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

Wilken, Susanne; Soares, Margarida LU ; Urrutia-Cordero, Pablo LU ; Ratcovich, Jens; Ekvall, Mattias K. LU ; Van Donk, Ellen and Hansson, Lars Anders LU (2018) In Limnology and Oceanography 63. p.142-155
Abstract

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,... (More)

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.

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author
organization
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type
Contribution to journal
publication status
published
subject
in
Limnology and Oceanography
volume
63
pages
14 pages
publisher
ASLO
external identifiers
  • scopus:85043462849
ISSN
1939-5590
DOI
10.1002/lno.10728
language
English
LU publication?
yes
id
1f899d30-e387-4a39-b5a0-158e1db17191
date added to LUP
2018-03-20 13:18:35
date last changed
2019-08-14 04:12:35
@article{1f899d30-e387-4a39-b5a0-158e1db17191,
  abstract     = {<p>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.</p>},
  author       = {Wilken, Susanne and Soares, Margarida and Urrutia-Cordero, Pablo and Ratcovich, Jens and Ekvall, Mattias K. and Van Donk, Ellen and Hansson, Lars Anders},
  issn         = {1939-5590},
  language     = {eng},
  month        = {03},
  pages        = {142--155},
  publisher    = {ASLO},
  series       = {Limnology and Oceanography},
  title        = {Primary producers or consumers? Increasing phytoplankton bacterivory along a gradient of lake warming and browning},
  url          = {http://dx.doi.org/10.1002/lno.10728},
  volume       = {63},
  year         = {2018},
}