Advanced

Long-term patterns of shifts between clear and turbid states in Lake Krankesjon and Lake Takern

Hargeby, Anders LU ; Blindow, Irmgard and Andersson, Gunnar (2007) In Ecosystems 10(1). p.29-36
Abstract
During the past century, Lake Takern and Lake Krankesjon, southern Sweden, have shifted repeatedly between a state of clear water and abundant submerged vegetation, and a state of turbid water and sparse vegetation. Long-term empirical data on such apparently alternative stable state dynamics are valuable as complements to modeling and experiments, although the causal mechanisms behind shifts are often difficult to identify in hindsight. Here, we summarize previous studies and discuss possible mechanisms behind the shifts. The most detailed information comes from monitoring of two recent shifts, one in each lake. In the 1980s, L. Krankesjon shifted to clear water following an expansion of sago pondweed, Potamogeton pectinatus. Water... (More)
During the past century, Lake Takern and Lake Krankesjon, southern Sweden, have shifted repeatedly between a state of clear water and abundant submerged vegetation, and a state of turbid water and sparse vegetation. Long-term empirical data on such apparently alternative stable state dynamics are valuable as complements to modeling and experiments, although the causal mechanisms behind shifts are often difficult to identify in hindsight. Here, we summarize previous studies and discuss possible mechanisms behind the shifts. The most detailed information comes from monitoring of two recent shifts, one in each lake. In the 1980s, L. Krankesjon shifted to clear water following an expansion of sago pondweed, Potamogeton pectinatus. Water clarity increased when the pondweed was replaced by characeans. Zooplankton biomass in summer declined and the concentration of total phosphorus (TP) was reduced to half the previous level. The fish community changed over several years, including an increasing recruitment of piscivorous perch (Perca fluviatilis). An opposite directed shift to turbid water occurred in Lake Takern in 1995, when biomass of phytoplankton increased in spring, at the expense of submerged vegetation. Consistent with the findings in L. Krankesjon, phyto- and zooplankton biomass increased and the average concentration of TP doubled. After the shift to clear water in L. Krankesjon, TP concentration has increased during the latest decade, supporting the idea that accumulation of nutrients may lead to a long-term destabilization of the clear water state. In L. Takern, data on TP are inconclusive, but organic nitrogen concentrations oscillated during a 25-year period of clear water. These observations indicate that intrinsic processes cause gradual or periodic changes in system stability, although we cannot exclude the possibility that external forces are also involved. During such phases of destabilization of the clear water state, even small disturbances could possibly trigger a shift, which may explain why causes behind shifts are hard to identify even when they occur during periods of extensive monitoring. (Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
ecosystem, time series, alternative stable states, long-term monitoring, shallow lakes, structure
in
Ecosystems
volume
10
issue
1
pages
29 - 36
publisher
Springer
external identifiers
  • wos:000246766000004
  • scopus:34249659562
ISSN
1432-9840
DOI
10.1007/s10021-006-9008-5
language
English
LU publication?
yes
id
295f7c16-cb35-4ebc-9773-903005b682a1 (old id 657878)
date added to LUP
2007-12-12 12:09:40
date last changed
2017-11-19 04:03:54
@article{295f7c16-cb35-4ebc-9773-903005b682a1,
  abstract     = {During the past century, Lake Takern and Lake Krankesjon, southern Sweden, have shifted repeatedly between a state of clear water and abundant submerged vegetation, and a state of turbid water and sparse vegetation. Long-term empirical data on such apparently alternative stable state dynamics are valuable as complements to modeling and experiments, although the causal mechanisms behind shifts are often difficult to identify in hindsight. Here, we summarize previous studies and discuss possible mechanisms behind the shifts. The most detailed information comes from monitoring of two recent shifts, one in each lake. In the 1980s, L. Krankesjon shifted to clear water following an expansion of sago pondweed, Potamogeton pectinatus. Water clarity increased when the pondweed was replaced by characeans. Zooplankton biomass in summer declined and the concentration of total phosphorus (TP) was reduced to half the previous level. The fish community changed over several years, including an increasing recruitment of piscivorous perch (Perca fluviatilis). An opposite directed shift to turbid water occurred in Lake Takern in 1995, when biomass of phytoplankton increased in spring, at the expense of submerged vegetation. Consistent with the findings in L. Krankesjon, phyto- and zooplankton biomass increased and the average concentration of TP doubled. After the shift to clear water in L. Krankesjon, TP concentration has increased during the latest decade, supporting the idea that accumulation of nutrients may lead to a long-term destabilization of the clear water state. In L. Takern, data on TP are inconclusive, but organic nitrogen concentrations oscillated during a 25-year period of clear water. These observations indicate that intrinsic processes cause gradual or periodic changes in system stability, although we cannot exclude the possibility that external forces are also involved. During such phases of destabilization of the clear water state, even small disturbances could possibly trigger a shift, which may explain why causes behind shifts are hard to identify even when they occur during periods of extensive monitoring.},
  author       = {Hargeby, Anders and Blindow, Irmgard and Andersson, Gunnar},
  issn         = {1432-9840},
  keyword      = {ecosystem,time series,alternative stable states,long-term monitoring,shallow lakes,structure},
  language     = {eng},
  number       = {1},
  pages        = {29--36},
  publisher    = {Springer},
  series       = {Ecosystems},
  title        = {Long-term patterns of shifts between clear and turbid states in Lake Krankesjon and Lake Takern},
  url          = {http://dx.doi.org/10.1007/s10021-006-9008-5},
  volume       = {10},
  year         = {2007},
}