A validation of coral geochemical records to reconstruct suspended sediment loads to the Great Barrier Reef lagoon

Stephen Lewis 100dpi
Led by: Dr Stephen Lewis, JCU


Project Summary

While coral geochemistry records are widely cited as evidence for increased suspended sediment loads delivered to the Great Barrier Reef since the 1850s, there has been little replication or quantification of the records. Indeed, most records are based on cores collected prior to the year 2000 when limited catchment monitoring data existed to ‘validate’ the interpretations that certain trace element ratios provided proxies of annual sediment loadings. This project will analyse the geochemistry of coral cores collected in 2012 from sites in the central GBR and compare the ratios to measured sediment and particulate nutrient loads from the Burdekin River.

Problem Statements


While previous studies have speculated that the Ba/Ca, Y/Ca and Mn/Ca ratios in corals are related to land use change and sediment loading from adjacent river catchments (e.g. McCulloch et al., 2003; Lewis et al., 2007), this would be the first study to directly examine the link between these trace element ratios in corals and measured sediment and particulate nutrient loads from the Burdekin River. If a correlation can be established, this novel, independent technique can be used to quantify pre- and post- European suspended sediment loads to the GBR.

How Research Addresses Problem

The outputs of the study will allow the changes in sediment loads to be better quantified and hence help inform the setting of water quality targets within the GBR Water Quality Protection Plan and help calibrate Source Catchments Modelling of pollutants exported to the GBR. For example, it appears that suspended sediment loads from the Burdekin River increased considerably following the stocking of the catchment with sheep and cattle in the late 1800s and early 1900s (Lewis et al., 2007), although the construction of the Burdekin Falls Dam in 1987 now traps a large amount of the sediment (~ 70%) delivered from the upper catchment area (Lewis et al., 2012).

Project Keywords

Sediment loads; Anthropogenic load; Particulate nutrients; Coral geochemistry; Ba/ca ratio.

Project Funding

This project is jointly funded through JCU, AIMS and the Australian Government’s National Environmental Science Programme.

Project Publications
NESP TWQ Project 1.3 Final Report
Final Report