title: The legacy of large regime shifts in shallow lakes.
abstract: Ecological shifts in shallow lakes from clear-water macrophyte-dominated to turbid-water phytoplankton-dominated are generally thought of as rapid short-term transitions. Diatom remains in sediment records from shallow lakes in the Prairie Pothole Region of North America provide new evidence that the long-term ecological stability of these lakes is defined by the legacy of large regime shifts. We examine the modern and historical stability of 11 shallow lakes. Currently, four of the lakes are in a clear-water state, three are consistently turbid-water, and four have been observed to change state from year to year (transitional). Lake sediment records spanning the past 150-200 yr suggest that (1) the diatom assemblage is characteristic of either clear or turbid lakes, (2) prior to significant landscape alteration, all of the lakes existed in a regime of a stable clear-water state, (3) lakes that are currently classified as turbid or transitional have experienced one strong regime shift over the past 150-200 yr and have since remained in a regime where turbid-water predominates, and (4) top-down impacts to the lake food-web from fish introductions appear to be the dominant driver of strong regime shifts and not increased nutrient availability. Based on our findings we demonstrate a method that could be used by lake managers to identify lakes that have an ecological history close to the clear-turbid regime threshold; such lakes might more easily be returned to a clear-water state through biomanipulation. The unfortunate reality is that many of these lakes are now part of a managed landscape and will likely require continued intervention.
authors.affiliation: St. Croix Watershed Research Station, Science Museum of Minnesota, 16910 152nd Street North, Marine on St. Croix, Minnesota, 55047, USA.
authors.forename: Joy M
authors.initials: JM
authors.lastname: Ramstack Hobbs
authors.affiliation: St. Croix Watershed Research Station, Science Museum of Minnesota, 16910 152nd Street North, Marine on St. Croix, Minnesota, 55047, USA.
authors.forename: William O
authors.initials: WO
authors.lastname: Hobbs
authors.affiliation: St. Croix Watershed Research Station, Science Museum of Minnesota, 16910 152nd Street North, Marine on St. Croix, Minnesota, 55047, USA.
authors.forename: Mark B
authors.initials: MB
authors.lastname: Edlund
authors.affiliation: Department of Biology, University of St. Thomas, 2115 Summit Avenue, St. Paul, Minnesota, 55105, USA.
authors.forename: Kyle D
authors.initials: KD
authors.lastname: Zimmer
authors.affiliation: Department of Geology, University of St. Thomas, 2115 Summit Avenue, St. Paul, Minnesota, 55105, USA.
authors.forename: Kevin M
authors.initials: KM
authors.lastname: Theissen
authors.affiliation: St. Croix Watershed Research Station, Science Museum of Minnesota, 16910 152nd Street North, Marine on St. Croix, Minnesota, 55047, USA.
authors.forename: Natalie
authors.initials: N
authors.lastname: Hoidal
authors.affiliation: Department of Biology, University of St. Thomas, 2115 Summit Avenue, St. Paul, Minnesota, 55105, USA.
authors.forename: Leah M
authors.initials: LM
authors.lastname: Domine
authors.affiliation: Wetland Wildlife Populations and Research Group, Minnesota Department of Natural Resources, 2114 Bemidji Avenue, Bemidji, Minnesota, 56601, USA.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Hanson
authors.affiliation: Fisheries Research, Minnesota Department of Natural Resources, 2114 Bemidji Avenue, Bemidji, Minnesota, 56601, USA.
authors.forename: Brian R
authors.initials: BR
authors.lastname: Herwig
authors.affiliation: Department of Ecology, Evolution, and Behavior, University of Minnesota, 1479 Gortner Avenue, St. Paul, Minnesota, 55108, USA.
authors.forename: James B
authors.initials: JB
authors.lastname: Cotner
mesh_terms: D000818:Animals; D017753:Ecosystem; D020387:Food Chain; D060106:Lakes; D009656:North America; D010839:Phytoplankton
keywords: Prairie Pothole Region; alternative stable state; diatom; hysteresis; regime shift; shallow lake