Top-down versus bottom-up control in planktonic systems: some case studies from the English Lake District
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COLIN S. REYNOLDS’ LEGACY
Review Paper
Top-down versus bottom-up control in planktonic systems: some case studies from the English Lake District D. G. George
Received: 31 January 2020 / Revised: 8 July 2020 / Accepted: 13 July 2020 Springer Nature Switzerland AG 2020
Abstract In this review, I use examples drawn from long-term studies in the English Lakes to highlight the limitations of top-down control in planktonic systems. These limitations are most obvious at the base of the food chain where there are large differences in the potential growth rates of the phytoplankton and zooplankton. Three of the examples are taken from a 40-year study of the impact of perch on Daphnia in the North Basin of Windermere, one on the rates of change measured in an experimental enclosure and one from an 18-year study of Daphnia dynamics in Esthwaite Water. The Windermere examples show that the commercial perch fishery established in 1941 had little effect on the abundance of Daphnia but the enrichment of the lake by war-time ploughing led to a short-lived increase in their reproductive rate. The other examples demonstrate that time plays an important part in all trophic interactions and shows that established patterns of phytoplankton succession are frequently disrupted by changes in the intensity of wind-induced mixing. The results are discussed in
Guest editors: Judit Padisa´k, J. Alex Elliott, Martin T. Dokulil & Luigi Naselli-Flores / New, old and evergreen frontiers in freshwater phytoplankton ecology: the legacy of Colin S. Reynolds D. G. George (&) Freshwater Biological Association, The Ferry Landing, Far Sawrey, Ambleside, Cumbria LA22 OLP, UK e-mail: [email protected]
relation to recent reviews of the efficacy of biomanipulation and the challenges of analysing complex interactions in dynamic systems. Keywords Zooplankton Phytoplankton Fish predation Land-use Paleolimnology Trophic dynamics
Introduction The question of whether planktonic systems are controlled from the top down by predation or from the bottom up by resources is a fundamental question in limnology. In the 1980s, it was the subject of intense debate as investigators designed a variety of field experiments to explore these interactions. In 1975 Shapiro et al. had coined the term biomanipulation to describe the process by which the biomass of phytoplankton could be reduced by stocking with fish that fed on large filter feeders. Some years later, Carpenter et al. (1985) introduced the term trophic cascade to describe the process and went on to design whole-lake experiments to demonstrate its effects (Carpenter & Kitchell, 1988; Carpenter et al., 2001). According to this theory, any changes made to the top of the trophic pyramid will cascade through the food chain to reduce the biomass of phytoplankton at the base. Plenty of evidence was soon accrued to demonstrate that
123
Hydrobiologia
piscivores could control planktivore numbers (Benndorf et al., 1984; Scavia et al., 1986) and that pla
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