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Pascale Cuet - One of the best experts on this subject based on the ideXlab platform.
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Is the response of coral calcification to seawater acidification related to Nutrient Loading?
Coral Reefs, 2011Co-Authors: Anne Chauvin, Vianney Denis, Pascale CuetAbstract:The effect of decreasing aragonite saturation state (Ω_Arag) of seawater (elevated pCO_2) on calcification rates of Acropora muricata was studied using nubbins prepared from parent colonies located at two sites of La Saline reef (La Réunion Island, western Indian Ocean): a back-reef site (BR) affected by Nutrient-enriched groundwater discharge (mainly nitrate), and a reef flat site (RF) with low terrigenous inputs. Protein and chlorophyll a content of the nubbins, as well as zooxanthellae abundance, were lower at RF than BR. Nubbins were incubated at ~27°C over 2 h under sunlight, in filtered seawater manipulated to get differing initial pCO_2 (1,440–340 μatm), Ω_Arag (1.4–4.0), and dissolved inorganic carbon (DIC) concentrations (2,100–1,850 μmol kg^−1). Increasing DIC concentrations at constant total alkalinity (A_T) resulted in a decrease in Ω_Arag and an increase in pCO_2. A_T at the beginning of the incubations was kept at a natural level of 2,193 ± 6 μmol kg^−1 (mean ± SD). Net photosynthesis (NP) and calcification were calculated from changes in pH and A_T during the incubations. Calcification decrease in response to doubling pCO_2 relative to preindustrial level was 22% for RF nubbins. When normalized to surface area of the nubbins, (1) NP and calcification were higher at BR than RF, (2) NP increased in high pCO_2 treatments at BR compared to low pCO_2 treatments, and (3) calcification was not related to Ω_Arag at BR. When normalized to NP, calcification was linearly related to Ω_Arag at both sites, and the slopes of the relationships were not significantly different. The increase in NP at BR in the high pCO_2 treatments may have increased calcification and thus masked the negative effect of low Ω_Arag on calcification. Removing the effect of NP variations at BR showed that calcification declined in a similar manner with decreased Ω_Arag (increased pCO_2) whatever the Nutrient Loading.
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is the response of coral calcification to seawater acidification related to Nutrient Loading
Coral Reefs, 2011Co-Authors: Anne Chauvin, Vianney Denis, Pascale CuetAbstract:The effect of decreasing aragonite saturation state (ΩArag) of seawater (elevated pCO2) on calcification rates of Acropora muricata was studied using nubbins prepared from parent colonies located at two sites of La Saline reef (La Reunion Island, western Indian Ocean): a back-reef site (BR) affected by Nutrient-enriched groundwater discharge (mainly nitrate), and a reef flat site (RF) with low terrigenous inputs. Protein and chlorophyll a content of the nubbins, as well as zooxanthellae abundance, were lower at RF than BR. Nubbins were incubated at ~27°C over 2 h under sunlight, in filtered seawater manipulated to get differing initial pCO2 (1,440–340 μatm), ΩArag (1.4–4.0), and dissolved inorganic carbon (DIC) concentrations (2,100–1,850 μmol kg−1). Increasing DIC concentrations at constant total alkalinity (AT) resulted in a decrease in ΩArag and an increase in pCO2. AT at the beginning of the incubations was kept at a natural level of 2,193 ± 6 μmol kg−1 (mean ± SD). Net photosynthesis (NP) and calcification were calculated from changes in pH and AT during the incubations. Calcification decrease in response to doubling pCO2 relative to preindustrial level was 22% for RF nubbins. When normalized to surface area of the nubbins, (1) NP and calcification were higher at BR than RF, (2) NP increased in high pCO2 treatments at BR compared to low pCO2 treatments, and (3) calcification was not related to ΩArag at BR. When normalized to NP, calcification was linearly related to ΩArag at both sites, and the slopes of the relationships were not significantly different. The increase in NP at BR in the high pCO2 treatments may have increased calcification and thus masked the negative effect of low ΩArag on calcification. Removing the effect of NP variations at BR showed that calcification declined in a similar manner with decreased ΩArag (increased pCO2) whatever the Nutrient Loading.
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Can response of coral calcification to seawater acidification be related to Nutrient Loading ?
2009Co-Authors: Anne Chauvin, Vianney Denis, Pascale CuetAbstract:Oral presentation about Can response of coral calcification to seawater acidification be related to Nutrient Loading ?
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Nutrient Loading affects the relationship between coral calcification and aragonite saturation state
2008Co-Authors: Pascale Cuet, Marlin J. Atkinson, A. Tribollet, J. Fleming, D. Schar, J. FalterAbstract:Oral presentation about Nutrient Loading affects the relationship between coral calcification and aragonite saturation state
Erik Jeppesen - One of the best experts on this subject based on the ideXlab platform.
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the influence of Nutrient Loading climate and water depth on nitrogen and phosphorus loss in shallow lakes a pan european mesocosm experiment
Hydrobiologia, 2016Co-Authors: Jan Coppens, Erik Jeppesen, Josef Hejzlar, Michal Sorf, şeyda Erdogan, Ulrike Scharfenberger, Aldoushy Mahdy, Peeter NogesAbstract:Losses of phosphorus (P) and nitrogen (N) have important influences on in-lake concentrations and Nutrient Loading to downstream ecosystems. We performed a series of mesocosm experiments along a latitudinal gradient from Sweden to Greece to investigate the factors influencing N and P loss under different climatic conditions. In six countries, a standardised mesocosm experiment with two water depths and two Nutrient levels was conducted concurrently between May and November 2011. Our results showed external Nutrient Loading to be of key importance for N and P loss in all countries. Almost all dissolved inorganic nitrogen (DIN) and soluble reactive phosphorus (SRP) were lost or taken up in biomass in all mesocosms. We found no consistent effect of temperature on DIN and SRP loss but a significant, though weak, negative effect of temperature on total nitrogen (TN) and total phosphorus (TP) loss in the deeper mesocosms, probably related to higher organic N and P accumulation in the water in the warmer countries. In shallow mesocosms, a positive trend in TN and TP loss with increasing temperature was observed, most likely related to macrophyte growth.
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shallow lake restoration by Nutrient Loading reduction some recent findings and challenges ahead
Hydrobiologia, 2007Co-Authors: Erik Jeppesen, Torben L Lauridsen, Martin Sondergaard, Mariana Meerhoff, Jens Peder JensenAbstract:Shallow lakes respond to Nutrient Loading reductions. Major findings in a recent multi-lake comparison of data from lakes with long time series revealed: that a new state of equilibrium was typically reached for phosphorus (P) after 10–15 years and for nitrogen (N) after <5–10 years; that the in-lake Total N:Total P and inorganic N:P ratios increased; that the phytoplankton and fish biomass often decreased; that the percentage of piscivores often increased as did the zooplankton:phytoplankton biomass ratio, the contribution of Daphnia to Zooplankton biomass, and cladoceran size. This indicates that enhanced resource and predator control often interact during recovery from eutrophication. So far, focus has been directed at reducing external Loading of P. However, one experimental study and cross-system analyses of data from many lakes in north temperate lakes indicate that nitrogen may play a more significant role for abundance and species richness of submerged plants than usually anticipated when total phos-phorus is moderate high. According to the alter-native states hypothesis we should expect ecological resistance to Nutrient Loading reduction and P hysteresis. We present results suggesting that the two alternative states are less stable than originally anticipated. How global warming af-fects the water clarity of shallow lakes is debat-able. We suggest that water clarity often will decrease due to either enhanced growth of phytoplankton or, if submerged macrophytes are stimulated, by reduced capacity of these plants to maintain clear-water conditions. The latter is supported by a cross-system comparison of lakes in Florida and Denmark. The proportion of small fish might increase and we might see higher aggregation of fish within the vegetation (leading to loss of Zooplankton refuges), more annual fish cohorts, more omnivorous feeding by fish and less specialist piscivory. Moreover, lakes may have prolonged growth seasons with a higher risk of long-lasting algal blooms and at places dense floating plant communities. The effects of global warming need to be taken into consideration by lake managers when setting future targets for critical Loading, as these may well have to be adjusted in the future. Finally, we highlight some of the future challenges we see in lake restoration research.
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ecological effects of reduced Nutrient Loading oligotrophication on lakes an introduction
Freshwater Biology, 2005Co-Authors: John N Anderson, Erik Jeppesen, Martin SondergaardAbstract:Summary 1. The variable ecological response of lakes to reduced Nutrient Loading (oligotrophication) at sites in Europe and North America was discussed at a workshop held in Silkeborg (Denmark) in January 2003. Studies of lake oligotrophication were presented based on both long-term monitoring and data generated by palaeolimnological methods. 2. This introduction to the special issue provides short summaries of a series of the papers presented and their limnological context. Results show that the majority of lakes had approached a new equilibrium of phosphorus (P) and nitrogen (N) concentrations 10–15 years (P) and 0–5 years (N) after a major reduction in Loading, irrespective of hydraulic retention time. Phytoplankton biomass decreased and a shift towards meso-oligotrophic species dominance occurred. The fish responded surprisingly fast to the Loading reduction in most lakes. As a result, the percentage of piscivores increased and total fish biomass declined markedly, which may explain an increase in the body size of cladocerans and an increase in the zooplankton to phytoplankton biomass ratio seen in many of the lakes. 3. Monitoring has in general been initiated after the effects of eutrophication became apparent. In this context palaeolimnological techniques become very useful because they allow limnologists to extend time scales of coverage and to define restoration targets and baseline conditions. Moreover, lake sediments pre-dating anthropogenic disturbance can be used to examine ecological response to, for instance, climate variability, allowing problems associated with multiple stressors to be addressed. 4. It is concluded that there is a great need for a synthetic, holistic approach to studying lake oligotrophication, combining multiple techniques of palaeolimnological sediment analysis with detailed but temporally limited long-term monitoring of chemical and biological variables. This is important, not least to assess future responses to Nutrient Loading reductions, as global warming will interact with a range of external stressors and ultimately affect lake management strategies to deal with the resultant feedbacks.
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response of submerged macrophytes in danish lakes to Nutrient Loading reductions and biomanipulation
Hydrobiologia, 2003Co-Authors: Torben L Lauridsen, Jens Peder Jensen, Erik Jeppesen, Martin SondergaardAbstract:During the last two decades the Nutrient Loading to Danish lakes has been reduced with the aim to improve water quality. However, because of internal P-Loading and biological resistance, the expected improvement has been delayed. Therefore, to reduce the duration of the recovery period and to accelerate recolonisation of submerged macrophytes, several lakes have been biomanipulated with the purpose of improving the top-down control by zooplankton. To elucidate the effects of these measures, we undertook an analysis of data on submerged macrophytes monitored annually in 17 lakes for 8 years. The results obtained show that the macrophyte coverage in non-biomanipulated lakes remained relatively stable following the external Nutrient reduction. However, a small increase in macrophyte coverage occurred in a few lakes. In two of the four biomanipulated lakes, in contrast, macrophyte coverage increased from 0 up to 80% within 2–4 years following manipulation. In the other two lakes macrophyte colonisation failed. However, in lakes with a successful recolonisation, large inter-annual variations in macrophyte coverage, varying between 2 and 80% among growth seasons, occurred. We conclude that the potential of macrophyte recolonisation after Nutrient Loading reduction on the short term is higher in biomanipulated lakes than in lakes subjected to Loading reduction only, although biomanipulation does not provide a guarantee for macrophyte recolonisation or a stable macrophyte community when colonisation occurs.
Anne Chauvin - One of the best experts on this subject based on the ideXlab platform.
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is the response of coral calcification to seawater acidification related to Nutrient Loading
Coral Reefs, 2011Co-Authors: Anne Chauvin, Vianney Denis, Pascale CuetAbstract:The effect of decreasing aragonite saturation state (ΩArag) of seawater (elevated pCO2) on calcification rates of Acropora muricata was studied using nubbins prepared from parent colonies located at two sites of La Saline reef (La Reunion Island, western Indian Ocean): a back-reef site (BR) affected by Nutrient-enriched groundwater discharge (mainly nitrate), and a reef flat site (RF) with low terrigenous inputs. Protein and chlorophyll a content of the nubbins, as well as zooxanthellae abundance, were lower at RF than BR. Nubbins were incubated at ~27°C over 2 h under sunlight, in filtered seawater manipulated to get differing initial pCO2 (1,440–340 μatm), ΩArag (1.4–4.0), and dissolved inorganic carbon (DIC) concentrations (2,100–1,850 μmol kg−1). Increasing DIC concentrations at constant total alkalinity (AT) resulted in a decrease in ΩArag and an increase in pCO2. AT at the beginning of the incubations was kept at a natural level of 2,193 ± 6 μmol kg−1 (mean ± SD). Net photosynthesis (NP) and calcification were calculated from changes in pH and AT during the incubations. Calcification decrease in response to doubling pCO2 relative to preindustrial level was 22% for RF nubbins. When normalized to surface area of the nubbins, (1) NP and calcification were higher at BR than RF, (2) NP increased in high pCO2 treatments at BR compared to low pCO2 treatments, and (3) calcification was not related to ΩArag at BR. When normalized to NP, calcification was linearly related to ΩArag at both sites, and the slopes of the relationships were not significantly different. The increase in NP at BR in the high pCO2 treatments may have increased calcification and thus masked the negative effect of low ΩArag on calcification. Removing the effect of NP variations at BR showed that calcification declined in a similar manner with decreased ΩArag (increased pCO2) whatever the Nutrient Loading.
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Is the response of coral calcification to seawater acidification related to Nutrient Loading?
Coral Reefs, 2011Co-Authors: Anne Chauvin, Vianney Denis, Pascale CuetAbstract:The effect of decreasing aragonite saturation state (Ω_Arag) of seawater (elevated pCO_2) on calcification rates of Acropora muricata was studied using nubbins prepared from parent colonies located at two sites of La Saline reef (La Réunion Island, western Indian Ocean): a back-reef site (BR) affected by Nutrient-enriched groundwater discharge (mainly nitrate), and a reef flat site (RF) with low terrigenous inputs. Protein and chlorophyll a content of the nubbins, as well as zooxanthellae abundance, were lower at RF than BR. Nubbins were incubated at ~27°C over 2 h under sunlight, in filtered seawater manipulated to get differing initial pCO_2 (1,440–340 μatm), Ω_Arag (1.4–4.0), and dissolved inorganic carbon (DIC) concentrations (2,100–1,850 μmol kg^−1). Increasing DIC concentrations at constant total alkalinity (A_T) resulted in a decrease in Ω_Arag and an increase in pCO_2. A_T at the beginning of the incubations was kept at a natural level of 2,193 ± 6 μmol kg^−1 (mean ± SD). Net photosynthesis (NP) and calcification were calculated from changes in pH and A_T during the incubations. Calcification decrease in response to doubling pCO_2 relative to preindustrial level was 22% for RF nubbins. When normalized to surface area of the nubbins, (1) NP and calcification were higher at BR than RF, (2) NP increased in high pCO_2 treatments at BR compared to low pCO_2 treatments, and (3) calcification was not related to Ω_Arag at BR. When normalized to NP, calcification was linearly related to Ω_Arag at both sites, and the slopes of the relationships were not significantly different. The increase in NP at BR in the high pCO_2 treatments may have increased calcification and thus masked the negative effect of low Ω_Arag on calcification. Removing the effect of NP variations at BR showed that calcification declined in a similar manner with decreased Ω_Arag (increased pCO_2) whatever the Nutrient Loading.
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Can response of coral calcification to seawater acidification be related to Nutrient Loading ?
2009Co-Authors: Anne Chauvin, Vianney Denis, Pascale CuetAbstract:Oral presentation about Can response of coral calcification to seawater acidification be related to Nutrient Loading ?
Martin Sondergaard - One of the best experts on this subject based on the ideXlab platform.
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shallow lake restoration by Nutrient Loading reduction some recent findings and challenges ahead
Hydrobiologia, 2007Co-Authors: Erik Jeppesen, Torben L Lauridsen, Martin Sondergaard, Mariana Meerhoff, Jens Peder JensenAbstract:Shallow lakes respond to Nutrient Loading reductions. Major findings in a recent multi-lake comparison of data from lakes with long time series revealed: that a new state of equilibrium was typically reached for phosphorus (P) after 10–15 years and for nitrogen (N) after <5–10 years; that the in-lake Total N:Total P and inorganic N:P ratios increased; that the phytoplankton and fish biomass often decreased; that the percentage of piscivores often increased as did the zooplankton:phytoplankton biomass ratio, the contribution of Daphnia to Zooplankton biomass, and cladoceran size. This indicates that enhanced resource and predator control often interact during recovery from eutrophication. So far, focus has been directed at reducing external Loading of P. However, one experimental study and cross-system analyses of data from many lakes in north temperate lakes indicate that nitrogen may play a more significant role for abundance and species richness of submerged plants than usually anticipated when total phos-phorus is moderate high. According to the alter-native states hypothesis we should expect ecological resistance to Nutrient Loading reduction and P hysteresis. We present results suggesting that the two alternative states are less stable than originally anticipated. How global warming af-fects the water clarity of shallow lakes is debat-able. We suggest that water clarity often will decrease due to either enhanced growth of phytoplankton or, if submerged macrophytes are stimulated, by reduced capacity of these plants to maintain clear-water conditions. The latter is supported by a cross-system comparison of lakes in Florida and Denmark. The proportion of small fish might increase and we might see higher aggregation of fish within the vegetation (leading to loss of Zooplankton refuges), more annual fish cohorts, more omnivorous feeding by fish and less specialist piscivory. Moreover, lakes may have prolonged growth seasons with a higher risk of long-lasting algal blooms and at places dense floating plant communities. The effects of global warming need to be taken into consideration by lake managers when setting future targets for critical Loading, as these may well have to be adjusted in the future. Finally, we highlight some of the future challenges we see in lake restoration research.
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ecological effects of reduced Nutrient Loading oligotrophication on lakes an introduction
Freshwater Biology, 2005Co-Authors: John N Anderson, Erik Jeppesen, Martin SondergaardAbstract:Summary 1. The variable ecological response of lakes to reduced Nutrient Loading (oligotrophication) at sites in Europe and North America was discussed at a workshop held in Silkeborg (Denmark) in January 2003. Studies of lake oligotrophication were presented based on both long-term monitoring and data generated by palaeolimnological methods. 2. This introduction to the special issue provides short summaries of a series of the papers presented and their limnological context. Results show that the majority of lakes had approached a new equilibrium of phosphorus (P) and nitrogen (N) concentrations 10–15 years (P) and 0–5 years (N) after a major reduction in Loading, irrespective of hydraulic retention time. Phytoplankton biomass decreased and a shift towards meso-oligotrophic species dominance occurred. The fish responded surprisingly fast to the Loading reduction in most lakes. As a result, the percentage of piscivores increased and total fish biomass declined markedly, which may explain an increase in the body size of cladocerans and an increase in the zooplankton to phytoplankton biomass ratio seen in many of the lakes. 3. Monitoring has in general been initiated after the effects of eutrophication became apparent. In this context palaeolimnological techniques become very useful because they allow limnologists to extend time scales of coverage and to define restoration targets and baseline conditions. Moreover, lake sediments pre-dating anthropogenic disturbance can be used to examine ecological response to, for instance, climate variability, allowing problems associated with multiple stressors to be addressed. 4. It is concluded that there is a great need for a synthetic, holistic approach to studying lake oligotrophication, combining multiple techniques of palaeolimnological sediment analysis with detailed but temporally limited long-term monitoring of chemical and biological variables. This is important, not least to assess future responses to Nutrient Loading reductions, as global warming will interact with a range of external stressors and ultimately affect lake management strategies to deal with the resultant feedbacks.
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response of submerged macrophytes in danish lakes to Nutrient Loading reductions and biomanipulation
Hydrobiologia, 2003Co-Authors: Torben L Lauridsen, Jens Peder Jensen, Erik Jeppesen, Martin SondergaardAbstract:During the last two decades the Nutrient Loading to Danish lakes has been reduced with the aim to improve water quality. However, because of internal P-Loading and biological resistance, the expected improvement has been delayed. Therefore, to reduce the duration of the recovery period and to accelerate recolonisation of submerged macrophytes, several lakes have been biomanipulated with the purpose of improving the top-down control by zooplankton. To elucidate the effects of these measures, we undertook an analysis of data on submerged macrophytes monitored annually in 17 lakes for 8 years. The results obtained show that the macrophyte coverage in non-biomanipulated lakes remained relatively stable following the external Nutrient reduction. However, a small increase in macrophyte coverage occurred in a few lakes. In two of the four biomanipulated lakes, in contrast, macrophyte coverage increased from 0 up to 80% within 2–4 years following manipulation. In the other two lakes macrophyte colonisation failed. However, in lakes with a successful recolonisation, large inter-annual variations in macrophyte coverage, varying between 2 and 80% among growth seasons, occurred. We conclude that the potential of macrophyte recolonisation after Nutrient Loading reduction on the short term is higher in biomanipulated lakes than in lakes subjected to Loading reduction only, although biomanipulation does not provide a guarantee for macrophyte recolonisation or a stable macrophyte community when colonisation occurs.
Wolf M. Mooij - One of the best experts on this subject based on the ideXlab platform.
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Exploring How Cyanobacterial Traits Affect Nutrient Loading Thresholds in Shallow Lakes : A Modelling Approach
Water, 2020Co-Authors: Manqi Chang, Sven Teurlincx, Jan H. Janse, Hans W. Paerl, Wolf M. Mooij, Annette B.g. JanssenAbstract:Globally, many shallow lakes have shifted from a clear macrophyte-dominated state to a turbid phytoplankton-dominated state due to eutrophication. Such shifts are often accompanied by toxic cyanobacterial blooms, with specialized traits including buoyancy regulation and nitrogen fixation. Previous work has focused on how these traits contribute to cyanobacterial competitiveness. Yet, little is known on how these traits affect the value of Nutrient Loading thresholds of shallow lakes. These thresholds are defined as the Nutrient Loading at which lakes shift water quality state. Here, we used a modelling approach to estimate the effects of traits on Nutrient Loading thresholds. We incorporated cyanobacterial traits in the process-based ecosystem model PCLake+, known for its ability to determine Nutrient Loading thresholds. Four scenarios were simulated, including cyanobacteria without traits, with buoyancy regulation, with nitrogen fixation, and with both traits. Nutrient Loading thresholds were obtained under N-limited, P-limited, and colimited conditions. Results show that cyanobacterial traits can impede lake restoration actions aimed at removing cyanobacterial blooms via Nutrient Loading reduction. However, these traits hardly affect the Nutrient Loading thresholds for clear lakes experiencing eutrophication. Our results provide references for Nutrient Loading thresholds and draw attention to cyanobacterial traits during the remediation of eutrophic water bodies.
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Success of lake restoration depends on spatial aspects of Nutrient Loading and hydrology.
The Science of the total environment, 2019Co-Authors: Annette B.g. Janssen, Jan H. Janse, Dianneke Van Wijk, Luuk P. A. Van Gerven, Elisabeth S. Bakker, Robert J. Brederveld, Donald L. Deangelis, Wolf M. MooijAbstract:Many aquatic ecosystems have deteriorated due to human activities and their restoration is often troublesome. It is proposed here that the restoration success of deteriorated lakes critically depends on hitherto largely neglected spatial heterogeneity in Nutrient Loading and hydrology. A modelling approach is used to study this hypothesis by considering four lake types with contrasting Nutrient Loading (point versus diffuse) and hydrology (seepage versus drainage). By comparing the longterm effect of common restoration measures (Nutrient load reduction, lake flushing or biomanipulation) in these four lake types, we found that restoration through reduction of Nutrient Loading is effective in all cases. In contrast, biomanipulation only works in seepage lakes with diffuse Nutrient inputs, while lake flushing will even be counterproductive in lakes with Nutrient point sources. The main conclusion of the presented analysis is that a priori assessment of spatial heterogeneity caused by Nutrient Loading and hydrology is essential for successful restoration of lake ecosystems.
