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A critical evaluation of coral Ba/Ca, Mn/Ca and Y/Ca ratios as indicators of terrestrial input: New data from the Great Barrier Reef, Australia

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dc.contributor Australian Inst Marine Sci
dc.contributor Res Sch Earth Sci
dc.contributor Australian Institute Of Marine Science
dc.contributor James Cook Univ
dc.contributor Catchment Reef Res Grp
dc.contributor Ctr Trop Water & Aquat Ecosyst Res Trop Water
dc.contributor Australian National University
dc.contributor Australian Natl Univ
dc.contributor James Cook University
dc.contributor Australian Res Council Ctr Excellence Coral Reef KINSLEY, LES LEWIS, STEPHEN E. LOUGH, JANICE M. MATSON, ERIC G. BAINBRIDGE, ZOE T. BRODIE, JON E. CANTIN, NEAL E. 2018-08-05T18:37:26Z 2018-08-05T18:37:26Z 2018-11-01T03:28:35Z 2018-08-05T18:37:26Z 2018-08-05T18:37:26Z 2018-11-01T03:28:35Z 2018-09-15
dc.identifier.citation Lewis SE, Lough JM, Cantin NE, Matson EG, Kinsley L, Bainbridge ZT, Brodie JE (2018) A critical evaluation of coral Ba/Ca, Mn/Ca and Y/Ca ratios as indicators of terrestrial input: New data from the Great Barrier Reef, Australia. GEOCHIMICA ET COSMOCHIMICA ACTA - vol 237 - pages 131-154
dc.identifier.issn 0016-7037
dc.description.abstract Coral trace element proxies of terrestrial runoff are widely applied to document and quantify historical changes in river discharge, constituent loads and land disturbance. However, some studies show poor replication between trace element records where cores from multiple coral colonies have been analyzed. Conflicting interpretations also exist on the environmental variable the coral trace element proxy is recording. Indeed, few studies have examined trace element behavior in the estuarine mixing zone that influence the coral records and only limited data on river discharge and constituent loads are available to validate the proxy records of terrestrial runoff. This study examined the behavior of Barium (Ba), Manganese (Mn) and Yttrium (Y) in the Burdekin River estuarine mixing zone, north-eastern Australia during several flood events and investigated the ability of coral Ba/Ca, Mn/Ca and Y/Ca ratios to record the variability of measured Burdekin River discharge and suspended sediment loads along a transect of replicate coral cores (10 cores from 5 locations). The results show limited evidence for Ba desorption from suspended sediments in the estuarine mixing zone while considerable desorption of Mn over a wide salinity mixing gradient was evident. Y showed evidence of removal in the initial mixing zone of the estuary (0-5 PSU) but displayed a relatively flat pattern thereafter indicating that it was not diluted by seawater mixing. The coral trace element records generally showed poor agreement within sites and the Ba/Ca ratios in some corals did not respond to regional river discharge, although coral luminescent lines were present in all cores and were significantly correlated with each other and Burdekin River discharge. While it was difficult to disentangle the influence of Burdekin River discharge and suspended sediment loads on the coral Ba/Ca proxy, several lines of evidence point towards discharge as the major contributor to this proxy in this region. A combination of factors likely influence the coral Ba/Ca ratio including an as yet undetermined physiological mechanism possibly related to crystallography or species, distance of the coral to the river mouth, variability in river discharge (including both annual totals and peaks, and local influences), variability in sediment load, the behavior of trace elements in the estuarine mixing zone, the hydrodynamics of flood plumes in the marine environment and the water depth of the coral. While the coral Mn/Ca and Y/Ca ratios did not respond to Burdekin River discharge events, the considerable desorption of Mn and the elevated Y throughout the estuarine mixing zone shows some promise in their ability to record long-term changes in suspended sediment loading and large terrestrial disturbances. Future studies examining coral records of terrestrial runoff should examine trace element behavior in the river estuarine mixing zone of influence, establish a correlation between the trace element and river discharge (such as luminescent lines) and demonstrate replication between different coral colonies. Crown Copyright (C) 2018 Published by Elsevier Ltd. All rights reserved.
dc.description.sponsorship We thank the crew of the R.V Cape Ferguson and Line Bay, Australian Institute of Marine Science for the collection of coral cores. Yi Hu and Shane Askew from the Advanced Analytical Centre, James Cook University analyzed the water samples and performed the scanning electron microscopy on the corals from Havannah Island, respectively. The water samples collected between 2007 and 2010 were collected with the support of the Australian Government's Marine and Tropical Sciences Research Facility grant awarded to JEB. We thank Katharina Fabricius, Michelle Devlin, Joelle Prange, Brett Baker, Paul Groves, Tom Coughlin, Jane Waterhouse, Alan Mitchell, Aaron Davis, Tom Stevens and Jessica Gorman for help in collecting some of the water samples. Benjamin Walther kindly provided his coral Ba/Ca record from Havannah Island. Dieter Tracey provided advice on figure construction. Emre Turak provided species identification and Tom Stevens and Cassandra Thompson took the photographs of the corals from Havannah Island. The coral cores were collected with support from the Australian Government's National Environmental Research Programme project led by Natalie Stoeckl and the cores were analyzed along with the 2016/ 17 water samples with support through funding from the Australian Government's National Environmental Science Programme, implemented in North Queensland by the Reef and Rainforest Research Centre Ltd. Additional funding was provided by the Queensland Government's Queensland Reef Water Quality Program. The coral cores were collected under Marine Parks Permit number G12/34943.1 from the Great Barrier Reef Marine Park Authority. We thank Daniel Sinclair and two anonymous reviewers for their constructive comments which greatly improved the manuscript.
dc.language English
dc.subject Flood Plume
dc.subject Sediment
dc.subject Trace-elements
dc.subject South China Sea
dc.subject Coral Geochemistry
dc.subject Porites Corals
dc.subject Geochemistry & Geophysics
dc.subject Spectral Luminescence
dc.subject Record
dc.subject Y/ca
dc.subject Burdekin River Catchment
dc.subject Ne Australia
dc.subject Fine Sediment
dc.subject Estuarine Mixing Zone
dc.subject Ba/ca
dc.subject Land-use Changes
dc.subject Mn/ca
dc.title A critical evaluation of coral Ba/Ca, Mn/Ca and Y/Ca ratios as indicators of terrestrial input: New data from the Great Barrier Reef, Australia
dc.type journal article
dc.identifier.doi 10.1016/j.gca.2018.06.017
dc.identifier.wos WOS:000439574400009

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