Light thresholds to prevent dredging impacts on the great barrier reef seagrass, Zostera muelleri ssp. capricorni

Chartrand, KM; Bryant, CV; Carter, AB; Ralph, PJ; Rasheed, MA

Light thresholds to prevent dredging impacts on the great barrier reef seagrass, Zostera muelleri ssp. capricorni

Chartrand, KM

Bryant, CV Carter, AB Ralph, PJ

Rasheed, MA

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Publication Type:: Journal Article
Citation:: Frontiers in Marine Science, 2016, 3 (JUL)
Issue Date:: 2016-01-01

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Field	Value	Language
dc.contributor.author	Chartrand, KM https://orcid.org/0000-0002-0030-961X	en_US
dc.contributor.author	Bryant, CV	en_US
dc.contributor.author	Carter, AB	en_US
dc.contributor.author	Ralph, PJ https://orcid.org/0000-0002-3103-7346	en_US
dc.contributor.author	Rasheed, MA	en_US
dc.date.issued	2016-01-01	en_US
dc.identifier.citation	Frontiers in Marine Science, 2016, 3 (JUL)	en_US
dc.identifier.uri	http://hdl.handle.net/10453/116728
dc.description.abstract	© 2016 Chartrand, Bryant, Carter, Ralph and Rasheed. Coastal seagrass habitats are at risk from a range of anthropogenic activities that modify the natural light environment, including dredging activities associated with coastal and port developments. On Australia's east coast, the tropical seagrass Zostera muelleri ssp. capricorni dominates intertidal mudbanks in sheltered embayments which are also preferred locations for harbors and port facilities. Dredging to establish and maintain shipping channels in these areas can degrade water quality and diminish light conditions that are required for seagrass growth. Based on this potential conflict, we simulated in-situ light attenuation events to measure effects on Z. muelleri ssp. capricorni condition. Semi-annual in situ shading studies conducted over 3 years were used to quantify the impact of prolonged light reduction on seagrass morphometrics (biomass, percent cover, and shoot density). Experimental manipulations were complimented with an assessment of 46 months of light history and concurrent natural seagrass change at the study site in Gladstone Harbour. There was a clear light-dependent effect on seagrass morphometrics during seagrass growing seasons, but no effect during senescent periods. Significant seagrass declines occurred between 4 and 8 weeks after shading during the growing seasons with light maintained in the range of 4-5 mol photons m-2 d-1. Sensitivity to shading declined when applied in 2-week intervals (fortnightly) rather than continuous over the same period. Field observations were correlated to manipulative experiments to derive an applied threshold of 6 mol photons m-2 d-1 which formed the basis of a reactive light-based management strategy which has been successfully implemented to ensure positive ecological outcomes for seagrass during a large-scale dredging program.	en_US
dc.relation	http://purl.org/au-research/grants/arc/LP110200454
dc.relation.ispartof	Frontiers in Marine Science	en_US
dc.relation.isbasedon	10.3389/fmars.2016.00106	en_US
dc.title	Light thresholds to prevent dredging impacts on the great barrier reef seagrass, Zostera muelleri ssp. capricorni	en_US
dc.type	Journal Article
utslib.citation.volume	JUL	en_US
utslib.citation.volume	3	en_US
utslib.for	0602 Ecology	en_US
utslib.for	060705 Plant Physiology	en_US
utslib.for	0405 Oceanography	en_US
pubs.embargo.period	Not known	en_US
pubs.organisational-group	/University of Technology Sydney
pubs.organisational-group	/University of Technology Sydney/Faculty of Science
pubs.organisational-group	/University of Technology Sydney/Strength - C3 - Climate Change Cluster
pubs.organisational-group	/University of Technology Sydney/Students
utslib.copyright.status	open_access
pubs.issue	JUL	en_US
pubs.publication-status	Published	en_US
pubs.volume	3	en_US

Abstract:

© 2016 Chartrand, Bryant, Carter, Ralph and Rasheed. Coastal seagrass habitats are at risk from a range of anthropogenic activities that modify the natural light environment, including dredging activities associated with coastal and port developments. On Australia's east coast, the tropical seagrass Zostera muelleri ssp. capricorni dominates intertidal mudbanks in sheltered embayments which are also preferred locations for harbors and port facilities. Dredging to establish and maintain shipping channels in these areas can degrade water quality and diminish light conditions that are required for seagrass growth. Based on this potential conflict, we simulated in-situ light attenuation events to measure effects on Z. muelleri ssp. capricorni condition. Semi-annual in situ shading studies conducted over 3 years were used to quantify the impact of prolonged light reduction on seagrass morphometrics (biomass, percent cover, and shoot density). Experimental manipulations were complimented with an assessment of 46 months of light history and concurrent natural seagrass change at the study site in Gladstone Harbour. There was a clear light-dependent effect on seagrass morphometrics during seagrass growing seasons, but no effect during senescent periods. Significant seagrass declines occurred between 4 and 8 weeks after shading during the growing seasons with light maintained in the range of 4-5 mol photons m-2 d-1. Sensitivity to shading declined when applied in 2-week intervals (fortnightly) rather than continuous over the same period. Field observations were correlated to manipulative experiments to derive an applied threshold of 6 mol photons m-2 d-1 which formed the basis of a reactive light-based management strategy which has been successfully implemented to ensure positive ecological outcomes for seagrass during a large-scale dredging program.

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http://hdl.handle.net/10453/116728