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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Warmer and browner waters decrease fish biomass production
Dorst, Renee M. Van; Gårdmark, Anna ; Svanbäck, Richard ; Beier, Ulrika ; Weyhenmeyer, Gesa A. ; Huss, Magnus - \ 2019
Global Change Biology 25 (2019)4. - ISSN 1354-1013 - p. 1395 - 1408.
biomass production - browning - Climate change - Eurasian perch - fish - individual body grwoth - lakes - length distribution - ontogeny - warming
Climate change studies have long focused on effects of increasing temperatures,
often without considering other simultaneously occurring environmental changes, such as browning of waters. Resolving how the combination of warming and browning of aquatic ecosystems affects fish biomass production is essential for future ecosystem functioning, fisheries, and food security. In this study, we analyzed individual‐ and population‐level fish data from 52 temperate and boreal lakes in Northern Europe, covering large gradients in water temperature and color (absorbance, 420 nm). We show that fish (Eurasian perch, Perca fluviatilis) biomass production decreased with both high water temperatures and brown water color, being lowest in warm and brown lakes. However, while both high temperature and brown water decreased fish biomass production, the mechanisms behind the decrease differed: temperature affected the fish biomass production mainly through a decrease in population standing stock biomass, and through shifts in size‐ and age‐distributions toward a higher proportion of young and small individuals in warm lakes; brown water color, on the other hand, mainly influenced fish biomass production through negative effects on individual body growth and length‐at‐ age. In addition to these
findings, we observed that the effects of temperature and brown water color on
individual‐level processes varied over ontogeny. Body growth only responded positively to higher temperatures among young perch, and brown water color had a stronger negative effect on body growth of old than on young individuals. Thus, to better understand and predict future fish biomass production, it is necessary to integrate both individual‐ and population‐level responses and to acknowledge within species variation. Our results suggest that global climate change, leading to browner and warmer waters, may negatively affect fish biomass production, and this effect may be stronger than caused by increased temperature or water color alone
A blooming business : Identifying limits to Lake Taihu's nutrient input
Janssen, Annette B.G. - \ 2017
Wageningen University. Promotor(en): Wolf Mooij, co-promotor(en): J.H. Janse; A.A. van Dam. - Wageningen : Wageningen University - ISBN 9789463431897 - 268
lakes - freshwater ecology - aquatic ecosystems - nutrients - cycling - nutrient flows - biodiversity - algae - models - critical loads - limnology - spatial variation - ecological restoration - china - meren - zoetwaterecologie - aquatische ecosystemen - voedingsstoffen - kringlopen - nutriëntenstromen - biodiversiteit - algen - modellen - critical loads - limnologie - ruimtelijke variatie - ecologisch herstel - china

Last century, Lake Taihu (China) became serious eutrophic due to excessive nutrient input. During the 1980s, the first algal blooms emerged in the lake, reaching disastrous proportions in 2007. During that year, the intake of drinking water had to be shut down and millions of people had to look for an alternative source of drinking water. This raises the question whether such problems can be avoided. Of crucial importance in avoiding and reducing toxic algal blooms is the identification of the maximum nutrient load ecosystems can absorb, while remaining in a good ecological state. In this thesis, I aim to determine the critical nutrient load for Lake Taihu. I approach the search for critical nutrient loads of Lake Taihu in five steps with diversity as an overarching topic throughout this thesis: diversity in lakes, diversity in models, diversity in spatial distribution of nutrient and water sources, diversity in the development of lakes around the earth and finally diversity within specific lakes. From the long list of available models I chose the model PCLake to use in my analysis because it is the most extensively used food web model applied for bifurcation analysis of shallow aquatic ecosystems. The approach has resulted in a range of critical nutrient loads for different parts of Lake Taihu. Furthermore, critical nutrient loads depend on management goals, i.e. the maximum allowable chlorophyll-a concentration. According to the model results, 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. This range contrasts to the single point of recovery that is often found for small shallow lakes. The range in critical nutrient loads found for Lake Taihu can be interpreted as providing a path of recovery for which each step leads to water quality improvement in certain parts of the lake. To reach total recovery, nutrient reduction seems to be the most promising management option.

Preserving Urmia Lake in a changing world : reconciling anthropogenic and climate drivers by hydrological modelling and policy assessment
Shadkam, Somayeh - \ 2017
Wageningen University. Promotor(en): P. Kabat, co-promotor(en): F. Ludwig; P.R. van Oel. - Wageningen : Wageningen University - ISBN 9789463431866 - 140
lakes - hydrology - climatic change - modeling - water resources - water management - environmental protection - iran - meren - hydrologie - klimaatverandering - modelleren - watervoorraden - waterbeheer - milieubescherming - iran

Urmia Lake, in north-western Iran, is an important internationally recognized natural area designated as a RAMSAR site and UNESCO Biosphere Reserve. Over the last 20 years, the surface area of Urmia Lake has declined by 80%. As a result, the salinity of the lake has sharply increased which is disturbing the ecosystems, local agriculture and livelihoods, regional health, as well as tourism, which could amplify economic, political and ethnic tensions in this already volatile region. In response to that, Iranian government established the ten-year “Urmia Lake Restoration Program (ULRP)” proposing six approaches in terms of controlling, protecting, surveying, studying and supplying water from other sources. This study first assessed the main reasons for the decreased inflow using the Variable Infiltration Capacity (VIC) hydrological model, including reservoirs and irrigation modules. The results showed that climate change was the main contributor to this inflow reduction. However, water resources development, particularly water use for irrigation, has played a substantial role as well. In the second step assessed Urmia lake inflow under future climate change and irrigation scenarios. Then, the (VIC) model was forced with bias-corrected climate model outputs for both the lowest (RCP2.6) and highest (RCP8.5) greenhouse-gas concentration scenarios to estimate future water availability. The results showed that the water resources plans are not robust to changes in climate. In other words, if future climate change is limited due to rapid mitigation measures (RCP2.6) the new strategy of reduction of irrigation water use can contribute to preserve Urmia Lake.

The next step of this study assessed the quantitative impacts of ULRP by introducing a constructive framework. The framework depicts real water saving by distinguishing between water withdrawals, depletion, and demand in the context of uncertainties in future demand and supply. The results showed that although the ULRP helps to increase inflow by up to 57% it is unlikely to fully reach its target for three main reasons. The first reason is decreasing return flows due to increasing irrigation efficiency. The second reason is increased depletion which is due to neglecting the fact that agricultural water demand is currently higher than available water for agriculture. The third reason is ignoring the potential impact of climate change. However, there still can be some additional none-quantifiable barriers and challenges that may cause the failure of the restoration plan. Therefore, in the last step, this study used two types of qualitative data to explore these aspects: first, the opinions from 40 experts and the in-situ observation of some of the ULRP implementation practices. The results indicate a number of challenges for the ULRP implementation including the water use regulations and the agricultural measures. In addition, (water) demand-side measures such as crop pattern changes were more supported, as opposed to supply-side measures.

This thesis showed that the sustainable approach to preserve Urmia Lake should incorporate both demand management (considering socioeconomic complexity) and flexible supply management strategies (to deal with uncertainties in climate variability and change) in a participatory approach. To be prepared for the future, also scenarios with reduced inflow into Urmia Lake, either due to climate change or water resources development, need to be considered to deal with considerable amounts of variability in the current system and with future changes in climate and socioeconomic conditions.

Eco-engineering for clarity : clearing blue-green ponds and lakes in an urbanized area
Waajen, Guido W.A.M. - \ 2017
Wageningen University. Promotor(en): M. Scheffer, co-promotor(en): M.F.L.L.W. Lürling. - Wageningen : Wageningen University - ISBN 9789463431095 - 306
ponds - lakes - ecological engineering - urban areas - cyanobacteria - eutrophication - water quality - water management - plassen - meren - natuurtechniek - stedelijke gebieden - cyanobacteriën - eutrofiëring - waterkwaliteit - waterbeheer

Small lakes and ponds are common features in urban areas and they contribute to the quality of citizens’ life. A poor water quality, however, can easily give rise to nuisance. A major cause for a poor water quality is a high concentration of plant-nourishing nutrients, eutrophication. In (semi-)standing waters, eutrophication often results in a high biomass of blue-green algae (cyanobacteria), turbid water and the disappearance of submerged aquatic plants. The cyanobacterial blooms can be accompanied with fish kills due to anoxia, the development of unpleasant surface scums and malodors. As cyanobacteria can produce potent toxins, they impose a serious risk for citizens’ health, pets and wildlife. The cyanobacterial blooms hamper the anthropogenic use of the water and can have negative economic impacts. Water managers experience that the reduction of cyanobacterial nuisance is arduous. As long-term positive effects of management interventions are not often achieved, there is need for effective approaches.

The objective of this study was to investigate the efficacy of promising methods to reduce cyanobacterial nuisance in city waters, targeting the clear water state and promoting the growth of aquatic plants. Various methods were tested, in the laboratory, in small and large compartments and were eventually applied in whole ponds and lakes. It is widely accepted that the reduction of nutrient inputs is essential for long-term positive effects. This study focused on the reduction of the input and the availability of the key-nutrient phosphorus. It was shown that cyanobacterial nuisance was wide spread in urban ponds and lakes in the Dutch province of North Brabant. The phosphorus inputs of four urban lakes in this province were addressed. The study lakes differed greatly in the phosphorus sources and loads, depending on site-specific characteristics. These differences affected the selection of measures. It was shown that in-lake measures were effective in realizing the long-term abatement of the cyanobacterial nuisance, provided the external phosphorus input was limited. If the external phosphorus input could not be limited sufficiently, in-lake measures did not result in the long-term reduction of cyanobacterial nuisance.

To reduce the bioavailable phosphorus stock in the lake with in-lake measures, sediment capping with a phosphorus-binding agent (lanthanum-modified bentonite, LMB) can be effective and cheaper than sediment removal by dredging. The additional use of a flocculant may have added value and suppressed cyanobacterial blooms quickly and effectively. Aquatic plants and macroinvertebrates responded positively to the achieved improvement of the water quality. Accumulation of lanthanum was shown in aquatic plants and fish, following LMB exposure. No toxic effects of lanthanum from LMB were observed. Depending on site-specific characteristics, dredging or LMB did not suffice to limit the available phosphorus stock in the lake. For this situation, the additional capping of the sediment with sand was tested and subsequently applied in a lake. Management of the fish biomass and lake reconstruction can support rehabilitation. The results of this study underpin the importance of a site-specific diagnosis (water system analysis). The diagnosis clarifies the underlying causes of cyanobacterial nuisances and is essential for a site-specific tailored set of measures. This study showed that a site-specific set of measures reduced cyanobacterial nuisance effectively for a long term.

As eutrophication control is not always feasible or might be effective only in the long run, curative measures are needed for symptom relief. Several curative end-of-pipe measures that are often suggested were evaluated: effective microorganisms (EM®), golden algae, plant extracts, ultrasound and artificial mixing of non-stratifying waters. No strong support for the efficacy of these measures could be shown. Next to the above mentioned application of flocculant, the use of freshwater quagga mussels is promising. The efficacy of the mussels was experimentally tested and it was shown that the introduction of mussels in a hypertrophic urban pond reduced the phytoplankton biomass, including cyanobacteria, and induced a clear water state. The quagga mussel is an invasive alien species and new introductions should be considered carefully.

Based on the results from this study, the thesis provides a road map for water managers for the reduction of cyanobacterial nuisances in urban ponds and lakes.

Ecophysiology and environmental distribution of organohalide-respiring bacteria
Lu, Y. - \ 2016
Wageningen University. Promotor(en): Hauke Smidt, co-promotor(en): Siavash Atashgahi. - Wageningen : Wageningen University - ISBN 9789462578418 - 239
bacteria - halides - ecophysiology - phylogenetics - genomics - lakes - halogens - pollutants - bacteriën - haliden - ecofysiologie - fylogenetica - genomica - meren - halogenen - verontreinigende stoffen

Organohalide-respiring bacteria (OHRB) are able to breathe natural and anthropogenically produced organohalides persistent in a broad range of oxygen-depleted environments. Therefore, these microorganisms are of high interest for organohalide-contaminated site bioremediation and natural halogen and carbon cycle. Nevertheless, to assess and adjust in situ bioremediation strategies and to enhance current understanding about the role of OHRB in natural habitats, thorough understanding of their ecophysiology and interaction with surrounding biotic and abiotic forces is necessary. To this end, this thesis focused on exploring ecophysiology and environmental distribution of OHRB in pristine and contaminated sites and unraveling their interactions with the co-existing microbial guilds in the community and geochemical parameters by application of a suite of physiological, molecular and geochemical analyses.

Based on a comprehensive overview of currently known organohalide-respiring isolates and their environmental distribution, the presence of yet unknown OHRB in extreme environments was proposed as the known organohalide-respiring isolates survive/thrive at a moderate range of pH and salinity in laboratory culture. Therefore, the OHRB were surveyed in alkaline and hypersaline sediments collected from Lake Strawbridge, Western Australia, that was known to emit organohalides. As a result, for the first time, the dechlorination of chloroform and perchloroethene (PCE) to dichloromethane and trichloroethene, respectively, was documented from an alkaline hypersaline pristine environment.

Corrinoids are essential cofactors for the activity of reductive dehalogenase enzymes. Ironically, some OHRB are reported to be corrinoid auxotrophs. Using transcriptional analysis and shotgun proteomics, here we show corrinoid auxotrophy in Dehalobacter restrictus PER-K23T. This detrimental deficiency seems to be compensated by up-regulation of relevant cobalamin salvaging and transport pathways to ensure sufficient corrinoid supply under partial corrinoid starvation. Hence, such OHRB incapable of de novo corrinoid synthesis will be dependent on non-dechlorinating community members to fulfill their nutritional needs indicating paramount importance of syntrophic interactions in supporting robust growth and activity of OHRB.

Bacterial community analysis of chlorinated benzene dechlorinating consortia derived from contaminated harbour sludge suggested members of the Bacteroidetes phylum and Clostridiales order as well as sulfate-reducing Deltaproteobacteria as putative stimulating guilds that provide electron donor and/or organic cofactors to OHRB i.e. D. mccartyi and Dehalobacter. However, despite well-controlled lab condition, syntrophic interactions could be influenced by geochemical parameters under field settings. Accordingly, analysis of geochemical and microbial determinants of OHR at a site biostimulated by glycerol injection further verified supportive role of fermenters and sulfate reducers under highly reduced condition following biostimulation. However, towards the end of field experiment, reducing condition faded and sulfate increased concurrent with the appearance of Epsilonproteobacteria and Deferribacteres as putative oxidizers of reduced sulfur compounds. The latter guilds might serve as detoxifiers of sulfide and thereby stimulate D. mccartyi, but could also be inhibitory as successors of the more important syntrophic fermenting and sulfate reducing bacteria.

In conclusion, this thesis expands our understanding of ecophysiology and environmental distribution of OHRB, addressing their presence in pristine environments as well as providing further evidence for their dependencies on other microbial community members in order to meet their nutritional requirements. Hence, research described here strengthens the scientific foundation for evaluating and optimizing strategies for the bioremediation of organohalide-contaminated sites and expands the natural niche of OHRB to extreme pristine environments.

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.
Dioxines en PCB's in Chinese wolhandkrab; invloed van grootte en variatie door het seizoen
Kotterman, M.J.J. ; Vries, P. de; Leeuwen, S.P.J. van; Hoogenboom, L.A.P. - \ 2015
IMARES Wageningen UR (Rapport / IMARES ) - 43 p.
krabben (schaaldieren) - decapoda - schaaldieren - dioxinen - polychloorbifenylen - rivieren - meren - nederland - crabs - shellfish - dioxins - polychlorinated biphenyls - rivers - lakes - netherlands
De monitoringsstudies naar de vervuilingsgraad van Chinese Wolhandkrab (WHK) die vanaf 2010 in Nederlandse wateren worden uitgevoerd tonen aan dat de WHK sterk vervuild kan zijn met polychloordibenzo-p-dioxines en -furanen (PCDD/F's, verderop aangeduid als 'dioxines'), met dioxine-achtige polychloorbifenylen (dl-PCB's) en met niet-dioxine achtige PCB’s (ndl-PCB’s). Deze contaminanten bevinden zich vooral in het vlees met hoge vetgehalten, de hepatopancreas (= middendarmklier) en gonaden (= geslachtsklier), vaak aangeduid met het 'bruine vlees' uit het lijf. Het witte spiervlees, uit poten, scharen en ook uit het lichaam, is vetarm en de concentraties dioxines en PCB’s zijn laag. Uit de voorgaande onderzoeken blijkt dat er een sterk geografische invloed is op de concentraties contaminanten in WHK; bijvoorbeeld WHK gevangen in de grote rivieren zijn sterker vervuild dan WHK uit het IJsselmeer. Over een eventuele tijdsafhankelijke variatie waardoor bijvoorbeeld gedurende het trekseizoen de concentraties contaminanten in de WHK sterk wisselen op een bepaalde locatie, is nog niets bekend. Er is wel reden om dat aan te nemen. WHK leggen in het trekseizoen grote afstanden af. De kans is daarom reëel dat de WHK die in een bepaald gebied worden gevangen van verschillende locaties afkomstig zijn, waardoor de concentraties contaminanten tussen individuele WHK kunnen verschillen.
A social analysis of contested fishing practices in Lake Victoria
Medard, M. - \ 2015
Wageningen University. Promotor(en): Han van Dijk, co-promotor(en): Paul Hebinck; R. Mwaipopo. - Wageningen : s.n. - ISBN 9789462572478 - 278
visserij - gemeenschappen - productiviteit - hulpbronnen - ontwikkeling - sociologie - organisatie - visserijbeheer - ondernemerschap - meren - tanzania - fisheries - communities - productivity - resources - development - sociology - organization - fishery management - entrepreneurship - lakes - tanzania

Thesis abstract

The thesis explored how the global market for Nile Perch fish has reconfigured the social and the natural in dramatic ways. The demand for Nile Perch and Dagaa played, willingly or unwillingly, an important role in converting its products into regionally and globally desired commodity. It has also simultaneously restructured the organisation of fisheries into a complex and aggressively managed sector. In fishing and fish trade, one needs to externalize costs and risks to the lower actors in the production and business hierarchy. From an historical point of view, power has shifted from many points of coordination and decision making into a few hands, those that own fishing camps and export processing factory. Moreover, illegal fishing and trading are continuous and corruption is rife to safe guard individual interest in turn shaping the local practices (governance) of Lake Victoria. Finally the debate about fisheries policies and fisheries regulation in L. Victoria does not address local realities and are largely irrelevant and that the real focus of power and driver of change is the international and regional markets for Nile Perch and Dagaa and global players with a lot of capital.

Dynamics in organic matter processing, ecosystem metabolism and trophic sources for consumers in the Mara River, Kenya
Masese, F.O. - \ 2015
Wageningen University. Promotor(en): K.A. Irvine, co-promotor(en): M.E. McClain; G.M. Gettel. - Leiden : CRC Press/Balkema - ISBN 9781138028159 - 195
organische stof - ecosystemen - landgebruik - ecosysteemdiensten - rivieren - meren - koolstof - stikstof - visserij - aquatische ecologie - organic matter - ecosystems - land use - ecosystem services - rivers - lakes - carbon - nitrogen - fisheries - aquatic ecology

To properly conserve, restore and manage riverine ecosystems and the services they provide, it is pertinent to understand their functional dynamics. However, there is still a major knowledge gap concerning the functioning of tropical rivers in terms of energy sources supporting riverine fisheries. I reviewed the anthropogenic influences on organic matter processes, energy sources and attributes of riverine food webs in the Lake Victoria basin, but also expanded the review to incorporate recent research findings from the tropics. Contrasting findings have been presented on the diversity of shredders and their role in organic matter processing in tropical streams. Recent tropical research has also highlighted the importance of autochthonous carbon, even in small forested streams. However similar studies are very limited in Afrotropical streams making it difficult to determine their place in emerging patterns of carbon flow in the tropics.

This study was conducted in the Mara River, which is an important transboundary river with its headwaters in the Mau Forest Complex in Kenya and draining to Lake Victoria through Tanzania. In its headwaters, the basin is drained by two main tributaries, the Amala and Nyangores Rivers which merge in the middle reaches to form the Mara River mainstem. The overall objective of this dissertation was to better understand the functioning of the Mara River by assessing the spatio-temporal dynamics of organic matter sources and supply under different land-use and flow conditions and the influence of these dynamics on energy flow for consumers in the river. I collected benthic macroinvertebrates from open- and closed-canopy streams and classified them into functional feeding groups (FFGs) using gut content analysis. In total, I identified 43 predators, 26 collectors, 19 scrapers and 19 shredders. Species richness was higher in closed-canopy forested streams where shredders were also the dominant group in terms of biomass. Seven shredder taxa occurred only in closed-canopy forested streams highlighting the importance of maintaining water and habitat quality, including the input of leaf litter of the right quality, in the studied streams. The findings suggest that Kenyan highland streams harbor a diverse shredder assemblage contrary to earlier findings that had identified a limited number of shredder taxa.

I subsequently used the composition of invertebrate functional feeding groups (FFGs) and the ecosystem process of leaf breakdown as structural and functional indicators, respectively, of ecosystem health in upland Kenyan streams. Coarse- and fine-mesh litterbags were used to

compare microbial (fine-mesh) with shredder + microbial (coarse-mesh) breakdown rates, and by extension, determine the role of shredders in litter processing of leaves of different tree species (native Croton macrostachyus and Syzygium cordatum and the exotic Eucalyptus globulus). Breakdown rates were generally higher in coarse- compared with fine-mesh litterbags for the native leaf species and the relative differences in breakdown rates among leaf species remained unaltered in both agriculture and forest streams. Shredders were relatively more important in forest compared with agriculture streams where microbial breakdown was more important. Moreover, shredder mediated leaf litter breakdown was dependent on leaf species, and was highest for C. macrostachyus and lowest for E. globulus, suggesting that replacement of indigenous riparian vegetation with poorer quality Eucalyptus species along streams has the potential to reduce nutrient cycling in streams.

To study organic matter dynamics is these streams, I assessed the influence of land use change on the composition and concentration of dissolved organic matter (DOM) and investigated its links with whole-stream ecosystem metabolism. Optical properties of DOM indicated notable shifts in composition along a land use gradient. Forest streams were associated with higher molecular weight and terrestrially derived DOM whereas agriculture streams were associated with autochthonously produced and low molecular weight DOM and photodegradation due to the open canopy. However, aromaticity was high at all sites irrespective of catchment land use. In agricultural areas high aromaticity likely originated from farmlands where soils are mobilized during tillage and carried into streams and rivers by runoff. Gross primary production (GPP) and ecosystem respiration (ER) were generally higher in agriculture streams, because of slightly open canopy and higher nutrient concentrations. The findings of this study are important because, in addition to reinforcing the role of tropical streams and rivers in the global carbon cycle, they highlight the consequences of land use change on ecosystem functioning in a region where land use activities are poised to intensify in response to human population growth.

Lastly, I used natural abundances of stable carbon (δ13C) and nitrogen (δ15N) isotopes to quantify spatial and temporal patterns of carbon flow in food webs in the longitudinal gradient of the Mara River. River reaches were selected that were under different levels of human and mammalian herbivore (livestock and wildlife) influences. Potential primary producers (terrestrial C3 and C4 producers and periphyton) and consumers (invertebrates and fish) were collected

during the dry and wet seasons to represent a range of contrasting flow conditions. I used Stable Isotope Analysis in R (SIAR) Bayesian mixing model to partition terrestrial and autochthonous sources of organic carbon supporting consumer trophic groups. Overall periphyton dominated contributions to consumers during the dry season. During the wet season, however, the importance of terrestrially-derived carbon for consumers was higher with the importance of C3 producers declining with distance from the forested upper reaches as the importance of C4 producers increased in river reaches receiving livestock and hippo inputs. This study highlights the importance of large mammalian herbivores on the functioning of riverine ecosystems and the implications of their loss from savanna landscapes that currently harbour remnant populations.

The results of this dissertation contribute data to discussions on the effects of land use change on the functioning of upland streams and food webs in savanna rivers with regard to carbon flow and the vectoring role played by large mammalian herbivores as they transfer terrestrial organic matter and nutrients into streams and rivers. This study also provides information and recommendations that will guide future research and management actions for the sustainability of the Mara River and linked ecosystems in the Lake Victoria basin.

Food quality dominates the impact of food quantity on Daphnia life history: possible implications for re-oligotrophication
Sarpe, D. ; Senerpont Domis, L.N. de; Declerck, S.A.J. ; Donk, E. van; Ibelings, B.W. - \ 2014
Inland Waters : Journal of the International Society of Limnology 4 (2014)4. - ISSN 2044-2041 - p. 363 - 368.
phosphorus limitation - nutrient limitation - long-term - lakes - carbon - eutrophication - growth
The elemental composition of phytoplankton is highly variable compared to the relatively narrow stoichiometry of zooplankton grazers. Using a full factorial design, we tested the effects of alterations in algal elemental composition (i.e., food quality) combined with food quantity on the life history of a Daphnia galeata clone from Lake IJsselmeer. Lower food quality reduced survival, growth, and reproduction. Food quantity became important at high food quality only. The strong effect of food quality indicates the potential for a stoichiometric bottleneck in Lake IJsselmeer, resulting in less high quality food for higher trophic levels as a result of re-oligotrophication.
Lanthanum from a modified clay used in eutrophication control is bioavailable to the marbled crayfish (Procambarus fallax f. virginalis)
Oosterhout, F. van; Goitom, E. ; Roessink, I. ; Lurling, M. - \ 2014
PLoS ONE 9 (2014)7. - ISSN 1932-6203 - 9 p.
phosphorus binding clay - copper nickel smelters - rare-earth-elements - heavy-metals - fresh-water - lakes - toxicity - accumulation - phoslock(r) - sediment
To mitigate eutrophication in fresh standing waters the focus is on phosphorus (P) control, i.e. on P inflows to a lake as well as a lake's sediment as internal P source. The in-lake application of the lanthanum (La) modified clays – i.e. La modified bentonite (Phoslock) or La modified kaolinite, aim at dephosphatising the water column and at reducing the release of P from a lake's sediment. Application of these clays raises the question whether La from these clays can become bioavailable to biota. We investigated the bioavailability of La from Phoslock in a controlled parallel groups experiment in which we measured the La in carapace, gills, ovaries, hepatopancreas and abdominal muscle after 0, 14 and 28 days of exposure to Phoslock. Expressing the treatment effect as the difference of the median concentration between the two treatment groups (Phoslock minus control group) yield the following effects, the plus sign (+) indicating an increase, concentrations in µg g-1 dry weight: Day 14: carapace +10.5 µg g-1, gills +112 µg g-1, ovaries +2.6 µg g-1, hepatopancreas +32.9 µg g-1 and abodminal muscle +3.2 µg g-1. Day 28: carapace +17.9 µg g-1; gills +182 µg g-1; ovaries +2.2 µg g-1; hepatopancreas +41.9 µg g-1 and abodminal muscle +7.6 µg g-1, all effects were statistically significant. As La from Phoslock is bio-available to and taken up by the marbled crayfishes (Procambarus fallax f. virginalis), we advocate that the application of in-lake chemical water treatments to mitigate eutrophication should be accompanied by a thorough study on potential side effects
Repeated Experimentation to Learn About a Flow-Pollutant Threshold
Groeneveld, R.A. ; Springborn, M. ; Costello, C. - \ 2014
Environmental and Resource Economics 58 (2014)4. - ISSN 0924-6460 - p. 627 - 647.
resource-management - lakes - environment - safety - shifts - quotas - taxes
We examine in discrete time the management of a flow pollutant that causes damage when it crosses a fixed but unknown threshold. The manager sequentially chooses a pollution level that allows learning about the threshold, thereby improving future decisions. If crossed, damage can be reversed at some cost. We analyze the conditions under which experimentation is optimal, and explore how experimentation depends on restoration costs, information about the threshold, and the discount rate. Our results suggest that the level of experimentation, defined as the difference between the optimal activity with and without learning, is non-monotonic in costs and decreasing in the discount rate. We identify two stopping boundaries for the experiment, depending on cost levels compared to the lower bound of the threshold’s interval. We show that when costs are high the stopping boundary under an infinite number of decisions is the same as when there are only two decision moments. A computational extension to more than two decisions suggests that an optimal sequence of experiments can cross the same threshold several times before experimentation ceases. These results shed light on a large class of environmental decision problems that has not been examined in the literature.
Disentangling the impacts of climate change, land use change and irrigation on the Central Rift Valley water system of Ethiopia
Getnet Debas, M. ; Hengsdijk, H. ; Ittersum, M.K. van - \ 2014
Agricultural Water Management 137 (2014). - ISSN 0378-3774 - p. 104 - 115.
kenya - basin - model - simulation - hydrology - support - lakes
The Central Rift Valley (CRV) of Ethiopia is a closed basin where claims on land and water have strongly increased over the past decade resulting in over-exploitation of the resources: a clear symptom is the declining trend in the water level of the terminal Lake Abyata. In this paper, we quantify the plausible recent impacts of climate change, land use change and irrigation water abstraction on water availability of Lake Abyata. We examined trends in lake levels, river discharges, basin rainfall, temperature and irrigation development (ca. 1975–2008), and computed the additional evapotranspiration loss resulting from temperature change and irrigated land. We also analysed land use change (1990–2007) and estimated the subsequent change in surface runoff. Temperature has increased linearly over 34 years (p <0.001) whereas rainfall has not changed significantly. Consequently, increased evapotranspiration consumed 62 and 145 Mm3 of additional water from lakes and land surface, respectively, during 1990–2007. Furthermore, an estimated 285 Mm3 yr-1 of water was abstracted for irrigation in 2009 of which approximately 170 Mm3 yr-1 is irrecoverable evapotranspiration loss. In addition, surface runoff has increased in the upper, and decreased in lower sub-basins of the CRV associated with extensive land use change (1990–2007). However, insight in the impact of the net increase in runoff of 260 Mm3 yr-1 on the water availability for Lake Abyata remains partial because of data and methodological limitations. We conclude that the potential for agricultural intensification and its hydrological implications should be considered jointly to prevent further deteriorating Lake Abyata.
Synergistic and species-specific effects of climate change and water colour on cyanobacterial toxicity and bloom formation
Ekvall, M.K. ; Faassen, E.J. ; Gustafsson, J.A. ; Lurling, M. ; Hansson, L. - \ 2013
Freshwater Biology 58 (2013)11. - ISSN 0046-5070 - p. 2414 - 2422.
dissolved organic-carbon - harmful cyanobacteria - subg. dolichospermum - drinking-water - genus anabaena - lakes - daphnia - toxins - biomanipulation - microcystins
Cyanobacterial blooms are a worldwide phenomenon in both marine and freshwater ecosystems and are predicted to occur more frequently due to global climate change. However, our future water resources may also simultaneously suffer from other environmental threats such as elevated amounts of humic content and consequent increased water colour, a phenomenon called 'brownification'. In order to investigate the effects of temperature and water colour in combination, we performed a mesocosm experiment combining a 3 °C increase in temperature and a doubling in water colour. With this, we created a projected future scenario for our water resources, and we specifically focused on how these changes would affect cyanobacterial bloom formation and toxicity. We showed that despite total cyanobacterial biomass remaining unaffected, the abundance of one individual cyanobacterial species, Microcystis botrys, increased in response to the combination of elevated temperature and increased water colour. Furthermore, population fluctuations in M. botrys explained the majority of the variations in microcystin concentrations, suggesting that this species was responsible for the more than 300% higher microcystin concentrations in the future scenario treatment compared to the ambient scenario. Hence, it was not a change in cyanobacterial biomass, but rather a species-specific response that had the most profound impact on bloom toxicity. We argue that understanding such species-specific responses to multiple stressors is crucial for proper management decisions because toxic blooms can significantly affect both biodiversity and ecosystem functioning, as well as ecosystem services such as drinking water supply and recreation. © 2013 John Wiley & Sons Ltd.
Verontreiniging Nederlandse schieraal 2009-2010 : onderzoek naar dioxines, PCB’s, organochloorverbindingen en gebromeerde vlamvertragers (PBDE’s) in schieraal uit Friese meren en het rivierengebied
Lee, M.K. van der; Leeuwen, S.P.J. van; Nieuwenhuizen-Hoek, M. van; Kotterman, M.J.J. ; Hoogenboom, L.A.P. - \ 2013
Wageningen [etc.] : RIKILT [etc.] (RIKILT-report 2013.004) - 29
palingen - european eels - dioxinen - ecotoxicologie - binnenwateren - meren - friesland - biesbosch - eels - dioxins - ecotoxicology - inland waters - lakes
Deze studie laat zien dat schieraal uit het rivierengebied in hoge mate verontreinigd is met een aantal contaminanten en de norm voor dioxines en dioxineachtige PCB's sterk overschrijdt. Schieraal uit de Friese meren is veel minder gecontamineerd en voldoet wel aan de normen.
Controlling eutrophication by combined bloom precipitation and sediment phosphorus inactivation
Lürling, M.F.L.L.W. ; Oosterhout, J.F.X. - \ 2013
Water Research 47 (2013)17. - ISSN 0043-1354 - p. 6527 - 6537.
meren - oppervlaktewaterkwaliteit - eutrofiëring - cyanobacteriën - sedimentatie - uitvlokking - lanthaan - bentoniet - tests - fosfor - ecologisch herstel - noord-brabant - lakes - surface water quality - eutrophication - cyanobacteria - sedimentation - flocculation - lanthanum - bentonite - tests - phosphorus - ecological restoration - noord-brabant - prymnesium-parvum haptophyceae - harmful cyanobacterial blooms - dissolved organic-matter - rare-earth-elements - of-the-art - microcystis-aeruginosa - lake restoration - local soils - polyaluminum chloride - phosphate adsorption
The hypothesis that the combination of the flocculent polyaluminium chloride (PAC) with the lanthanum-modified bentonite Phoslock® (Flock & Lock) could sink effectively a water bloom of cyanobacteria and could shift a turbid, cyanobacteria infested lake to a clear water lake was tested in a controlled laboratory experiment and a whole lake experiment. In the laboratory, a relatively low dose of the flocculent PAC (2.2 and 4.4 mg Al l-1) was insufficient to sediment positively buoyant cyanobacteria (Microcystis aeruginosa). Similarly, the lanthanum modified clay (dosed at 390 mg l-1) was insufficient to sediment the positively buoyant cyanobacteria. However, the combination of PAC and Phoslock® effectively sedimented cyanobacteria flocks. Likewise, a combined treatment of 2 tons PAC and 18 tons Phoslock® in Lake Rauwbraken in April 2008 effectively sedimented a developing cyanobacteria bloom of Aphanizomenon flos-aquae. The average chlorophyll-a concentration in the two years prior to this Flock & Lock treatment was 19.5 (±36.5) µg l-1, while it was as low as 3.7 (±4.5) µg l-1 in the years following the treatment. The combined treatment effectively reduced the amount of total phosphorus (TP) in the water column from on average 169 (±126) µg P l-1 before the application to 14 (±15) µg P l-1 after the treatment. Based on mean summer chlorophyll-a and TP concentrations, the lake was shifted from a eutrophic/hypertrophic state to an oligo/mesotrophic state. From directly after treatment in April 2008 until and including 2013, Lake Rauwbraken remained in an oligo-mesotrophic clear water state with TP reduced to less than 10% of the pre-treatment. This result shows that eutrophication in relatively small, isolated, stratifying lakes can be restored by targeting both water column and sediment P using a combination of flocculent and solid phase P-sorbent
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
Dioxines en PCB's in rode aal uit Nederlandse binnenwateren: resultaten tussen 2006 en 2012
Leeuwen, S.P.J. van; Kotterman, M.J.J. ; Hoek-van Nieuwenhuizen, M. van; Lee, M.K. van der; Hoogenboom, L.A.P. - \ 2013
Wageningen : RIKILT Wageningen UR (Rapport / RIKILT 2013.010) - 73
palingen - waterverontreiniging - ecotoxicologie - dioxinen - meren - binnenwateren - rivierengebied - ijsselmeer - friesland - eels - water pollution - ecotoxicology - dioxins - lakes - inland waters - lake ijssel
Aal (ook bekend als Europese paling - Anguilla) wordt beroepsmatig bevist en op de markt gebracht. Contaminanten zoals dioxines en polychloorbifenylen (PCB's) worden aangetoond in aal uit de Nederlandse wateren. Normoverschrijdende dioxine- en PCB-gehalten in rode aal uit de grote rivieren en het benedenrivierengebied hebben in 2011 geleid tot sluiting van deze gebieden voor de aalvangst. In schonere wateren zoals het IJsselmeer en de Friese meren is aalvangst wel toegestaan.
Bijdrage landbouw aan de NH3-depositie in de Nieuwkoopse Plassen : analyse van de effecten van aanvullende maatregelen
Kros, J. ; Voogd, J.C.H. ; Gies, T.J.A. - \ 2012
Wageningen : Alterra, Wageningen-UR (Alterra-rapport 2377) - 42
emissiereductie - ammoniak - landbouw - melkveehouderij - bemesting - dierlijke meststoffen - natuurgebieden - meren - natura 2000 - zuid-holland - emission reduction - ammonia - agriculture - dairy farming - fertilizer application - animal manures - natural areas - lakes
In het Natura 2000-gebied Nieuwkoopse Plassen & De Haeck is de stikstofdepositie hoog ten opzichte van de instandhoudingsdoelstellingen voor natuur in dit gebied. Bij het vaststellen van stikstofdepositie in dit gebied vormt de bijdrage van de ammoniakemissie vanuit de landbouw in de nabije omgeving een knelpunt bij het realiseren van de beoogde natuurdoelstellingen. Om inzicht te krijgen in deze problematiek is in dit rapport een analyse gegeven van de bijdrage van de landbouwemissies aan de ammoniakdepositie, uitgesplitst naar verschillende landbouwbronnen (stal en opslag, aanwending dierlijke mest, kunstmest gebruik en beweiding) in zones van 0-0,5 km; 0,5-1 km; 1- 3 km en 3-10 km. Daarnaast wordt inzicht gegeven in de te verwachten daling van de ammoniakdepositie door het doorvoeren van landelijke maatregelen en aanvullende gebiedsgerichte brongerichte maatregelen in en rondom het Natura 2000 gebied.
Final report on impact of catchment scale processes and climate change on cause-effect and recovery-chains
Verdonschot, P.F.M. ; Keizer-Vlek, H.E. ; Spears, B. ; Brucet, S. ; Johnson, R. ; Feld, C. ; Kernan, M. - \ 2012
Brussel : European Commission - 116
ecologisch herstel - beheer van waterbekkens - rivieren - meren - estuaria - kustwateren - degradatie - biologische indicatoren - verzuring - eutrofiëring - morfologie - ecologische beoordeling - ecological restoration - watershed management - rivers - lakes - estuaries - coastal water - degradation - biological indicators - acidification - eutrophication - morphology - ecological assessment
Catchment wide integrated basin management requires knowledge on cause-effect and recovery chains within water bodies as well as on the interactions between water bodies and categories. In the WISER WP6.4 recovery processes in rivers, lakes and estuarine and coastal waters were evaluated. The major objectives were: - to analyse and compare (cause-effect and) recovery chains within water categories based on processes and structural and functional features; - to detect commonalities among different chains in different water categories ( to compare recovery chains between water categories); - to link recovery chains to over-arching biological processes and global change; - to develop a method to combine recovery effects in a summarising ‘catchment’ metric. The main stressors studied to reach these objectives were acidification, eutrophication and hydromorphological changes.
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