, Mg and Si concentrations in plant samples followed the same trend as in the soil pore water, in contrast to metal concentrations. Olivine addition increased Ni and Cr availability in the soil pore water, but the concentrations of these elements in plant tissue did not increase and were even below detection limit for the majority of samples. While the influence of olivine on metal concentrations in plant samples was not affected by rain treatment, the influence of olivine on nutrients in the plants and plant growth was. Fine olivine addition enhanced the plants resistance to drought as it reduced the decrease in biomass with weekly rain treatment compared to daily rain treatment. This positive effect of olivine addition can be due to the increased weathering rate in combination with enhancement of soil properties like increased soil water retention. In this way, the use of olivine as a fertilizer on agricultural fields can mitigate climate change while it can also contribute to the solution for increased food demand.

This chapter presents the causes of physical and ecological degradation of estuaries in relation to human activities and climate change. The direct and indirect effects of degradation on ecosystem services and fish are listed, as well as the key questions that need to be answered in order to undertake rehabilitation and restoration actions. Ecohydrology and ecoengineering are indispensable tools to be mobilised alongside a variety of models to guide actions in favour of habitat and whole estuary functioning. Finally, several examples of restoration are presented to move from theory to practice. The restoration of estuaries has often become essential to ensure sustainable fish communities and requires a holistic view of the problems and a coordination of efforts to ensure the success of the actions undertaken.

Meltwater runoff from glaciers carries particles, so-called glacial flour that may affect planktonic organisms and the functioning of marine ecosystems. Protist microplankton is at the base of marine food webs and thus plays an important role in sustaining important ecosystem services. To assess the effect of glacial flour on photoautotrophic, heterotrophic and mixotrophic microplankton, the spatial distribution of these trophic groups was studied in four Greenlandic fjords during summer. The results suggest that the abundance of the autotrophic microplankton was affected by the glacier melt-water due to reduced light penetration and nutrient availability. The abundance of heterotrophic and mixotrophic microplankton were not apparently affected by the glacier meltwater. Incubation experi-ments were conducted on the natural population and in laboratory cultures of two mixoplanktonic cil-iate species. The experiments on the natural population revealed that none of the trophic groups were affected by the suspended material at concentrations up to 50 mg L-1. The experiments on cultures gave no indication that glacial flour was ingested by the mixoplanktonic ciliates. Growth rates of cul-tured ciliates were not affected by the glacial flour addition. These results suggest that heterotrophic and mixotrophic microplankton are not affected by glacial flour as much as autotrophic microplankton.(c) 2022 The Author(s). Published by Elsevier GmbH. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Climate change can result in multiple indirect alterations of the environment in riverine ecosystems, due to changes in precipitation and runoff. Flow velocity, concentrations of CO2 and nutrients are thereby expected to change, and consequences of the combination of those effects for macrophytes, a key organism group, are still poorly understood. This was tested in a racetrack flume experiment on macrophyte species Berula erecta, an amphibious species growing fully submerged in the experiment. In a full-factorial design, plants were exposed to two different CO2 concentrations, two nutrient concentrations (N, P and Si) and two flow velocities. Apart from individual dose–response tests, two climate change scenarios were tested: a wet scenario simulating heavy precipitation and runoff with high flow velocity, high CO2 and high nutrient concentrations and a dry scenario simulating evapotranspiration with low flow velocity, high CO2 and high nutrient concentrations. Growth rate, biomass, morphology, chlorophyll and nutrient content were measured. Berula erecta responded strongly to both scenarios. Biomass and relative growth rate increased, leaf BSi content decreased, and especially in the wet scenario macrophytes had shorter stems and formed stolons with new ramets: the plants invested in horizontal growth to avoid hydrodynamic stress. Moreover, the C/N ratio was higher, leading to lower quality of macrophyte tissue as food source, and chlorophyll concentration was lower in the high CO2 treatment. It can be concluded that combined stressors caused by climate change strongly affect macrophytes, which may indirectly have consequences for other organisms of the aquatic ecosystem that depend on macrophytes.

Since the early 2000s, there have been substantial efforts to transform the concept of ecosystem services into practice. Spatial assessment tools are being developed to evaluate the impact of spatial planning on a wide range of ecosystem services. However, the actual implementation in decision-making remains limited. To improve implementation, tools that are tailored to local conditions can provide accurate, meaningful information. Instead of a generic and widely-applicable tool, we developed a regional, spatially-explicit tool (ECOPLAN-SE) to analyse the impact of changes in land use on the delivery of 18 ecosystem services in Flanders (Belgium). The tool incorporates ecosystem services relevant to policy-makers and managers and makes use of detailed local data and knowledge. By providing an easy-to-use tool, including the required spatial geodatasets, time investment and the learning curve remain limited for the user. With this tool, constraints to implement ecosystem service assessments in local decision-making are drastically reduced. We believe that region-specific decision support systems, like ECOPLAN-SE, are indispensable intermediates between the conceptual ecosystem service frameworks and the practical implementation in planning processes. ispartof: One Ecosystem vol:5 status: Published online

In this study we explore the sub-lethal effects of two malaria vector control pesticides, deltamethrin and dichlorodiphenyltrichloroethane (DDT), on Xenopus laevis by incorporating different levels of biological organisation. Pesticide accumulation in frog tissue was measured alongside liver metabolomics and individual swimming behaviour to assess whether changes presented at these different levels, and if such changes could be linked between levels. Results showed evidence of concentration dependent accumulation of DDT and its metabolites, but no measurable accumulation of deltamethrin in adult X. laevis after 96 h of exposure. Both DDT and deltamethrin were shown to cause alterations in the liver metabolome of X. laevis. We also showed that some of these changes can be enhanced in exposure to a mixture of these two pesticides. Initial behavioural responses recorded directly after exposure were seen in the form of decreased activity, less alterations between mobility states, and less time spent at the water surface. This response persisted after 96 h of exposure to a mixture of the two pesticides. This study shows that sub-lethal exposure to pesticides can alter the biochemical homeostasis of frogs with the potential to cascade onto behavioural and ecological levels in mixture exposure scenarios.

Much uncertainty exists about the vulnerability of valuable tidal marsh ecosystems to relative sea level rise. Previous assessments of resilience to sea level rise, to which marshes can adjust by sediment accretion and elevation gain, revealed contrasting results, depending on contemporary or Holocene geological data. By analyzing globally distributed contemporary data, we found that marsh sediment accretion increases in parity with sea level rise, seemingly confirming previously claimed marsh resilience. However, subsidence of the substrate shows a nonlinear increase with accretion. As a result, marsh elevation gain is constrained in relation to sea level rise, and deficits emerge that are consistent with Holocene observations of tidal marsh vulnerability.

Groundwater fluxes in tidal marshes largely control key ecosystem functions and services, such as vegetation growth, soil carbon sequestration, and nutrient cycling. In tidal marshes restored on formerly embanked agricultural land, groundwater fluxes are often limited as compared to nearby natural marshes, as a result of historical agricultural soil compaction. To improve the functioning of restored tidal marshes, knowledge is needed on how much certain design options can optimize soil-groundwater interactions in future restoration projects. Based on measured data on soil properties and tidally induced groundwater dynamics, we calibrated and evaluated a 2D vertical model of a creek-marsh cross-section, accounting for both saturated and unsaturated groundwater flow and solute transport in a variably saturated groundwater flow model. We found that model simulations of common restoration practices such as soil amendments (increasing the depth of porous soil on top of the compact layer) and creek excavation (increasing the creek density) increase the soil aeration depth and time, the drainage depth and the solute flux, and decrease the residence time of solutes in the porewater. Our simulations indicate that increasing the depth to the compact layer from 20 cm to 40 cm, or increasing the creek density from 1 creek to 2 creeks along a 50 m marsh transect (while maintaining the total creek cross-sectional area), in both cases more than doubles the volume of water processed by the marsh soil. We discuss that this may stimulate nutrient cycling. As such, our study demonstrates that groundwater modelling can support the design of marsh restoration measures aiming to optimize groundwater fluxes and related ecosystem services.

Aquatic macrophytes can have a significant impact on their associated community of epiphytic algae and bacteria through the provisioning of structural habitat complexity through different growth forms, the exudation of nutrients and the release of allelochemicals. In turn, this effect on epiphytic biofilm biomass and nutrient content has a potential effect on the macroinvertebrates that depend on epiphyton as a food source. We studied the effect of living macrophytes and their growth form on biofilm development in a semi‐controlled replicated microcosm experiment. Conditions of a nutrient‐poor water layer and nutrient‐rich sediment were created to study the effects of nutrient exudation by living macrophytes. We compared biofilm quantity and quality on structurally simple (Vallisneria spiralis) versus complex (Egeria densa) living plants and artificial analogues. Subsequently, the biofilm that had developed on the plants was fed, in a laboratory growth experiment, to two species of macroinvertebrate grazers (the snail Haitia acuta and the mayfly nymph Cloeon dipterum). This enabled us to assess if and how the macrophyte‐induced effects on the epiphyton can influence macroinvertebrate grazers. Living macrophytes were found to have a significant effect on epiphytic algal cover, which was mostly expressed by a lower cover on living macrophytes compared to their artificial analogues. Additionally, epiphyton cover on artificial macrophytes was found to be higher on complex structures compared to simple ones, yet this was not observed on living macrophytes. Plant specific traits, such as the release of allelopathic substances, competition for nutrients and DIC, and the amount of CaCO3 deposition on plant surfaces might explain these results. The density of epiphytic bacteria was found to be negatively correlated with biofilm Ca content from macrophytes in every treatment except living E. densa, which differed in leaf anatomy from the other plants by possessing polar leaves. Furthermore, biofilm on living macrophytes had lower C:N:P molar ratios compared to that on artificial plants, which is likely to be explained by nutrient exudation by the living plants. Although it was expected that a more nutritious biofilm would lead to increased grazer growth, this was observed only for H. acuta on E. densa. Because biofilm quantity was not a limiting factor, this lack of effect may be caused by compensatory feeding. It can be concluded that, depending on their traits, living macrophytes can have a positive effect on macroinvertebrate grazers by providing a large surface area for colonisation by epiphytic algae and bacteria, by improving biofilm stoichiometry and by stimulating bacterial growth.

The vulnerability of the world’s tidal marshes to sea-level rise threatens their substantial contribution to fisheries, coastal protection, biodiversity conservation and carbon sequestration. Feedbacks between relative sea-level rise (RSLR) and the rate of mineral and organic sediment accumulation in tidal wetlands, and hence elevation gain, have been proposed to ameliorate this risk. Here we report on changes in tidal marsh elevation and shoreline position in relation to our network of 387 fixed benchmarks in tidal marshes on four continents measured for an average of 10 years. During this period RSLR at these marshes reached on average 6.6 mm yr-1, compared to 0.34 mm yr-1 over the past millenia. While the rate of sediment accretion corresponded to RSLR, the loss of elevation to shallow subsidence increased in proportion to the accretion rate. This caused a deficit between elevation gain and RSLR which increased consistently with the rate of RSLR regardless of position within the tidal frame, suggesting that long-term in situ tidal marsh survival is unlikely. While higher tidal range (>3m) conferred a greater stability in measures of shoreline change and vegetation cover, other regions showed a tendency towards instability and retreat.

Estuaries often show regions in which Chlorophyll-a (Chl-a) accumulates. The location and magnitude corresponding to such accumulation result from a complex interplay between processes such as river flushing, salinity, nutrients, phytoplankton grazing, and the light climate in the water column. Of particular interest is the long-term evolution of the estuary-scale Chl-a distribution in the Scheldt estuary (Belgium/Netherlands) in spring. From 2004–2007, we observed a limited spring-bloom in the brackish region. This bloom intensified in 2008–2014 and disappeared after 2015. This long-term evolution in Chl-a has been linked to simultaneous long-term trends in the suspended particulate matter (SPM) distribution and the improvement of the water quality, which affects grazing of Chl-a by zooplankton. However, this hypothesis has not been systematically investigated. In this paper, we apply two approaches to test this hypothesis. In the first approach, we analyze long-term in situ observations covering the full estuary. These observations include the SPM concentration, zooplankton abundance, and other variables affecting the Chl-a concentration, and show a long-term estuary-scale evolution in not only the SPM distribution but also in zooplankton abundance, freshwater discharge, and maximum photosynthetic rate. In the second approach, we apply a model approach supported by these observations to determine which of the changed conditions may explain the observed change in Chl-a. Our results suggest that a change in SPM alone cannot explain the Chl-a observations. Instead, mortality rate and grazing by zooplankton mainly explains the long-term estuary-scale evolution of Chl-a in spring. Our results highlight that insight into the zooplankton dynamics is essential to understand the phytoplankton (cf. Chl-a) dynamics in the Scheldt estuary.

Along estuaries and coasts, tidal marsh restoration projects are increasingly being executed on formerly embanked agricultural land to regain the ecosystem services provided by tidal wetlands. There are, however, more and more indications that restored tidal marshes do not deliver these ecosystem services to the same extent as natural tidal marshes. In particular, we found that marsh restoration on a compacted agricultural soil (which has a very low porosity and hydraulic conductivity) leads to reduced groundwater fluxes and soil aeration, which may imply decreased soil-water interactions, reduced biogeochemical cycling and impaired vegetation development.We studied the subsurface hydrology in the restored marsh Lippenbroek (Scheldt estuary, Belgium). To investigate spatial and temporal variation of groundwater fluxes in the restored tidal marsh, we developed a real-time groundwater flux sensor (iFLUX sensor) that enables us to measure both the groundwater flow velocity and flow direction in real-time. With these instruments installed at multiple locations and depths in the marsh soil, we were able to capture the effects of the tidal regime and soil stratigraphy on groundwater flow in high detail.Furthermore, we set up a 2D vertical model in HYDRUS with a domain representing a creek and marsh cross-section. The model enables variably saturated flow calculations for groundwater flow and solute transport in dual porosity soils. Input parameters for the model were obtained by soil sampling and laboratory measurements of saturated hydraulic conductivity and soil water retention curves. Simulated results are in good agreement with in situ measured groundwater levels in monitoring wells.With a scenario analysis, we showed that in a scenario in which the compact subsoil is absent, 6 times more water passes through the marsh soil during a spring tide – neap tide cycle compared to the reference scenario in which the compact soil starts at a depth of 60 cm. In the compact layer, which is always saturated, flow rates are so low that this layer is expected not to contribute to nutrient cycling.We then simulated the effect of (i) creek excavation (by varying the number of creeks in the domain) and (ii) soil amendments (by varying the depth to the compact layer) on groundwater flow in newly restored tidal marshes. We found that increasing the creek density from 1 creek to 2 creeks per 50 m marsh, or changing the depth to the compact layer from 20 cm to 40 cm, both more than doubles the volume of water processed by the marsh soil. As such , our study demonstrates that groundwater modelling is a useful tool in support of designing marsh restoration measures aiming to optimize groundwater fluxes and related ecosystem services.

Macrophytes are important organisms in running water systems, having a decisive role in ecological processes and interactions. Their temporal and spatial distribution in streams can be highly variable, and this is often determined by flow velocity. In this study, macrophyte growth, morphology and nutrient stoichiometry were studied monthly during one growing season in reaches with different flow velocity and flow velocity distribution and, as a result, different distributional plant patterns in an Austrian lowland stream, dominated by evergreen macrophyte species,Berula erecta. Flow velocity, water depth, fine sediment layer depth and metabolism were measured in the stream and the correlation with plant biomass and morphological traits was tested. We aimed to study differences between reaches with different distributional plant patterns and whether common interactions between macrophytes and flow velocity can also be observed when vegetation is evergreen. Plant biomass showed seasonal variation, with the highest values in June and the lowest in February. In the reach with low flow velocity and homogeneous macrophyte distribution, biomass peaked in summer and plant morphology changed with the seasons, whereas biomass and morphology in the reach with high flow velocity and patchy distribution were more constant throughout the year. Plant carbon, nitrogen and phosphorus content were higher in spring and autumn than in summer, whereas biogenic silica accumulated over the course of the growth season. Stream metabolism was strongly correlated with macrophyte biomass, and this correlation was stronger in the reach with homogeneous macrophyte distribution than in the reach with a patchy distribution. Moreover, average leaf area and stem length were positively correlated with fine sediment layer depth, and negatively with flow velocity. The results stress the importance of macrophyte growth and morphology in river processes like metabolism, hydromorphology and nutrient dynamics: especially plant morphology plays an important role in macrophyte-flow interactions.

There is increasing recognition that soils fulfil many functions for society. Each soil can deliver a range of functions, but some soils are more effective at some functions than others due to their intrinsic properties. In this study we mapped four different soil functions on agricultural lands across the European Union. For each soil function, indicators were developed to evaluate their performance. To calculate the indicators and assess the interdependencies between the soil functions, data from continental long-term simulation with the DayCent model were used to build crop-specific Bayesian networks. These Bayesian Networks were then used to calculate the soil functions' performance and trade-offs between the soil functions under current conditions. For each soil function the maximum potential was estimated across the European Union and changes in trade-offs were assessed. By deriving current and potential soil function delivery from Bayesian networks a better understanding is gained of how different soil functions and their interdependencies can differ depending on soil, climate and management. Highlights When increasing a soil function, how do trade-offs affect the other functions under different conditions? Bayesian networks evaluate trade-offs between soil functions and estimate their maximal delivery. Maximizing a soil function has varied effects on other functions depending on soil, climate and management. Differences in trade-offs make some locations more suitable for increasing a soil function then others.

Many estuaries exhibit seasonality in the estuary-scale distribution of suspended particulate matter (SPM). This SPM distribution depends on various factors, including freshwater discharge, salinity intrusion, erodibility, and the ability of cohesive SPM to flocculate into larger aggregates. Various authors indicate that biotic factors, such as the presence of algae and their excretion of sticky transparent exopolymer particles (TEP), affect the flocculation and erosion processes. Consequently, seasonality in these biotic factors may play a role in the observed seasonality in SPM. Whereas the impact of abiotic factors on seasonality in SPM is well studied, the relative contribution of biotically induced seasonality is largely unknown. In this study, we employ two approaches to assess the aggregated importance of biotically induced seasonality in flocculation and erosion on seasonality in SPM in the Scheldt estuary. In the first approach, we focus on seasonality of in situ observations in the Scheldt estuary of turbidity, floc size, Chlorophyll-a, and TEP, showing that the abiotic parameters show seasonality, while seasonality in TEP is ambiguous. The second approach concerns a reverse engineering method to calibrate biotically affected parameters of a coupled sediment transport-flocculation model to turbidity observations, allowing us to compare the modeled SPM concentrations to the observations. Driven by seasonality in freshwater discharge, the model captures the observed seasonality in SPM without requiring biotically induced seasonality in flocculation and erosion, which is supported by the absence of seasonality in TEP.

As an estuary being restored, the Scheldt (Belgium/The Netherlands) offers an interesting setting to study the response of organisms and ecosystems to changing conditions. In this regard, this study specifically deals with the spatio-temporal distribution and possible genetic differentiation among the species complex Eurytemora affinis (Copepoda, Calanoida). Until the 1990s, E. affinis typically occurred downstream the estuary. In parallel to water quality improvement, E. affinis since recently also occurs upstream in the estuary and in some of the tributaries. In a former study, Gasmi et al. (2014), found little genetic differentiation between the upstream population and downstream one, which is probably at the origin of the upstream population. However, surprisingly, two different genetic entities of the E. affinis complex were present: one in the main stream of the Scheldt estuary and one in its tributaries. This present work aims at understanding how independent tributaries, situated at opposite sides of the estuary, can host a single genetic entity while another one is present only in the main estuary. A dense sampling in the main stream and the two main tributaries was made in May 2014 (12 locations) and four ISSR primers producing 78 polymorphic loci were used to perform a molecular analysis. Bayesian and hierarchical analysis revealed that the results are more mixed and the different genetic entities are less well delimited than reported in our former study based on samples collected in 2012. A genetical mix between tributary and upstream populations is now observed. This suggests that a homogenization process of the E. affinis populations is in progress in parallel to the improvement of water quality. These results are discussed and several explanations are proposed.

Phytoplankton primary production (PP) in turbid estuaries is often limited by light-availability. Two important factors altering light-climate are solar irradiance at the water surface and exponential light-extinction coefficient within the water column. Additionally, the depth of the water body changes the light-climate and corresponding PP by altering the ratio of the euphotic and mixing depth in a well-mixed estuary. These three parameters are highly variable yet are often assumed to be constant by both experimental scientists and modelers because of a lack of data or to reduce complexity. Because assuming constant parameters introduces an error, we utilize an idealized model of depth-integrated primary production to analyze the (individual) impact of temporal variability in these three parameters. We only consider the main tidal and solar constituents in temporal variability of the forcings and apply a second-order moment approximation to analyze the bias introduced to time-averaged PP estimates by neglecting temporal fluctuations. We demonstrate that the sign and magnitude of this bias are system-specific and depend on two non-dimensional parameters that characterize the system. The first is equivalent to the ratio of mixing and photic depth. The second accounts for typical incident irradiance and the photosynthetic parameters of the phytoplankton population present. To demonstrate the applicability of our approach, we apply the model to two cases in the Scheldt estuary (Belgium) in the brackish and freshwater part. In the first application, we study the impact of fluctuations on phytoplankton in dynamic equilibrium, where biomass is assumed to be constant. We show that variability in solar irradiance has the largest impact on time-averaged PP in dynamic equilibrium, resulting in a 30 percent decrease compared to time-invariant forcing. By comparing with a numerical integrator, we show that a second-order moment approximation correctly predicts the order of magnitude of the impact of temporal variability of the individual parameters. In the second application, we study the impact of fluctuations on unbounded exponential phytoplankton growth. Also here, fluctuations in solar irradiance have the largest impact and lead to a significant decrease in exponential growth. In this case study, we show that temporal fluctuations delay the onset of the biomass by two weeks and decrease the biomass by a factor 14 after two weeks compared to time invariant forcing. Additionally, we show that the temporal fluctuations induce low-frequency variability in phytoplankton biomass with similar periodicity as the spring-neap cycle, making it difficult to observe these phenomena in real-world time series.

In places where tidal marshes were formerly embanked for agricultural land use, these marshes are nowadays increasingly restored with the aim to regain important ecosystem services. However, there is growing evidence that restored tidal marshes and their services develop slowly and differ from natural tidal marshes in many aspects. Here we focus on groundwater dynamics, because these affect several key ecosystem functions and services, such as nutrient cycling and vegetation development. We hypothesize that groundwater dynamics in restored tidal marshes are reduced as compared to natural marshes because of the difference in soil structure. In the macro-tidal Schelde estuary (Belgium), in both a natural and a restored (since 2006) freshwater tidal marsh, we measured depth profiles of soil properties (grain size distribution, LOI (loss on ignition), moisture content and bulk density) and temporal dynamics of groundwater levels along a transect with increasing distance from a tidal creek. X-ray micro CT-scanning was used to quantify soil macroporosity. The restored marsh has a two-layered soil stratigraphy with a topsoil of freshly accreted sediment (ranging in depth between 10 and 60 cm, deposited since 2006) and a subsoil of compact relict agricultural soil. We found that both the soil in the natural marsh and the topsoil of the restored marsh consist of loosely packed sediment rich in macropores and organic matter, whereas the relict agricultural soil in the restored marsh is densely packed and has few macropores. Our results show that groundwater level fluctuations in the restored marsh are restricted to the top layer of newly deposited sediment (i.e. on average 0.08 m depth). Groundwater level fluctuations in the natural marsh occur over a larger depth of the soil profile (i.e. on average 0.28 m depth). As a consequence, the reduced groundwater dynamics in restored tidal marshes are expected to alter the subsurface fluxes of water and nutrients, the source-sink function and the development of marsh vegetation.

The weathering of silicates is a major control on atmospheric CO2 at geologic timescales. It was proposed to enhance this process to actively remove CO2 from the atmosphere. While there are some studies that propose and theoretically analyze the application of rock powder to agricultural land, results from field experiments are still scarce. In order to evaluate the efficiency and side effects of Enhanced Weathering (EW), a mesocosm experiment was set up and agricultural soil from Belgium was amended with olivine-bearing dunite ground to two different grain sizes, while distinguishing setups with and without crops. Based on measurements of Mg, Si, pH, and DIC, the additional weathering effect of olivine could be confirmed. Calculated weathering rates are up to 3 orders of magnitude lower than found in other studies. The calculated CO2 consumption by weathering based on the outlet water of the mesocosm systems was low with 2.3–4.9 tCO2km-2a-1 if compared with previous theoretical estimates. Suspected causes were the removal or dilution of Mg as a weathering product by processes like adsorption, mineralization, plant uptake, evapotranspiration, and/or preferential flow, not specifically addressed in previous EW experiments for CO2 consumption. The observation that Mg concentrations in the upper soil layers were about 1 order of magnitude higher than in the outlet water indicates that a careful tracking of weathering indicators like Mg in the field is essential for a precise estimate of the CO2 consumption potential of EW, specifically under global deployment scenarios with a high diversity of ecosystem settings. Porewater Mg∕Si molar ratios suggest that dissolved Si is reprecipitating, forming a cation-depleted Si layer on the reactive mineral surface of freshly ground rocks. The release of potentially harmful trace elements is an acknowledged side effect of EW. Primarily Ni and Cr are elevated in the soil solution, while Ni concentrations exceed the limits of drinking water quality. The use of olivine, rich in Ni and Cr, is not recommended, and alternative rock sources are suggested for the application.

Sediment transport in estuaries and the formation of estuarine turbidity maxima (ETM) highly depend on the ability of suspended particulate matter (SPM) to flocculate into larger aggregates. While most literature focuses on the small-scale impact of biological flocculants on the formation of larger aggregates, the influence of the flocculation process on large-scale estuarine SPM profiles is still largely unknown. In this paper, we study the impact of flocculation of SPM on the formation of ETM. For this, a semianalytical width-integrated model called iFlow is utilized and extended by a flocculation model. Starting from a complex one-class flocculation model, we show that flocculation may be described as a linear relation between settling velocity and suspended sediment concentration to capture its leading-order effect on the ETM formation. The model is applied to a winter case in the Scheldt estuary (Belgium, Netherlands) and calibrated to a unique, long-term, two-dimensional set of turbidity (cf. SPM) observations. First, model results with and without the effect of flocculation are compared, showing that the spatial and temporal variations of the settling velocity due to flocculation are essential to reproduce the observed magnitude of the suspended sediment concentrations and its dependence on river discharge. Second, flocculation results in tidally averaged land-inward sediment transport. Third, we conduct a sensitivity analysis of the freshwater discharge and floc breakup parameter, which shows that flocculation can cause additional estuarine turbidity maxima and can prevent flushing of the ETM for high freshwater inflow.

Many macrophyte species in lowland streams exhibit signs of grazing and herbivore damage, even though herbivory by aquatic macroinvertebrates and fish is generally considered to be of little importance. In this study, we collected evidence for the hypothesis that herbivory on macrophytes by macroinvertebrates and fish is more widespread than assumed. We measured the dual stable isotope signatures (C-13 and N-15) of organic matter, epiphyton, submerged macrophytes, macroinvertebrates and fish in a Belgian lowland stream. There was a clear distinction in isotopic signatures of the different basal resources, allowing the use of the SIAR mixing model. These calculations revealed the consumption of macrophyte tissue not only by the phytophagous larvae of Nymphula nitidulata Hufnagel (Lepidoptera: Crambidae), but also by Baetidae nymphs (Ephemeroptera), Orthocladiinae larvae (Diptera: Chironomidae), the crayfish Orconectus limosusRafinesque (Decapoda: Cambaridae) and the fish Gobio gobio L. (Cypriniformes: Cyprinidae) which are classified as feeding on other resources. Although the potential share of macrophyte biomass in the diet of macroinvertebrates and fish was demonstrated to be up to 49%, this amount is only a small percentage of the total standing macrophyte biomass in a lowland stream. However, the impact of this herbivory may still be substantial because consumption may comprise a significant fraction of the daily primary production. Additionally, small-scale herbivory may still have a negative impact on macrophyte growth and survival, for example through consumption of apical meristems and the increased susceptibility to diseases and toxins if the macrophyte's epidermis is damaged.

Despite the importance of water purification to society, it is one of the more difficult wetland ecosystem services to quantify. It remains an issue in ecosystem service assessments where rapid estimates are needed, and poor-quality indicators are overused. We attempted to quantify the water purification service of South African palmiet wetlands (valley-bottom peatlands highly threatened by agriculture). First, we used an instantaneous catchment-scale mass balance sampling approach, which compared the fate of various water quality parameters over degraded and pristine sections of palmiet wetlands. We found that pristine palmiet wetlands acted as a sink for water, major cations, anions, dissolved silicon and nutrients, though there was relatively high variation in these trends. There are important limitations to this catchment-scale approach, including the fact that at this large scale there are multiple mechanisms (internal wetland processes as well as external inputs) at work that are impossible to untangle with limited data. Therefore, secondly, we performed a small field-scale field survey of a wetland fragment to corroborate the catchment-scale results. There was a reasonable level of agreement between the results of the two techniques. We conclude that it appears possible to estimate the water purification function of these valley-bottom wetlands using this catchment-scale approach.

Plant functional traits (PFTs) underpin ecosystem processes and therefore ecosystem service provision. If PFTs are possible to detect and discriminate spectrally, then it may be possible to use remote sensing applications to map ecosystem processes or services within and across landscapes. As a first step towards this application, we explored whether functional groups of 22 dominant South African wetland species were spectrally separable based on their PFTs. We measured 23 biochemical and morphological PFTs in combination with spectra from 350 to 2349 nm using a handheld radiometer. First, we evaluated the possibility of accurately predicting morphological and biochemical PFTs from reflectance spectra using three approaches: spectrum averaging, redundancy analysis (RDA), and partial least squares regression (PLSR). Second, we established whether functional groups and species were spectrally distinguishable. We found seven PFTs to be important in at least two of the three approaches: four morphological and three biochemicals. Morphological traits that were important were leaf area (PLSR: r² = 0.40, regression: r² = 0.41), specific leaf area (r² = 0.67), leaf mass (r² = 0.43, r² = 0.38), and leaf length/width ratio (r² = 0.62). Biochemical traits that play a role in the structural composition of vegetation, like lignin content (r² = 0.98, r² = 0.54), concentration (r² = 0.45) and cellulose content (r² = 0.57, r² = 0.49), were found to be important by at least two of the analyses. Three other traits were important in at least one of the analyses: total biomass (r² = 0.56), leaf C/N ratio (r² = 0.99), and cellulose concentration (r² = 0.76). Redundancy analysis suggests that there is a large percentage (52%) of the spectrum not explained by the PFTs measured in this study. However, spectral discrimination of functional groups, and even species, appears promising, mostly in the ultraviolet A part of the spectrum. This has interesting applications for mapping PFTs using remote sensing techniques, and therefore for estimating related ecosystem processes and services. ispartof: REMOTE SENSING OF ENVIRONMENT vol:210 pages:25-34 status: published

The concept of ecosystem services (ES) has facilitated the identification, mapping and communication about the many non-marketable benefits of green infrastructure. These benefits are important to consider during a spatial planning process. For spatial prioritisation of sites, with a high societal importance, there is need to filter this information to insightful spatial indicators. The mapping of ES-hotspots and identification of ES-bundles have been put forward as promising methods for spatial prioritisation and the assessment of multifunctionality. While "hotspot mapping" and "ES-bundles" speak to the imagination of many, it is open to many different interpretations. In addition, there is a risk that the commonly applied hotspot mapping of single services and subsequent overlay analysis does not capture true hotspots of multifunctionality, where we expect multiple services to co-occur, but at lower intensities. Therefore, hotspot mapping should be applied on ES-bundles, rather than single ES. Yet, there are few methods to objectively identify and map such bundles of co-occurring services. In this research we propose dimension reduction principal component analysis (PCA), as a solution to identify and map bundles of ES. This technique is an established technique in remote sensing, where it is used to reduce unnecessary clutter in a data set. This research shows that if the methods for quantification and mapping of ES are sufficiently independent and biophysically sound, the PCA method can reveal multifunctionality between services and lead to (new) insights that can be used for better informed decisions on management and planning. The PCA graphs, ES-bundle maps and the integrated RGB-visualisation are objective and factual outputs of a statistical analysis that can be used for communication and discussion with stakeholders. It gives insight in co-occurrence of services and challenges to look for answers to why things are the way they are. Although scale effects did not play an important role in the results of this study, we advise to use this method on relatively small scales and repeat analysis rather than generalizing large scale results to the local scale or transfer findings between study sites as land-use patterns (and its interplay with abiotic conditions) are the result of many different socio-ecological developments throughout history, which can obviously differ from region to region.

The threat to wildlife from chemical exposure exists regardless of the presence of conservation boundaries. An issue exacerbated by the use of environmentally persistent insecticides for vector control and long-range transport of legacy persistent organic pollutants. In this comparative study between two important conservation regions in South Africa, Kruger National Park (KNP) and Ndumo Game Reserve (NGR), we assessed organochlorine pesticide (OCP) accumulation in several anuran species collected from within the conservation regions. The two conservation regions differ in size and subsequent proximity of collection sites to OCP input sources. Detectable concentrations of OCPs were present in ∼ half the frogs analysed from KNP and ∼all frogs from NGR and total OCP loads were similar between regions, where measured in the same species. The OCP profiles in KNP frogs were representative of legacy pesticides likely introduced via long-range transport, whereas NGR profiles showed influence of current use of DDT consistent with close proximity to sources. This indicates amphibians can accumulate OCPs within conservation regions and that the exposure of non-target organisms inside conservation regions to current use pesticides has a strong association with proximity to sources. These results serve to inform conservation management decision making with regard to the non-target organism effects of chemical interventions such as vector control pesticide use in and around conservation regions.

Improved understanding of water flow and solute transport through the unsaturated zone is important for the sustainable management of soils. As soils are complex and heterogeneous systems, quantification of the transport processes is difficult. More knowledge on the relationship between solute transport process, soil structure, hydrologic initial and boundary conditions, and observation scale is needed here.Modeling unsaturated flow and transport with mathematical or numerical methods is an important tool for predicting the infiltration and redistribution of soil water and the transport of solutes in the unsaturated zone. Flow and transport models are commonly used to support the decision making process in agricultural management, environmental impact assessment, toxic waste control, remediation design, and subsurface cleanup monitoring. The movement of contaminants through porou media describs by the combination of advection, diffusion-dispersion and chemical retardation. The most common model that describes solute transport by convection and dispersion is the convection-dispersion equation (CDE). This equation describes the change in concentration at any point along the flow path as a function of time. This paper is mainly dedicated to a discussion of basic processes for modelling of water flow and contaminant transport in saturated and unsaturated soils. After a brief description of the classical approach for simulating water flow and solute transport in porous media, issues related to water and solute trasport equation in soil.