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

Abstract

[1] 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 (d 18 O) and Sr/Ca results from two Diploastrea cores collected in Fiji (16°49 0 S, 179°14 0 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 d 18 O-SST relationships and that despite some sacrifice of the seasonal d 18 O 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.

Geochemistry-based coral palaeoclimate studies and the potential of ‘non-traditional’ (non-massive Porites) corals: Recent developments and future progression

“…However, in situ monitoring programs are expensive to set up and maintain (Castillo and Lima, 2010), with limited loggers available in coral reef environments. In light of this, gridded SST datasets acquired by satellites (Castillo and Lima, 2010), or optimally interpolated datasets combining both satellite and in situ observations (Reynolds and Smith, 1994;Reynolds et al, 2002) are commonly used in the calibration processes (e.g., Bagnato et al, 2004;Gallup et al, 2006;Hetzinger et al, 2006;Wu et al, 2013). Satellite derived datasets are cheaper to acquire, and provide a larger spatial representation of SST that can be beneficial to large scale palaeoclimate reconstructions.…”

“…This offset represents a significant difference between satellite measured sea 'skin' temperature and that of the upper water column where corals reefs grow. (Reynaud-Vaganay et al, 1999); 2 Diploastrea heliopora septa (Bagnato et al, 2004); 3 Diploastrea heliopora columella (Bagnato et al, 2004); 4 Diploria strigosa (Hetzinger et al, 2006); 5 Montastrea faveolata (DeLong et al, 2011); 6 Montastrea faveolata (Smith et al, 2006); 7 Porites lutea (Yu et al, 2005b); 8 Porites lutea (Gagan et al, 1998); 9 Siderastrea siderea (Maupin et al, 2008); 10 Siderastrea siderea (DeLong et al, 2011); 11 Stylophora pistillata (Reynaud-Vaganay et al, 1999). B) Sr/Ca signatures.…”

SPCZ migration and ENSO events during the 20th century as revealed by climate proxies from a Fiji coral

“…In contrast, the Sr/Ca (a commonly used SST proxy measured in corals [Gagan et al, 2000]) from other Fiji coral cores (Porites and Diploastrea spp) is not always linearly related to SST at inter-annual time scales Bagnato et al, 2004]. While SST and SSS fluctuations were not clearly separated, Porites d 18 O and Sr/Ca records were in good agreement with records of a Disploastrea coral [Bagnato et al, 2004], the coral d 18 O matching well with the Pacific Decadal Oscillation Index, based on SST variations in the North Pacific . It suggests that classical linear regressions cannot be applied to Fiji coral climate proxies because interdecadal changes in Sr/Ca are likely affected by other factors than SST.…”

Reconstruction of the East China Sea palaeoenvironment at 16 ka by comparison of fossil and modern Faviidae corals from the Ryukyus, southwestern Japan

“…Moreover, corals may record the ambient environment with an annual, seasonal or even finer time resolution, whereas other palaeoceanographic recorders such as planktonic foraminiferal assemblages generally do not produce records with similar time resolution. Porites, a genus of massive corals, is most commonly used in palaeoceanographic studies, but other genera (Watanabe et al, 2003;Bagnato et al, 2004;Hetzinger et al, 2006) have also proved to be excellent environmental recorders.…”