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Original Research ARTICLE Provisionally accepted The full-text will be published soon. Notify me

Front. Mar. Sci. | doi: 10.3389/fmars.2019.00516

Photophysiological responses of canopy-forming kelp species to short-term acute warming

 Heidi L. Burdett1, 2*, Honor Wright2 and  Dan A. Smale3
  • 1The Lyell Centre, United Kingdom
  • 2School of Energy, Geoscience, Infrastructure and Society, Heriot-Watt University, United Kingdom
  • 3Marine Biological Association of the United Kingdom, United Kingdom

The frequency of short-term oceanic warming events (‘marine heatwaves’ [MHWs] or heat spikes) has increased over the past century and is projected to further increase because of anthropogenic climate change. Given that marine organisms are strongly influenced by temperature, an increased occurrence of warming events could alter the structure of populations, communities and ecosystems. The distribution and ecophysiological performance of kelp species – globally important foundation species that play significant roles in nutrient cycling and habitat creation in temperate coastal systems – is particularly constrained by temperature. However, their photophysiological responses to warming events remains unclear, which hinders attempts to understand and predict the effects of ocean warming on kelp populations and the ecosystems they underpin. Here, we experimentally simulated a heat spike (+2°C and +4°C in magnitude, 3 days in duration, compared with ambient controls) and examined the photophysiological responses of two canopy-forming kelp species widely distributed across the northeast Atlantic - Laminaria digitata and L. hyperborea. Both species were resilient to the realistic warming treatments in terms of their photosynthetic characteristics. However, we found that L. digitata individuals, which were collected from populations found towards the upper limit of this species’ thermal range, exhibited increased oxygen production at higher temperatures, particularly after multiple days of exposure to the warming event. Laminaria digitata also exhibited a greater poise for dissipating excess energy through non-photochemical pathways. In contrast, L. hyperborea, which extends further south into warmer waters and tends to occupy deeper reefs that are almost constantly submerged, appeared to be photo-physiologically insensitive to the heat spike. This study enhances our mechanistic understanding of the photophysiological and photoprotective responses of kelps to short-term acute warming events – features which are likely to emerge as important drivers of ecological change in coming decades.

Keywords: Kelp, photophysiology, PAM fluorescence, Marine heatwave, Laminaria digitata, Laminaria hyperborea, macroalgae

Received: 15 Feb 2019; Accepted: 06 Aug 2019.

Edited by:

Ke Chen, Woods Hole Oceanographic Institution, United States

Reviewed by:

Mariana Mayer Pinto, University of New South Wales, Australia
Danielle Denley, Dalhousie University, Canada  

Copyright: © 2019 Burdett, Wright and Smale. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Heidi L. Burdett, The Lyell Centre, Edinburgh, United Kingdom, h.burdett@hw.ac.uk