NOAA/WDS Paleoclimatology - Mackay-region, Great Barrier Reef, Porites spp. rare earth element and yttrium concentrations from select years 1950-2002 CE

Rare earth element and yttrium (REY) concentrations were measured from two nearshore Porites sp. corals collected from Round Top Is. and Keswick Is., at 5 km and 32 km offshore from Mackay, Queensland, on the southern Great Barrier Reef, Australia. The REY patterns from the Round Top coral differed from the Keswick coral in 5 respects: (1) greater REY concentrations; (2) preferentially enriched light rare earth elements (LREEs); (3) reduced slope across the heavy rare earth elements (HREEs); (4) more negative cerium (Ce) anomaly; and (5) lower yttrium (Y) to holmium (Ho) ratios. These patterns suggest greater terrestrial exposure and higher biological productivity at Round Top Is. Total abundance of REY in both corals increased over time between 1950 and 2002. The rate of increase at Round Top Is. was 3-fold greater than at Keswick Is., thus the innermost site was likely more influenced by weathering from rapid agricultural expansion in the adjacent Pioneer River catchment. The Y/Ho ratio decreased over time in both corals, but as the coral values were substantially higher than ambient seawater, more research is suggested to identify the cause.