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Optimising reef-scale CO2 removal by seaweed to buffer ocean acidification

Citation

Mongin, M and Baird, ME and Hadley, S and Lenton, A, Optimising reef-scale CO2 removal by seaweed to buffer ocean acidification, Environmental Research Letters, 11, (3) Article 034023. ISSN 1748-9326 (2016) [Refereed Article]


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Copyright Statement

2016 IOP Publishing Ltd. Licensed under Creative Commons Attribution 3.0 Unported (CC BY 3.0) http://creativecommons.org/licenses/by/3.0/

DOI: doi:10.1088/1748-9326/11/3/034023

Abstract

The equilibration of rising atmospheric CO2 with the ocean is lowering pH in tropical waters by about 0.01 every decade. Coral reefs and the ecosystems they support are regarded as one of the most vulnerable ecosystems to ocean acidification, threatening their long-term viability. In response to this threat, different strategies for buffering the impact of ocean acidification have been proposed. As the pH experienced by individual corals on a natural reef system depends on many processes over different time scales, the efficacy of these buffering strategies remains largely unknown. Here we assess the feasibility and potential efficacy of a reef-scale (a few kilometers) carbon removal strategy, through the addition of seaweed (fleshy multicellular algae) farms within the Great Barrier Reef at the Heron Island reef. First, using diagnostic time-dependent age tracers in a hydrodynamic model, we determine the optimal location and size of the seaweed farm. Secondly, we analytically calculate the optimal density of the seaweed and harvesting strategy, finding, for the seaweed growth parameters used, a biomass of 42gNm-2 with a harvesting rate of up 3.2gNm-2 d-1 maximises the carbon sequestration and removal. Numerical experiments show that an optimally located 1.9km2 farm and optimally harvested seaweed (removing biomass above 42gNm-2 every 7d) increased aragonite saturation by 0.1 over 24km2 of the Heron Island reef. Thus, the most effective seaweed farm can only delay the impacts of global ocean acidification at the reef scale by 7-21 years, depending on future global carbon emissions. Our results highlight that only a kilometer-scale farm can partially mitigate global ocean acidification for a particular reef.

Item Details

Item Type:Refereed Article
Keywords:ocean acidification, Great Barrier Reef, carbonate chemistry, marine management, coral reef
Research Division:Earth Sciences
Research Group:Oceanography
Research Field:Chemical Oceanography
Objective Division:Environment
Objective Group:Climate and Climate Change
Objective Field:Climate Change Mitigation Strategies
UTAS Author:Mongin, M (Mr Mathieu Mongin)
UTAS Author:Hadley, S (Mr Scott Hadley)
UTAS Author:Lenton, A (Dr Andrew Lenton)
ID Code:118105
Year Published:2016
Web of Science® Times Cited:10
Deposited By:Directorate
Deposited On:2017-07-04
Last Modified:2017-11-01
Downloads:83 View Download Statistics

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