Biomanipulation of hypereutrophic ponds: when it works and why it fails

Abstract

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.

Repeated Fish Removal to Restore Lakes: Case Study of Lake Væng, Denmark—Two Biomanipulations during 30 Years of Monitoring

“…The effects of both biomanipulation attempts in Lake Vaeng were comparable with those obtained in other shallow Danish lakes [10], and in many other parts of the world as well [9,11,29]. We are not able to ascertain whether the fish biomass was lower before the second than before the first biomanipulation in Lake Vaeng, but the chemical and biological effects of the second biomanipulation appear to be just as strong as after the first biomanipulation, even though 30% less fish was removed.…”

“…Numerous examples of biomanipulation have been given in the literature during the past 30 years, including more general approaches integrating the results from a number of case studies [6,[9][10][11]. Overall, clear effects of biomanipulation have often been recorded, among these a trophic cascade impacting most trophic levels; however, the effects have sometimes been weak [12][13][14].…”

“…Furthermore, a sufficient number of fish need to be removed, depending also on TP concentrations [18]. In shallow lakes, extensive cover of submerged macrophytes is important for stabilising and maintaining clear water conditions [19], and the overall biomanipulation success may depend on the internal nutrient loading and the interacting effects of nutrient concentrations, fish recolonization and macrophyte abundance [11,14,20].…”

Ciliates in Planktonic Food Webs: Communication and Adaptive Response

“…Biomanipulation is a management technique to enhance water quality by controlling phytoplankton biomass via increasing the rate at which algae are removed by zooplankton (Benndorf 1995;Shapiro et al 1975); to achieve the latter, a lake is stocked with piscivorous fish that reduces the populations of (zoo)planktivorous fish. Biomanipulation was mainly applied at the height of the eutrophication but is still being used occasionally (e.g., Ha et al 2013;Peretyatko et al 2012). This method was supported by the finding that predator control at a higher trophic level may 'cascade down' to the lower levels of the food web (Carpenter et al 1985;Dinasquet et al 2012).…”

Changes in Phytoplankton and Water Quality during Sustainable Restoration of an Urban Lake Used for Recreation and Water Supply

“…This is evidenced by numerous species of r-selection strategy in the phytoplankton, which can serve as a food source for large cladocerans [73][74][75][76], especially in 2009 and 2011. The stocking with hatching of pike in 2009, though intense, was not very effective, as survival from such hatching is very limited [76].…”