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Phytoplankton diversity loss along a gradient of future warming and brownification in freshwater mesocosms

Urrutia-Cordero, Pablo LU ; Ekvall, Mattias K. LU ; Ratcovich, Jens; Soares, Margarida LU ; Wilken, Susanne; Zhang, Huan LU and Hansson, Lars Anders LU (2017) In Freshwater Biology 62(11). p.1869-1878
Abstract

Globally, freshwater ecosystems are warming at unprecedented rates and northern temperate lakes are simultaneously experiencing increased runoff of humic substances (brownification), with little known consequences for future conservation of biodiversity and ecosystem functioning. We employed an outdoor mesocosm experiment during spring and summer to investigate the combined effects of gradually increasing warming and brownification perturbations on the phytoplankton community structure (biodiversity and composition) and functioning (biomass). While we did not observe overall significant treatment effects on total phytoplankton biomasses, we show that predicted increases in warming and brownification can reduce biodiversity considerably,... (More)

Globally, freshwater ecosystems are warming at unprecedented rates and northern temperate lakes are simultaneously experiencing increased runoff of humic substances (brownification), with little known consequences for future conservation of biodiversity and ecosystem functioning. We employed an outdoor mesocosm experiment during spring and summer to investigate the combined effects of gradually increasing warming and brownification perturbations on the phytoplankton community structure (biodiversity and composition) and functioning (biomass). While we did not observe overall significant treatment effects on total phytoplankton biomasses, we show that predicted increases in warming and brownification can reduce biodiversity considerably, occasionally up to 90% of Shannon diversity estimates. Our results demonstrate that the loss of biodiversity is driven by the dominance of mixotrophic algae (Dinobryon and Cryptomonas), whereas several other phytoplankton taxa may be temporarily displaced from the community, including Cyclotella, Desmodesmus, Monoraphidium, Tetraedron, Nitzschia and Golenkinia. The observed loss of biodiversity coincided with an increase in bacterial production providing resources for potential mixotrophs along the gradient of warming and brownification. This coupling between bacterial production and mixotrophs was likely a major cause behind the competitive displacement of obligate phototrophs and supports evidence for the importance of consumer–prey dynamics in shaping environmental impacts on phytoplankton communities. We conclude that warming and brownification are likely to cause a profound loss of biodiversity by indirectly affecting competitive interactions among phytoplankton taxa. Importantly, our results did not show an abrupt loss of biodiversity; instead the reduction in taxa richness levelled off after exceeding a threshold of warming and brownification. These results exemplify the complex nonlinear responses of biodiversity to environmental perturbations and provide further insights for predicting biodiversity patterns to the future warming and brownification of freshwaters.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
biodiversity, climate change, food webs, mesocosms, phytoplankton
in
Freshwater Biology
volume
62
issue
11
pages
10 pages
publisher
Wiley-Blackwell
external identifiers
  • scopus:85031501258
  • wos:000412992700006
ISSN
0046-5070
DOI
10.1111/fwb.13027
language
English
LU publication?
yes
id
b46ec0a8-0205-4a8d-80af-d8bf1510b851
date added to LUP
2017-10-26 07:53:59
date last changed
2018-01-16 13:24:13
@article{b46ec0a8-0205-4a8d-80af-d8bf1510b851,
  abstract     = {<p>Globally, freshwater ecosystems are warming at unprecedented rates and northern temperate lakes are simultaneously experiencing increased runoff of humic substances (brownification), with little known consequences for future conservation of biodiversity and ecosystem functioning. We employed an outdoor mesocosm experiment during spring and summer to investigate the combined effects of gradually increasing warming and brownification perturbations on the phytoplankton community structure (biodiversity and composition) and functioning (biomass). While we did not observe overall significant treatment effects on total phytoplankton biomasses, we show that predicted increases in warming and brownification can reduce biodiversity considerably, occasionally up to 90% of Shannon diversity estimates. Our results demonstrate that the loss of biodiversity is driven by the dominance of mixotrophic algae (Dinobryon and Cryptomonas), whereas several other phytoplankton taxa may be temporarily displaced from the community, including Cyclotella, Desmodesmus, Monoraphidium, Tetraedron, Nitzschia and Golenkinia. The observed loss of biodiversity coincided with an increase in bacterial production providing resources for potential mixotrophs along the gradient of warming and brownification. This coupling between bacterial production and mixotrophs was likely a major cause behind the competitive displacement of obligate phototrophs and supports evidence for the importance of consumer–prey dynamics in shaping environmental impacts on phytoplankton communities. We conclude that warming and brownification are likely to cause a profound loss of biodiversity by indirectly affecting competitive interactions among phytoplankton taxa. Importantly, our results did not show an abrupt loss of biodiversity; instead the reduction in taxa richness levelled off after exceeding a threshold of warming and brownification. These results exemplify the complex nonlinear responses of biodiversity to environmental perturbations and provide further insights for predicting biodiversity patterns to the future warming and brownification of freshwaters.</p>},
  author       = {Urrutia-Cordero, Pablo and Ekvall, Mattias K. and Ratcovich, Jens and Soares, Margarida and Wilken, Susanne and Zhang, Huan and Hansson, Lars Anders},
  issn         = {0046-5070},
  keyword      = {biodiversity,climate change,food webs,mesocosms,phytoplankton},
  language     = {eng},
  month        = {11},
  number       = {11},
  pages        = {1869--1878},
  publisher    = {Wiley-Blackwell},
  series       = {Freshwater Biology},
  title        = {Phytoplankton diversity loss along a gradient of future warming and brownification in freshwater mesocosms},
  url          = {http://dx.doi.org/10.1111/fwb.13027},
  volume       = {62},
  year         = {2017},
}