Satellite-derived photic depth on the Great Barrier Reef: spatio-temporal patterns of water clarity

Weeks, Scarla, Werdell, P. Jeremy, Schaffelke, Britta, Canto, Marites, Lee, Zhongping, Wilding, John G. and Feldman, Gene C. (2012) Satellite-derived photic depth on the Great Barrier Reef: spatio-temporal patterns of water clarity. Remote Sensing, 4 12: 3781-3795. doi:10.3390/rs4123781

Author Weeks, Scarla
Werdell, P. Jeremy
Schaffelke, Britta
Canto, Marites
Lee, Zhongping
Wilding, John G.
Feldman, Gene C.
Total Author Count Override 7
Title Satellite-derived photic depth on the Great Barrier Reef: spatio-temporal patterns of water clarity
Journal name Remote Sensing   Check publisher's open access policy
ISSN 2072-4292
Publication date 2012-12
Sub-type Article (original research)
DOI 10.3390/rs4123781
Open Access Status DOI
Volume 4
Issue 12
Start page 3781
End page 3795
Total pages 15
Place of publication Basel, Switzerland
Publisher M D P I AG
Collection year 2013
Language eng
Formatted abstract
Detecting changes to the transparency of the water column is critical for understanding the responses of marine organisms, such as corals, to light availability. Long-term patterns in water transparency determine geographical and depth distributions, while acute reductions cause short-term stress, potentially mortality and may increase the organisms’ vulnerability to other environmental stressors. Here, we investigated the optimal, operational algorithm for light attenuation through the water column across the scale of the Great Barrier Reef (GBR), Australia. We implemented and tested a quasi-analytical algorithm to determine the photic depth in GBR waters and matched regional Secchi depth (ZSD) data to MODIS-Aqua (2002–2010) and SeaWiFS (1997–2010) satellite data. The results of the in situ ZSD/satellite data matchup showed a simple bias offset between the in situ and satellite retrievals. Using a Type II linear regression of log-transformed satellite and in situ data, we estimated ZSD and implemented the validated ZSD algorithm to generate a decadal satellite time series (2002–2012) for the GBR. Water clarity varied significantly in space and time. Seasonal effects were distinct, with lower values during the austral summer, most likely due to river runoff and increased vertical mixing, and a decline in water clarity between 2008–2012, reflecting a prevailing La Niña weather pattern. The decline in water clarity was most pronounced in the inshore area, where a significant decrease in mean inner shelf ZSD of 2.1 m (from 8.3 m to 6.2 m) occurred over the decade. Empirical Orthogonal Function Analysis determined the dominance of Mode 1 (51.3%), with the greatest variation in water clarity along the mid-shelf, reflecting the strong influence of oceanic intrusions on the spatio-temporal patterns of water clarity. The newly developed photic depth product has many potential applications for the GBR from water quality monitoring to analyses of ecosystem responses to changes in water clarity.
Keyword Water clarity
Photic depth
Secchi depth
Great Barrier Reef
Spatio-temporal patterns
Biophysical processes
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Geography, Planning and Environmental Management Publications
Official 2013 Collection
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Citation counts: TR Web of Science Citation Count  Cited 18 times in Thomson Reuters Web of Science Article | Citations
Scopus Citation Count Cited 18 times in Scopus Article | Citations
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