Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Geoengineering in lakes: welcome attraction or fatal distraction?
    Mackay, E. ; Maberly, S.C. ; Pan, G. ; Reitzel, K. ; Lurling, M.F.L.L.W. - \ 2014
    Inland Waters : Journal of the International Society of Limnology 4 (2014). - ISSN 2044-2041 - p. 349 - 356.
    modified bentonite clay - phosphate adsorption - phosphorus release - shallow lakes - water-quality - sediment - nutrient - aluminum - removal - phoslock(r)
    The use of geoengineering techniques for phosphorus management offers the promise of greater and quicker chemical and ecological recovery. It can be attractive when used with other restoration measures but should not be considered a panacea. The range of materials being proposed for use as well as the in-lake processes targeted for manipulation continues to grow. With increasing political imperatives to meet regulatory goals for water quality, we recommend a coordinated approach to the scientific understanding, costs, and integration of geoengineering with other approaches to lake management.
    Advancing projections of phytoplankton responses to climate change through ensemble modelling
    Trolle, D. ; Elliott, J.A. ; Mooij, W.M. - \ 2014
    Environmental Modelling & Software 61 (2014). - ISSN 1364-8152 - p. 371 - 379.
    fresh-water cyanobacteria - shallow lakes - multimodel ensembles - environmental-change - community structure - blooms - restoration - temperature - predictions - challenges
    A global trend of increasing health hazards associated with proliferation of toxin-producing cyanobacteria makes the ability to project phytoplankton dynamics of paramount importance. Whilst ensemble (multi-)modelling approaches have been used for a number of years to improve the robustness of weather forecasts this approach has until now never been adopted for ecosystem modelling. We show that the average simulated phytoplankton biomass derived from three different aquatic ecosystem models is generally superior to any of the three individual models in describing observed phytoplankton biomass in a typical temperate lake ecosystem, and we simulate a series of climate change projections. While this is the first multi-model ensemble approach applied for some of the most complex aquatic ecosystem models available, we consider it sets a precedent for what will become commonplace methodology in the future, as it enables increased robustness of model projections, and scenario uncertainty estimation due to differences in model structures.
    Serving many at once: How a database approach can create unity in dynamical ecosystem modelling
    Mooij, W.M. ; Brederveld, R.J. ; Klein, J.J.M. de; DeAngelis, D.L. ; Downing, A.S. ; Faber, M. ; Gerla, D.J. ; Hipsey, M.R. ; Hoen, J. 't; Janse, J.H. ; Janssen, A.B.G. ; Jeuken, M. ; Kooi, B.W. ; Lischke, B. ; Petzoldt, T. ; Postma, L. ; Schep, S.A. ; Scholten, H. ; Teurlincx, S. ; Thiange, C. ; Trolle, D. ; Dam, A.A. van; Gerven, L.P.A. van; Nes, E.H. van; Kuiper, J.J. - \ 2014
    Environmental Modelling & Software 61 (2014). - ISSN 1364-8152 - p. 266 - 273.
    shallow lakes - simulation - eutrophication - management - package - pclake
    Simulation modelling in ecology is a field that is becoming increasingly compartmentalized. Here we propose a Database Approach To Modelling (DATM) to create unity in dynamical ecosystem modelling with differential equations. In this approach the storage of ecological knowledge is independent of the language and platform in which the model will be run. To create an instance of the model, the information in the database is translated and augmented with the language and platform specifics. This process is automated so that a new instance can be created each time the database is updated. We describe the approach using the simple Lotka-Volterra model and the complex ecosystem model for shallow lakes PCLake, which we automatically implement in the frameworks OSIRIS, GRIND for MATLAB, ACSL, R, DUFLOW and DELWAQ. A clear advantage of working in a database is the overview it provides. The simplicity of the approach only adds to its elegance. © 2014 The Authors.
    Eutrophic urban ponds suffer from cyanobacterial blooms: Dutch examples
    Waaijenberg, G.W.A.M. ; Faassen, E.J. ; Lurling, M. - \ 2014
    Environmental Science and Pollution Research 21 (2014)16. - ISSN 0944-1344 - p. 9983 - 9994.
    shallow lakes - water bodies - toxic cyanobacteria - northern poland - phosphorus flux - microcystins - fresh - phytoplankton - netherlands - health
    Ponds play an important role in urban areas. However, cyanobacterial blooms counteract the societal need for a good water quality and pose serious health risks for citizens and pets. To provide insight into the extent and possible causes of cyanobacterial problems in urban ponds, we conducted a survey on cyanobacterial blooms and studied three ponds in detail. Among 3,500 urban ponds in the urbanized Dutch province of North Brabant, 125 showed cyanobacterial blooms in the period 2009-2012. This covered 79 % of all locations registered for cyanobacterial blooms, despite the fact that urban ponds comprise only 11 % of the area of surface water in North Brabant. Dominant bloom-forming genera in urban ponds were Microcystis, Anabaena and Planktothrix. In the three ponds selected for further study, the microcystin concentration of the water peaked at 77 µg l-1 and in scums at 64,000 µg l-1, which is considered highly toxic. Microcystin-RR and microcystin-LR were the most prevalent variants in these waters and in scums. Cyanobacterial chlorophyll-a peaked in August with concentrations up to 962 µg l-1 outside of scums. The ponds were highly eutrophic with mean total phosphorus concentrations between 0.16 and 0.44 mg l-1, and the sediments were rich in potential releasable phosphorus. High fish stocks dominated by carp lead to bioturbation, which also favours blooms. As urban ponds in North Brabant, and likely in other regions, regularly suffer from cyanobacterial blooms and citizens may easily have contact with the water and may ingest cyanobacterial material during recreational activities, particularly swimming, control of health risk is of importance. Monitoring of cyanobacteria and cyanobacterial toxins in urban ponds is a first step to control health risks. Mitigation strategies should focus on external sources of eutrophication and consider the effect of sediment P release and bioturbation by fish.
    Predictability of plankton communities in an unpredictable world
    Lurling, M. ; Senerpont Domis, L.N. de - \ 2013
    Freshwater Biology 58 (2013)3. - ISSN 0046-5070 - p. 455 - 462.
    long-term dynamics - climate-change - shallow lakes - warmer climates - esthwaite water - daphnia-pulex - fresh-waters - peg-model - phytoplankton - blooms
    1.Plankton ecology contributes significantly to ecological theory building, because plankton organisms are relatively easy to manipulate and have short generation times and a relatively small set of traits making them an ideal experimental model system for addressing both general ecological questions as well more system-specific questions. 2.Since the environment is changing at an unprecedented rate, there is an ongoing demand for predictions from plankton ecology on the consequences of global change. 3.In 2010, a colloquium was held on three subjects: chaos versus predictability in plankton dynamics, global patterns versus regional differences in plankton dynamics and climate-induced changes in plankton dynamics. 4.Papers in this Special Issue propose a new model of plankton dynamics under climate change in different climate zones; offer increased attention to the role of winters in resetting population dynamics; discuss the effects of climate change on ecological stoichiometry and efficiency of trophic transfer; describe the relative and interacting effects of changes in temperature and hydrology on plankton; and analyse the effects of climate change on host-parasite dynamics. 5.Important research gaps include increased monitoring of understudied climatic zones, adaptation of plankton organisms to altered environmental conditions, interactions of climate change with legacy nutrients, interactions with other anthropogenic pressures and interactions with the infochemical network. © 2013 Blackwell Publishing Ltd.
    The role of subtropical zooplankton as grazers of phytoplankton under different predation levels
    Lacerot, G. ; Kruk, C. ; Lurling, M. ; Scheffer, M. - \ 2013
    Freshwater Biology 58 (2013)3. - ISSN 0046-5070 - p. 494 - 503.
    fish community structure - shallow lakes - jenynsia-multidentata - trophic interactions - size distribution - biomanipulation - dynamics - climate - restoration - cladocerans
    1.Large zooplankton such as Daphnia play a fundamental role as consumers of phytoplankton in temperate lakes. These organisms are scarce in subtropical lakes where smaller cladocerans or copepods take this niche. However, such smaller grazers appear to be less able to exert an effective top-down control on the phytoplankton community. 2.We experimentally analysed the ability of zooplankton typical of subtropical, nutrient-rich lakes to graze effectively on the phytoplankton community. We conducted two outdoor mesocosm experiments in a hypertrophic lake, with combinations of three different zooplankton densities and three different omnivorous fish densities. In the first experiment, the zooplankton community was dominated by a small-sized cladoceran (Moina micrura) and in the second by a calanoid copepod (Notodiaptomus incompositus). The phytoplankton community also differed between experiments, with dominance of large size classes and less palatable species in the first experiment and edible sizes in the second. 3.In both experiments, the effect of fish on the largest zooplankton was strong and negative, and low fish densities were sufficient to eliminate the larger zooplankton. Fish presence had positive effects on the biovolume of the largest phytoplankton size fraction (30-100µm) in the first experiment. This effect was more pronounced in combination with high zooplankton biomass, suggesting that nutrient recycling by both fish and zooplankton may have been an important mechanism promoting phytoplankton growth. 4.None of the zooplankton communities tested had significant top-down effects on the phytoplankton community. In view of the phytoplankton species that dominated the communities at the end of both experiments, inedibility, toxicity and antigrazer defences may explain the absence of significant effects of zooplankton grazing. 5.Our results support the idea that in subtropical nutrient-rich lakes, drastic removal of small omnivorous fish may be needed to allow an increase in zooplankton biomass. In addition, our results imply that for such a change to result in effective top-down control of phytoplankton, a shift in zooplankton community composition is essential too, as the experimental increase in small-sized grazers had little effect on the phytoplankton communities.
    Plankton dynamics under different climatic conditions in space and time
    Senerpont Domis, L.N. de; Elser, J.J. ; Huszar, V.L.M. ; Ibelings, B.W. ; Jeppesen, E. ; Kosten, S. ; Mooij, W.M. ; Roland, F. ; Sommer, U. ; Donk, E. van; Winder, M. ; Lurling, M. - \ 2013
    Freshwater Biology 58 (2013)3. - ISSN 0046-5070 - p. 463 - 482.
    north-atlantic oscillation - top-down control - amazonian floodplain lake - fresh-water cladocerans - central-european lake - driven regime shifts - high arctic lakes - shallow lakes - food webs - seasonal succession
    1.Different components of the climate system have been shown to affect temporal dynamics in natural plankton communities on scales varying from days to years. The seasonal dynamics in temperate lake plankton communities, with emphasis on both physical and biological forcing factors, were captured in the 1980s in a conceptual framework, the Plankton Ecology Group (PEG) model. 2.Taking the PEG model as our starting point, we discuss anticipated changes in seasonal and long-term plankton dynamics and extend this model to other climate regions, particularly polar and tropical latitudes. Based on our improved post-PEG understanding of plankton dynamics, we also evaluate the role of microbial plankton, parasites and fish in governing plankton dynamics and distribution. 3.In polar lakes, there is usually just a single peak in plankton biomass in summer. Lengthening of the growing season under warmer conditions may lead to higher and more prolonged phytoplankton productivity. Climate-induced increases in nutrient loading in these oligotrophic waters may contribute to higher phytoplankton biomass and subsequent higher zooplankton and fish productivity. 4.In temperate lakes, a seasonal pattern with two plankton biomass peaks - in spring and summer - can shift to one with a single but longer and larger biomass peak as nutrient loading increases, with associated higher populations of zooplanktivorous fish. Climate change will exacerbate these trends by increasing nutrient loading through increased internal nutrient inputs (due to warming) and increased catchment inputs (in the case of more precipitation). 5.In tropical systems, temporal variability in precipitation can be an important driver of the seasonal development of plankton. Increases in precipitation intensity may reset the seasonal dynamics of plankton communities and favour species adapted to highly variable environments. The existing intense predation by fish on larger zooplankters may increase further, resulting in a perennially low zooplankton biomass. 6.Bacteria were not included in the original PEG model. Seasonally, bacteria vary less than the phytoplankton but often follow its patterns, particularly in colder lakes. In warmer lakes, and with future warming, a greater influx of allochthonous carbon may obscure this pattern. 7.Our analyses indicate that the consequences of climate change for plankton dynamics are, to a large extent, system specific, depending on characteristics such as food-web structure and nutrient loading. Indirect effects through nutrient loading may be more important than direct effects of temperature increase, especially for phytoplankton. However, with warming a general picture emerges of increases in bacterivory, greater cyanobacterial dominance and smaller-bodied zooplankton that are more heavily impacted by fish predation. © 2012 Blackwell Publishing Ltd.
    Bimodality in stable isotope composition facilitates the tracing of carbon transfer from macrophytes to higher trophic levels
    Mendonca, R. ; Kosten, S. ; Lacerot, G. ; Mazzeo, N. ; Roland, F. ; Ometto, J.P. ; Paz, A. ; Bueno, O.C. ; Gomes, A.C.M.M. ; Scheffer, M. - \ 2013
    Hydrobiologia 710 (2013)1. - ISSN 0018-8158 - p. 205 - 218.
    fresh-water macrophytes - aquatic cam plant - inorganic carbon - eutrophic lake - shallow lakes - photosynthetic characteristics - concentrating mechanisms - submerged macrophytes - microbial loop - food webs
    Even though the suitability of macrophytes to act as a carbon source to food webs has been questioned by some studies, some others indicate that macrophyte-derived carbon may play an important role in the trophic transfer of organic matter in the food web of shallow lakes. To evaluate the importance of macrophytes to food webs, we collected primary producers-macrophytes and periphyton-and consumers from 19 South American shallow lakes and analyzed their carbon stable isotopes composition (d13C). Despite the diversity of inorganic carbon sources available in our study lakes, the macrophytes' d13C signatures showed a clear bimodal distribution: 13C-depleted and 13C-enriched, averaging at -27. 2 and -13. 5‰, respectively. We argue that the use of either CO2 or HCO3 - by the macrophytes largely caused the bimodal pattern in d13C signals. The contribution of carbon from macrophytes to the lake's food webs was not straightforward in most of the lakes because the macrophytes' isotopic composition was quite similar to the isotopic composition of periphyton, phytoplankton, and terrestrial carbon. However, in some lakes where the macrophytes had a distinct isotopic signature, our data suggest that macrophytes can represent an important carbon source to shallow lake food webs. © 2012 Springer Science+Business Media Dordrecht
    Case study on the efficacy of a lanthanum-enriched clay (Phoslock) in controlling eutrophication in Lake Het Groene Eiland (The Netherlands)
    Lurling, M. ; Oosterhout, J.F.X. - \ 2013
    Hydrobiologia 710 (2013)1. - ISSN 0018-8158 - p. 253 - 263.
    rare-earth-elements - harmful cyanobacterial blooms - phosphorus binding clay - shallow lakes - organic-matter - nutrient - water - restoration - sediment - impact
    Lake Het Groene Eiland was created in the beginning of 2008 by construction of dikes for isolating it from the surrounding 220-ha water body. This so-called claustrum of 5 ha was treated using lanthanum-modified clay (Phoslock®) to control eutrophication and mitigate cyanobacterial nuisance. Cyanobacteria chlorophyll-a were significantly lower in the claustrum than those in the reference water body, where a massive bloom developed in summer, 2008. However, PO4-P and TP did not statistically differ in these two waters. TN and NO3-N were significantly lower in the claustrum, where dense submerged macrophytes beds developed. Lanthanum concentrations were elevated after the applications of the modified clay in the claustrum, but filterable lanthanum dropped rapidly below the Dutch standard of 10.1 µg l-1. During winter, dozens of Canada geese resided at the claustrum. Geese droppings contained an average of 2 mg PO4-P g-1 dry weight and 12 mg NH3-N g-1 dry weight and might present a growing source of nutrients to the water. Constructing the claustrum enabled unrestricted bathing in subsequent three summers, as no swimming bans had to be issued due to cyanobacteria blooms. However, the role of the modified clay in this positive outcome remains unclear, and longevity of the measures questionable.
    Comparison of cyanobacterial and green algal growth rates at different temperatures
    Lurling, M. ; Faassen, E.J. ; Kosten, S. ; Eshetu, Z. ; Huszar, V.M. - \ 2013
    Freshwater Biology 58 (2013)3. - ISSN 0046-5070 - p. 552 - 559.
    fresh-water zooplankton - climate-change - shallow lakes - community structure - microcystis-aeruginosa - phytoplankton - blooms - allelopathy - nutrient - daphnia
    1.The hypothesis that cyanobacteria have higher optimum growth temperatures and higher growth rates at the optimum as compared to chlorophytes was tested by running a controlled experiment with eight cyanobacteria species and eight chlorophyte species at six different temperatures (20-35°C) and by performing a literature survey. 2.In the experiment, all organisms except the chlorophyte Monoraphidium minutum grew well up to 35°C. The chlorophyte Chlamydomonas reinhardtii was the fastest-growing organism over the entire temperature range (20-35°C). 3.Mean optimum growth temperatures were similar for cyanobacteria (29.2°C) and chlorophytes (29.2°C). These results are concordant with published data, yielding slightly higher mean optimum growth temperatures for cyanobacteria (27.2°C) than for chlorophytes (26.3°C). 4.Mean growth rates of cyanobacteria at 20°C (0.42day-1) were significantly lower than those of chlorophytes at 20°C (0.62day-1). However, at all other temperatures, there were no differences between mean growth rates of cyanobacteria and chlorophytes. 5.Mean growth rates at the optimum temperature were similar for cyanobacteria (0.92day-1) and chlorophytes (0.96day-1). However, analysis of published data revealed that growth rates of cyanobacteria (0.65day-1) were significantly lower than those of chlorophytes (0.93day-1) at their optimum temperatures. 6.Although climate warming will probably lead to an intensification of cyanobacterial blooms, our results indicate that this might not be as a result of higher growth rates of cyanobacteria compared with their chlorophyte competitors. The competitive advantage of cyanobacteria can more likely be attributed to their ability to migrate vertically and prevent sedimentation in warmer and more strongly stratified waters and to their resistance to grazing, especially when warming reduces zooplankton body size. © 2012 Blackwell Publishing Ltd.
    Lake responses following lanthanum-modified bentonite clay (Phoslock) application: an analysis of water column lanthanum data from 16 case study lakes
    Spears, B.M. ; Lürling, M.F.L.L.W. ; Yasseri, S. ; Castro-Castellon, A.T. ; Gibbs, M. ; Meis, S. ; McDonald, C. ; McIntosh, J. ; Sleep, D. ; Oosterhout, F. van - \ 2013
    Water Research 47 (2013)15. - ISSN 0043-1354 - p. 5930 - 5942.
    oppervlaktewaterkwaliteit - grondwaterkwaliteit - eutrofiëring - meren - ecologisch herstel - terugwinning - remediatie - bestrijdingsmethoden - lanthaan - bentoniet - fosfor - sediment - ecologische risicoschatting - aquatische ecologie - surface water quality - groundwater quality - eutrophication - lakes - ecological restoration - recovery - remediation - control methods - lanthanum - bentonite - phosphorus - sediment - ecological risk assessment - aquatic ecology - phosphorus-binding clay - shallow lakes - unintended consequences - loch leven - restoration - removal - daphnia - quality - netherlands
    Phoslock is a lanthanum (La) modified bentonite clay that is being increasingly used as a geo-engineering tool for the control of legacy phosphorus (P) release from lake bed sediments to overlying waters. This study investigates the potential for negative ecological impacts from elevated La concentrations associated with the use of Phoslock across 16 case study lakes. Impact-recovery trajectories associated with total lanthanum (TLa) and filterable La (FLa) concentrations in surface and bottom waters were quantified over a period of up to 60 months following Phoslock application. Both surface and bottom water TLa and FLa concentrations were
    Changing weather conditions and floating plants in temperate drainage ditches
    Peeters, E.T.H.M. ; Zuidam, B.G. van; Zuidam, J.P. van; Nes, E.H. van; Kosten, S. ; Heuts, P.G.M. ; Roijackers, R.M.M. ; Netten, J.J.C. ; Scheffer, M. - \ 2013
    Journal of Applied Ecology 50 (2013)3. - ISSN 0021-8901 - p. 585 - 593.
    climate-change - submerged macrophytes - aquatic macrophytes - species richness - shallow lakes - lemna-minor - eutrophication - growth - phytoplankton - phenology
    Dominance of free-floating plants such as duckweed is undesirable as it indicates eutrophication. The objectives of this study are to investigate whether the onset of duckweed dominance is related to weather conditions by analysing field observations, to evaluate the effect of different climate scenarios on the timing of duckweed dominance using a model and to evaluate to what extent nutrient levels should be lowered to counteract effects of global warming. To analyse the onset of duckweed dominance in relation to weather conditions, duckweed cover in Dutch ditches was correlated with weather conditions for the period 1980-2005. Furthermore, a model was developed that describes biomass development over time as a function of temperature, light and nutrient availability, crowding and mortality. This model was used to evaluate the effects of climate change scenarios and the effects of lowering nutrients. The onset of duckweed dominance in the field advanced by approximately 14 days with an increase of 1 °C in the average maximum daily winter temperature. The modelled biomass development correlated well with the field observations. Scenarios showed that expected climate change will affect onset and duration of duckweed dominance in temperate ditches. Reducing nutrient levels may counteract the effect of warming. Synthesis and applications. Global warming may lead to an increase in the dominance of free-floating plants in drainage ditches in the Netherlands. The expected reductions in nutrient-loading to surface waters as a result of different measures taken so far are likely not sufficient to counteract these effects of warming. Therefore, additional measures should be taken to avoid a further deterioration of the ecological water quality in ditches. © 2013 The Authors. Journal of Applied Ecology © 2013 British Ecological Society.
    Does predator interference cause alternative stable states in multispecies communities?
    Feng, J. ; Dakos, V. ; Nes, E.H. van - \ 2012
    Theoretical Population Biology 82 (2012)3. - ISSN 0040-5809 - p. 170 - 176.
    mutual interference - marine ecosystems - shallow lakes - regime shifts - thresholds - enrichment - paradox - stabilization - resilience - stability
    Whereas it is well known that simple ecological mechanisms may promote stability in simple species models, their consequences for stability and resilience in multispecies communities are largely unexplored. Here, we studied the effect of predator interference on the occurrence of alternative attractors and complex dynamics in randomly constructed multispecies predator-prey communities. We studied three types of interference: random interference ("asymmetric"), random interference but symmetrical between pairs of predators ("symmetric"), and interference among only the same species ("conspecific"). In all cases predator interference increased the average number of alternative attractors, whereas at the same time it reduced the emergence of oscillatory or chaotic dynamics. Our findings demonstrate a contrasting effect of predator interference on the stability of a community: on the one hand it reduces cycles and chaos in the dynamics, on the other hand predator interference increases the likelihood that communities may undergo critical transitions between multiple stable states.
    Controlling toxic cyanobacteria: effects of dredging and phosphorus-binding clay on cyanobacteria and microcystins
    Lürling, M.F.L.L.W. ; Faassen, E.J. - \ 2012
    Water Research 46 (2012)5. - ISSN 0043-1354 - p. 1447 - 1459.
    oppervlaktewaterkwaliteit - meren - herstelbeheer - eutrofiëring - cyanobacteriën - lanthaan - klei - vergelijkend onderzoek - aquatische ecologie - surface water quality - lakes - restoration management - eutrophication - cyanobacteria - lanthanum - clay - comparative research - aquatic ecology - rare-earth-elements - lake restoration - organic-matter - shallow lakes - sediment removal - northern poland - urban lake - blooms - water - fresh
    Sediment dredging and Phoslock(®) addition were applied individually and in combination in an enclosure experiment in a Dutch hypertrophic urban pond. These measures were applied to control eutrophication and reduce the risk of exposure to cyanobacterial toxins. Over the 58 days course of the experiment, cyanobacteria (predominantly Microcystis aeruginosa) gradually decreased until they dropped below the level of detection in the combined treated enclosures, they were reduced in dredged enclosures, but remained flourishing in controls and Phoslock(®) treated enclosures. Cyanobacteria were, however, less abundant in the enclosures (medians chlorophyll-a 30-87 µg l(-1)) than in the pond (median chlorophyll-a 162 µg l(-1)), where also a thick surface scum covered one-third of the pond for many weeks. Soluble reactive phosphorus (SRP), total phosphorus and total nitrogen concentrations were significantly lower in the combined dredged and Phoslock(®) treated enclosures than in controls. Median SRP concentrations were 24 µg P l(-1) in the combined treatment, 58 µg P l(-1) in dredged enclosures, and 90 µg P l(-1) in controls and 95 µg P l(-1) in Phoslock(®) treated enclosures. Hence, the combined treatment was most effective in decreasing SRP and TP, and in lowering cyanobacterial biomass. Microcystin (MC) concentrations were analyzed by LC-MS/MS. MC concentrations and cyanobacterial biomass were positively correlated in all treatments. Mean MC concentrations in controls (71 µg l(-1)), Phoslock(®) treated enclosures (37 µg l(-1)) and dredged enclosures (25 µg l(-1)) exceeded the provisional guideline of 20 µg l(-1), whereas mean MC concentrations were 13 µg l(-1) in the combined treated enclosures. All samples contained the MC variants dmMC-RR, MC-RR, MC-YR, dmMC-LR and MC-LR; traces of MC-LY and nodularin were detected in few samples. The different treatments did not change the relative contribution of the variants to the MC pool; MC profiles in all treatments and the pond showed dominance of MC-RR followed by MC-LR. In the surface scum of the pond, total MC concentration was extremely high (64000 µg l(-1) or 1300 µg g(-1) DW), which poses a serious health hazard to children playing on the banks of the pond. Based on our results and pond characteristics, we propose combined sediment dredging and Phoslock(®) addition, fish removal and strong reduction of duck feeding by the neighborhood as most promising measures controlling cyanobacterial hazards in this pond.
    The role of ecological models in linking ecological risk assessment to ecosystem services in agroecosystems
    Galic, N.G. ; Schmolke, A. ; Forbes, V. ; Baveco, J.M. ; Brink, P.J. van den - \ 2012
    Science of the Total Environment 415 (2012). - ISSN 0048-9697 - p. 93 - 100.
    shallow lakes - population-dynamics - potential application - decision-making - economic value - land-use - honeybee - chemicals - wildlife - biomanipulation
    Agricultural practices are essential for sustaining the human population, but at the same time they can directly disrupt ecosystem functioning. Ecological risk assessment (ERA) aims to estimate possible adverse effects of human activities on ecosystems and their parts. Current ERA practices, however, incorporate very little ecology and base the risk estimates on the results of standard tests with several standard species. The main obstacles for a more ecologically relevant ERA are the lack of clear protection goals and the inherent complexity of ecosystems that is hard to approach empirically. In this paper, we argue that the ecosystem services framework offers an opportunity to define clear and ecologically relevant protection goals. At the same time, ecological models provide the tools to address ecological complexity to the degree needed to link measurement endpoints and ecosystem services, and to quantify service provision and possible adverse effects from human activities. We focus on the ecosystem services relevant for agroecosystem functioning, including pollination, biocontrol and eutrophication effects and present modeling studies relevant for quantification of each of the services. The challenges of the ecosystem services approach are discussed as well as the limitations of ecological models in the context of ERA. A broad, multi-stakeholder dialog is necessary to aid the definition of protection goals in terms of services delivered by ecosystems and their parts. The need to capture spatio-temporal dynamics and possible interactions among service providers pose challenges for ecological models as a basis for decision making. However, we argue that both fields are advancing quickly and can prove very valuable in achieving more ecologically relevant ERA.
    Allied attack: climate change and eutrophication
    Moss, B. ; Kosten, S. ; Meerhoff, M. ; Battarbee, R.W. ; Jeppesen, E. ; Mazzeo, N. ; Havens, K. ; Lacerot, G. ; Liu, Z. ; Meester, L. de; Paerl, H. ; Scheffer, M. - \ 2011
    Inland Waters : Journal of the International Society of Limnology 1 (2011)2. - ISSN 2044-2041 - p. 101 - 105.
    voedingsstoffen - eutrofiëring - zoetwaterecologie - kustwateren - klimaatverandering - binnenwateren - meren - waterplanten - nutrients - eutrophication - freshwater ecology - coastal water - climatic change - inland waters - lakes - aquatic plants - shallow lakes - community structure - organic-carbon - temperature - zooplankton - methane - mesocosms - ecosystem - blooms - mineralization
    Global warming and eutrophication in fresh and coastal waters may mutually reinforce the symptoms they express and thus the problems they cause
    Declines in the tuber-feeding waterbird guild at Shengjin Lake National Nature Reserve, China - a barometer of submerged macrophyte collapse
    Fox, A. ; Cao, L. ; Zhang, Y. ; Barter, M. ; Zhao, M.J. ; Meng, F.J. ; Wang, S.L. - \ 2011
    Aquatic conservation: marine and freshwater ecosystems 21 (2011)1. - ISSN 1052-7613 - p. 82 - 91.
    yangtze-river basin - vallisneria-spiralis - shallow lakes - poyang lake - birds - impacts - identification - phosphorus - province - swans
    1. The Yangtze floodplain is globally unique for its extensive ephemeral wetlands, recharged by summer monsoon precipitation. The annual cycle of inundation and water table recession favours submerged macrophytes, including Vallisneria that overwinters in desiccated substrates as tubers, which provide high-energy winter food for tuber-feeding waterbirds that were formerly abundant in the region. 2. Large declines among the tuber-feeding waterbirds swan goose Anser cygnoides (L.), tundra swan Cygnus columbianus (Ord) and hooded crane Grus monacha Temminck between 2004/2005 and 2009/2010 at Shengjin Lake, Anhui Province, suggest that major changes in food availability have occurred there. 3. Based on observations of feeding behaviour and energy budgets of these species, it was calculated that at least 5.0 and 8.9¿km2 of Vallisneria beds in 2004 and 2005, respectively, would be needed to support observed numbers of these species, compared with less than 1.5¿km2 found in 2009 and 2010. 4. An incomplete macrophyte survey in summer 2000 located at least 7.7¿km2 of Vallisneria beds in the Upper Lake, where none was present during resurveys in 2008 and 2009. Declines in tuber-feeding waterbirds at Shengjin Lake coincide with the disappearance of their submerged macrophyte food plants, possibly as a result of eutrophication since the mid-2000s. 5. Widespread declines and concentration of tuber-eating wintering waterbirds at other sites elsewhere in the Yangtze floodplain may also reflect the local collapse of submerged macrophytes and of ecosystem services that these wetlands provide to the human communities.
    Differential response to climatic variation of free-floating and submerged macrophytes in ditches
    Netten, J.J.C. ; Zuidam, J.P. van; Kosten, S. ; Peeters, E.T.H.M. - \ 2011
    Freshwater Biology 56 (2011)9. - ISSN 0046-5070 - p. 1761 - 1768.
    waterplanten - klimaatverandering - sloten - zoetwaterecologie - nederland - aquatic plants - climatic change - ditches - freshwater ecology - netherlands - north-atlantic oscillation - plankton dynamics - drainage ditches - shallow lakes - eutrophication - temperature - mesocosms - dominance - states - model
    1. Experimental studies have indicated in freshwater ecosystems that a shift in dominance from submerged to free-floating macrophytes may occur with climate change because of increased water surface temperatures and eutrophication. Field evidence is, however, rare. 2. Here, we analysed long-term (26 years) dynamics of macrophyte cover in Dutch ditches in relation to Dutch weather variables and the North Atlantic Oscillation (NAO) winter index. The latter appears to be a good proxy for Dutch weather conditions. 3. Cover of both free-floating macrophytes and evergreen overwintering submerged macrophytes was positively related to mild winters (positive NAO winter index). On the other hand, high cover of submerged macrophytes that die back in winter coincided with cold winters (negative NAO winter index). Our results therefore suggest that the effect of weather on macrophyte species depends strongly on their overwintering strategy. 4. The positive relation of free-floating macrophytes with the NAO winter index was significantly stronger in ditches in organic soil than in those in inorganic soil. This may be because of increased nutrient loading associated with increased decomposition of organic matter and increased run-off to these ditches during mild wet winters. 5. Our results suggest that mild winters in a changing climate may cause submerged macrophytes with an evergreen overwintering strategy and free-floating macrophytes to outcompete submerged macrophytes that die back in winter.
    Abrupt regime shifts in space and time along rivers and connected lake systems
    Hilt, S. ; Köhler, J. ; Kozerski, H.P. ; Nes, E.H. van; Scheffer, M. - \ 2011
    Oikos 120 (2011)5. - ISSN 0030-1299 - p. 766 - 775.
    advection-dominated systems - alternative stable state - shallow lakes - submerged macrophytes - chlorophyll-a - water-quality - flow - ecosystems - streams - phytoplankton
    Regime shifts between clear and turbid water states are commonly found in shallow lakes. These shifts are attributed to a positive feedback between water clarity and submerged macrophytes (underwater plants). Altering the retention time of the water may influence these interactions and thus potentially reduce the probability of alternative stable states. Here we assessed the effect of water retention time on the occurrence of alternative states in water quality of flushed lakes, chains of lakes and rivers using a spatially explicit simple model. Our results indicate that increased flushing of lakes rapidly decreases the range of parameters with alternative stable states up to their total disappearance at a flushing rate of about 50% the algal growth rate. Similarly, in a chain of lakes or in rivers with low flowing velocity, our model predicts that alternative stable states can only occur for systems with a high retention time. Despite the lack of hysteresis at lower water retention times, we predict that abrupt changes between clear and turbid states are still possible both in time and in space. Over a wide range of parameters, the equilibrium state of the chain of lakes shows a steep gradient of vegetation cover. Further, the transient dynamics of the model often include rapid shifts in time. For example, a local regime shift that occurs upstream may propagate through the whole lake chain or river due to a domino effect. All results of the simple model could qualitatively be reproduced with a more mechanistic model. The abrupt rather than gradual response of submerged macrophytes to reduced turbidity levels still makes river systems rather resilient to management measure. The importance of the initial turbidity and the observed domino effect suggest that restoration measures should start upstream and that these measures should eventually trigger regime shifts downstream
    Challenges and opportunities for integrating lake ecosystem modelling approaches
    Mooij, W.M. ; Trolle, D. ; Jeppesen, E. ; Arhonditsis, G. ; Belolipetsky, P.V. ; Chitamwebwa, D.B.R. ; Degermendzhy, A.G. ; DeAngelis, D.L. ; Domis, L.N.D. ; Downing, A.S. ; Elliott, J.A. ; Fragoso, C.R. ; Gaedke, U. ; Genova, S.N. ; Gulati, R.D. ; Hakanson, L. ; Hamilton, D.P. ; Hipsey, M.R. ; Hoen, J. 't; Hulsmann, S. ; Los, F.H. ; Makler-Pick, V. ; Petzoldt, T. ; Prokopkin, I.G. ; Rinke, K. ; Schep, S.A. ; Tominaga, K. ; Dam, A.A. van; Nes, E.H. van; Wells, S.A. ; Janse, J.H. - \ 2010
    Aquatic Ecology 44 (2010)3. - ISSN 1386-2588 - p. 633 - 667.
    fresh-water ecosystems - of-the-art - daphnia population-dynamics - trophic state indicators - predator-prey system - causes regime shifts - library salmo-oo - shallow lakes - climate-change - submerged macrophytes
    A large number and wide variety of lake ecosystem models have been developed and published during the past four decades. We identify two challenges for making further progress in this field. One such challenge is to avoid developing more models largely following the concept of others ('reinventing the wheel'). The other challenge is to avoid focusing on only one type of model, while ignoring new and diverse approaches that have become available ('having tunnel vision'). In this paper, we aim at improving the awareness of existing models and knowledge of concurrent approaches in lake ecosystem modelling, without covering all possible model tools and avenues. First, we present a broad variety of modelling approaches. To illustrate these approaches, we give brief descriptions of rather arbitrarily selected sets of specific models. We deal with static models (steady state and regression models), complex dynamic models (CAEDYM, CE-QUAL-W2, Delft 3D-ECO, LakeMab, LakeWeb, MyLake, PCLake, PROTECH, SALMO), structurally dynamic models and minimal dynamic models. We also discuss a group of approaches that could all be classified as individual based: super-individual models (Piscator, Charisma), physiologically structured models, stage-structured models and traitbased models. We briefly mention genetic algorithms, neural networks, Kalman filters and fuzzy logic. Thereafter, we zoom in, as an in-depth example, on the multi-decadal development and application of the lake ecosystem model PCLake and related models (PCLake Metamodel, Lake Shira Model, IPH-TRIM3D-PCLake). In the discussion, we argue that while the historical development of each approach and model is understandable given its 'leading principle', there are many opportunities for combining approaches. We take the point of view that a single 'right' approach does not exist and should not be strived for. Instead, multiple modelling approaches, applied concurrently to a given problem, can help develop an integrative view on the functioning of lake ecosystems. We end with a set of specific recommendations that may be of help in the further development of lake ecosystem models.
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