26 Sep 2023
 | 26 Sep 2023
Status: this preprint is open for discussion.

Multifactorial effects of warming, low irradiance, and low salinity on Arctic kelps

Anaïs Lebrun, Cale Andrew Miller, Marc Meynadier, Steeve Comeau, Pierre Urrutti, Samir Alliouane, Robert Schlegel, Jean-Pierre Gattuso, and Frédéric Gazeau

Abstract. The Arctic is projected to warm by 2 to 5 °C by the end of the century. Warming causes melting of glaciers, shrinking of the areas covered by sea ice, and increased terrestrial runoff from snowfields and permafrost thawing. Warming, decreasing coastal underwater irradiance, and lower salinity are potentially threatening polar marine organisms, including kelps, that are key species of hard-bottom shallow communities. The present study investigates the physiological responses of four kelp species (Alaria esculenta, Laminaria digitata, Saccharina latissima, and Hedophyllum nigripes) to warming, low irradiance, and low salinity through a perturbation experiment conducted in ex situ mesocosms. Kelps were exposed during six weeks to four experimental treatments: an unmanipulated control, a warming condition mimicking future coastlines unimpacted by glacier melting under the CO2 emission scenario SSP5-8.5, and two multifactorial conditions combining warming, low salinity, and low irradiance reproducing the future coastal Arctic exposed to terrestrial runoff following two CO2 emission scenarios (SSP2-4.5 and SSP5-8.5). The physiological effects on A. esculenta, L. digitata and S. latissima were investigated and gene expression patterns of S. latissima and H. nigripes were analyzed. Specimens of A. esculenta increased their chlorophyll a content when exposed to low irradiance conditions, suggesting that they may be resilient to an increase in glacier and river runoff and become more dominant at greater depths. S. latissima showed a lower carbon:nitrogen (C:N) ratio at higher nitrate concentrations, suggesting coastal erosion and permafrost thawing could benefit the organism in the future Arctic. In contrast, L. digitata showed no responses to the conditions tested on any of the investigated physiological parameters. The gene expressions of H. nigripes and S. latissima underscores their ability and underline temperature as a key influencing factor. Based on these results, it is expected that kelp communities will undergo changes in species composition that will vary at local scale as a function of the changes in environmental drivers. For future research, potential cascading effects on the associated fauna and the whole ecosystem are important to anticipate the ecological, cultural, and economic impacts of climate change in the Arctic.

Anaïs Lebrun et al.

Status: open (until 06 Jan 2024)

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  • RC1: 'Comment on egusphere-2023-1875', Anonymous Referee #1, 03 Oct 2023 reply

Anaïs Lebrun et al.

Anaïs Lebrun et al.


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Short summary
We tested the effects of warming, low salinity, and low irradiance on Arctic kelps. We show that Alaria esculenta is adapted to low light conditions, which might explain why it is becoming dominant at depth. Saccharina latissima exhibited nitrogen limitation suggesting coastal erosion and permafrost thawing could benefit it. Laminaria digitata did not respond to the treatments. Gene expression of Hedophyllum nigripes and S. latissima indicated acclimation to the experimental treatments.