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.

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Cost-effective management of coastal eutrophication : A case study for the yangtze river basin
Strokal, M. ; Kahil, T. ; Wada, Y. ; Albiac, J. ; Bai, Z. ; Ermolieva, T. ; Langan, S. ; Ma, L. ; Oenema, O. ; Wagner, F. ; Zhu, X. ; Kroeze, C. - \ 2020
Resources, Conservation and Recycling 154 (2020). - ISSN 0921-3449
Cost-effective management - Eutrophication - Integrated modelling - Nitrogen and phosphorus - Nutrient management - Waste recycling

Many water resources are threatened with nutrient pollution worldwide. This holds for rivers exporting increasing amounts of nutrients from the intensification of food production systems and further urbanization. This riverine nutrient transport causes coastal eutrophication. This study aims to identify cost-effective management options to simultaneously reach environmental targets for river export of nitrogen and phosphorus by the Yangtze River (China) in 2050. A newly developed modelling approach is used that integrates the Model to Assess River Inputs of Nutrients to seAs (MARINA) with a cost-optimization procedure, and accounts for socio-economic developments, land use and climate changes in a spatially explicit way. The environmental targets for river export of nutrients aim to reduce the gap between baseline and desirable nutrient export. Our baseline is based on MARINA projections for future river export of nutrients, while the desirable nutrient export reflects a low eutrophication potential. Results show the possibilities to close the gap in river export of both nutrients by 80–90% at a cost of 1–3 billion $ per year in 2050. Recycling of animal waste on cropland is an important cost-effective option; reducing synthetic fertilizer inputs provides an opportunity to compensate for the additional costs of the recycling and treatment of manure and wastewater. Our study provides new insights on the combination of cost-effective management options for sub-basins of the Yangtze. This can support the design of cost-effective and sub-basin specific management options for reducing future water pollution.

Cyanobacteria dominance drives zooplankton functional dispersion
Josué, Iollanda I.P. ; Cardoso, Simone J. ; Miranda, Marcela ; Mucci, Maíra ; Ger, Kemal Ali ; Roland, Fabio ; Marinho, Marcelo Manzi - \ 2019
Hydrobiologia 831 (2019)1. - ISSN 0018-8158 - p. 149 - 161.
Biodiversity - Eutrophication - Freshwater - Microbial food quality - Plankton

Accelerated eutrophication reduces water quality and shifts plankton communities. However, its effects on the aquatic food web and ecosystem functions remain poorly understood. Within this context, functional ecology can provide valuable links relating community traits to ecosystem functioning. In this study, we assessed the effects of eutrophication and cyanobacteria blooms on zooplankton functional diversity in a tropical hypereutrophic lake. Phytoplankton and zooplankton communities and limnological characteristics of a tropical Brazilian Lake (Southeast, Brazil) were monitored monthly from April 2013 to October 2014. Lake eutrophication indicators were total phosphorus, total chlorophyll-a, and chlorophyll-a per group (blue, green, and brown). The variation of major phytoplankton taxonomic group biomass was calculated and used as a proxy for changes in phytoplankton composition. Zooplankton functional diversity was assessed through functional dispersion and the community-weighted mean trait value. Regressions were performed between the lake eutrophication indicators, the phytoplankton biomass variation, and zooplankton functional dispersion. Our results suggest that eutrophication and cyanobacterial dominance change the composition of zooplankton traits and reduce functional dispersion, leading to zooplankton niche overlap. These findings are important because they provide a meaningful view of phytoplankton-zooplankton trophic interactions and contribute to an improved understanding their functional effects on aquatic ecosystems.

The impact of warming and nutrients on algae production and microcystins in seston from the iconic lake lesser Prespa, Greece
Maliaka, Valentini ; Faassen, Elisabeth J. ; Smolders, Alfons J.P. ; Lürling, Miquel - \ 2018
Toxins 10 (2018)4. - ISSN 2072-6651
Bioassay - Climate change - Cyanotoxins - Eutrophication - Nutrient addition
Lake Lesser Prespa and its adjacent pond, Vromolimni in Greece, is a shallow freshwater system and a highly protected area hosting an exceptional biodiversity. The occurrence of microcystins (MCs) producing cyanobacterial blooms in these waters during recent years can be harmful to the wildlife. We tested the hypothesis that both cyanobacterial biomass and MCs are strongly influenced by nutrients (eutrophication) and warming (climate change). Lake and pond water was collected from two sites in each water body in 2013 and incubated at three temperatures (20°C, 25°C, 30°C) with or without additional nutrients (nitrogen +N, phosphorus +P and both +N and +P). Based on both biovolume and chlorophyll-a concentrations, cyanobacteria in water from Lesser Prespa were promoted primarily by combined N and P additions and to a lesser extent by N alone. Warming seemed to yield more cyanobacteria biomass in these treatments. In water from Vromolimni, both N alone and N+P additions increased cyanobacteria and a warming effect was hardly discernible. MC concentrations were strongly increased by N and N+P additions in water from all four sites, which also promoted the more toxic variant MC-LR. Hence, both water bodies seem particularly vulnerable to further N-loading enhancing MC related risks.
Response of submerged macrophyte communities to external and internal restoration measures in north temperate shallow lakes
Hilt, Sabine ; Alirangues Nuñez, Marta M. ; Bakker, Elisabeth S. ; Blindow, Irmgard ; Davidson, Thomas A. ; Gillefalk, Mikael ; Hansson, Lars Anders ; Janse, Jan H. ; Janssen, Annette B.G. ; Jeppesen, Erik ; Kabus, Timm ; Kelly, Andrea ; Köhler, Jan ; Lauridsen, Torben L. ; Mooij, Wolf M. ; Noordhuis, Ruurd ; Phillips, Geoff ; Rücker, Jacqueline ; Schuster, Hans Heinrich ; Søndergaard, Martin ; Teurlincx, Sven ; Weyer, Klaus van de; Donk, Ellen van; Waterstraat, Arno ; Willby, Nigel ; Sayer, Carl D. - \ 2018
Frontiers in Plant Science 9 (2018). - ISSN 1664-462X
Aquaticplants - Biomanipulation - Eutrophication - Lakerestoration - Nutrient loadreduction - PCLake - Plant traits - Regime shift
Submerged macrophytes play a key role in north temperate shallow lakes by stabilizing clear-water conditions. Eutrophication has resulted in macrophyte loss and shifts to turbid conditions in many lakes. Considerable efforts have been devoted to shallow lake restoration in many countries, but long-term success depends on a stable recovery of submerged macrophytes. However, recovery patterns vary widely and remain to be fully understood. We hypothesize that reduced external nutrient loading leads to an intermediate recovery state with clear spring and turbid summer conditions similar to the pattern described for eutrophication. In contrast, lake internal restoration measures can result in transient clear-water conditions both in spring and summer and reversals to turbid conditions. Furthermore, we hypothesize that these contrasting restoration measures result in different macrophyte species composition, with added implications for seasonal dynamics due to differences in plant traits. To test these hypotheses, we analyzed data on water quality and submerged macrophytes from 49 north temperate shallow lakes that were in a turbid state and subjected to restoration measures. To study the dynamics of macrophytes during nutrient load reduction, we adapted the ecosystem model PCLake. Our survey and model simulations revealed the existence of an intermediate recovery state upon reduced external nutrient loading, characterized by spring clear-water phases and turbid summers, whereas internal lake restoration measures often resulted in clear-water conditions in spring and summer with returns to turbid conditions after some years. External and internal lake restoration measures resulted in different macrophyte communities. The intermediate recovery state following reduced nutrient loading is characterized by a few macrophyte species (mainly pondweeds) that can resist wave action allowing survival in shallowareas, germinate early in spring, have energy-rich vegetative propagules facilitating rapid initial growth and that can complete their life cycle by early summer. Later in the growing season these plants are, according to our simulations, outcompeted by periphyton, leading to late-summer phytoplankton blooms. Internal lake restoration measures often coincide with a rapid but transient colonization by hornworts, waterweeds or charophytes. Stable clear-water conditions and a diverse macrophyte flora only occurred decades after external nutrient load reduction or when measures were combined.
The impact of water hyacinth (Eichhornia crassipes) on greenhouse gas emission and nutrient mobilization depends on rooting and plant coverage
Oliveira-Junior, Ernandes Sobreira ; Tang, Yingying ; Berg, Sanne J.P. van den; Cardoso, Simone J. ; Lamers, Leon P.M. ; Kosten, Sarian - \ 2018
Aquatic Botany 145 (2018). - ISSN 0304-3770 - p. 1 - 9.
Carbon dioxide - Eutrophication - Floating plant - Invasive species - Methane - Nutrient dynamics
Water hyacinth stands are known to affect both nutrient concentrations in the water and carbon exchange with the atmosphere. However, both enhanced and reduced greenhouse gas (GHG) emissions have been reported in relation to water hyacinth presence. This controversy may be explained by variation in plant density and rooting. High growth rates indicate its capacity to mobilize and store nutrients in the tissues, and assimilate large amounts of carbon dioxide (CO2). Simultaneously the plant can stimulate methane (CH4) emission. This may occur when plants are rooting in the sediment due to CH4 shuttling from the sediment, through the plant, into the atmosphere. To unravel the potential influences of water hyacinth on nutrient dynamics and GHG fluxes, we performed an experiment in which plant coverage and root access to the sediment were manipulated. Plants reduced phosphorus concentrations in water and pore-water, independent of coverage and rooting, also rooting plants grown at high coverage showed higher plant N:P ratios. CH4 emissions were highest at high coverage and were further increased by rooting, indicating that plant-mediated transport indeed takes place. However, the overall GHG budget in terms of CO2 equivalents still resulted in the water hyacinth vegetation being near neutral, or even a net sink with respect to GHG exchange. The plant-induced enhancement of CH4 emissions suggests that the plant can be an effective CO2-to-biomass-to-CH4 converter. Our results show that plant coverage and water depth – regulating sediment-root contact – should be taken into account when estimating water hyacinth's effect on GHG emissions.
Spatial identification of critical nutrient loads of large shallow lakes : Implications for Lake Taihu (China)
Janssen, Annette B.G. ; Jager, Victor C.L. de; Janse, Jan H. ; Kong, Xiangzhen ; Liu, Sien ; Ye, Qinghua ; Mooij, Wolf M. - \ 2017
Water Research 119 (2017). - ISSN 0043-1354 - p. 276 - 287.
Algal blooms - Bifurcation analysis - Eutrophication - Load-response curve - PCLake - Spatial heterogeneity
Ongoing eutrophication frequently causes toxic phytoplankton blooms. This induces huge worldwide challenges for drinking water quality, food security and public health. Of crucial importance in avoiding and reducing blooms is to determine the maximum nutrient load ecosystems can absorb, while remaining in a good ecological state. These so called critical nutrient loads for lakes depend on the shape of the load-response curve. Due to spatial variation within lakes, load-response curves and therefore critical nutrient loads could vary throughout the lake. In this study we determine spatial patterns in critical nutrient loads for Lake Taihu (China) with a novel modelling approach called Spatial Ecosystem Bifurcation Analysis (SEBA). SEBA evaluates the impact of the lake's total external nutrient load on the local lake dynamics, resulting in a map of critical nutrient loads for different locations throughout the lake. Our analysis shows that the largest part of Lake Taihu follows a nonlinear load-response curve without hysteresis. The corresponding critical nutrient loads vary within the lake and depend on management goals, i.e. the maximum allowable chlorophyll concentration. According to our model, total nutrient loads need to be more than halved to reach chlorophyll-a concentrations of 30–40 μg L−1 in most sections of the lake. To prevent phytoplankton blooms with 20 μg L−1 chlorophyll-a throughout Lake Taihu, both phosphorus and nitrogen loads need a nearly 90% reduction. We conclude that our approach is of great value to determine critical nutrient loads of lake ecosystems such as Taihu and likely of spatially heterogeneous ecosystems in general.
Critical assessment of chitosan as coagulant to remove cyanobacteria
Lurling, Miguel ; Noyma, Natalia Pessoa ; Magalhães, Leonardo de; Miranda, Marcela ; Mucci, Maíra ; Oosterhout, F. van; Huszar, Vera L.M. ; Marinho, Marcelo Manzi - \ 2017
Harmful Algae 66 (2017). - ISSN 1568-9883 - p. 1 - 12.
Cyanobacterial blooms - Eutrophication - Flock and sink - Mitigation - Nuisance control

Removal of cyanobacteria from the water column using a coagulant and a ballast compound is a promising technique to mitigate nuisance. As coagulant the organic, biodegradable polymer chitosan has been promoted. Results in this study show that elevated pH, as may be common during cyanobacterial blooms, as well as high alkalinity may hamper the coagulation of chitosan and thus impair its ability to effectively remove positively buoyant cyanobacteria from the water column. The underlying mechanism is likely a shielding of the protonated groups by anions. Inasmuch as there are many chitosan formulations, thorough testing of each chitosan prior to its application is essential. Results obtained in glass tubes were similar to those from standard jar tests demonstrating that glass tube tests can be used for testing effects of coagulants and ballasts in cyanobacteria removal whilst allowing far more replicates. There was no relation between zeta potential and precipitated cyanobacteria. Given the well-known antibacterial activity of chitosan and recent findings of anti-cyanobacterial effects, pre-application tests are needed to decipher if chitosan may cause cell leakage of cyanotoxins. Efficiency- and side-effect testing are crucial for water managers to determine if the selected approach can be used in tailor-made interventions to control cyanobacterial blooms and to mitigate eutrophication.

Chitosan as coagulant on cyanobacteria in lake restoration management may cause rapid cell lysis
Nunes Teixeira Mucci, Maira ; Noyma, Natalia Pessoa ; Magalhães, Leonardo de; Miranda, Marcela ; Oosterhout, Frank van; Guedes, Iamê Alves ; Huszar, Vera L.M. ; Marinho, Marcelo Manzi ; Lürling, Miquel - \ 2017
Water Research 118 (2017). - ISSN 0043-1354 - p. 121 - 130.
Cell lysis - Cell viability - Cyanobacterial blooms - Eutrophication - Lake restoration - Photosystem II efficiency

Combining coagulant and ballast to remove cyanobacteria from the water column is a promising restoration technique to mitigate cyanobacterial nuisance in surface waters. The organic, biodegradable polymer chitosan has been promoted as a coagulant and is viewed as non-toxic. In this study, we show that chitosan may rapidly compromise membrane integrity and kill certain cyanobacteria leading to release of cell contents in the water. A strain of Cylindrospermopsis raciborskii and one strain of Planktothrix agardhii were most sensitive. A 1.3 h exposure to a low dose of 0.5 mg l−1 chitosan already almost completely killed these cultures resulting in release of cell contents. After 24 h, reductions in PSII efficiencies of all cyanobacteria tested were observed. EC50 values varied from around 0.5 mg l−1 chitosan for the two sensitive strains, via about 5 mg l−1 chitosan for an Aphanizomenon flos-aquae strain, a toxic P. agardhii strain and two Anabaena cylindrica cultures, to more than 8 mg l−1 chitosan for a Microcystis aeruginosa strain and another A. flos-aquae strain. Differences in sensitivity to chitosan might be related to polymeric substances that surround cyanobacteria. Rapid lysis of toxic strains is likely and when chitosan flocking and sinking of cyanobacteria is considered in lake restoration, flocculation efficacy studies should be complemented with investigation on the effects of chitosan on the cyanobacteria assemblage being targeted.

Long-term trends in nutrient budgets of the western Dutch Wadden Sea (1976–2012)
Jung, A.S. ; Brinkman, A.G. ; Folmer, E.O. ; Herman, Peter M.J. ; Veer, Henk W. van der; Philippart, C.J.M. - \ 2017
Journal of Sea Research 127 (2017). - ISSN 1385-1101 - p. 82 - 94.
Wadden Sea - Coastal North Sea - Nutrient exchange - Nitrogen - Phosphorus - Eutrophication - Nutrient budgets
Long-term field observations of nitrogen [N] and phosphorus [P] concentrations were used to construct nutriënt budgets for the western Dutch Wadden Sea between 1976 and 2012. Nutrients come into the western Dutch Wadden Sea via river runoff, through exchange with the coastal zone of the North Sea, neighbouring tidal basins and through atmospheric deposition (for N). The highest concentrations in phosphorus and nitrogen were observed
in themid-1980s. Improved phosphorus removal atwaste water treatment plants, management of fertilization in agriculture and removal of phosphates from detergents led to reduced riverine nutrient inputs and, consequently, reduced nutrient concentrations in theWadden Sea. The budgets suggest that the period of the initial net import of phosphorus and nitrogen switched to a net export in 1981 for nitrogen and in 1992 for phosphorus. Such different behaviour in nutrient budgets during the rise and fall of external nutriënt concentrations may be the result of different sediment-water exchange dynamics for P and N. It is hypothesized that during the period of increasing eutrophication (1976–1981) P, and to a lesser degree N, were stored in sediments as organic and inorganic nutrients. In the following period (1981–1992) external nutrient concentrations
(especially in the North Sea) decreased, but P concentrations in the Wadden Sea remained high due to prolonged sediment release, whilst denitrification removed substantial amounts of N. From1992 onwards, P andN budgetswere closed by net loss,most probably because P stores were then depleted and denitrification continued. Under the present conditions (lower rates of sediment import and depleted P stores), nutrient concentrations in this area are expected to be more strongly influenced by wind-driven exchange with the North Sea and precipitation-driven discharge from Lake IJssel. This implies that the consequences of climate change will be more important, than during the 1970s and 1980s.
Pathways for the effects of increased nitrogen deposition on fauna
Nijssen, M.E. ; Wallis de Vries, M.F. ; Siepel, H. - \ 2017
Biological Conservation 212 (2017)pt. B. - ISSN 0006-3207 - p. 423 - 431.
Acidification - Chemical stress - Eutrophication - Food web - Microclimate - Plant stoichiometry imbalance
Effects of increased N deposition, caused by agricultural practices and combustion of fossil fuels in traffic and industry, have been studied in detail for soil and water chemistry as well as for vegetation and ecosystem functioning. Knowledge on fauna is limited to descriptive and correlative data for a small number of species or communities. Therefore, mechanisms behind effects of N deposition on animal species and diversity remain unclear, which hampers optimisation of nature restoration and conservation measures.The aim of this review is to identify and structure possible different pathways in which fauna is affected by high N deposition. We identify ten pathways leading to six basic potentially negative bottlenecks: (1) chemical stress, (2) a levelled and humid microclimate, (3) decrease in reproductive habitat, (4) changes in food plant quantity, (5) changes in nutritional quality of food plants and (6) changes in availability of prey or host species due to cumulative effects in the food web. Depending on species and habitat type, different pathways play a dominant role and interference between different pathways can strengthen or weaken the net effect of N deposition.Although all identified pathways and bottlenecks are supported by peer reviewed literature, we conclude that scientific evidence on the causal relationship between increased N deposition and effects on fauna in the complete causal chain is still insufficient. We recommend that future research should aim to clarify the causal mechanisms underlying the observed changes in species composition attributed to N deposition. The most severe gaps in knowledge concern subtle changes in plant chemistry and changes in availability of prey and host species to higher trophic levels.
Efficacy of Coagulants and Ballast Compounds in Removal of Cyanobacteria (Microcystis) from Water of the Tropical Lagoon Jacarepaguá (Rio de Janeiro, Brazil)
Magalhães, Leonardo de; Noyma, Natália Pessoa ; Furtado, Luciana Lima ; Nunes Teixeira Mucci, Maira ; Oosterhout, Frank van; Huszar, Vera L.M. ; Marinho, Marcelo Manzi ; Lurling, Miguel - \ 2017
Estuaries and coasts 40 (2017)1. - ISSN 1559-2723 - p. 121 - 133.
Bloom control - Chitosan - Cyanobacteria - Eutrophication - Mitigation - PAC

Eutrophication is considered the most important water quality problem in freshwaters and coastal waters worldwide promoting frequent occurrence of blooms of potentially toxic cyanobacteria. Removal of cyanobacteria from the water column using a combination of coagulant and ballast is a promising technique for mitigation and an alternative to the use of algaecides. In laboratory, we tested experimentally the efficiency of two coagulants, polyaluminium chloride (PAC) and chitosan (made of shrimp shells), alone and combined with two ballasts: red soil (RS) and the own lagoon sediment, to remove natural populations of cyanobacteria, from an urban brackish coastal lagoon. PAC was a very effective coagulant when applied at low doses (≤8 mg Al L−1) and settled the cyanobacteria, while at high doses (≥16 mg Al L−1) large flocks aggregated in the top of test tubes. In contrast, chitosan was not able to form flocks, even in high doses (>16 mg L−1) and did not efficiently settle down cyanobacteria when combined with ballast. The RS itself removed 33–47 % of the cyanobacteria. This removal was strongly enhanced when combined with PAC in a dose-dependent matter; 8 mg Al L−1 was considered the best dose to be applied. The lagoon sediment alone did not promote any settling of cyanobacteria but removal was high when combined with PAC. Combined coagulant and ballast seems a very efficient, cheap, fast and safe curative measure to lessen the harmful cyanobacteria bloom nuisance in periods when particularly needed, such as around the 2016 Olympics in Jacarepaguá Lagoon.

The interaction between cyanobacteria and zooplankton in a more eutrophic world
Ger, Kemal Ali ; Urrutia-Cordero, Pablo ; Frost, Paul C. ; Hansson, Lars Anders ; Sarnelle, Orlando ; Wilson, Alan E. ; Lurling, Miguel - \ 2016
Harmful Algae 54 (2016). - ISSN 1568-9883 - p. 128 - 144.
Co-evolution - Eutrophication - Grazing - Local-adaptation - Plankton

As blooms of cyanobacteria expand and intensify in freshwater systems globally, there is increasing interest in their ecological effects. In addition to being public health hazards, cyanobacteria have long been considered a poor quality food for key zooplankton grazers that link phytoplankton to higher trophic levels. While past laboratory studies have found negative effects of nutritional constraints and defensive traits (i.e., toxicity and colonial or filamentous morphology) on the fitness of large generalist grazers (i.e., Daphnia), cyanobacterial blooms often co-exist with high biomass of small-bodied zooplankton in nature. Indeed, recent studies highlight the remarkable diversity and flexibility in zooplankton responses to cyanobacterial prey. Reviewed here are results from a wide range of laboratory and field experiments examining the interaction of cyanobacteria and a diverse zooplankton taxa including cladocerans, copepods, and heterotrophic protists from temperate to tropical freshwater systems. This synthesis shows that longer exposure to cyanobacteria can shift zooplankton communities toward better-adapted species, select for more tolerant genotypes within a species, and induce traits within the lifetime of individual zooplankton. In turn, the function of bloom-dominated plankton ecosystems, the coupling between primary producers and grazers, the stability of blooms, and the potential to use top down biomanipulation for controlling cyanobacteria depend largely on the species, abundance, and traits of interacting cyanobacteria and zooplankton. Understanding the drivers and consequences of zooplankton traits, such as physiological detoxification and selective vs. generalist grazing behavior, are therefore of major importance for future studies. Ultimately, co-evolutionary dynamics between cyanobacteria and their grazers may emerge as a critical regulator of blooms.

Excessive nitrogen and phosphorus in European rivers : 2000-2050
Blaas, Harry ; Kroeze, Carolien - \ 2016
Ecological Indicators 67 (2016). - ISSN 1470-160X - p. 328 - 337.
Algal blooms - Coastal waters - Eutrophication - Indicator - Nutrients - Rivers

Rivers export nutrients to coastal waters. Excess nutrient export may result in harmful algal blooms and hypoxia, affecting biodiversity, fisheries, and recreation. The purpose of this study is to quantify for European rivers (1) the extent to which N and P loads exceed levels that minimize the risk of harmful algal blooms and (2) the relative shares of sources of N and P in rivers. This may help to identify effective management strategies to reduce coastal eutrophication. We focus on 48 rivers in 27 countries of the European Union (EU27). We used the Global Nutrient Export from Watersheds (NEWS) model to analyze nutrient export by rivers and the associated potentials for coastal eutrophication as reflected by Indicator for Coastal Eutrophication Potential (ICEP). In 2000, 38 of the 48 EU rivers indicated in our study had an ICEP > 0, indicating a relatively high potential for harmful algal blooms. These 38 rivers cover 60% of EU27 land area. Between 2000 and 2050 nutrient export by European rivers is projected to decrease. However, by 2050 still 34 EU rivers, covering 48% of the land area, have an ICEP > 0. This indicates that in these scenarios little progress is made in terms of environmental improvement. About one-third of the rivers with ICEP > 0 are N limited, and about two-thirds P limited. In N-limited rivers reducing N loads is a more effective way to reduce the risk for coastal eutrophication than reducing P, and vice versa. For N-limited rivers agriculture or sewage are the dominant sources of nutrients in river water. In P-limited rivers, sewage is found to be the dominant source of P, except for rivers draining into the Atlantic Ocean, where agriculture can also be dominant. A basin-specific approach is needed to effectively reduce N and P loads.

The impact of bird herbivory on macrophytes and the resilience of the clear-water state in shallow lakes : a model study
Altena, Cassandra van; Bakker, Elisabeth S. ; Kuiper, Jan J. ; Mooij, Wolf M. - \ 2016
Hydrobiologia 777 (2016)1. - ISSN 0018-8158 - p. 197 - 207.
Alternative stable states - Ecosystem model - Eutrophication - Grazing - Top-down versus bottom-up control - Water quality management

Shallow lakes have the potential to switch between two alternative stable states: a clear macrophyte-dominated and a turbid phytoplankton-dominated state. Observational and experimental studies show that in some lakes herbivory by birds may severely decrease macrophyte biomass, while in other lakes, the removed biomass by herbivory is compensated by regrowth. These contradictory outcomes might arise because of interplay between top-down control by bird herbivory and bottom-up effects by nutrient loading on macrophytes. Here, we use the ecosystem model PCLake to study top-down and bottom-up control of macrophytes by coots and nutrient loading. Our model predicted that (1) herbivory by birds lowers the critical nutrient loading at which the regime shift occurs; (2) bird impact on macrophyte biomass through herbivory increases with nutrient loading; and (3) improved food quality enhances the impact of birds on macrophytes, thus decreasing the resilience of the clear-water state even further. The fact that bird herbivory can have a large impact on macrophyte biomass and can facilitate a regime shift implies that the presence of waterfowl should be taken into account in the estimation of critical nutrient loadings to be used in water quality management.

Calidad de agua de la bahía interior de Puno, lago Titicaca durante el verano del 2011
Farfán, Diana Beltrán F. ; Calli, Rocio Palomino P. ; Terrazas, Edmundo Moreno G. ; Peralta, Cesar G. ; Montesinos, Daniel - \ 2015
Revista Peruana de Biología 22 (2015)3. - ISSN 1561-0837 - p. 335 - 340.
Eutrophication - Titicaca lake - Wastewater - Water quality

Water quality of the inner Puno Bay was evaluated; we established 12 stations, and were assessed monthly from December 2010 to April 2011. Physicochemical water parameters were determined with EPA and APHA standard methods. Nutrients were determined spectrophotometrically. The parameters of temperature, dissolved oxygen, pH, phosphates, nitrates and nitrites of water show that the outlet of the stabilization lagoon of Puno City (Espinar Island) is a critical area of contamination at the inner Puno Bay. Transparency values were low. The electrical conductivity of water showed high values. Alkalinity values were high (75 - 150 mg/L) and very high (> 150 mg/L), indicating a high content of carbonates and bicarbonates. Water hardness were high (121- 180 mg/L) and very high (> 180 mg/L). High levels of fecal coliform in waters near the island Espinar would be the result of wastewater discharges from the Puno city, without proper treatment.

GLOBIO-Aquatic, a global model of human impact on the biodiversity of inland aquatic ecosystems
Janse, J.H. ; Kuiper, J.J. ; Weijters, M.J. ; Westerbeek, E.P. ; Jeuken, M.H.J.L. ; Bakkenes, M. ; Alkemade, R. ; Mooij, W.M. ; Verhoeven, J.T.A. - \ 2015
Environmental Science & Policy 48 (2015). - ISSN 1462-9011 - p. 99 - 114.
Catchment - Cyanobacteria - Eutrophication - Hydrological disturbance - Lakes - Land use change - Rivers - Scenario analysis - Wetlands

Biodiversity in freshwater ecosystems - rivers, lakes and wetlands - is undergoing rapid global decline. Major drivers are land use change, eutrophication, hydrological disturbance, climate change, overexploitation and invasive species. We developed a global model for assessing the dominant human impacts on inland aquatic biodiversity. The system consists of a biodiversity model, named GLOBIO-Aquatic, that is embedded in the IMAGE model framework, i.e. linked to models for demography, economy, land use changes, climate change, nutrient emissions, a global hydrological model and a global map of water bodies. The biodiversity model is based on a recompilation of existing data, thereby scaling-up from local/regional case-studies to global trends. We compared species composition in impacted lakes, rivers and wetlands to that in comparable undisturbed systems. We focussed on broad categories of human-induced pressures that are relevant at the global scale. The drivers currently included are catchment land use changes and nutrient loading affecting water quality, and hydrological disturbance and climate change affecting water quantity. The resulting relative mean abundance of original species is used as indicator for biodiversity intactness. For lakes, we used dominance of harmful algal blooms as an additional indicator. The results show that there is a significant negative relation between biodiversity intactness and these stressors in all types of freshwater ecosystems. In heavily used catchments, standing water bodies would lose about 80% of their biodiversity intactness and running waters about 70%, while severe hydrological disturbance would result in losses of about 80% in running waters and more than 50% in floodplain wetlands. As an illustration, an analysis using the OECD 'baseline scenario' shows a considerable decline of the biodiversity intactness in still existing water bodies in 2000, especially in temperate and subtropical regions, and a further decline especially in tropical regions in 2050. Historical loss of wetland areas is not yet included in these results. The model may inform policy makers at the global level in what regions aquatic biodiversity will be affected most and by what causes, and allows for scenario analysis to evaluate policy options.

Stewardship to tackle global phosphorus inefficiency : The case of Europe
Withers, P.J.A. ; Dijk, K.C. van; Neset, T.S.S. ; Nesme, Thomas ; Oenema, Oene ; Rubæk, G.H. ; Schoumans, O.F. ; Smit, Bert ; Pellerin, Sylvain - \ 2015
Ambio 44 (2015)2. - ISSN 0044-7447 - p. 193 - 206.
Europe - Eutrophication - Human health - Inefficiency - Phosphorus - Resources - Sustainability

The inefficient use of phosphorus (P) in the food chain is a threat to the global aquatic environment and the health and well-being of citizens, and it is depleting an essential finite natural resource critical for future food security and ecosystem function. We outline a strategic framework of 5R stewardship (Re-align P inputs, Reduce P losses, Recycle P in bioresources, Recover P in wastes, and Redefine P in food systems) to help identify and deliver a range of integrated, cost-effective, and feasible technological innovations to improve P use efficiency in society and reduce Europe’s dependence on P imports. Their combined adoption facilitated by interactive policies, co-operation between upstream and downstream stakeholders (researchers, investors, producers, distributors, and consumers), and more harmonized approaches to P accounting would maximize the resource and environmental benefits and help deliver a more competitive, circular, and sustainable European economy. The case of Europe provides a blueprint for global P stewardship.

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