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Summer primary production of Arctic kelp communities is more affected by duration than magnitude of simulated marine heatwaves
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  • Cale Miller,
  • Frédéric Gazeau,
  • Anaïs Lebrun,
  • Samir Alliouane,
  • Pierre Urrutti,
  • Robert Schlegel,
  • Jean-Pierre Gattuso,
  • Steeve Comeau
Cale Miller
Utrecht University

Corresponding Author:[email protected]

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Frédéric Gazeau
CNRS
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Anaïs Lebrun
Sorbonne Universite
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Samir Alliouane
CNRS
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Pierre Urrutti
Sorbonne Universite
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Robert Schlegel
Sorbonne Universite
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Jean-Pierre Gattuso
CNRS
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Steeve Comeau
CNRS
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Abstract

Fjord systems in the Norwegian Arctic are experiencing an increasing frequency and magnitude of marine heatwaves. These episodic heat stress events can have varying degrees of acute impacts on primary production and nutrient uptake of mixed kelp communities, as well as modifying the biogeochemical cycling in nearshore systems where vast areas of kelp create structural habitat. To assess the impact of future marine heatwaves on kelp communities, we conducted a 23 d mesocosm experiment exposing mixed kelp communities to warming and heatwave scenarios projected for the year 2100. Three treatments were considered: a constant warming (+1.8C from the control), a medium magnitude and long duration heatwave event (+2.8C from the control for 13 d), and two short-term, more intense, heatwaves (5 d long scenarios with peaks at +3.9C from the control). The results show that both marine heatwave treatments reduced net community production whereas the constant warm temperature treatment displayed no difference from the control. The long marine heatwave scenario resulted in reduced accumulated net community production, indicating that prolonged exposure had a greater severity than two high magnitude, short-term heatwave events. We estimated an 11C temperature threshold at which negative effects to primary production appeared present. We highlight that marine heatwaves can induce sublethal effects on kelp communities by depressing net community production. These results are placed in the context of potential physiological resilience of kelp communities and implications of reduced net community production to future Arctic fjord environmental conditions.
Submitted to Ecology and Evolution
11 Jun 2024Submission Checks Completed
11 Jun 2024Assigned to Editor
11 Jul 2024Review(s) Completed, Editorial Evaluation Pending
11 Jul 2024Editorial Decision: Revise Minor
31 Jul 20241st Revision Received
01 Aug 2024Submission Checks Completed
01 Aug 2024Assigned to Editor
01 Aug 2024Review(s) Completed, Editorial Evaluation Pending
01 Aug 2024Editorial Decision: Accept