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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Lanthanum in Water, Sediment, Macrophytes and chironomid larvae following application of Lanthanum modified bentonite to lake Rauwbraken (The Netherlands)
Oosterhout, Frank van; Waajen, Guido ; Yasseri, Said ; Manzi Marinho, Marcelo ; Pessoa Noyma, Natália ; Mucci, Maíra ; Douglas, Grant ; Lürling, Miquel - \ 2020
Science of the Total Environment 706 (2020). - ISSN 0048-9697
Bioavailable - Filterable lanthanum - Lake management - Phoslock® - Sediment release

Lanthanum Modified Bentonite (LMB; Phoslock®) is used to mitigate eutrophication by binding phosphate released from sediments. This study investigated the fate of lanthanum (La) from LMB in water, sediment, macrophytes, and chironomid larvae in Lake Rauwbraken (The Netherlands). Before the LMB application, water column filterable La (FLa) was 0.02 µg L−1, total La (TLa) was 0.22 µg L−1. In sediment the total La ranged 0.03–1.86 g m−2. The day after the application the maximum FLa concentration in the water column was 44 µg L−1, TLa was 528 µg L−1, exceeding the Dutch Maximum Permissible Concentrations (MPC) of 10.1 µg L−1 by three to fourfold. TLa declined below the MPC after 15 days, FLa after 75 days. After ten years, FLa was 0.4 µg L−1 and TLa was 0.7 µg L−1. Over the post-application years, FLa and TLa showed statistically significant downward trends. While the LMB settled homogeneously on sediment, after 3 years it redistributed to 0.2–5.4 g La m−2 within shallow zones, and 30.7 g m−2 to 40.0 g La m−2 in deeper zones. In the upper 20 cm of sediment, La concentrations were 7–6702 mg kg −1 dry weight (DW) compared to 0.5–7.0 mg kg−1 before application. Pre-application anaerobic sediment release of FLa was 0.006 mg m−2 day−1. Three months after the application it was 1.02 mg m−2 day−1. Three years later it was 0.063 mg m−2 day−1. Before application La in plants was 0.8–5.1 mg La kg−1 DW, post-application values were up to 2925 mg La kg−1 DW. In chironomid larvae, La increased from 1.7 µg g−1 DW before application to 1421 µg g−1 DW after one month, 3 years later it was 277 µg g−1 DW. Filtration experiments indicate FLa is not truly dissolved free La3+ cations.

Separate collection of lightweight packages by 21 individual Dutch households in 2017
Thoden van Velzen, Ulphard ; Brouwer, Marieke - \ 2019
Wageningen University & Research
waste collection - plastic waste
It contains the composition of the mixed municipal solid waste (MSW) and lightweight packaging waste (LWP) (locally named PMD) of 21 households in two municipalities (Oosterhout and Waalwijk) and of the reference samples of the whole municipalities; mixed MSW and LWP taken from municipal cross-docking stations
Managing Eutrophication in a Tropical Brackish Water Lagoon : Testing Lanthanum-Modified Clay and Coagulant for Internal Load Reduction and Cyanobacteria Bloom Removal
Magalhães, Leonardo de; Noyma, Natalia Pessoa ; Furtado, Luciana Lima ; Drummond, Erick ; Leite, Vivian Balthazar Gonçalves ; Mucci, Maíra ; Oosterhout, Frank van; Moraes Huszar, Vera Lúcia de; Lürling, Miquel ; Marinho, Marcelo Manzi - \ 2019
Estuaries and coasts 42 (2019)2. - ISSN 1559-2723 - p. 390 - 402.
Geo-engineering - Lake restoration - PAC - Phoslock - Phosphorus control - Sediment release

The release of phosphorus (P) stored in the sediment may cause long-term delay in the recovery of lakes, ponds, and lagoons from eutrophication. In this paper, we tested on a laboratory scale the efficacy of the flocculant polyaluminium chloride (PAC) and a strong P-binding agent (lanthanum-modified bentonite, LMB) on their ability to flocculate a cyanobacterial bloom and hamper P release from a hypertrophic, brackish lagoon sediment. In addition, critical P loading was estimated through PCLake. We showed that cyanobacteria could be effectively settled using a PAC dose of 2 mg Al L−1 combined with 400-mg L−1 LMB; PAC 8 mg Al L−1 alone could also remove cyanobacteria, although its performance was improved adding low concentrations of LMB. The efficacy of LMB to bind P released from the sediment was tested based on potentially available sediment P. A dose of 400 g LMB m−2 significantly reduced the P release from sediment to over-standing water (either deionized water or water from the lagoon with and without cyanobacteria). In sediment cores, LMB + PAC reduced sediment P flux from 9.9 (± 3.3) to − 4.6 (± 0.3) mg P m−2 day−1 for the experimental period of 3 months. The internal P load was 14 times higher than the estimated P critical load (0.7 mg P m−2 day−1), thus even if all the external P sources would be ceased, the water quality will not improve promptly. Hence, the combined LMB + PAC treatment seems a promising in-lake intervention to diminish internal P load bellow the critical load. Such intervention is able to speed up recovery in the brackish lagoon once external loading has been tackled and at a cost of less than 5% of the estimated dredging costs.

Response of natural cyanobacteria and algae assemblages to a nutrient pulse and elevated temperature
Lürling, Miquel ; Mello, Mariana Mendese ; Oosterhout, Frank van; Senerpont Domis, Lisette de; Marinho, Marcelo M. - \ 2018
Frontiers in Microbiology 9 (2018)AUG. - ISSN 1664-302X
Blooms - Climate change - Competition - Global warming - Optimum growth

Eutrophication (nutrient over-enrichment) is the primary worldwide water quality issue often leading to nuisance cyanobacterial blooms. Climate change is predicted to cause further rise of cyanobacteria blooms as cyanobacteria can have a competitive advantage at elevated temperatures. We tested the hypothesis that simultaneous rise in nutrients and temperature will promote cyanobacteria more than a single increase in one of the two drivers. To this end, controlled experiments were run with seston from 39 different urban water bodies varying in trophic state from mesotrophic to hypertrophic. These experiments were carried out at two different temperatures, 20°C (ambient) and 25°C (warming scenario) with or without the addition of a surplus of nutrients (eutrophication scenario). To facilitate comparisons, we quantified the effect size of the different treatments, using cyanobacterial and algal chlorophyll a concentrations as a response variable. Cyanobacterial and algal chlorophyll a concentrations were determined with a PHYTO-PAM phytoplankton analyzer. Warming caused an 18% increase in cyanobacterial chlorophyll-α, while algal chlorophyll-α concentrations were on average 8% higher at 25°C than at 20°C. A nutrient pulse had a much stronger effect on chlorophyll-α concentrations than warming. Cyanobacterial chlorophyll-α concentrations in nutrient enriched incubations at 20 or 25°C were similar and 9 times higher than in the incubations without nutrient pulse. Likewise, algal chlorophyll-α concentrations were 6 times higher. The results of this study confirm that warming alone yields marginally higher cyanobacteria chlorophyll-α concentrations, yet that a pulse of additional nutrients is boosting blooms. The responses of seston originating from mesotrophic waters seemed less strong than those from eutrophic waters, which indicates that nutrient control strategies -catchment as well as in-system measures- could increase the resilience of surface waters to the negative effects of climate change.

Effects of polyaluminum chloride and lanthanum-modified bentonite on the growth rates of three Cylindrospermopsis raciborskii strains
Araújo, Fabiana ; Oosterhout, Frank Van; Becker, Vanessa ; Attayde, José Luiz ; Lürling, Miquel - \ 2018
PLoS ONE 13 (2018)4. - ISSN 1932-6203
In tropical and subtropical lakes, eutrophication often leads to nuisance blooms of Cylindrospermopsis raciborskii. In laboratory experiments, we tested the combined effects of flocculant polyaluminum chloride (PAC) and lanthanum-modified bentonite (LMB) on the sinking and growth rates of three C. raciborskii strains. We tested the hypothesis that the combination of PAC and LMB would (1) effectively sink C. raciborskii in a test tube experiment and (2) impair C. raciborskii growth, irrespective of the biomass of the inoculum (bloom) and the strain in the growth experiment. We tested the recommended (LMB1) and a three-times higher dose of LMB (LMB3). The combined addition of PAC and LMB enhanced the sedimentation of all C. raciborskii strains. Moreover, both the PAC and LMB doses decreased the phosphate concentration. PAC and LMB1 decreased the growth rate of all strains, but the efficacy depended on the biomass and strain. The combined addition of PAC and LMB3 inhibited the growth of all strains independently of the biomass and strain. We conclude that a low dose of PAC in combination with the recommended dose of LMB decreases C. raciborskii blooms and that the efficiency of the technique depends on the biomass of the bloom. A higher dose of LMB is needed to obtain a more efficient control of C. raciborskii blooms.
Moet Oosterhout fijnstofvangers aanschaffen?
Molen, Michiel van der - \ 2017
Effect of suspended clay on growth rates of the cyanobacterium Cylindrospermopsis raciborskii
Brasil, Jandeson ; Huszar, Vera L.M. ; Attayde, José L. ; Marinho, Marcelo M. ; Oosterhout, Frank Van; Lürling, Miquel - \ 2017
Fundamental and Applied Limnology 191 (2017)1. - ISSN 1863-9135 - p. 13 - 23.
Cyanobacteria - Inorganic turbidity - Light availability - Sedimentation - Suspended solids
Recent studies have shown that sediment resuspension may lead to the collapse of C. raciborskii dominance, which suggests that clay might have a negative effect on the growth of C. raciborskii. To test the hypothesis that suspended clay creates an unfavorable environment for growth of C. raciborskii, we exposed four different strains of this species to various concentrations of the clays kaolinite and bentonite, and monitored the biomass of each strain over the course of 1-week microcosm experiments. Contrary to our hypothesis, C. raciborskii was able to grow in suspensions of both clays. While kaolinite clay caused higher turbidity than bentonite, the growth rates of all four C. raciborskii strains were higher in kaolinite than in bentonite suspensions. C. raciborskii could still grow in clay concentrations that cause turbidity far above the levels found in natural lakes. Our study suggests that the reported collapse of C. raciborskii blooms with high concentrations of suspended sediments in tropical shallow lakes is probably not caused by the effects of suspended clay on light attenuation, but rather is a consequence of cell sinking or, possibly a response to disturbance events responsible for sediment suspension.
Bio-accumulation of lanthanum from lanthanum modified bentonite treatments in lake restoration
Waajen, G. ; Oosterhout, F. van; Lürling, M. - \ 2017
Environmental Pollution 230 (2017). - ISSN 0269-7491 - p. 911 - 918.
Cyanobacteria - Ecotoxicity - Eutrophication control - Health risk - Phoslock
Lanthanum (La) modified bentonite (LMB) is one of the available mitigating agents used for the reduction of the phosphorus (P) recycling in eutrophic lakes. The potential toxicity of the La from LMB to aquatic organisms is a matter of concern. In this study the accumulation of La was investigated in the macrophyte Elodea nuttallii, in chironomid larvae and in several fish species during periods up to five years following in situ LMB applications. The application of LMB increased the La concentration of exposed plants and animals. During the first growing season following LMB applications, the La content of E. nuttallii increased 78 fold (3.98–310.68 μg La g−1 DW) to 127 fold (2.46–311.44 μg La g−1). During the second growing season following application, the La content decreased but was still raised compared to plants that had not been exposed. The La content of chironomids was doubled in the two years following LMB application, although the increase was not significant. Raised La concentrations in fish liver, bone, muscle and skin were observed two and five years following to LMB application. Liver tissues showed the highest La increase, ranging from 6 fold (0.046–0.285 μg La g−1 DW) to ∼20 fold (0.080–1.886 μg La g−1, and 0.122–2.109 μg La g−1) two years following application and from 6 fold (0.046–0.262 μg La g−1) to 13 fold (0.013–0.167 μg La g−1) after five years in pelagic and littoral fish. The La content of the liver from Anguilla anguilla (eel) had increased 94 fold (0.034–3.176 μg La g−1) two years and 133 fold (0.034–4.538 μg La g−1) five years following LMB application. No acute and chronic effects of La accumulation were observed and human health risks are considered negligible. We advocate the long-term study of effects of La accumulation following future LMB applications.
Effects of dredging and lanthanum-modified clay on water quality variables in an enclosure study in a hypertrophic pond
Lürling, Miquel ; Waajen, Guido ; Engels, Bart ; Oosterhout, Frank van - \ 2017
Water 9 (2017)6. - ISSN 2073-4441 - 24 p.
cyanobacterial bloom - Eutrophication control - Lake management - Lake restoration - Mitigation - Principle response curve

An enclosure experiment was conducted between July and September 2009 to compare the effectiveness of a phosphate fixative, the lanthanum-modified bentonite clay Phoslock® (LMB), dredging, and their combination in controlling eutrophication in a hypertrophic urban pond in Heesch, The Netherlands. In total, 25 water quality variables were monitored. Multivariate analysis revealed that the combination LMB-treated and dredged enclosures deviated most from the pond (reference) and the controls, and showed the strongest eutrophication reduction. Overall, dredging significantly increased transparency, lowered turbidity, and improved the oxygen conditions in the enclosures compared to non-dredged ones. Nonetheless, one dredged enclosure deviated dramatically from the others, which might reflect methodological issues with dredging. The LMB treatment appeared to be less effective at mitigating eutrophication than dredging, and phosphate concentrations even increased during the experiment in the LMB-treated enclosures. Chemical equilibrium modeling suggested that humic substances could have formed complexes with lanthanum (La) from the LMB, rendering it unavailable for intercepting P over the course of the enclosure experiment. Residual lanthanum concentrations in combination dredging and LMB treatments exceeded the Dutch standard 10-fold. Total zooplankton abundance, and particularly Cladocera, increased in all enclosures over the course of the experiment. The limited effect of LMB in the enclosure experiment and the violation of the Dutch La standard when combined with dredging disqualify LMB as an intervention agent in the restoration of the pond.

Coagulant plus ballast technique provides a rapid mitigation of cyanobacterial nuisance
Noyma, Natalia Pessoa ; Magalhães, Leonardo De; Miranda, Marcela ; Nunes Teixeira Mucci, Maira ; Oosterhout, Frank van; Moraes Huszar, Vera Lúcia de; Marinho, Marcelo Manzi ; Lima, Eduardo R.A. ; Lurling, Miquel - \ 2017
PLoS ONE 12 (2017)6. - ISSN 1932-6203 - 16 p.

Cyanobacteria blooms are a risk to environmental health and public safety due to the potent toxins certain cyanobacteria can produce. These nuisance organisms can be removed from water bodies by biomass flocculation and sedimentation. Here, we studied the efficacy of combinations of a low dose coagulant (poly-aluminium chloride-PAC-or chitosan) with different ballast compounds (red soil, bauxite, gravel, aluminium modified zeolite and lanthanum modified bentonite) to remove cyanobacterial biomass from water collected in Funil Reservoir (Brazil). We tested the effect of different cyanobacterial biomass concentrations on removal efficiency. We also examined if zeta potential was altered by treatments. Addition of low doses of PAC and chitosan (1±8 mg Al L-1) to the cyanobacterial suspensions caused flock formation, but did not settle the cyanobacteria. When those low dose coagulants were combined with ballast, effective settling in a dose-dependent way up to 99.7% removal of the flocks could be achieved without any effect on the zeta potential and thus without potential membrane damage. Removal efficacy was influenced by the cyanobacterial biomass and at higher biomass more ballast was needed to achieve good removal. The combined coagulant-ballast technique provides a promising alternative to algaecides in lakes, ponds and reservoirs.

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.

Eutrophication and warming boost cyanobacterial biomass and microcystins
Lurling, Miguel ; Oosterhout, Jean ; Faassen, Els - \ 2017
Toxins 9 (2017)2. - ISSN 2072-6651
Cell quota - Climate change - Cyanobacterial blooms - Cyanotoxins - Mitigation - Seston
Eutrophication and warming are key drivers of cyanobacterial blooms, but their combined effects on microcystin (MC) concentrations are less studied. We tested the hypothesis that warming promotes cyanobacterial abundance in a natural plankton community and that eutrophication enhances cyanobacterial biomass and MC concentrations. We incubated natural seston from a eutrophic pond under normal, high, and extreme temperatures (i.e., 20, 25, and 30 °C) with and without additional nutrients added (eutrophication) mimicking a pulse as could be expected from projected summer storms under climate change. Eutrophication increased algal-and cyanobacterial biomass by 26 and 8 times, respectively, and led to 24 times higher MC concentrations. This effect was augmented with higher temperatures leading to 45 times higher MC concentrations at 25 °C, with 11 times more cyanobacterial chlorophyll-a and 25 times more eukaryote algal chlorophyll-a. At 30 °C, MC concentrations were 42 times higher, with cyanobacterial chlorophyll-a being 17 times and eukaryote algal chlorophyll-a being 24 times higher. In contrast, warming alone did not yield more cyanobacteria or MCs, because the in situ community had already depleted the available nutrient pool. MC per potential MC producing cell declined at higher temperatures under nutrient enrichments, which was confirmed by a controlled experiment with two laboratory strains of Microcystis aeruginosa. Nevertheless, MC concentrations were much higher at the increased temperature and nutrient treatment than under warming alone due to strongly promoted biomass, lifting N-imitation and promotion of potential MC producers like Microcystis. This study exemplifies the vulnerability of eutrophic urban waters to predicted future summer climate change effects that might aggravate cyanobacterial nuisance.
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.

Management of eutrophication in Lake De Kuil (The Netherlands) using combined flocculant - lanthanum modified bentonite treatment
Waaijen, G. ; Oosterhout, F. van; Douglas, G.C. ; Lurling, M.F.L.L.W. - \ 2016
Water Research 97 (2016). - ISSN 0043-1354 - p. 83 - 95.
Eutrophication of Lake De Kuil (The Netherlands, 6.7 ha, maximum depth 9 m) has frequently caused cyanobacterial blooms resulting in swimming bans or the issue of water quality warnings during summer. The eutrophication was mainly driven by sediment phosphorus (P)-release. The external P-loading was in the range of the critical loading for phytoplankton blooms. Hence, the reduction of the internal P-loading provided a promising way to reduce cyanobacterial blooms. To mitigate the cyanobacterial blooms, the combination of a low dose flocculant (iron(III)chloride; Flock) and a solid phase phosphate fixative (lanthanum modified bentonite; Lock) was applied in May 2009. This combined approach both removed cyanobacterial biomass from the water column and also intercepted P released from the bottom sediments. Immediately after treatment, the Secchi depth increased from 1.5 m up to 5 m. Sediment P-release decreased from 5.2 mg P m−2 d−1 (2009) to 0.4 mg P m−2 d−1 (2010) but increased in later years. Mean summer concentrations of total P decreased from 0.05 mg L−1 (1992–2008) to 0.02 mg L−1 (2009–2014) and chlorophyll-a from 16 μg L−1 (1992–2008) to 6 μg L−1 (2009–2014). Mean summer Secchi depth increased from 2.31 m (1992–2008) to 3.12 m (2009–2014). The coverage of macrophytes tripled from 2009 to 2011. In the winter of 2010/2011 Planktothrix rubescens bloomed, but cyanobacterial biomass decreased during the summers after the Flock and Lock treatment in comparison to prior years. After the Flock & Lock the bathing water requirements have been fulfilled for six consecutive summers. As the sediment P-release has gradually increased in recent years, there is a risk of a reversion from the present mesotrophic state to a eutrophic state.
Controlling cyanobacterial blooms through effective flocculation and sedimentation with combined use of flocculants and phosphorus adsorbing natural soil and modified clay
Pessoa Noyma, Natalia ; Magalhaes, L. de; Furtado, L.L. ; Nunes Teixeira Mucci, M. ; Oosterhout, M. van; Huszar, V.L.M. ; Marinho, M.M. ; Lurling, M.F.L.L.W. - \ 2016
Water Research 97 (2016). - ISSN 0043-1354 - p. 26 - 38.
Cyanobacteria bloom - Geo-engineering in lakes - Lake restoration - Local red soil - Phosphorus mitigation
Eutrophication often results in blooms of toxic cyanobacteria that hamper the use of lakes and reservoirs. In this paper, we experimentally evaluated the efficacy of a metal salt (poly-aluminium chloride, PAC) and chitosan, alone and combined with different doses of the lanthanum modified bentonite Phoslock® (LMB) or local red soil (LRS) to sediment positively buoyant cyanobacteria from Funil Reservoir, Brazil, (22°30’S, 44°45’W). We also tested the effect of calcium peroxide (CaO2) on suspended and settled cyanobacterial photosystem efficiency, and evaluated the soluble reactive P (SRP) adsorbing capacity of both LMB and LRS under oxic and anoxic conditions. Our data showed that buoyant cyanobacteria could be flocked and effectively precipitated using a combination of PAC or chitosan with LMB or LRS. The SRP sorption capacity of LMB was higher than that of LRS. The maximum P adsorption was lowered under anoxic conditions especially for LRS ballast. CaO2 addition impaired photosystem efficiency at 1 mg L-1 or higher and killed precipitated cyanobacteria at 4 mg L-1 or higher. A drawback was that oxygen production from the peroxide gave positive buoyancy again to the settled flocs. Therefore, further experimentations with slow release pellets are recommended.
Elevated pCO2 causes a shift towards more toxic microcystin variants in nitrogen limited Microcystis aeruginosa
Liu, J. ; Oosterhout, J.F.X. ; Faassen, E.J. ; Lurling, M.F.L.L.W. ; Helmsing, N.R. ; Waal, D.B. van der - \ 2016
FEMS microbiology ecology 92 (2016)2. - ISSN 0168-6496 - 8 p.
Elevated pCO2 may promote phytoplankton growth, and potentially alleviate carbon limitation during dense blooms. Under nitrogen-limited conditions, elevated pCO2 may furthermore alter the phytoplankton carbon: nitrogen (C:N) balance and thereby the synthesis of secondary metabolites, such as cyanobacterial toxins. A common group of these toxins are microcystins, with variants that not only differ in C:N stoichiometry, but also in toxicity. Here, we hypothesized that elevated pCO2 will increase the cellular C:N ratios of cyanobacteria, thereby promoting the more toxic microcystin variants with higher C:N ratios. To test this hypothesis, we performed chemostat experiments under nitrogen-limited conditions, exposing three Microcystis aeruginosa strains to two pCO2 treatments: 400 and 1200 μatm. Biomass, cellular C:N ratios and total microcystin contents at steady state remained largely unaltered in all three strains. Across strains and treatments, however, cellular microcystin content decreased with increasing cellular C:N ratios, suggesting a general stoichiometric regulation. Furthermore, as predicted, microcystin variants with higher C:N ratios generally increased with elevated pCO2, while the variant with a low C:N ratio decreased. Thus, elevated pCO2 under nitrogen-limited conditions may shift the cellular microcystin composition towards the more toxic variants. Such CO2 driven changes may have consequences for the toxicity of Microcystis blooms.
Geo-engineering experiments in two urban ponds to control eutrophication
Waaijen, G. ; Oosterhout, J.F.X. ; Douglas, G.C. ; Lurling, M.F.L.L.W. - \ 2016
Water Research 97 (2016). - ISSN 0043-1354 - p. 69 - 82.
lakes - restoration management - ecological restoration - eutrophication - field experimentation - dredging - bentonite - water quality - phytoplankton - water treatment - meren - herstelbeheer - ecologisch herstel - eutrofiëring - experimenteel veldonderzoek - baggeren - bentoniet - waterkwaliteit - fytoplankton - waterzuivering
Many urban ponds experience detrimental algal blooms as the result of eutrophication. During a two year field experiment, the efficacy of five in situ treatments to mitigate eutrophication effects in urban ponds was studied. The treatments targeted the sediment phosphorus release and were intended to switch the ponds from a turbid phytoplankton-dominated state to a clear-water state with a low phytoplankton biomass. Two eutrophic urban ponds were each divided into six compartments (300–400 m2; 210–700 m3). In each pond the following treatments were tested: dredging in combination with biomanipulation (involving fish biomass control and the introduction of macrophytes) with and without the addition of the flocculant polyaluminiumchloride, interception and reduction of sediment phosphorus release with lanthanum-modified bentonite (Phoslock®) in combination with biomanipulation with and without polyaluminiumchloride; biomanipulation alone; and a control. Trial results support the hypothesis that the combination of biomanipulation and measures targeting the sediment phosphorus release can be effective in reducing the phytoplankton biomass and establishing and maintaining a clear-water state, provided the external phosphorus loading is limited. During the experimental period dredging combined with biomanipulation showed mean chlorophyll-a concentrations of 5.3 and 6.2 μg L−1, compared to 268.9 and 52.4 μg L−1 in the control compartments. Lanthanum-modified bentonite can be an effective alternative to dredging and in combination with biomanipulation it showed mean chlorophyll-a concentrations of 5.9 and 7.6 μg L−1. Biomanipulation alone did not establish a clear-water state or only during a limited period. As the two experimental sites differed in their reaction to the treatments, it is important to choose the most promising treatment depending on site specific characteristics. In recovering the water quality status of urban ponds, continuing attention is required to the concurrent reduction of external phosphorus loading and to maintaining an appropriate fish community.
A meta-analysis of water quality and aquatic macrophyte responses in 18 lakes treated with lanthanum modified bentonite (PHOSLOCK®)
Spears, B.M. ; Mackay, E. ; Yasseri, S. ; Gunn, I.D.M. ; Waters, K.E. ; Andrews, C. ; Cole, S. ; Ville, M. de; Kelly, M. ; Meis, S. ; Moore, A.L. ; Nurnberg, G.K. ; Oosterhout, Frank van; Lurling, M.F.L.L.W. - \ 2016
Water Research 97 (2016). - ISSN 0043-1354 - p. 111 - 121.
Lanthanum (La) modified bentonite is being increasingly used as a geo-engineering tool for the control of phosphorus (P) release from lake bed sediments to overlying waters. However, little is known about its effectiveness in controlling P across a wide range of lake conditions or of its potential to promote rapid ecological recovery. We combined data from 18 treated lakes to examine the lake population responses in the 24 months following La-bentonite application (range of La-bentonite loads: 1.4-6.7 tonnes ha-1) in concentrations of surface water total phosphorus (TP; data available from 15 lakes), soluble reactive phosphorus (SRP; 14 lakes), and chlorophyll a (15 lakes), and in Secchi disk depths (15 lakes), aquatic macrophyte species numbers (6 lakes) and aquatic macrophyte maximum colonisation depths (4 lakes) across the treated lakes. Data availability varied across the lakes and variables, and in general monitoring was more frequent closer to the application dates. Median annual TP concentrations decreased significantly across the lakes, following the La-bentonite applications (from 0.08 mg L-1 in the 24 months pre-application to 0.03 mg L-1 in the 24 months post-application), particularly in autumn (0.08 mg L-1 to 0.03 mg L-1) and winter (0.08 mg L-1 to 0.02 mg L-1). Significant decreases in SRP concentrations over annual (0.019 mg L-1 to 0.005 mg L-1), summer (0.018 mg L-1 to 0.004 mg L-1), autumn (0.019 mg L-1 to 0.005 mg L-1) and winter (0.033 mg L-1 to 0.005 mg L-1) periods were also reported. P concentrations following La-bentonite application varied across the lakes and were correlated positively with dissolved organic carbon concentrations. Relatively weak, but significant responses were reported for summer chlorophyll a concentrations and Secchi disk depths following La-bentonite applications, the 75th percentile values decreasing from 119 µg L-1 to 74 µg L-1 and increasing from 398 cm to 506 cm, respectively. Aquatic macrophyte species numbers and maximum colonisation depths increased following La-bentonite application from a median of 5.5 species to 7.0 species and a median of 1.8 m to 2.5 m, respectively. The aquatic macrophyte responses varied significantly between lakes. La-bentonite application resulted in a general improvement in water quality leading to an improvement in the aquatic macrophyte community within 24 months. However, because, the responses were highly site-specific, we stress the need for comprehensive pre- and post-application assessments of processes driving ecological structure and function in candidate lakes to inform future use of this and similar products.
Humic substances interfere with phosphate removal by lanthanum modified clay in controlling eutrophication
Lurling, M.F.L.L.W. ; Waaijenberg, G.W.A.M. ; Oosterhout, J.F.X. - \ 2014
Water Research 54 (2014). - ISSN 0043-1354 - p. 78 - 88.
waterbodems - fosfaten - eutrofiëring - bioremediëring - laboratoriumproeven - water bottoms - phosphates - eutrophication - bioremediation - laboratory tests - rare-earth-elements - phosphorus-binding clay - organic-matter removal - modified bentonite clay - natural-waters - cyanobacterial toxins - polyaluminum chloride - cation binding - ion-binding - fresh-water
The lanthanum (La) modified bentonite Phoslock® has been proposed as dephosphatisation technique aiming at removing Filterable Reactive Phosphorus (FRP) from the water and blocking the release of FRP from the sediment. In the modified clay La is expected the active ingredient. We conducted controlled laboratory experiments to measure the FRP removal by Phoslock® in the presence and absence of humic substances, as La complexation with humic substances might lower the effectiveness of La (Phoslock®) to bind FRP. The results of our study support the hypothesis that the presence of humic substances can interfere with the FRP removal by the La-modified bentonite. Both a short-term (1 d) and long-term (42 d) experiment were in agreement with predictions derived from chemical equilibrium modelling and showed lower FRP removal in presence of humic substances. This implies that in DOC-rich inland waters the applicability of exclusively Phoslock® as FRP binder should be met critically. In addition, we observed a strong increase of filterable La in presence of humic substances reaching in a week more than 270 µg La l-1 that would infer a violation of the Dutch La standard for surface water, which is 10.1 µg La l-1. Hence, humic substances are an important factor that should be given attention when considering chemical FRP inactivation as they might play a substantial role in lowering the efficacy of metal-based FRP-sorbents, which makes measurements of humic substances (DOC) as well as controlled experiments vital.
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