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John A Strand – 1st expert on this subject based on the ideXlab platform

  • dynamics of submerged macrophyte populations in response to Biomanipulation
    Freshwater Biology, 2001
    Co-Authors: John A Strand, Stefan E B Weisner


    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, 1999
    Co-Authors: John A Strand


    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, 1998
    Co-Authors: Larsanders Hansson, Helene Annadotter, Eva Bergman, Stellan F Hamrin, Erik Jeppesen, Timo Kairesalo, Eira Luokkanen, Perake Nilsson, Martin Sondergaard, John A Strand


    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 – 2nd expert on this subject based on the ideXlab platform

  • could artificial plant beds favour microcrustaceans during Biomanipulation of eutrophic shallow lakes
    Hydrobiologia, 2017
    Co-Authors: David Balayla, Thomas Boll, Carolina Trochine, Erik Jeppesen


    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, 2017
    Co-Authors: Yali Tang, Xiufeng Zhang, Erik Jeppesen


    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, 2012
    Co-Authors: Martin Sondergaard, Thomas Boll, Liselotte S Johansson, Torben L Lauridsen, Frank Landkildehus, Thomas A Davidson, Frede Ostergaard Andersen, Erik Jeppesen


    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.

Larsanders Hansson – 3rd expert on this subject based on the ideXlab platform

  • Biomanipulation of Aquatic Ecosystems
    Encyclopedia of Inland Waters, 2020
    Co-Authors: Larsanders Hansson, Christer Brönmark


    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, 2016
    Co-Authors: Pablo Urrutiacordero, Mattias K Ekvall, Larsanders Hansson


    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, 2014
    Co-Authors: Mattias K Ekvall, Pablo Urrutiacordero, Larsanders Hansson


    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.