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Primary producers or consumers? Increasing phytoplankton bacterivory along a gradient of lake warming and browning

Author:
  • Susanne Wilken
  • Margarida Soares
  • Pablo Urrutia-Cordero
  • Jens Ratcovich
  • Mattias K. Ekvall
  • Ellen Van Donk
  • Lars Anders Hansson
Publishing year: 2018-03-01
Language: English
Pages: 142-155
Publication/Series: Limnology and Oceanography
Volume: 63
Document type: Journal article
Publisher: ASLO

Abstract english

Eukaryotic phytoplankton form the basis of aquatic food webs and play a key role in the global carbon cycle. Many of these evolutionarily diverse microalgae are also capable of feeding on other microbes, and hence simultaneously act both as primary producers and consumers. The net ecosystem impact of such mixotrophs depends on their nutritional strategy which is likely to alter with environmental change. Many temperate lakes are currently warming at unprecedented rates and are simultaneously increasing in water color (browning) due to increased run-off of humic substances. We hypothesized that the resulting reduction in light intensity and increased bacterial abundances would favor mixotrophic phytoplankton over obligate autotrophs, while higher temperatures might boost their rates of bacterivory. We tested these hypotheses in a mesocosm experiment simulating a gradient of increasing temperature and water color in temperate shallow lakes as expected to occur over the coming century. Mixotrophs showed a faster increase in abundance under the climate change scenario during spring, when they dominated the phytoplankton community. Furthermore, both bacterial abundances and rates of phytoplankton bacterivory increased under future climate conditions. Bacterivory contributed significantly to phytoplankton resource acquisition under future climate conditions, while remaining negligible throughout most of the season in treatments resembling today's conditions. Hence, to our knowledge, we here provide the first evidence for an increasing importance of bacterivory by phytoplankton in future temperate shallow lakes. Such a change in phytoplankton nutritional strategies will likely impact biogeochemical cycles and highlights the need to conceptually integrate mixotrophy into current ecosystem models.

Keywords

  • Oceanography, Hydrology, Water Resources

Other

Published
  • Microbial Ecology
  • ISSN: 1939-5590
Lars-Anders Hansson
E-mail: lars-anders [dot] hansson [at] biol [dot] lu [dot] se

Professor

Aquatic ecology

+46 46 222 41 69

E-C140

50

Professor

NanoLund

14

Research group

Aquatic Ecology

Other projects I´m involved in

Doctoral students and postdocs

PhD students, main supervisor

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