Evaluating the use of the massive coral Diploastrea heliopora for paleoclimate reconstruction

To date, coral‐based paleoclimate research in the Pacific has primarily utilized core samples from the genus Porites and has been most successful reconstructing past variability on interannual timescales, particularly the El Niño Southern Oscillation (ENSO). The Indo‐Pacific coral genus Diploastrea, however, owing to its slower extension rate, denser structure, and longer lifespan, can potentially preserve geochemical proxy records 2–3 times longer than Porites cores of the same length. Before its potential can be realized, Diploastrea must first be calibrated and its climate signal assessed. We present oxygen isotope (δ18O) and Sr/Ca results from two Diploastrea cores collected in Fiji (16°49′S, 179°14′E) that allow for simultaneous evaluation of this coral's paleoclimatic utility and the reproducibility of each tracer at this site. Comparison to a Porites record from the same location allows for further evaluation of Diploastrea as a paleoclimatic archive. We demonstrate that Diploastrea's septal and columellar material yield similar δ18O‐SST relationships and that despite some sacrifice of the seasonal δ18O amplitude, bulk sampling of either region is satisfactory for resolving interannual and lower frequency modes of climatic variability. Therefore paleoclimate reconstructions employing either a septal or columellar sampling regime of this genus may be useful at filling in spatial and temporal sampling gaps which currently hinder the reconstruction of long‐term changes in major climate fields in the western Pacific.