| publications-1241 |
PEER REVIEWED ARTICLE |
2015 |
Niina Kotamäki , Anita Pätynen , Antti Taskinen , Timo Huttula , Olli Malve |
Statistical Dimensioning of Nutrient Loading Reduction: LLR Assessment Tool for Lake Managers |
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10.1007/s00267-015-0514-0 |
Simulation & Modeling |
Natural Water Bodies |
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No abstract available |
603378 |
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| publications-1242 |
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2016 |
Jiao Gu , Zenghong Xu , Hui Jin , Xiaoyu Ning , Hu He , Jinlei Yu , Erik Jeppesen , Kuanyi Li |
Response of Vallisneria natans to Increasing Nitrogen Loading Depends on Sediment Nutrient Characteristics |
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10.3390/w8120563 |
Data Management & Analytics |
Wastewater Treatment Plants |
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High nitrogen (N) loading may contribute to recession of submerged macrophytes in shallow lakes; yet, its influences vary depending on environmental conditions. In August 2013, we conducted a 28-day factorial-designed field mesocosm experiment in Lake Taihu at the Taihu Laboratory for Lake Ecosystem Research (TLLER) to examine the effects of high N loading on the growth of Vallisneria natans in systems with contrasting sediment types. We ran the experiments with two levels of nutrient loadingâpresent-day external nutrient loading (average P: 5 Îźg¡Lâ1¡dayâ1, N: 130 Îźg¡Lâ1¡dayâ1) and P: 5 Îźg¡Lâ1¡dayâ1, and with three times higher N loading (N: 390 Îźg¡Lâ1¡dayâ1) and used sediment with two contrasting nutrient levels. V. natans growth decreased significantly with increasing N loading, the effect being dependent, however, on the nutrient status of the sediment. In low nutrient sediment, relative growth rates, leaf biomass and root biomass decreased by 11.9%, 18.2% and 23.3%, respectively, at high rather than low N loading, while the decline was larger (44.0%, 32.7% and 41.8%, respectively) when using high nutrient sediment. The larger effect in the nutrient-rich sediment may reflect an observed higher shading of phytoplankton and excess nutrient accumulation in plant tissue, though potential toxic effects of the high-nutrient sediment may also have contributed. Our study confirms the occurrence of a negative effect of increasing N loading on submerged plant growth in shallow nutrient-enriched lakes and further shows that this effect is augmented when the plants grow in nutrient-rich sediment. External N control may, therefore, help to protect or restore submerged macrophytes, especially when the sediment is enriched with nutrients and organic matter. |
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| publications-1243 |
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2016 |
MarĂa Gutierrez , Melina Devercelli , Sandra Brucet , Torben Lauridsen , Martin Søndergaard , Erik Jeppesen |
Is Recovery of Large-Bodied Zooplankton after Nutrient Loading Reduction Hampered by Climate Warming? A Long-Term Study of Shallow Hypertrophic Lake Søbygaard, Denmark |
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10.3390/w8080341 |
Uncategorized |
Uncategorized |
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Nutrient fluctuations and climate warming can synergistically affect trophic dynamics in lakes, resulting in enhanced symptoms of eutrophication, thereby potentially counteracting restoration measures. We performed a long-term study (23 years) of zooplankton in Danish Lake Søbygaard, which is in recovery after nutrient loading reduction, but now faces the effects of climate warming. We hypothesized that the recovery of large-bodied zooplankton after nutrient loading reduction would be hampered by climate warming through indirect effects on fish size structure. We found a shift in macrozooplankton from initial dominance of Daphnia spp. towards Bosmina spp. as well as a decline in the body size of copepods and an increase in the abundance of nauplii. These changes coincided with the increase in small sized fish as a result of rising water temperature. Despite a reduction in body size, the total biomass of cladocerans increased coinciding with a diminished fish catch per unit effort (CPUE), and likely then an overall reduction in the predation on zooplankton. A cascading effect to phytoplankton was evidenced by enhanced zooplankton:phytoplankton and cladoceran:phytoplankton ratios and a decrease in Chl-a:TP and Chl-a:TN ratios. Our results indicate that climate warming, through changes in the size structure of fish community, has major effects on zooplankton size structure. In Lake Søbygaard, the decline in zooplankton size did not prevent, but modulated, the positive cascading effect on phytoplankton through an expected diminished fish CPUE related to nutrient loading reduction. |
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| publications-1244 |
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2016 |
En Hu , Hu He , Yaling Su , Erik Jeppesen , Zhengwen Liu |
Use of Multi-Carbon Sources by Zooplankton in an Oligotrophic Lake in the Tibetan Plateau |
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10.3390/w8120565 |
Data Management & Analytics |
Uncategorized |
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We applied natural abundance stable isotope δ13C and radiocarbon â14C analyses to investigate trophic linkages between zooplankton and their potential food sources (phytoplankton, submersed plants, and allochthonous organic carbon) in Lake Nam Co, one of the largest oligosaline and oligotrophic lakes in the Tibetan Plateau, in south-west China. The δ13C and â14C levels of the calanoid copepod Arctodiaptomus altissimus pectinatus indicate that it uses different carbon sources. Thus, based on a two-isotope mixing model, our results suggested that recently synthesized but 14C-depleted primary producers (phytoplankton and submersed plants) were the most important sources of carbon, together contributing 92.2% of the zooplankton biomass. Allochthonous organic carbon and dissolved organic carbon constituted 4.7% and 3.1% of the carbon in the diet of zooplankton, respectively. Our findings from Lake Nam Co suggest that the carbon in the food webs of lakes located in a glaciated environment originates from various sources of different ages. |
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| publications-1245 |
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2016 |
Jinlei Yu , Zhengwen Liu , Kuanyi Li , Feizhou Chen , Baohua Guan , Yaohui Hu , Ping Zhong , Yali Tang , Xuefeng Zhao , Hu He , Haiyi Zeng , Erik Jepp |
Restoration of Shallow Lakes in Subtropical and Tropical China: Response of Nutrients and Water Clarity to Biomanipulation by Fish Removal and Submerged Plant Transplantation |
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10.3390/w8100438 |
Data Management & Analytics |
Natural Water Bodies |
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Fish removal has been used to restore temperate lakes, and positive effects on ecological state and water clarity have frequently been recorded in many lakes. Recently, a supplementary measure, transplantation of submerged macrophytes after fish removal, has been applied to restore warm Chinese shallow lakes in order to compensate for the expected lack of increasing grazing control of phytoplankton after the biomanipulation. These measures have successfully shifted turbid warm lakes to a clear water state, but little is known about the responses to restoration of key physico-chemical variables. We analyzed the seasonal variation in nutrient concentrations in two subtropical and one tropical biomanipulated shallow Chinese lakes subjected to restoration. In all three lakes, a marked decline occurred in the concentrations of lake total nitrogen (TN), total phosphorus (TP), total suspended solids (TSS), and chlorophyll a (Chl a), while the transparency (SD:WD ratio, Secchi depth to water depth ratio) increased. A clear water state was established, lasting so far for 7 to 23 months, and TN, TP, Chl a, and TSS levels in the three restored lakes decreased to, on average, 49%, 58%, 41%, and 18% of the level prior to restoration and/or the level in a reference lake, respectively, while the annual mean SD:WD ratio exhibited a 1.5â4 fold increase. In conclusion, lake restoration by transplantation of submerged macrophytes after fish removal had major positive effects on the physico-chemical variables in our study lakes. However, continuous control of omnivorous and herbivorous fish biomass is recommended as the fish typically present in warm, shallow lakes to some extent feed on submerged macrophytes, when available. |
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| publications-1246 |
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2017 |
Meryem BeklioÄlu , Tuba Bucak , Jan Coppens , Gizem Bezirci , Ă. TavĹanoÄlu , A. ĂakÄąroÄlu , Eti Levi , Ĺeyda ErdoÄan , Nur Filiz , Korhan Ă |
Restoration of Eutrophic Lakes with Fluctuating Water Levels: A 20-Year Monitoring Study of Two Inter-Connected Lakes |
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10.3390/w9020127 |
Simulation & Modeling |
River Basins |
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Eutrophication continues to be the most important problem preventing a favorable environmental state and detrimentally impacting the ecosystem services of lakes. The current study describes the results of analyses of 20 year monitoring data from two interconnected Anatolian lakes, Lakes Mogan and Eymir, receiving sewage effluents and undergoing restoration. The first step of restoration in both lakes was sewage effluent diversion. Additionally, in hypertrophic Lake Eymir, biomanipulation was conducted, involving removal of benthi-planktivorous fish and prohibition of pike fishing. The monitoring period included high (H) and low (L) water levels (WL) enabling elucidation of the effects of hydrological changes on lake restoration. In shallower Lake Mogan, macrophyte abundance increased after the sewage effluent diversion in periods with low water levels even at turbid water. In comparatively deeper Lake Eymir, the first biomanipulation led to a clear water state with abundant macrophyte coverage. However, shortly after biomanipulation, the water clarity declined, coinciding with low water level (LWL) periods during which nutrient concentrations increased. A second biomanipulation was conducted, mostly during high water level (HWL) period, resulting in a major decrease in nutrient concentrations and clearer water, but without an expansion of macrophytes. We conclude that repetitive fish removal may induce recovery but its success may be confounded by high availability of nutrients and adverse hydrological conditions. |
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| publications-1247 |
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2017 |
Jian Gao , Ping Zhong , Jiajia Ning , Zhengwen Liu , Erik Jeppesen |
Herbivory of Omnivorous Fish Shapes the Food Web Structure of a Chinese Tropical Eutrophic Lake: Evidence from Stable Isotope and Fish Gut Content Analyses |
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10.3390/w9010069 |
Simulation & Modeling |
Natural Water Bodies |
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Studies suggest that, unlike the situation in temperate lakes, high biomasses of omnivorous fish are maintained in subtropical and tropical lakes when they shift from a turbid phytoplankton-dominated state to a clear water macrophyte-dominated state, and the predation pressure on large-bodied zooplankton therefore remains high. Whether this reflects a higher degree of herbivory in warm lakes than in temperate lakes is debatable. We combined food web studies using stable isotopes with gut content analyses of the most dominant fish species to elucidate similarities and differences in food web structure between a clear water macrophyte-dominated basin (MDB) and a turbid phytoplankton-dominated basin (PDB) of Huizhou West Lake, a shallow tropical Chinese lake. The δ13Câδ15N biplot of fish and invertebrates revealed community-wide differences in isotope-based metrics of the food webs between MDB and PDB. The range of consumer δ15N (NR) was lower in MDB than in PDB, indicating shorter food web length in MDB. The mean nearest neighbor distance (MNND) and standard deviation around MNND (SDNND) were higher in MDB than in PDB, showing a markedly low fish trophic overlap and a more uneven packing of species in niches in MDB than in PDB. The range of fish δ13C (CR) of consumers was more extensive in MDB than in PDB, indicating a wider feeding range for fish in MDB. Mixing model results showed that macrophytes and associated periphyton constituted a large fraction of basal production sources for the fish in MDB, while particulate organic matter (POM) contributed a large fraction in PDB. In MDB, the diet of the dominant fish species, crucian carp (Carassius carassius), consisted mainly of vegetal matter (macrophytes and periphyton) and zooplankton, while detritus was the most important food item in PDB. Our results suggest that carbon from macrophytes with associated periphyton may constitute an important food resource for omnivorous fish, and this may strongly affect the feeding niche and the strength of the top-down trophic cascade between fish and zooplankton in the restored, macrophyte-dominated basin of the lake. This dual effect (consumption of macrophytes and zooplankton) may reduce the chances of maintaining the clear water state at the prevailing nutrient levels in the lake, and regular removal of large crucian carp may therefore be needed to maintain a healthy ecosystem state. |
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| publications-1248 |
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2017 |
Hu He , Xuguang Luo , Hui Jin , Jiao Gu , Erik Jeppesen , Zhengwen Liu , Kuanyi Li |
Effects of Exposed Artificial Substrate on the Competition between Phytoplankton and Benthic Algae: Implications for Shallow Lake Restoration |
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10.3390/w9010024 |
IoT & Sensors |
Natural Water Bodies |
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Phytoplankton and benthic algae coexist in shallow lakes and the outcome of the competition between these two photoautotrophs can markedly influence water clarity. It is well established that exposed artificial substrate in eutrophic waters can remove nutrients and fine particles from the water column via the attached periphyton canopy. However, the effects of the introduction of artificial substrate on the competition between planktonic and benthic primary producers remain to be elucidated. We conducted a short-term outdoor mesocosm experiment to test the hypothesis that the nutrient and light changes induced by exposed artificial substrate (polythene nets) would benefit the benthic algae. Artificial substrate significantly reduced total nitrogen and phosphorus concentrations and water clarity improved, the latter due to the substrate-induced reduction of both organic and inorganic suspended solids. Consequently, as judged from changes in chlorophyll a (Chl-a) concentrations in water and sediment, respectively, exposed artificial substrate significantly reduced the phytoplankton biomass, while benthic algae biomass increased. Our results thus indicate that exposed artificial substrate may be used as a tool to re-establish benthic primary production in eutrophic shallow lakes after an external nutrient loading reduction, paving the way for a benthic- or a macrophyte-dominated system. Longer term and larger scale experiments are, however, needed before any firm conclusions can be drawn on this. |
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| publications-1249 |
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2017 |
Erik Jeppesen , Martin Søndergaard , Zhengwen Liu |
Lake Restoration and Management in a Climate Change Perspective: An Introduction |
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10.3390/w9020122 |
Data Management & Analytics |
River Basins |
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Lakes all around the globe are under severe pressure due to an increasing anthropogenic impact from a growing population in a more developed world. Accordingly, today, many lakes are highly eutrophic and suffer from severe blooms of often toxic cyanobacteria and may become even more eutrophic in the future unless strong lake management actions are taken. Recent research has further shown that global warming and subsequent changes in water use will further exacerbate the eutrophication process in lakes. There is therefore a growing demand for lake restoration and insight into sustainable lake management. The measures to be taken, however, depend on the climate and other local conditions. This special issue addresses lake restoration and management with special emphasis on the restoration of eutrophicated lakes within a climate change perspective. The papers included collectively highlight that the ongoing climate change affects lake water quality by (1) changes in external and internal nutrient loading; (2) higher frequency of extreme events (such as hurricanes); (3) temperatureâinduced changes in biota, biotic interactions; and (4) water level. Lower nutrient loading is therefore needed in a future warmer world to achieve the same ecological state as today. Several papers discuss lake restoration methods within a climate change perspective and show practical results, notably of various attempts of biomanipulation. Finally, some papers discuss the effects of other anthropogenic stressors and their interaction with climate. |
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| publications-1250 |
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2017 |
Martin Søndergaard , Torben Lauridsen , Liselotte Johansson , Erik Jeppesen |
Repeated Fish Removal to Restore Lakes: Case Study of Lake VĂŚng, DenmarkâTwo Biomanipulations during 30 Years of Monitoring |
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10.3390/w9010043 |
Uncategorized |
Uncategorized |
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Biomanipulation by fish removal has been used in many shallow lakes as a method to improve lake water quality. Here, we present and analyse 30 years of chemical and biological data from the shallow and 16 ha large Lake VĂŚng, Denmark, which has been biomanipulated twice with a 20-year interval by removing roach (Rutilus rutilus) and bream (Abramis brama). After both biomanipulations, Lake VĂŚng shifted from a turbid, phytoplankton-dominated state to a clear, water macrophyte-dominated state. Chlorophyll a was reduced from 60â80 Îźg¡Lâ1 to 10â30 Îźg¡Lâ1 and the coverage of submerged macrophytes, dominated by Elodea canadensis, increased from <0.1% to 70%â80%. Mean summer total phosphorus was reduced from about 0.12 to 0.07 mg¡Lâ1 and total nitrogen decreased from 1.0 to 0.4 mg¡Lâ1. On a seasonal scale, phosphorus and chlorophyll concentrations changed from a summer maximum during turbid conditions to a winter maximum under clear conditions. The future of Lake VĂŚng is uncertain and a relatively high phosphorus loading via the groundwater, and the accumulation of a mobile P pool in the sediment make it likely that the lake eventually will return to turbid conditions. Repeated fish removals might be a relevant management strategy to apply in shallow lakes with a relatively high external nutrient loading. |
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