Too Hot to Handle: Unprecedented Seagrass Death Driven by Marine Heatwave in a World Heritage Area

Authors

Simone Strydom, Australia Department of Biodiversity, Conservation and Attractions; Edith Cowan University - Joondalup, Australia
Kathy Murray, Australia Department of Biodiversity, Conservation and Attractions
Shaun Wilson, Australia Department of Biodiversity, Conservation and Attractions; The University of Western Australia
Bart Huntley, Australia Department of Biodiversity, Conservation and Attractions
Michael Rule, Australia Department of Biodiversity, Conservation and Attractions
Michael Heithaus, Florida International University
Cindy Bessey, Florida International University
Gary A. Kendrick, The University of Western Australia
Derek Burkholder, Nova Southeastern UniversityFollow
Thomas Holmes, Australia Department of Biodiversity, Conservation and Attractions
Matthew W. Fraser, The University of Western Australia
Katherine Zdunic, Australia Department of Biodiversity, Conservation and Attractions

Document Type

Article

Publication Title

Global Change Biology

ISSN

1354-1013

Publication Date

3-4-2020

Keywords

Habitat map, Marine heatwave, Seagrass, Seascape, Seawater temperature, Shark Bay, World Heritage Area

Abstract

The increased occurrence of extreme climate events, such as marine heatwaves (MHWs), has resulted in substantial ecological impacts worldwide. To date metrics of thermal stress within marine systems have focussed on coral communities, and less is known about measuring stress relevant to other primary producers, such as seagrasses. An extreme MHW occurred across the Western Australian coastline in the austral summer of 2010/2011, exposing marine communities to summer seawater temperatures 2‐5 °C warmer than average. Using a combination of satellite imagery and in situ assessments, we provide detailed maps of seagrass coverage across the entire Shark Bay World Heritage Area (ca. 13,000 km²) before (2002, 2010) and after the MHW (2014, 2016). Our temporal analysis of these maps documents the single largest loss in dense seagrass extent globally (1,310 km²) following an acute disturbance. Total change in seagrass extent was spatially heterogenous, with the most extensive declines occurring in the Western Gulf, Wooramel Bank and Faure Sill. Spatial variation in seagrass loss was best explained by a model that included an interaction between two heat stress metrics, the most substantial loss occurring when degree heat weeks (DHWm) was ≥ 10 and the number of days exposed to extreme sea surface temperature during the MHW (DaysOver) was ≥ 94. Ground‐truthing at 622 points indicated that change in seagrass cover was predominantly due to loss of Amphibolis antarctica rather than Posidonia australis, the other prominent seagrass at Shark Bay. As seawater temperatures continue to rise and the incidence of MHWs increase globally, this work will provide a basis for identifying areas of meadow degradation, or stability and recovery; and potential areas of resilience.

DOI

10.1111/gcb.15065

First Page

1

Last Page

34

Comments

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NSUWorks Citation

Simone Strydom, Kathy Murray, Shaun Wilson, Bart Huntley, Michael Rule, Michael Heithaus, Cindy Bessey, Gary A. Kendrick, Derek Burkholder, Thomas Holmes, Matthew W. Fraser, and Katherine Zdunic. 2020. Too Hot to Handle: Unprecedented Seagrass Death Driven by Marine Heatwave in a World Heritage Area .Global Change Biology : 1 -34. https://nsuworks.nova.edu/occ_facarticles/1071.