The Experts below are selected from a list of 3576 Experts worldwide ranked by ideXlab platform
John A Strand - One of the best experts on this subject based on the ideXlab platform.
-
dynamics of submerged macrophyte populations in response to Biomanipulation
Freshwater Biology, 2001Co-Authors: John A Strand, Stefan E B WeisnerAbstract:1. A 6-year study (1992-97) of changes in submerged vegetation after Biomanipulation was carried out in the eutrophicated Lake Finjasjon, Southern Sweden. Ten sites around the lake were revisited each year. At each site five samples of above-ground biomass were taken at 10 cm water depth intervals. An investigation of the seed bank at the 10 sites, and a grazing experiment where birds and large fish were excluded was also conducted. 2. Between 1992 and 1996, in shallow areas (water depth 95% of the increase in biomass and plant cover. The following year (1997), however, cover and above-ground biomass decreased, mainly attributable to the total disappearance of E. canadensis. Secchi depth increased after Biomanipulation until 1996, but decreased again in 1997. 3. Total and mean number of submerged species increased after Biomanipulation, probably as a result of the improved light climate. However, after the initial increase in species number there was a decrease during the following years, possibly attributed to competition from the rapidly expanding E. canadensis and M. spicatum. The lack of increase in species number after the disappearance of E. canadensis in 1997 implies that other factors also affected species richness. 4. A viable seed bank was not necessary for a rapid recolonization of submerged macrophytes, nor did grazing by waterfowl or fish delay the re-colonization of submerged macrophytes. 5. Submerged macrophytes are capable of rapid recolonization if conditions improve, even in large lakes such as Finjasjon (11 km(2)). Species that spread by fragments will increase rapidly and probably outcompete other species. 6. The results indicate that after the initial Secchi depth increase, probably caused by high zooplankton densities, submerged vegetation further improved the light climate. The decrease in macrophyte biomass in 1997 may have caused the observed increase in phosphorus and chlorophyll a, and the decrease in Secchi depth. We suggest that nutrient competition from periphyton, attached to the macrophytes, may be an important factor in limiting phytoplankton production, although other factors (e.g. zooplankton grazing) are also of importance, especially as triggers for the shift to a clear-water state.
-
the development of submerged macrophytes in lake ringsjon after Biomanipulation
Hydrobiologia, 1999Co-Authors: John A StrandAbstract:The maximum water depth of submerged vegetation and the number of sites colonized by submerged macrophytes in Lake Ringsjon were studied in 1992, 1993 and 1996, and compared with data from 1947 and 1988, in order to investigate the development of submerged macrophytes after the Biomanipulation of the lake (completed 1992). The submerged vegetation has declined considerably since 1947, both in species number and outer water depth. The submerged macrophytes in Lake Ringsjon did not show any clear improvement in outer water depth or number of sites colonized after Biomanipulation. The lack of any larger increase in Secchi depth after Biomanipulation along with a shortage of suitable habitats (i.e. substrate), waterfowl grazing and species composition of the macrophyte populations are discussed as possible reasons for the poor development of submerged macrophytes in Lake Ringsjon.
-
Biomanipulation as an application of food chain theory constraints synthesis and recommendations for temperate lakes
Ecosystems, 1998Co-Authors: Larsanders Hansson, Helene Annadotter, Eva Bergman, Stellan F Hamrin, Erik Jeppesen, Timo Kairesalo, Eira Luokkanen, Perake Nilsson, Martin Sondergaard, John A StrandAbstract:The aim of this review is to identify problems, find general patterns, and extract recommendations for successful Biomanipulation. An important conclusion is that the pelagic food chain from fish to algae may not be the only process affected by a Biomanipulation. Instead, this process should be viewed as the “trigger” for secondary processes, such as establishment of submerged macrophytes, reduced internal loading of nutrients, and reduced resuspension of particles from the sediment. However, fish reduction also leads to a high recruitment of young-of-the-year (YOY) fish, which feed extensively on zooplankton. This expansion of YOY the first years after fish reduction is probably a major reason for less successful Biomanipulations. Recent, large-scale Biomanipulations have made it possible to update earlier recommendations regarding when, where, and how Biomanipulation should be performed. More applicable recommendations include (1) the reduction in the biomass of planktivorous fish should be 75% or more; (2) the fish reduction should be performed efficiently and rapidly (within 1–3 years); (3) efforts should be made to reduce the number of benthic feeding fish; (4) the recruitment of YOY fish should be reduced; (5) the conditions for establishment of submerged macrophytes should be improved; and (6) the external input of nutrients (phosphorus and nitrogen) should be reduced as much as possible before the Biomanipulation. Recent Biomanipulations have shown that, correctly performed, the method also achieves results in large, relatively deep and eutrophic lakes, at least in a 5-year perspective. Although repeated measures may be necessary, the general conclusion is that Biomanipulation is not only possible, but also a relatively inexpensive and attractive method for management of eutrophic lakes, and in particular as a follow-up measure to reduced nutrient load.
Erik Jeppesen - One of the best experts on this subject based on the ideXlab platform.
-
could artificial plant beds favour microcrustaceans during Biomanipulation of eutrophic shallow lakes
Hydrobiologia, 2017Co-Authors: David Balayla, Thomas Boll, Carolina Trochine, Erik JeppesenAbstract:Introduction of artificial plants may facilitate the transition from a turbid to a clear-water state in shallow lakes, particularly when plant establishment is delayed. We investigated the usefulness of artificial plants as a restoration tool in an experimental setup mimicking open submerged plant beds with high plant density [80%, HPD] and low plant density [20%, LPD] in shallow Lake Vaeng, Denmark, having undergone Biomanipulation in the form of extensive fish removal. Biological measures of the fish, and of both free-swimming (FSM) and plant-attached microcrustaceans (PAM) within the experimental beds and in the lake, were obtained from before, during and after Biomanipulation. We found that microcrustacean measures (density, biomass and Cladocera:FSM) were significantly larger in the HPD beds, before and during fish removal, while the effect of plants was not significant after Biomanipulation, with low fish biomass. On PAM, these effects were less pronounced and only significant after Biomanipulation. Microcrustaceans were larger-bodied at HPD in all years, for both FSM and PAM. In conclusion, artificial plant beds acted as an effective microcrustacea refuge against fish, particularly for the FSM at HPD and in the years with high fish densities, providing further evidence that artificial plant beds could assist lake restoration efforts.
-
Biomanipulation induced reduction of sediment phosphorus release in a tropical shallow lake
Hydrobiologia, 2017Co-Authors: Yali Tang, Xiufeng Zhang, Erik JeppesenAbstract:Biomanipulation via fish regulation combined with submerged plant introduction is an effective measure to restore eutrophic shallow lakes. Improved water quality and clarity promote growth of benthic algae, which with submerged plants may limit sediment phosphorus (P) release, thereby reinforce lake recovery. Our study sought to evaluate the effect of such a Biomanipulation on water quality, benthic algal development and sediment P release in a shallow, tropical lake by (1) comparing porewater and lake water quality, light intensity and benthic algal development in restored and unrestored sections; (2) conducting a 32P radiotracer experiment to track P release from sediment cores sampled from both sections. The Biomanipulation led to lower total P, total dissolved P, and soluble reactive P concentrations in lake water, lower phytoplankton biomass, and increased light intensity at sediment surface, stimulating benthic algal development. Moreover, sediment 32P release was lower in the restored than unrestored section. Concurrently, dissolved oxygen levels in upper layers of the sediment cores were higher in the restored section. Our study indicates that the Biomanipulation improved water quality and enhanced growth of benthic algae, thereby reducing sediment P release, which may be one of the main mechanisms to create successful restoration.
-
changes in benthic macroinvertebrate abundance and lake isotope c n signals following Biomanipulation an 18 year study in shallow lake vaeng denmark
Hydrobiologia, 2012Co-Authors: Martin Sondergaard, Thomas Boll, Liselotte S Johansson, Torben L Lauridsen, Frank Landkildehus, Thomas A Davidson, Frede Ostergaard Andersen, Erik JeppesenAbstract:Change in the abundance of benthic macroinvertebrates and the stable isotope composition (C, N) of benthic invertebrates and zooplankton in Lake Vaeng, Denmark, was investigated over an 18-year period following Biomanipulation (removal of cyprinids). During the first nine years after Biomanipulation, the lake was clear and submerged macrophytes were abundant; after this period, a shift occurred to low plant abundance and high turbidity. Two years after the Biomanipulation, total density of benthic macroinvertebrates reached a maximum of 17042 (±2335 SE) individuals m−2 and the density was overall higher when the lake was in a clear state. Redundancy analysis (RDA) suggested macrophyte abundance and total nitrogen (TN) concentration were the dominant structuring forces on the benthic macroinvertebrate assemblage. Stable isotope analysis revealed that δ13C of macroinvertebrates and zooplankton was markedly higher in years with high submerged macrophyte abundance than in years without macrophytes, most likely reflecting elevated δ13C of phytoplankton and periphyton mediated by a macrophyte-induced lowering of lake water CO2 concentrations. We conclude that the strong relationship between macrophyte coverage and δ13C of macroinvertebrates and cladocerans may be useful in paleoecological studies of past changes in the dynamics of shallow lakes, as change in macrophyte abundance may be tracked by the δ13C of invertebrate remains in the sediment.
-
Biomanipulation as an application of food chain theory constraints synthesis and recommendations for temperate lakes
Ecosystems, 1998Co-Authors: Larsanders Hansson, Helene Annadotter, Eva Bergman, Stellan F Hamrin, Erik Jeppesen, Timo Kairesalo, Eira Luokkanen, Perake Nilsson, Martin Sondergaard, John A StrandAbstract:The aim of this review is to identify problems, find general patterns, and extract recommendations for successful Biomanipulation. An important conclusion is that the pelagic food chain from fish to algae may not be the only process affected by a Biomanipulation. Instead, this process should be viewed as the “trigger” for secondary processes, such as establishment of submerged macrophytes, reduced internal loading of nutrients, and reduced resuspension of particles from the sediment. However, fish reduction also leads to a high recruitment of young-of-the-year (YOY) fish, which feed extensively on zooplankton. This expansion of YOY the first years after fish reduction is probably a major reason for less successful Biomanipulations. Recent, large-scale Biomanipulations have made it possible to update earlier recommendations regarding when, where, and how Biomanipulation should be performed. More applicable recommendations include (1) the reduction in the biomass of planktivorous fish should be 75% or more; (2) the fish reduction should be performed efficiently and rapidly (within 1–3 years); (3) efforts should be made to reduce the number of benthic feeding fish; (4) the recruitment of YOY fish should be reduced; (5) the conditions for establishment of submerged macrophytes should be improved; and (6) the external input of nutrients (phosphorus and nitrogen) should be reduced as much as possible before the Biomanipulation. Recent Biomanipulations have shown that, correctly performed, the method also achieves results in large, relatively deep and eutrophic lakes, at least in a 5-year perspective. Although repeated measures may be necessary, the general conclusion is that Biomanipulation is not only possible, but also a relatively inexpensive and attractive method for management of eutrophic lakes, and in particular as a follow-up measure to reduced nutrient load.
Larsanders Hansson - One of the best experts on this subject based on the ideXlab platform.
-
Biomanipulation of Aquatic Ecosystems
Encyclopedia of Inland Waters, 2020Co-Authors: Larsanders Hansson, Christer BrönmarkAbstract:Eutrophic lakes and reservoirs have continued to experience severe algal blooms and fish kills despite measures taken to reduce external nutrient loading. An important method to improve the conditions in such lakes is to reduce the biomass of planktivorous fish (fish feeding on zooplankton), thereby reducing their predation on zooplankton so that grazing pressure of zooplankton on phytoplankton increases. This method is called ‘Biomanipulation’ and should, at least in theory, lead to clearer water. Biomanipulation has been attempted in many lakes, especially in the temperate regions, with varied success. However, changes in the food chain interactions may not be the only process initiated by Biomanipulation. Instead, this process should be viewed as the ‘trigger’ for secondary processes, such as establishment and an appreciable increase of submerged macrophytes, reduced resuspension of particles from the sediment, and reduced internal loading of nutrients. However, fish reduction also results in a high recruitment of young-of-the-year fish. This increase in abundance of juvenile fish during the first years after a fish reduction is probably the major cause behind less successful or failed cases of Biomanipulation.
-
controlling harmful cyanobacteria taxa specific responses of cyanobacteria to grazing by large bodied daphnia in a Biomanipulation scenario
PLOS ONE, 2016Co-Authors: Pablo Urrutiacordero, Mattias K Ekvall, Larsanders HanssonAbstract:Lake restoration practices based on reducing fish predation and promoting the dominance of large-bodied Daphnia grazers (i.e., Biomanipulation) have been the focus of much debate due to inconsistent success in suppressing harmful cyanobacterial blooms. While most studies have explored effects of large-bodied Daphnia on cyanobacterial growth at the community level and/or on few dominant species, predictions of such restoration practices demand further understanding on taxa-specific responses in diverse cyanobacterial communities. In order to address these questions, we conducted three grazing experiments during summer in a eutrophic lake where the natural phytoplankton community was exposed to an increasing gradient in biomass of the large-bodied Daphnia magna. This allowed evaluating taxa-specific responses of cyanobacteria to Daphnia grazing throughout the growing season in a desired Biomanipulation scenario with limited fish predation. Total cyanobacterial and phytoplankton biomasses responded negatively to Daphnia grazing both in early and late summer, regardless of different cyanobacterial densities. Large-bodied Daphnia were capable of suppressing the abundance of Aphanizomenon, Dolichospermum, Microcystis and Planktothrix bloom-forming cyanobacteria. However, the growth of the filamentous Dolichospermum crassum was positively affected by grazing during a period when this cyanobacterium dominated the community. The eutrophic lake was subjected to Biomanipulation since 2005 and nineteen years of lake monitoring data (1996–2014) revealed that reducing fish predation increased the mean abundance (50%) and body-size (20%) of Daphnia, as well as suppressed the total amount of nutrients and the growth of the dominant cyanobacterial taxa, Microcystis and Planktothrix. Altogether our results suggest that lake restoration practices solely based on grazer control by large-bodied Daphnia can be effective, but may not be sufficient to control the overgrowth of all cyanobacterial diversity. Although controlling harmful cyanobacterial blooms should preferably include other measures, such as nutrient reductions, our experimental assessment of taxa-specific cyanobacterial responses to large-bodied Daphnia and long-term monitoring data highlights the potential of such Biomanipulations to enhance the ecological and societal value of eutrophic water bodies.
-
linking cascading effects of fish predation and zooplankton grazing to reduced cyanobacterial biomass and toxin levels following Biomanipulation
PLOS ONE, 2014Co-Authors: Mattias K Ekvall, Pablo Urrutiacordero, Larsanders HanssonAbstract:Eutrophication has been one of the largest environmental problems in aquatic ecosystems during the past decades, leading to dense, and often toxic, cyanobacterial blooms. In a way to counteract these problems many lakes have been subject to restoration through Biomanipulation. Here we combine 13 years of monitoring data with experimental assessment of grazing efficiency of a naturally occurring zooplankton community and a, from a human perspective, desired community of large Daphnia to assess the effects of an altered trophic cascade associated with Biomanipulation. Lake monitoring data show that the relative proportion of Daphnia spp. grazers in June has increased following years of Biomanipulation and that this increase coincides with a drop in cyanobacterial biomass and lowered microcystin concentrations compared to before the Biomanipulation. In June, the proportion of Daphnia spp. (on a biomass basis) went from around 3% in 2005 (the first year of Biomanipulation) up to around 58% in 2012. During months when the proportion of Daphnia spp. remained unchanged (July and August) no effect on lower trophic levels was observed. Our field grazing experiment revealed that Daphnia were more efficient in controlling the standing biomass of cyanobacteria, as grazing by the natural zooplankton community never even compensated for the algal growth during the experiment and sometimes even promoted cyanobacterial growth. Furthermore, although the total cyanobacterial toxin levels remained unaffected by both grazer communities in the experimental study, the Daphnia dominated community promoted the transfer of toxins to the extracellular, dissolved phase, likely through feeding on cyanobacteria. Our results show that Biomanipulation by fish removal is a useful tool for lake management, leading to a top-down mediated trophic cascade, through alterations in the grazer community, to reduced cyanobacterial biomass and lowered cyanobacterial toxin levels. This improved water quality enhances both the ecological and societal value of lakes as units for ecosystem services.
-
Biomanipulation a tool in marine ecosystem management and restoration
Ecological Applications, 2010Co-Authors: Martin Lindegren, Christian Mollmann, Larsanders HanssonAbstract:Widespread losses of production and conservation values make large-scale ecosystem restoration increasingly urgent. Ecological restoration by means of Biomanipulation, i.e., by fishing out planktivores to reduce the predation pressure on herbivorous zooplankton, has proved to be an effective tool in restoring degraded lakes and coastal ecosystems. Whether Biomanipulation may prove a useful restoration method in open and structurally complex marine ecosystems is, however, still unknown. To promote a recovery of the collapsed stock of Eastern Baltic cod (Gadus morhua), large-scale Biomanipulation of sprat (Sprattus sprattus), the main planktivore in the Baltic Sea, has been suggested as a possible management approach. We study the effect of Biomanipulation on sprat using a statistical food-web model, which integrates internal interactions between the main fish species of the Central Baltic Sea, with external forcing through commercial fishing, zooplankton, and climate. By running multiple, stochastic simulations of reductions in sprat spawning stock biomass (SSB) only minor increases in cod SSB were detected, none of which brought the cod significantly above ecologically safe levels. On the contrary, reductions in cod fishing mortality and/or improved climatic conditions would promote a significant recovery of the stock. By this we demonstrate that an ecosystem-scale Biomanipulation, with the main focus of reinstating the dominance of cod in the Baltic Sea may likely be ecologically ineffective, operationally difficult, and costly. We argue that reducing exploitation pressure on Eastern Baltic cod to ecologically sound levels is a far more appealing management strategy in promoting a long-term recovery and a sustainable fishery of the stock.
-
Simulating the effects of Biomanipulation on the food web of Lake Ringsjön
Hydrobiologia, 1999Co-Authors: Anders Persson, Andreas Barkman, Larsanders HanssonAbstract:A dynamic, process-oriented, deterministic and phosphorus-based model was developed to simulate the food web dynamics of Lake Ringsjon, in particular the long-term effects of Biomanipulation in terms of reduction of omnivorous fish. The model contains 14 state variables, each with a differential equation describing sources and sinks of phosphorus. The state variables encompass piscivorous and omnivorous fish, zooplankton, phytoplankton, sediment and lake water. The model simulates densities of fish and phytoplankton adequately, both before and after Biomanipulation, although the actual lake phytoplankton density varied more year-to-year compared to the model predictions. According to the model, a Biomanipulation will cause an increase in zooplankton biomass. This prediction contradicts available field data from the lake which do not indicate any significant change in zooplankton biomass resulting from the performed Biomanipulation. This discrepancy may partly be attributed to structural uncertainties in the model, related to the size structure of predators on zooplankton, i.e. the omnivorous fish community. The simulations suggest that phosphorus was routed along the pelagic food chain to a larger extent after omnivorous fish were removed, whereas the amount of phosphorus routed via the sediment and benthivorous fish decreased following fish removal. Accordingly, translocation of phosphorus from sediment to water by benthivorous fish is predicted to be substantially reduced by Biomanipulation, resulting in an overall reduction in the release of new phosphorus to phytoplankton. Irrespective of simulated fishing effort (reduction of ≤0.5% d−1 for two years), the model predicts that P-release from the sediment and the external load will remain sufficiently high to force the system back to its previous state within a decade. Thus, recurrent Biomanipulations and/or combined abatement strategies may be necessary to maintain low phytoplankton density. Known structural model uncertainties may however affect the robustness of such detailed predictions about the system resilience.
Ludwig Triest - One of the best experts on this subject based on the ideXlab platform.
-
Biomanipulation as a nature based solution to reduce cyanobacterial blooms
Aquatic Ecology, 2016Co-Authors: Ludwig Triest, Iris Stiers, Stijn Van OnsemAbstract:We considered the limnological literature for an overview of Biomanipulation methods that were implemented to avoid or reduce cyanobacterial bloom development in ponds and lakes. For this purpose, we reviewed 48 publications representing 34 whole-lake and large-scale case studies of different Biomanipulation approaches clearly mentioning the extent of a cyanobacteria bloom problem and the cyanobacteria taxa involved. This delivered complementary information to the suite of review papers already providing elaborated syntheses on Biomanipulation and associated ecotechnological measures as a restoration tool for overall eutrophication reduction and control. We considered nature-based solutions such as fish removal and associated water drawdown, addition of piscivorous fish, filter-feeding planktivorous fish, Daphnia or bivalves, re-introduction of macrophytes and a combination of accompanying restoration methods. Reasons for success or failure to control cyanobacterial blooms of especially Anabaena, Pseudanabaena, Aphanizomenon, Aphanocapsa, Limnothrix, Microcystis, Oscillatoria or Spirulina spp. could be explained through bottlenecks encountered with fish removal, stocking densities, cascading effects, associated zooplankton grazing, diet shifts away from cyanobacteria, macrophyte recovery, nutrient or pH status. Threshold values to avoid failures are synthesized from experiments or monitoring studies and presented in a conceptual scheme about cyanobacteria reduction through (1) direct abatement of existing blooms and forcing/maximization of biotic key interactions (2) reducing risk of blooms and improving lake or pond multi-functionality and (3) avoiding blooms, balancing biotic communities and enhancing existing ecosystem services. More information will be required on temporal dynamics and abundances of cyanobacteria taxa in whole-lake pre- and post-Biomanipulation conditions to better evaluate the applicability and effectiveness of such nature-based solutions.
-
Identification of total phosphate, submerged vegetation cover and zooplankton size thresholds for success of Biomanipulation in peri-urban eutrophic ponds
Hydrobiologia, 2013Co-Authors: Sylvia De Backer, Samuel Teissier, Ludwig TriestAbstract:In small shallow lakes and ponds, the clear-water state can generally be maintained at higher nutrient concentrations compared to larger shallow lakes. The main objective of this study was to identify thresholds for total phosphorus (TP), submerged vegetation cover and zooplankton size that determine Biomanipulation success in peri-urban eutrophic ponds. Additionally, the relationship between transparency and TP is discussed with regard to similar relationships and thresholds reported for shallow lakes. Using classification trees, a threshold TP concentration of 0.300 mg P L−1 was determined below which a clear-water state was generally maintained after Biomanipulation. When the average TP concentration was >0.300 mg P L−1, the stability of the clear-water state largely depended on the presence of sufficiently large zooplankton (>0.87 mm) or a submerged vegetation cover of >82% at some point during the year. This threshold TP concentration is considerably higher than the threshold of 0.1 mg L−1 which is generally suggested for longer-term success of Biomanipulation in shallow lakes. Such threshold nutrient concentration is important when restoring ecological quality in eutrophic small lakes and ponds. Extended follow-up of Biomanipulation success in eutrophic ponds could provide more insight into the feasibility of these thresholds on the longer term.
-
stabilizing the clear water state in eutrophic ponds after Biomanipulation submerged vegetation versus fish recolonization
Hydrobiologia, 2012Co-Authors: Sylvia De Backer, Samuel Teissier, Ludwig TriestAbstract:Biomanipulation through fish removal is a tool commonly used to restore a clear-water state in lakes. Biomanipulation of ponds is, however, less well documented, although their importance for biodiversity conservation and public amenities is undisputed. In ponds, a more complete fish removal can be carried out as compared to lakes and therefore a stronger response is expected. Fish recolonization can, however, potentially compromise the longer term success of Biomanipulation. Therefore, we investigated the impact of fish recolonization on zooplankton, phytoplankton, and nutrients for several years after complete drawdown and fish removal in function of submerged vegetation cover in 12 peri-urban eutrophic ponds situated in Brussels (Belgium). Fish recolonization after Biomanipulation had a considerable impact on zooplankton grazers, reducing their size and density substantially, independent of the extent of submerged vegetation cover. Only ponds with 30% submerged vegetation cover, macrophytes prevented an increase in phytoplankton growth despite the disappearance of large zooplankton grazers. Our results suggest that macrophytes, rather than by providing a refuge for zooplankton grazers, control phytoplankton through other associated mechanisms and confirm that the recovery of submerged macrophytes is essential for Biomanipulation success. Although the longer term effect of Biomanipulation is disputable, increased ecological quality could be maintained for several years, which is particularly interesting in an urban area where nutrient loading reduction is often not feasible.
-
Biomanipulation of hypereutrophic ponds when it works and why it fails
Environmental Monitoring and Assessment, 2012Co-Authors: Anatoly Peretyatko, Sylvia De Backer, Samuel Teissier, Ludwig TriestAbstract:Phytoplankton, zooplankton, submerged vegetation and main nutrients have been monitored in 48 eutrophic ponds from the Brussels Capital Region (Belgium) between 2005 and 2008. Nine ponds have been biomanipulated in order to improve their ecological quality and prevent the occurrence of noxious cyanobacterial blooms. The 4-year study of a large number of ponds allowed identification of the factors having the strongest influence on phytoplankton growth. Continuous monitoring of the biomanipulated ponds allowed the significance of changes caused by Biomanipulation to be tested as well as the main reasons of Biomanipulation successes and failures to be elucidated. The main factors controlling phytoplankton in the ponds studied appeared to be grazing by large cladocerans and inhibition of phytoplankton growth by submerged vegetation. Biomanipulation resulted in a significant decrease in phytoplankton biomass in general and biomass of bloom-forming cyanobacteria in particular that were associated with a significant increase in large Cladocera density and size. In six out of nine ponds Biomanipulation resulted in the restoration of submerged vegetation. The maintenance of the restored clearwater state in the biomanipulated ponds was strongly dependent on fish recolonisation and nutrient level. In the absence of fish, the clearwater state could be maintained by submerged vegetation or large zooplankton grazing alone. In case of fish recolonisation, restoration of extensive submerged vegetation could buffer, to a considerable degree, the effect of fish except for ponds with high nutrient levels.
E Van Donk - One of the best experts on this subject based on the ideXlab platform.
-
The effects of Biomanipulation on the biogeochemistry, carbon isotopic composition and pelagic food web relations of a shallow peat lake
2020Co-Authors: B M Bontes, Bastiaan Willem Ibelings, H T S Boschker, Jack J Middelburg, E Van DonkAbstract:In this study we investigated the effects of ex- perimental Biomanipulation on community structure, ecosys- tem metabolism, carbon biogeochemistry and stable isotope composition of a shallow eutrophic lake in the Netherlands. Three different Biomanipulation treatments were applied. In two parts of the lake, isolated from the rest, fish was removed and one part was used as a reference treatment in which no Biomanipulation was applied. Stable isotopes have proved useful to trace trophic interactions at higher food web lev- els but until now methodological limitations have restricted species specific isotope analysis in the plankton community. We applied a new approach based on the combination of fluo- rescence activated cell sorting (FACS) and isotope ratio mass spectrometry (IRMS) to trace carbon flow through the plank- tonic food web. With this method we aimed at obtaining group specific 13 C signatures of phytoplankton and to trace possible shifts in 13 C resulting from fish removal. Biomanipulation led to an increase in transparency and macrophyte biomass and decrease in phytoplankton abun- dance, but zooplankton numbers did not increase. Fish re- moval also resulted in high pH, high O2, low CO2 and more negative 13 CDIC values than expected, which is attributed to chemical enhanced diffusion with large negative fractiona- tion. Despite high temporal variation we detected differences between the isotopic signatures of the primary producers and between the different treatments. The fractionation values of green algae ( 21‰) and diatoms ( 23‰) were similar and independent of treatment, while fractionation factors of filamentous cyanobacteria were variable between the treat- ments that differed in CO2 availability. 13 C-labeling of the phytoplankton groups showed that Biomanipulation led to in- creased growth rates of green algae and diatoms at the ex- pense of cyanobacteria. Finally, consumers seemed general- ists to the available food sources.
-
the effects of Biomanipulation on the biogeochemistry carbon isotopic composition and pelagic food web relations of a shallow lake
Biogeosciences, 2005Co-Authors: B M Bontes, Bastiaan Willem Ibelings, H T S Boschker, Jack J Middelburg, E Van DonkAbstract:Abstract. In this study we investigated the effects of experimental Biomanipulation on community structure, ecosystem metabolism, carbon biogeochemistry and stable isotope composition of a shallow eutrophic lake in the Netherlands. Three different Biomanipulation treatments were applied. In two parts of the lake, isolated from the rest, fish was removed and one part was used as a reference treatment in which no Biomanipulation was applied. Stable isotopes have proved useful to trace trophic interactions at higher food web levels but until now methodological limitations have restricted species specific isotope analysis in the plankton community. We applied a new approach based on the combination of fluorescence activated cell sorting (FACS) and isotope ratio mass spectrometry (IRMS) to trace carbon flow through the planktonic food web. With this method we aimed at obtaining group specific δ 13 C signatures of phytoplankton and to trace possible shifts in δ 13 C resulting from fish removal. Biomanipulation led to an increase in transparency and macrophyte biomass and decrease in phytoplankton abundance, but zooplankton numbers did not increase. Fish removal also resulted in high pH, high O 2 , low CO 2 and more negative δ 13 C DIC values than expected, which is attributed to chemical enhanced diffusion with large negative fractionation. Despite high temporal variation we detected differences between the isotopic signatures of the primary producers and between the different treatments. The fractionation values of green algae (~21) and diatoms (~23) were similar and independent of treatment, while fractionation factors of filamentous cyanobacteria were variable between the treatments that differed in CO 2 availability. 13 C-labeling of the phytoplankton groups showed that Biomanipulation led to increased growth rates of green algae and diatoms at the expense of cyanobacteria. Finally, consumers seemed generalists to the available food sources.
-
The first Biomanipulation conference: a synthesis
Hydrobiologia, 1990Co-Authors: E.h.r.r. Lammens, M L Meijer, Ramesh D. Gulati, E Van DonkAbstract:At the First Biomanipulation Conference held in Amsterdam (8–11 August 1989), studies presented considered mainly trophic interactions in lakes, enclosures and laboratory systems. Studies on the interactions between phytoplankton and zooplankton emphasized the edibility of the phytoplankton in relation to the zooplankton size structure and the trophic state. Most lake experiments involved 50–100% reduction in fish standing stock or alternatively heavy stocking with piscivorous fish. The most dramatic effects of Biomanipulation were found in shallow, eutrophic lakes which exhibited radical changes in ecosystem structure because of changes in light climate and consequently, luxuriant development of macrophytes. There was still much controversy about the top-down effects in relation to trophic state, especially those concerning the role of fish and zooplankton in the development and succession of phytoplankton. Many experiments showed indirect effects within the food web, emphasizing the importance of feedbacks and the complexity of the food web rather than the simplicity of the food chain. The stabilizing effects of refugia for zooplankton and fish on the ecosystem were stressed. Shallow lakes responded generally more rapidly to Biomanipulation and this was most successfully accomplished when TP concentration was
-
the first Biomanipulation conference a synthesis
Hydrobiologia, 1990Co-Authors: E.h.r.r. Lammens, M L Meijer, Ramesh D. Gulati, E Van DonkAbstract:At the First Biomanipulation Conference held in Amsterdam (8–11 August 1989), studies presented considered mainly trophic interactions in lakes, enclosures and laboratory systems. Studies on the interactions between phytoplankton and zooplankton emphasized the edibility of the phytoplankton in relation to the zooplankton size structure and the trophic state. Most lake experiments involved 50–100% reduction in fish standing stock or alternatively heavy stocking with piscivorous fish. The most dramatic effects of Biomanipulation were found in shallow, eutrophic lakes which exhibited radical changes in ecosystem structure because of changes in light climate and consequently, luxuriant development of macrophytes. There was still much controversy about the top-down effects in relation to trophic state, especially those concerning the role of fish and zooplankton in the development and succession of phytoplankton. Many experiments showed indirect effects within the food web, emphasizing the importance of feedbacks and the complexity of the food web rather than the simplicity of the food chain. The stabilizing effects of refugia for zooplankton and fish on the ecosystem were stressed. Shallow lakes responded generally more rapidly to Biomanipulation and this was most successfully accomplished when TP concentration was<50µg l−1, even though in a few cases at 10–20 fold higher TP concentrations (mostly PO4-P lakes) the results achieved could be maintained for two or more summers. For a guaranteed success of the measures an almost complete removal of fish appeared to be indispensible; moreover in many cases removal of benthivorous fish appeared to be even more important than that of planktivorous fish.
