High resolution geochemical analysis of massive Porites spp. corals from the Wet Tropics, Great Barrier Reef: rare earth elements, yttrium and barium as indicators of terrigenous input

Abstract

Abstract Catchment modification and increased sediment loads in coastal regions are impacting many of the world's coral reefs, yet relevant water quality data are limited by the availability of instrumental records. Massive Porites spp. corals offer the potential to reconstruct water quality by use of the geochemical proxies that are incorporated into their skeleton. Here we present ∼ monthly resolved rare earth element (REE), yttrium (Y) and barium/calcium (Ba/Ca) concentrations obtained from four Porites corals collected across a known water quality gradient from the Great Barrier Reef, Australia. Sub-annual REE time series patterns were comparable among corals despite having significantly different concentrations. Whilst Ba/Ca did not reflect the known water quality gradient of the region, Y/holmium ratios reflected broad cross shelf water quality gradients and REE concentrations reflected local scale variance in water quality. This study demonstrates that REE analysis of Porites corals offers great potential for assessing changes in water quality in reef environments.