DOI: 10.25921/3nnq-yx96
title: NOAA/WDS Paleoclimatology - Great Barrier Reef Coral Growth Data - Extension, Density, and Calcification

description: Reef-building corals are under increasing physiological stress from a changing climate and ocean absorption of increasing atmospheric carbon dioxide. We investigated 328 colonies of massive Porites corals from 69 reefs of the Great Barrier Reef (GBR) in Australia. Their skeletal records show that throughout the GBR, calcification has declined by 14.2% since 1990, predominantly because extension (linear growth) has declined by 13.3%. The data suggest that such a severe and sudden decline in calcification is unprecedented in at least the past 400 years. Calcification increases linearly with increasing large-scale sea surface temperature but responds nonlinearly to annual temperature anomalies. The causes of the decline remain unknown; however, this study suggests that increasing temperature stress and a declining saturation state of seawater aragonite may be diminishing the ability of GBR corals to deposit calcium carbonate.
description: Great Barrier Reef Coral Extension, Density, and Calcification data from 60 Porites coral cores covering the entire length of the Great Barrier Reef, Australia. Data set contains extension (cm/yr), density (g/cm3), and calcification (g/cm2/yr) from 60 individual cores. The Australian Institute of Marine Science began collecting cores from very large massive colonies of Porites on the Great Barrier Reef in the early 1980s. Such cores cannot normally be identified to species. The cores were mounted and sawn to remove slices that were about 6-7mm thick. All slices were X-rayed and skeletal density measured along a central track on each slice using a gamma densitometer. The high density portion of annual density bands in Porites from the Great Barrier Reef appears to form usually between October and March, the Southern Hemisphere summer. Peaks in the density profiles were successively counted backwards from the last (outermost or youngest) peak. Density was assumed to peak in January and the most recent peak was dated from the date of collection of the core. Dates were then assigned to all peaks in the series. Time series of the following skeletal growth parameters were then obtained: 1) Average annual density (g.cm-3); 2) Annual linear extension measured between low density troughs (cm.yr-1); 3) Annual calcification (g.cm-2.yr-1) the product of annual average density and annual linear extension. These data were obtained from 60 coral cores taken from 39 sites on the Great Barrier Reef. The density profiles do not always display regular, obvious annual peaks and we could not be absolutely sure of the dating for some profiles. We consider there may be errors of + or - 2-3 years in the starting date of some of these series. This data set replaces IGBP PAGES/WDCA CONTRIBUTION SERIES NUMBER: 2001-024 previously lodged with NOAA Paleoclimatology Data Center. It includes measurements from an expanded range of coral cores and remeasuring and redating of all old and new material. The new measurements included simultaneous measurements of coral luminescence (not included in the data set) which allowed for improved chronological control. The earlier data set was also based on annual extension being measured between adjacent density maxima whereas the new data set is based on linear extension being measured between adjacent density minima.