Short-term fish predation destroys resilience of zooplankton communities and prevents recovery of phytoplankton control by zooplankton grazing

PLoS One. 2019 Feb 15;14(2):e0212351. doi: 10.1371/journal.pone.0212351. eCollection 2019.

Abstract

Planktivorous fish predation directly affects zooplankton biomass, community and size structure, and may indirectly induce a trophic cascade to phytoplankton. However, it is not clear how quickly the zooplankton community structure and the cascading effects on phytoplankton recover to the unaffected state (i.e. resilience) once short-term predation by fish stops. The resilience has implications for the ecological quality and restoration measures in aquatic ecosystems. To assess the short-term zooplankton resilience against fish predation, we conducted a mesocosm experiment consisting of 10 enclosures, 6 with fish and 4 without fish. Plankton communities from a natural lake were used to establish phytoplankton and zooplankton in the mesocosms. High biomasses (about 20 g wet mass m-3) of juvenile planktivorous fish (perch, Perca fluviatilis) were allowed to feed on zooplankton in fish enclosures for four days. Thereafter, we removed fish and observed the recovery of the zooplankton community and its cascading effect on trophic interactions in comparison with no fish enclosures for four weeks. Short-term fish predation impaired resilience in zooplankton community by modifying community composition, as large zooplankton, such as calanoids, decreased just after fish predation and did not re-appear afterwards, whereas small cladocerans and rotifers proliferated. Total zooplankton biomass increased quickly within two weeks after fish removal, and at the end even exceeded the biomass measured before fish addition. Despite high biomass, the dominance of small zooplankton released phytoplankton from grazer control in fish enclosures. Accordingly, the zooplankton community did not recover from the effect of fish predation, indicating low short-term resilience. In contrast, in no fish enclosures without predation disturbance, a high zooplankton:phytoplankton biomass ratio accompanied by low phytoplankton yield (Chlorophyll-a:Total phosphorus ratio) reflected phytoplankton control by zooplankton over the experimental period. Comprehensive views on short and long-term resilience of zooplankton communities are essential for restoration and management strategies of aquatic ecosystems to better predict responses to global warming, such as higher densities of planktivorous fish.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Biomass
  • Ecosystem*
  • Food Chain
  • Perches / physiology*
  • Phytoplankton / growth & development*
  • Phytoplankton / physiology
  • Predatory Behavior
  • Zooplankton / growth & development*
  • Zooplankton / physiology

Grants and funding

This study was funded by “International Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB) Fellowship Programme‚ Freshwater Science” (https://www.igb-berlin.de/en/fellowship-programme) to ZE. ZE was further supported by Predoctoral Fellowship and International Research Stay Grant from UVic-UCC, and International Mobility Grant of Antiga Caxia Mannleu & BBVA Foundation. SB and TM were supported by the Deutsche Forschungsgemeinschaft (http://www.dfg.de/en/) (DFG, grant no. Me 1686/7-1). MB was supported by International Research Stay Grant from UVic-UCC. The publication of this article was funded by the Open Access Fund of the Leibniz Association and the Open Access Fund of the Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.