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Impaired growth and survival of tropical macroalgae (Sargassum spp.) at elevated temperatures

Citation

Graba-Landry, A and Loffler, Z and McClure, EC and Pratchett, MS and Hoey, AS, Impaired growth and survival of tropical macroalgae (Sargassum spp.) at elevated temperatures, Coral Reefs, 39 pp. 475-486. ISSN 0722-4028 (2020) [Refereed Article]


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DOI: doi:10.1007/s00338-020-01909-7

Abstract

Increasing ocean temperatures associated with ongoing climate change have resulted in regional reductions in the cover of live coral and increasing concerns that coral reefs will be overgrown by macroalgae. The likelihood of macroalgal overgrowth will, however, depend on the thermal sensitivities of the macroalgae themselves. We exposed recently settled propagules of the common canopy-forming macroalga Sargassum swartzii and adult thalli of three species of Sargassum (S. swatzii, S. cristaefolium, S. polycystum) to three experimental temperatures: ambient, + 2 C, and + 3.5 C, reflective of summer minimum, mean, and maximum temperatures for the region. Growth and survival of Sargassum swartzii propagules were assessed over 48 days, and the growth, physical toughness, elemental composition, and susceptibility to herbivory of adult thalli were assessed after short-term exposure (2-weeks) to experimental temperatures. Growth and survival of S. swartzii propagules were reduced by 43% and 84%, respectively, when cultured at the elevated (+ 3.5 C) temperature compared to ambient temperature. Similarly, elevated temperature resulted in a 1749% decline in the growth of adult Sargassum thalli relative to controls. Susceptability of S. swartzii and S. cristaefolium to herbivory (i.e. mass removed by herbivores) was 50% less for thalli cultured at elevated (+ 3.5 C) compared to ambient temperature, but this pattern was not related to changes in the physical or chemical properties of the thalli as a result of elevated temperature. The negative effects of elevated temperatures on the growth and survival of both Sargassum propagules and adult thalli will likely restrict the capacity of Sargassum, and potentially other macroalgae, to establish in new areas, and may also threaten the persistence of existing macroalgal meadows under future ocean temperatures. The thermal sensitivities of tropical Sargassum, together with those of corals, suggest ongoing ocean warming may lead to novel reef ecosystems that are low in both coral cover and macroalgal cover.

Item Details

Item Type:Refereed Article
Keywords:macroalgae, warming, coral reefs, phase shift, plant-herbivore interactions, propagules
Research Division:Environmental Sciences
Research Group:Climate change impacts and adaptation
Research Field:Ecological impacts of climate change and ecological adaptation
Objective Division:Environmental Policy, Climate Change and Natural Hazards
Objective Group:Adaptation to climate change
Objective Field:Ecosystem adaptation to climate change
UTAS Author:Graba-Landry, A (Dr Alexia Graba-Landry)
ID Code:147564
Year Published:2020
Web of Science® Times Cited:10
Deposited By:Sustainable Marine Research Collaboration
Deposited On:2021-11-08
Last Modified:2021-11-10
Downloads:0

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