title: Benthic-planktonic coupling, regime shifts, and whole-lake primary production in shallow lakes.
abstract: Alternative stable states in shallow lakes are typically characterized by submerged macrophyte (clear-water state) or phytoplankton (turbid state) dominance. However, a clear-water state may occur in eutrophic lakes even when macrophytes are absent. To test whether sediment algae could cause a regime shift in the absence of macrophytes, we developed a model of benthic (periphyton) and planktonic (phytoplankton) primary production using parameters derived from a shallow macrophyte-free lake that shifted from a turbid to a clear-water state following fish removal (biomanipulation). The model includes a negative feedback effect of periphyton on phosphorus (P) release from sediments. This in turn induces a positive feedback between phytoplankton production and P release. Scenarios incorporating a gradient of external P loading rates revealed that (1) periphyton and phytoplankton both contributed substantially to whole-lake production over a broad range of external P loading in a clear-water state; (2) during the clear-water state, the loss of benthic production was gradually replaced by phytoplankton production, leaving whole-lake production largely unchanged; (3) the responses of lakes to biomanipulation and increased external P loading were both dependent on lake morphometry; and (4) the capacity of periphyton to buffer the effects of increased external P loading and maintain a clear-water state was highly sensitive to relationships between light availability at the sediment surface and the of P release. Our model suggests a mechanism for the persistence of alternative states in shallow macrophyte-free lakes and demonstrates that regime shifts may trigger profound changes in ecosystem structure and function.
authors.affiliation: Graduate School of Kuroshio Science, Kochi University, Kochi 780-8520, Japan. genkai@kochi-u.ac.jp
authors.forename: Motomi
authors.initials: M
authors.lastname: Genkai-Kato
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Vadeboncoeur
authors.forename: Lone
authors.initials: L
authors.lastname: Liboriussen
authors.forename: Erik
authors.initials: E
authors.lastname: Jeppesen
mesh_terms: D000220:Adaptation, Biological; D017753:Ecosystem; D060106:Lakes; D010933:Plankton / Q000502:physiology*; D011157:Population Dynamics