First attempt to apply whole-lake food-web manipulation on a large scale in The Netherlands

Abstract

Lake Breukeleveen (180 ha, mean depth 1.45 m), a compartment of the eutrophic Loosdrecht lakes system, was selected to study the effects of whole-lake foodweb manipulation on a large scale. In Lake Loosdrecht (dominated by filamentous cyanobacteria), due to water management measures taken from 1970-1984 (sewerage systems, dephosphorization) the external P load has been reduced from 1.2 g m-2 y-1 to 0.35 g m -2 y -i. The water transparency (Secchi-depth ca. 30 cm), however, has not improved. The aim of the food-web manipulation in Lake Breukeleveen was not only to improve the light climate of the lake, but also to study if the successfull effects observed in small lakes (a few ha) can be upscaled. In March 1989 the standing crop of planktivorous and bentivorous fish populations was reduced by intensive fishery, from ca. 150 kg ha-1 to ca. 57 kg ha-1. The lake was made unaccessible to fish migrating from the other lakes and it was stocked with large-sized daphnids and 0 ÷ pike. However, water transparency did not increase in the following summer and autumn 1989, which is in contrast with great improvement in the light conditions previously observed in smaller lakes. The main explanations for the negative outcome in Lake Breukeleveen are: 1)the rapid increase of the planktivorous fish biomass and carnivorous cladocerans, predating on the zooplankton community; 2) suppression of the large daphnids by the high concentrations of filamentous cyanobacteria; 3) high turbidity of the lake due to resuspension of bottom material induced by wind, unlike in smaller lakes, and thus inability of submerged macrophytes to develop and to stabilize the ecosystem.

Individual and population‐level food consumption by cyprinids and percids in a mesotrophic lake

“…Removal of planktivorous fish is considered to be an effective tool in biomanipulation by changing the composition of the zooplankton community from small sized to large zooplankters, like Daphnia, which are more effective grazers on phytoplankton (e.g. In many cases, bioturbation and recycling of nutrients from the sediment (bottom-up effects) by cyprinids, rather than zooplanktivory, have concluded to be the main factors linking fish to water quality (Horppila & Kairesalo 1990;Tatrai et al 1990;van Donk et al 1990;Horppila et al 1998). Planktivorous fish also accelerate recycling of nutrients and thereby algal production, but they do not load the open water column with ''new'' nutrients from outside of the cycle as benthivorous fish do (Shapiro & Carlson 1982).…”

Top‐down or Bottom‐up Effects by Fish: Issues of Concern in Biomanipulation of Lakes

“…The effects of zooplanktivory are attenuated because they cascade down the food web (McQueen et al 1986, 1989), whereas the other effects of benthivorous and omnivorous fish bypass the cascade and directly affect nutrient availability. Nutrient excretion by fish, bioturbation, and fish mortality have been shown in numerous studies to affect water quality without changing the cladoceran community (Drenner et al 1986;Tátrai & Istvanovics 1986;Threlkeld 1987;Horppila & Kairesalo 1990;Tátrai et al 1990;van Donk et al 1990;McQueen et al 1992). In fact, these effects can be considered bottom‐up forces (Tátrai et al 1990;Hamrin 1993), so changes in their abundance may have more prompt effects than those of obligatory planktivorous fish.…”

Trophic interactions in a shallow lake following a reduction in nutrient loading: a long-term study

“…Necessary additional measures may include control of the internal load by the removal of nutrient rich sediments (Bengsston et al, 1975;Moss et al, 1986) and/or biomanipulation . This usually involves removal of zooplanktivorous fish (Moss, 1990;Van Donk et al, 1990a;Giussani et al, 1990; to promote large-bodied cladoceran populations to control undesirable phytoplankton (the so-called trophic cascade response) (Gulati etal., 1990). Even where several measures have been taken to improve water quality and reinstate submerged plant populations, stability may be difficult to achieve (Benndorff, 1990;Shapiro, 1990).…”