Response of submerged macrophyte communities to external and internal restoration measures in north temperate shallow lakes

Sabine Hilt*, Marta M. Alirangues Nuñez, Elisabeth S. Bakker, Irmgard Blindow, Thomas A. Davidson, Mikael Gillefalk, Lars Anders Hansson, Jan H. Janse, Annette B.G. Janssen, Erik Jeppesen, Timm Kabus, Andrea Kelly, Jan Köhler, Torben L. Lauridsen, Wolf M. Mooij, Ruurd Noordhuis, Geoff Phillips, Jacqueline Rücker, Hans Heinrich Schuster, Martin SøndergaardSven Teurlincx, Klaus van de Weyer, Ellen van Donk, Arno Waterstraat, Nigel Willby, Carl D. Sayer

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

31 Citations (Scopus)

Abstract

Submerged macrophytes play a key role in north temperate shallow lakes by stabilizing clear-water conditions. Eutrophication has resulted in macrophyte loss and shifts to turbid conditions in many lakes. Considerable efforts have been devoted to shallow lake restoration in many countries, but long-term success depends on a stable recovery of submerged macrophytes. However, recovery patterns vary widely and remain to be fully understood. We hypothesize that reduced external nutrient loading leads to an intermediate recovery state with clear spring and turbid summer conditions similar to the pattern described for eutrophication. In contrast, lake internal restoration measures can result in transient clear-water conditions both in spring and summer and reversals to turbid conditions. Furthermore, we hypothesize that these contrasting restoration measures result in different macrophyte species composition, with added implications for seasonal dynamics due to differences in plant traits. To test these hypotheses, we analyzed data on water quality and submerged macrophytes from 49 north temperate shallow lakes that were in a turbid state and subjected to restoration measures. To study the dynamics of macrophytes during nutrient load reduction, we adapted the ecosystem model PCLake. Our survey and model simulations revealed the existence of an intermediate recovery state upon reduced external nutrient loading, characterized by spring clear-water phases and turbid summers, whereas internal lake restoration measures often resulted in clear-water conditions in spring and summer with returns to turbid conditions after some years. External and internal lake restoration measures resulted in different macrophyte communities. The intermediate recovery state following reduced nutrient loading is characterized by a few macrophyte species (mainly pondweeds) that can resist wave action allowing survival in shallowareas, germinate early in spring, have energy-rich vegetative propagules facilitating rapid initial growth and that can complete their life cycle by early summer. Later in the growing season these plants are, according to our simulations, outcompeted by periphyton, leading to late-summer phytoplankton blooms. Internal lake restoration measures often coincide with a rapid but transient colonization by hornworts, waterweeds or charophytes. Stable clear-water conditions and a diverse macrophyte flora only occurred decades after external nutrient load reduction or when measures were combined.
Original languageEnglish
Article number194
JournalFrontiers in Plant Science
Volume9
DOIs
Publication statusPublished - 19 Feb 2018

Keywords

  • Aquaticplants
  • Biomanipulation
  • Eutrophication
  • Lakerestoration
  • Nutrient loadreduction
  • PCLake
  • Plant traits
  • Regime shift

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    Hilt, S., Alirangues Nuñez, M. M., Bakker, E. S., Blindow, I., Davidson, T. A., Gillefalk, M., ... Sayer, C. D. (2018). Response of submerged macrophyte communities to external and internal restoration measures in north temperate shallow lakes. Frontiers in Plant Science, 9, [194]. https://doi.org/10.3389/fpls.2018.00194