Supplemental Information s14

Supplemental Information

Palaeoecological evidence of a historical collapse of corals on the inshore Great Barrier Reef following European settlement

George Roff*, Tara R Clark, Claire Reymond, Jian-xin Zhao, Yuexing Feng,

Laurence J McCook, Terence J Done, John M Pandolfi

* Email: [email protected]

Contents:

Figure S1

Supporting Methods

Tables S1, S2

1 1. Supporting Figures

Figure S1. Representative photographs of life and death assemblages among sites at

Pelorus Reef. Site A and C show death assemblages dominated by thick arborescent

Acropora framework, while Site B shows high cover of foliaceous Pavona cactus and the transition of Pavona to Acropora assemblages through asexual fragmentation of

Pavona.

2 2. Supporting Methods

Sample selection and U-series dating

Approximately 1g of carefully cleaned material from each sub-sample was used for

U-series dating using a VG Sector-54 WARP-filtered high-abundance-sensitivity thermal ionisation mass spectrometer (TIMS) at the Radiogenic Isotope Facility

(RIF), the University of Queensland, following the analytical protocols described in detail in Zhao et al. and Yu et al. . Each sub-sample was spiked with a 229Th-233U-236U mixed tracer and dissolved in double-distilled nitric acid. After complete digestion, a few drops of H2O2 were added, and the sample beakers tightly closed and placed on a hotplate at 90°C overnight to decompose any trace amounts of organic matter and to ensure complete tracer-sample mixing. After standard Fe hydroxide co-precipitation to pre-concentrate U and Th, the precipitates were redissolved in 0.2 ml 7 M double- distilled HNO3 and purified using standard ion-exchange methods . U and Th fractions were loaded separately onto carefully examined ultra-pure zone-refined rhenium single filaments, sandwiched into two graphite layers (see Zhao et al. for filament purity and detailed procedures for dating very young carbonates). Th isotopic ratios 232Th/229Th and 229Th/230Th were measured manually, whereas 233U/235U, 234U/235U and 233U/236U, automatically on the Daly ion counter of the TIMS in peak-jumping mode. The U isotopic ratios were corrected for mass fractionation by normalising to

233U/236U = 0.96341 in the spike . These ratios, together with the sample and mixed tracer weights, were used to calculate 230Th/238U and 234U/238U activity ratios as well as

U and Th concentrations. U-series ages were then calculated using Isoplot/Ex 3.0

Program . Decay constants used are those reported by Cheng et al. . The operating abundance sensitivity of the TIMS measured at one mass distance in the mass range of U and Th is less than 70 ppb, suggesting the tailing effect on 230Th from 232Th is

3 negligible. During routine U-series isotope measurements on the TIMS in our laboratory, an international uraninite standard HU-1 was frequently measured to monitor the instrument conditions and analytical reproducibility. Long-term repeated measurements of 234U/238U atomic ratios in the HU-1 standard yielded a mean value of

54.888 ± 0.050 (2σ, N = 26), which is identical to the analytical uncertainty obtained by Cheng et al. .

For TIMS measurements of samples with very young ages, one of the main contributors to age error is the procedural blank from sample preparation and the colloidal graphite used to load samples onto filaments. The procedural 230Th blank which is mainly derived from the chemistry, was determined to be 1.52 ± 0.31 ×10-9 nmol (n = 12); contributing 0.35 to 0.96 yr to the 230Th ages of the samples in this study, varying according to the weights and U levels of individual samples.

Procedural blanks for 238U were 0.5-2.0 ×10-5 nmol, which is negligible for coral samples containing ~3 ppm U. Procedural blanks for 232Th were higher and more variable, with a mean of 6.25 ± 3.04 ×10-9 nmol (N=12). We attribute this relatively high 232Th blank to the new colloidal graphite used in the lab as recent multi-collector

ICP-MS analysis of similar procedural blanks show 232Th to be 5-10 times lower.

230Th blank in the graphite is negligible as monitoring of the blank graphite filaments shows that the ion counts on mass 230 are consistently low; indistinguishable form the dark noise of the TIMS, which is ~0.2 cps . 230Th, 232Th and 238U blank contributions have been extracted when calculating 230Th/232Th and 230Th/238U ratios and corresponding 230Th ages of the samples.

4 In addition to TIMS measurements, a large number of samples were also dated more recently by our newly installed Nu Plasma multi-collector inductively coupled plasma mass spectrometer (MC-ICP-MS). Compared with TIMS, the chemical separation procedure for MC-ICP-MS is simplified, and only 250-500 mg material and a 229Th-

233U mixed tracer were used. After chemical separation, the Th fraction was mixed with a small percentage of U (sufficient to achieve 3-4 volts of 238U signal) and the mixture was diluted to 3-ml in 2% HNO3. The U-Th mixed solution was then injected into the MC-ICP-MS through a DSN-100 desolvation system with an uptake rate of around 0.12 ml per minute. U-Th isotopic ratio measurement was performed on the

Nu Plasma MC-ICP-MS following the analytical protocol described by Hellstrom , with minor modifications to the detector configuration (e.g. the 235U on IC0 sequence of Hellstrom was not used in our protocol, instead we used 233U for IC0/Faraday gain calibration). The natural 238U/235U value of 137.88 was used for mass fractionation correction for both U and Th isotopic ratio measurements. The second electron multiplier IC2 was filtered with a fitted retardation lens to increase the abundance sensitivity by 10 folds to minimize large tailing of the 232Th signal into the 230Th peak, which is potentially very serious for impure carbonates with high 232Th/230Th. The working abundance sensitivity on IC2 is <500 ppb at one mass distance from the large peak in the U-Th mass range, thus tailing from 232Th to mass 230 is typically <5% of

230Th peak even for the dirtiest samples with 232Th/230Th >100,000. For samples with

232Th/230Th <10,000, this tailing is typically <1%. The tailing contribution was extracted from 230Th signal by simultaneous measurements of baselines at masses

230.5 and 229.5. The geometric mean of the two half-mass-unit baseline measurements was used in the online acquisition program. The working sensitivity of the instrument is about 0.5-0.6 volt per ppb for U and 0.4-0.5 volt per ppb of Th. Each

5 sample took about 20 minutes to measure. In between samples, a vigorous 15-minute cleaning procedure was undertaken and all isotopes were monitored and raw counts measured on their respective detectors to ensure no carry-over memories from previous samples. Measurements of samples, standards, and carryover memories were performed fully automatically using a CETAC ASX-110 autosampler. A long-term monitoring of the carryover memories over 15 months shows that 230Th memory is consistently less than 0.1 counts per second, which is negligible for most samples.

The memories for all other isotopes are also negligible. To ensure the reproducibility of the data, we spiked our CRM-112A (or called STM-960) U metal standard solution with the same mixed tracer and carried out column chemistry together with the samples. Repeated measurements of the U metal standard gave an age of 74.8±0.1 years (~1936 AD), within error of the result reported by McCulloch and Mortimer .

Similarly we spiked a 10-ppb CRM-112A solution and measured it directly without column chemistry (with 230Th signal only a few counts per second). The results gave dates identical within error of the above age. The procedural blanks on our MC-ICP-

MS are considerably smaller, with mean measured 238U, 232Th and 230Th blanks of

1.6x10-5, 1.7x10-5 and 2.5x10-10 nmol (or 3.7 pg, 3.8 pg, 0.06 fg), respectively. 230Th blank extractions for our samples of ~0.5 g in size correspond to only about 0.2 year.

Initial 230Th correction

As the samples in this study are extremely young, with very low radiogenic 230Th, the proportion of the initial 230Th component is much higher, making a significant contribution to the measured 230Th/238U ratios, which must be corrected for in order to

230 230 232 work out a reliable Th age of the sample. Three different Th/ Th0 ratios were applied for the initial 230Th correction, including a mean value of 0.65±25% calculated

6 from ICP-MS Th/U measurements of ~40 local sediments from the Burdekin River catchment area, which is confirmed by direct measurements of uncleaned sediment- rich coral samples of known ages (Clark et al., in prep), a mean value of 1.0±25%

230 232 calculated from 14 direct measurements of Th/ Th0 in live corals of known ages in the Palm Islands region, and a model value calculated for each sample using a two- component mixing equation (see Supplementary Table 4 footnote) that accounts for the proportion of a terrestrially derived 230Th component (represented by the

230 232 sediments from the Burdekin River catchment area with Th/ Th0 = 0.65±25%)

230 incorporated into the skeleton post-mortem, and a hydrogenous Th component

230 incorporated into the skeleton during growth (represented by measured Th0 in live

230 232 230 corals in the region with Th/ Th0 = 1.0±25%). The corrected Th ages based on the above two-component mixing model are listed in Table S2. Despite vigorous cleaning applied to all the dated samples, a large number of samples still contain high

232Th indicative of high-level contamination from terrestrial sediments, resulting in low measured 230Th/232Th activity ratios in these samples. As a result, initial 230Th corrections for these high-Th samples have a significant impact on the corrected 230Th ages and their age uncertainties, with error magnifications up to >10 times if compared with the uncorrected 230Th age uncertainties (typically ~1% or less), which are only related to analytical errors.

7 3. Supporting Tables

Table S1. Benthic cover across sites at Pelorus Island, central Great Barrier Reef

(percent cover ± SE)

Benthic category Site A Site B Site C Living coral 3.5 ± 0.6 36.3 ± 7.7 4.4 ± 0.8 Dead coral 77.2 ± 3.7 31.3 ± 5.4 59.4 ± 4.4 Soft coral 10.6 ± 2 12.5 ± 1.2 26.8 ± 7.4 Algae 2.0 ± 1.8 5.4 ± 4.4 0.2 ± 0.1 Substrate 6.5 ± 3.9 14.4 ± 7.9 9.2 ± 3.1

Table S2. U-series ages of corals obtained from death assemblages and sediment cores. Coral samples obtained from historical assemblages and cores from sites at

Pelorus Reef, central Great Barrier Reef.

8 Uncorr, 230Th Corr. 230Th age Date of corr. 230Th Age Sample Name Site Genera Assemblage Method U (ppm) 232Th (ppb) (230Th/ 232Th) (230Th/238U) (234U/ 238U) age (a) (a) chemistry (AD)

0.004637 ± PN1AE A Acropora Core TIMS 2.8159 ± 0.0034 8.484 ± 0.036 4.67 ± 0.10 1.1461 ± 0.0013 441.3 ± 8.2 377 ± 15 2009.9 1633 ± 15 0.000086 0.005278 ± PN3AA A Acropora Core TIMS 3.6752 ± 0.0048 1.318 ± 0.003 44.66 ± 0.46 1.1465 ± 0.0017 502.2 ± 4.8 492.8 ± 5.2 2009.9 1517.1 ± 5.2 0.000050 0.005020 ± PN3iAB A Acropora Core TIMS 3.3090 ± 0.0040 5.273 ± 0.030 9.56 ± 0.14 1.1460 ± 0.0015 477.8 ± 4.9 442.9 ± 8.7 2009.9 1567.1 ± 8.7 0.000052 0.005387 ± PN4AA A Acropora Core TIMS 3.7792 ± 0.0047 2.378 ± 0.010 25.97 ± 0.29 1.1478 ± 0.0011 512.1 ± 4.3 497.2 ± 5.3 2009.9 1512.7 ± 5.3 0.000045 0.000398 ± Pel.A.AC B Acropora Core TIMS 3.2717 ± 0.0026 3.120 ± 0.021 1.27 ± 0.028 1.1491 ± 0.0014 37.7 ± 0.7 15.3 ± 4.5 2008.2 1992.9 ± 4.5 0.000008 0.005650 ± Pel.A.AP B Acropora Core TIMS 3.2409 ± 0.0037 0.617 ± 0.002 89.99 ± 0.83 1.1460 ± 0.0015 537.9 ± 3.8 532.0 ± 4.1 2008.2 1476.2 ± 4.1 0.000040 0.001053 ± Pel.B.AC B Acropora Core TIMS 3.3313 ± 0.0027 4.123 ± 0.035 2.58 ± 0.08 1.1462 ± 0.0013 100.1 ± 2.3 72.0 ± 6.11 2008.2 1936.2 ± 6.1 0.000024 0.009131 ± Pel.B.AR B Acropora Core TIMS 3.2218 ± 0.0032 3.361 ± 0.022 26.56 ± 0.27 1.1461 ± 0.0012 870.7 ± 4.1 847.3 ± 6.4 2008.2 1160.9 ± 6.4 0.000042 0.004304 ± PB1AP B Acropora Core TIMS 3.6231 ± 0.0051 3.865 ± 0.022 12.24 ± 0.20 1.1437 ± 0.0013 410.4 ± 5.3 386.3 ± 7.2 2009.9 1623.6 ± 7.2 0.000055 0.001033 ± PB2ANP B Acropora Core TIMS 3.5122 ± 0.0050 3.553 ± 0.011 3.10 ± 0.16 1.1457 ± 0.0013 98.2 ± 5.1 74.8 ± 7.0 2009.9 1935.1 ± 7.0 0.000054 0.000846 ± PB3ATQ B Acropora Core TIMS 3.6610 ± 0.0046 1.578 ± 0.003 5.96 ± 0.09 1.1473 ± 0.0013 80.3 ± 1.3 68.9 ± 2.6 2009.9 1941.0 ± 2.6 0.000014 0.001853 ± PelPB1 B Acropora Core MC 2.9626 ± 0.0029 6.994 ± 0.007 24.01 ± 0.06 1.1447 ± 0.0008 1796.3 ± 5.0 1744.4 ±11.3 2010.5 266.0 ± 11.5 0.000020 0.001193 ± PelPB2 B Acropora Core MC 3.0659 ± 0.0037 7.204 ± 0.007 23.67 ± 0.07 1.1445 ± 0.0008 1764.6 ± 6.0 1713.1 ±11.8 2010.5 297.4 ± 11.9 0.000024 0.012479 ± PS1AC C Acropora Core TIMS 3.9037 ± 0.0057 5.005 ± 0.023 29.53 ± 0.24 1.1461 ± 0.0014 1191.5 ± 6.2 1164.2 ± 8.4 2009.9 845.8 ± 8.4 0.000063 0.003987 ± PS3AA C Acropora Core TIMS 3.8586 ± 0.0051 3.628 ± 0.016 12.87 ± 0.28 1.1460 ± 0.0016 379.4 ± 7.2 358.1 ± 8.4 2009.9 1651.8 ± 8.4 0.000075

9 Date of Sample Assembl Uncorr, Corr. 230Th corr. 230Th Age Site Genera Method U (ppm) 232Th (ppb) (230Th/ 232Th) (230Th/238U) (234U/ 238U) chemistr Name age 230Th age (a) age (a) (AD) y PS4AA C Acropora Core TIMS 3.5782 ± 0.0052 0.410 ± 0.002 49.06 ± 0.69 0.001853 ± 1.1474 ± 0.0014 175.9 ± 1.8 172.2 ±2.0 2009.9 1837.7 ± 2.0 0.000019 PA3A1 A Acropora Death TIMS 3.1038 ± 0.0030 0.456 ± 0.002 13.39 ± 0.27 0.000648 ± 1.1466 ± 0.0017 61.5 ± 1.1 56.6 ± 1.5 2007.9 1951.3 ± 1.5 0.000012 PA4A1 A Acropora Death TIMS 3.1040 ± 0.0028 2.122 ± 0.016 3.68 ± 0.08 0.000829 ± 1.1431 ± 0.0013 79.0 ± 1.2 61.9 ± 3.7 2007.9 1946.0 ± 3.7 0.000013 PA5A1 A Acropora Death TIMS 3.1042 ± 0.0024 2.496 ± 0.008 4.02 ± 0.06 0.001065 ± 1.1466 ± 0.0016 101.2 ± 1.5 81.8 ± 4.2 2008.2 1926.5 ± 4.2 0.000015 PA6A1 A Acropora Death TIMS 3.0848 ± 0.0028 0.611 ± 0.002 10.21 ± 0.23 0.000667 ± 1.1442 ± 0.0010 63.4 ± 1.4 56.7 ± 2.0 2008.2 1951.5 ± 2.0 0.000015 PA6A2 A Acropora Death TIMS 4.6813 ± 0.0046 1.916 ± 0.014 5.11 ± 0.11 0.000689 ± 1.1466 ± 0.0010 65.4 ± 1.1 55.1 ± 2.4 2008.2 1953.1 ± 2.4 0.000012 PA7A2 A Acropora Death TIMS 3.0063 ± 0.0036 0.653 ± 0.003 8.89 ± 0.25 0.000636 ± 1.1476 ± 0.0022 60.4 ± 1.6 53.0 ± 2.2 2008.2 1955.2 ± 2.2 0.000017 PA7A1 A Acropora Death TIMS 3.2100 ± 0.0024 13.124 ± 0.047 0.89 ± 0.02 0.001193 ± 1.1467 ± 0.0009 113.7 ± 2.2 27.2 ±17.5 2007.9 1980.7 ± 17.5 0.000023 PA18 A Acropora Death MC 3.2426 ± 0.0017 6.180 ± 0.007 1.69 ± 0.02 0.001064 ± 1.1464 ± 0.0008 101.4 ± 0.9 59.8 ± 8.4 2011.5 1951.7 ± 8.4 0.000009 PA4A A Acropora Death MC 3.1945 ± 0.0018 5.455 ± 0.004 1.63 ± 0.02 0.000918 ± 1.1449 ± 0.0014 87.6 ± 1.0 50.0 ± 7.6 2011.5 1961.5 ± 7.6 0.000010 PA4AC A Acropora Death MC 3.2537 ± 0.0011 6.687 ± 0.005 1.73 ± 0.01 0.001172 ± 1.1455 ± 0.0010 111.7 ± 0.7 67.1 ± 9.0 2011.5 1944.4 ± 9.0 0.000007 PA5A A Acropora Death MC 3.0610 ± 0.0016 6.723 ± 0.006 1.98 ± 0.02 0.001432 ± 1.1440 ± 0.0012 136.7 ± 1.2 89.0 ± 9.6 2011.5 1922.6 ± 9.6 0.000012 PA5AB A Acropora Death MC 3.1996 ± 0.0019 9.921 ± 0.007 1.58 ± 0.01 0.001612 ± 1.1445 ± 0.0013 153.9 ± 1.3 87.7 ± 13.1 2011.5 1923.8 ± 13.3 0.000013 PA2B A Acropora Death MC 3.1935 ± 0.0014 3.835 ± 0.004 3.08 ± 0.03 0.001219 ± 1.1463 ± 0.0009 116.2 ± 1.0 89.0 ± 5.5 2011.5 1922.5 ± 5.5 0.000011 PA2A A Acropora Death MC 3.1160 ± 0.0016 7.164 ± 0.006 1.52 ± 0.02 0.001151 ± 1.1459 ± 0.0014 109.7 ± 1.0 59.9 ± 10.0 2011.5 1951.6 ± 10.0 0.000011 PA6B A Acropora Death MC 3.0989 ± 0.0013 1.544 ± 0.001 4.53 ± 0.07 0.000743 ± 1.1469 ± 0.0008 70.8 ± 1.0 58.0 ± 2.8 2011.5 1953.5 ± 2.8 0.000011

10 Uncorr, Date of Sample Assembl Corr. 230Th corr. 230Th Age Site Genera Method U (ppm) 232Th (ppb) (230Th/ 232Th) (230Th/238U) (234U/ 238U) 230Th age chemistr Name age age (a) (AD) (a) y PA6BA A Acropora Death MC 2.8998 ± 0.0017 0.618 ± 0.001 10.58± 0.10 0.000741 ± 1.1442 ± 0.0011 70.8 ± 0.7 64.1 ± 1.5 2011.5 1947.4 ± 1.5 0.000007 PA6BB A Acropora Death MC 3.0331 ± 0.0022 0.651 ± 0.001 10.19 ± 0.11 0.000721 ± 1.1439 ± 0.0013 68.9 ± 0.7 62.1 ± 1.5 2011.5 1949.4 ± 1.5 0.000008 PA3BBC A Acropora Death MC 2.9154 ± 0.0012 0.405 ± 0.000 15.72 ± 0.23 0.000719 ± 1.1452 ± 0.0009 68.6 ± 1.0 64.2 ± 1.3 2011.5 1947.3 ± 1.3 0.000010 PA6BC A Acropora Death MC 3.0365 ± 0.0024 0.435 ± 0.001 14.36 ± 0.22 0.000678 ± 1.1455 ± 0.0014 64.7 ± 1.0 60.2 ± 1.3 2011.5 1951.3 ± 1.3 0.000010 PA8A A Acropora Death MC 3.0771 ± 0.0019 13.050 ± 0.012 1.3 ± 0.01 0.001816 ± 1.1451 ± 0.0011 173.3 ± 1.6 83.6 ± 18.1 2011.5 1928.0 ± 18.1 0.000017 PelS2T41 B Acropora Death MC 3.1785 ± 0.0014 12.238 ± 0.009 0.83 ± 0.01 0.001052 ± 1.1452 ± 0.0008 100.4 ± 1.2 18.8 ± 16.4 2011.5 1992.7 ± 16.4 0.000012 PelS2T31C B Acropora Death MC 3.6953 ± 0.0019 11.462 ± 0.010 1.93 ± 0.01 0.001973 ± 1.1448 ± 0.0009 188.4 ± 1.4 122.5 ± 13.3 2011.5 1889.0 ± 13.3 0.000014 PelS2T31A B Acropora Death MC 3.3213 ± 0.0017 9.620 ± 0.013 1.01 ± 0.01 0.000968 ± 1.1469 ± 0.0008 92.2 ± 1.2 30.4 ± 12.4 2011.5 1981.1 ± 12.4 0.000012 PelS2T42 B Acropora Death MC 3.0371 ± 0.0013 14.977 ± 0.017 1.22 ± 0.01 0.001980 ± 1.1464 ± 0.0008 188.7 ± 1.8 84.9 ± 20.9 2011.5 1926.6 ± 20.9 0.000019 PelS2T35 B Acropora Death MC 3.4987 ± 0.0014 36.418 ± 0.048 1.33 ± 0.01 0.004556 ± 1.1461 ± 0.0007 434.9 ± 2.9 218.9 ± 43.3 2011.5 1792.6 ± 43.3 0.000030 PelS2T31B B Acropora Death MC 3.5489 ± 0.0017 15.310 ± 0.015 0.0 ± 0.01 0.001278 ± 1.1474 ± 0.0008 121.7 ± 1.5 31.0 ± 18.2 2011.5 1980.5 ± 18.2 0.000016 PelS2T45A B Acropora Death MC 3.3229 ± 0.0018 11.845 ± 0.014 1.25 ± 0.02 0.001463 ± 1.1465 ± 0.0007 139.4 ± 1.5 63.9 ± 15.2 2011.5 1947.6 ± 15.2 0.000016 PelS2T43 B Acropora Death MC 3.6822 ± 0.0017 10.016 ± 0.013 3.08 ± 0.03 0.002761 ± 1.1473 ± 0.0008 263.1 ± 2.2 205.1 ± 11.8 2011.5 1806.4 ± 11.8 0.000023 PelS2T32 B Acropora Death MC 3.5369 ± 0.0012 19.872 ± 0.019 1.13 ± 0.01 0.002087 ± 1.1469 ± 0.0008 198.9 ± 1.5 81.4 ± 23.6 2011.5 1930.1 ± 23.6 0.000015 PelS2T45B B Acropora Death MC 3.5571 ± 0.0019 13.520 ± 0.015 1.42 ± 0.01 0.001771 ± 1.1473 ± 0.0008 168.6 ± 1.1 88.5 ± 16.1 2011.5 1923.0 ± 16.1 0.000012 PelS2T34 B Acropora Death MC 3.6805 ± 0.0016 8.573 ± 0.008 3.88 ± 0.03 0.002979 ± 1.1471 ± 0.0011 284.0 ± 1.7 234.0 ± 10.1 2011.5 1777.5 ± 10.1 0.000017 PelS2T44 B Acropora Death MC 3.3047 ± 0.0014 16.837 ± 0.014 0.96 ± 0.02 0.001619 ± 1.1464 ± 0.0011 154.3 ± 2.3 47.4 ± 21.5 2011.5 1964.1 ± 21.5 0.000024 PB8A1 B Pavona Death TIMS 3.6412 ± 0.0033 0.422 ± 0.002 34.96 ± 0.98 0.001334 ± 1.1488 ± 0.0010 126.5 ± 3.2 122.7 ± 3.3 2007.9 1885.3 ± 3.3 0.000034 PB1A1 B Pavona Death TIMS 4.0108 ± 0.0054 1.959 ± 0.010 1.04 ± 0.03 0.000167 ± 1.1482 ± 0.0014 15.9 ± 0.5 3.5 ± 2.5 2007.9 2004.4 ± 2.5 0.000005

11 Uncorr, Date of Sample Assembl Corr. 230Th corr. 230Th Age Site Genera Method U (ppm) 232Th (ppb) (230Th/ 232Th) (230Th/238U) (234U/ 238U) 230Th age chemistr Name age age (a) (AD) (a) y PB4A1 B Pavona Death TIMS 3.3284 ± 0.0047 1.658 ± 0.007 1.46 ± 0.09 0.000239 ± 1.1511 ± 0.0022 22.6 ± 1.4 9.60 ± 2.97 2007.9 1998.3 ± 3.0 0.000015 PB4B1 B Pavona Death TIMS 3.0587 ± 0.0024 4.968 ± 0.015 0.93 ± 0.04 0.000495 ± 1.1453 ± 0.0012 47.1 ± 2.0 10.77 ± 7.55 2007.9 1997.1 ± 7.6 0.000021 PB4B2 B Pavona Death TIMS 3.2965 ± 0.0047 0.625 ± 0.003 4.80 ± 0.12 0.000300 ± 1.1473 ± 0.0016 28.5 ± 0.7 21.98 ± 1.49 2007.9 1985.9 ± 1.5 0.000008 PB7A1 B Pavona Death TIMS 3.4750 ± 0.0043 0.778 ± 0.004 3.15 ± 0.09 0.000232 ± 1.1441 ± 0.0016 22.1 ± 0.7 14.74 ± 1.63 2007.9 1993.1 ± 1.6 0.000007 PB7B1 B Pavona Death TIMS 3.7102 ± 0.0041 4.446 ± 0.032 0.99 ± 0.03 0.000391 ± 1.1463 ± 0.0015 37.1 ± 0.8 10.04 ± 5.48 2007.9 1997.8 ± 5.5 0.000008 PB7B2 B Pavona Death TIMS 3.3834 ± 0.0035 0.966 ± 0.003 2.00 ± 0.05 0.000188 ± 1.1455 ± 0.0012 17.9 ± 0.5 9.17 ± 1.82 2007.9 1998.7 ± 1.8 0.000005 PB1A B Pavona Death MC 3.7850 ± 0.0019 0.395 ± 0.001 2.62 ± 0.13 0.000090 ± 1.1472 ± 0.0008 8.6 ± 0.4 5.33 ± 0.78 2011.5 2006.2 ± 0.8 0.000004 PB8BB B Pavona Death MC 4.0933 ± 0.0023 2.309 ± 0.003 7.56 ± 0.08 0.001405 ± 1.1478 ± 0.0009 133.7 ± 1.3 120.20 ± 3.00 2011.5 1891.3 ± 3.0 0.000013 PB8BA B Pavona Death MC 3.8768 ± 0.0019 2.628 ± 0.002 6.31 ± 0.07 0.001411 ± 1.1461 ± 0.0012 134.5 ± 1.3 118.49 ± 3.47 2011.5 1893.0 ± 3.5 0.000014 PB7A B Pavona Death MC 4.2572 ± 0.0017 2.806 ± 0.003 1.12 ± 0.03 0.000243 ± 1.1482 ± 0.0008 23.1 ± 0.6 7.75 ± 3.14 2011.5 2003.8 ± 3.1 0.000007 PB7AB B Pavona Death MC 3.8193 ± 0.0018 7.730 ± 0.008 0.76 ± 0.01 0.000509 ± 1.1456 ± 0.0009 48.6 ± 0.4 4.92 ± 8.76 2011.5 2006.6 ± 8.8 0.000008 PB3AB B Pavona Death MC 4.1501 ± 0.0022 7.974 ± 0.009 0.95 ± 0.02 0.000600 ± 1.1455 ± 0.0008 57.2 ± 1.0 15.85 ± 8.34 2011.5 1995.7 ± 8.3 0.000011 PB3B B Pavona Death MC 4.1741 ± 0.0022 5.868 ± 0.006 1.25 ± 0.02 0.000580 ± 1.1463 ± 0.0009 55.3 ± 0.9 24.53 ± 6.22 2011.5 1987.0 ± 6.2 0.000009 PC2A1 C Acropora Death TIMS 2.9871 ± 0.0022 1.242 ± 0.008 6.29 ± 0.14 0.000863 ± 1.1470 ± 0.0010 81.9 ± 1.5 70.24 ± 2.78 2007.9 1937.6 ± 2.8 0.000016 PC2B1 C Acropora Death TIMS 2.9067 ± 0.0021 0.938 ± 0.005 8.25 ± 0.30 0.000877 ± 1.1470 ± 0.0009 83.3 ± 2.8 73.42 ± 3.44 2007.9 1934.5 ± 3.4 0.000030 PC4B2 C Acropora Death TIMS 2.9981 ± 0.0024 1.798 ± 0.009 4.48 ± 0.07 0.000886 ± 1.1483 ± 0.0012 84.0 ± 1.2 68.65 ± 3.31 2007.9 1939.2 ± 3.3 0.000012 PC5A1 C Acropora Death TIMS 3.1040 ± 0.0017 2.875 ± 0.013 3.14 ± 0.07 0.000960 ± 1.1466 ± 0.0009 91.2 ± 1.8 69.27 ± 4.78 2007.9 1938.6 ± 4.8 0.000019 PC4A1 C Acropora Death TIMS 2.9766 ± 0.0029 1.281 ± 0.004 6.09 ± 0.14 0.000863 ± 1.1478 ± 0.0018 81.9 ± 1.9 69.93 ± 3.06 2008.2 1938.3 ± 3.1 0.000020 PC6A1 C Acropora Death TIMS 2.9435 ± 0.0033 0.438 ± 0.003 13.66 ± 0.47 0.000670 ± 1.1471 ± 0.0023 63.6 ± 2.0 58.53 ± 2.24 2008.2 1949.7 ± 2.2 0.000021 PC8A1 C Acropora Death TIMS 3.0261 ± 0.0031 0.412 ± 0.003 19.54 ± 0.62 0.000876 ± 1.1468 ± 0.0012 83.2 ± 2.3 78.60 ± 2.46 2008.2 1929.6 ± 2.5 0.000024 PC2A C Acropora Death MC 3.1465 ± 0.0010 13.266 ± 0.010 1.25± 0.01 0.001738 ± 1.1454 ± 0.0009 165.8 ± 1.2 76.71 ± 17.87 2011.5 1934.8 ± 17.9 0.000013 PC2C C Acropora Death MC 2.8699 ± 0.0009 32.497 ± 0.033 0.89± 0.01 0.003304 ± 1.1450 ± 0.0008 315.6 ± 2.1 80.02 ± 2011.5 1931.5 ± 47.2 0.000022 47.21

12 Uncorr, Sample Assembla Corr. 230Th Date of corr. 230Th Age Site Genera Method U (ppm) 232Th (ppb) (230Th/ 232Th) (230Th/238U) (234U/ 238U) 230Th age Name ge age (a) chemistry (AD) (a) PC3AA C Acropora Death MC 3.0120 ± 0.0014 2.505 ± 0.002 3.56±0.05 0.000976 ± 1.1451 ± 0.0011 93.1 ± 1.3 73.33 ± 4.15 2011.5 1938.3 ± 4.2 0.000013 PC3AB C Acropora Death MC 3.0384 ± 0.0018 12.768 ± 0.010 1.22 ±0.01 0.001693 ± 1.1441 ± 0.0010 161.7 ± 1.6 72.64 ± 17.89 2011.5 1938.9 ± 17.9 0.000017 PC4B C Acropora Death MC 3.2006 ± 0.0014 12.295 ± 0.013 1.30± 0.02 0.001648 ± 1.1457 ± 0.0007 157.1 ± 1.8 75.76 ± 16.37 2011.5 1935.7 ± 16.4 0.000018 PC5A C Acropora Death MC 3.1650 ± 0.0016 2.069 ± 0.003 4.61± 0.1 0.000993 ± 1.1472 ± 0.0008 94.6 ± 1.9 78.61 ± 3.69 2011.5 1932.9 ± 3.7 0.000019 PC5B C Acropora Death MC 3.0323 ± 0.0014 16.706 ± 0.018 1.13± 0.01 0.002044 ± 1.1448 ± 0.0008 195.1 ± 2.2 79.27 ± 23.28 2011.5 1932.2 ± 23.3 0.000023 PC8A C Acropora Death MC 3.1782 ± 0.0013 4.477 ± 0.004 2.08 ± 0.02 0.000965 ± 1.1471 ± 0.0009 91.9 ± 0.9 60.51 ± 6.34 2011.5 1951.0 ± 6.3 0.000009 PC8B C Acropora Death MC 3.2708 ± 0.0011 14.825 ± 0.011 1.09 ± 0.01 0.001631 ± 1.1460 ± 0.0005 155.5 ± 1.1 60.04 ± 19.13 2011.5 1951.5 ± 19.1 0.000011

1. Ratios in parentheses are activity ratios calculated from atomic ratios. 2. Errors are 2σ. 234 234 λ234T 234 234 238 -10 -1 3. δ U(T)= δ U(O)e where δ U=[( U/ U)-1]×1000 and the age (T) is calculated using ISOPLOT 3.0 () using decay constants λ238 = 1.55125 × 10 yr (), λ234 = (2.8262 ± -6 -1 -6 -1 0.0057) × 10 yr (revised value p.24, ), λ230 = (9.158 ± 0.028) × 10 yr (p.27, ) 230 230 230 232 4. To account for both hydrogenous and terrestrially derived Th0, the corrected (corr.) Th age of each sample was calculated using a sample specific initial ( Th/ Th) value calculated using the equation:

 230 Th   232 Th   230 Th    232 Th  232 Th   230 Th       live        dead live       232 Th   232 Th   232 Th    232 Th   232 Th     mix  dead   live   dead    sed 

232 232 232 232 230 232 where Thdead is the measured Th value (ppb) in the non-living coral sample. Thlive is the mean measured Th value (ppb) and Th/ Thlive is the mean initial Th value calculated 230 232 from live Porites corals collected from adjacent reefs within the inshore central GBR (Havannah Island, Orpheus Island and Pandora Reef). Th/ Thsed is the initial Th value for sediments collected from the region.

13 References

1. Zhao J.X., Hu K.D., Collerson K.D., Xu T. 2001 Thermal ionization mass spectrometry U- series dating of a hominid site near Nanjing, China. Geology 29(1), 27-30. 2. Yu K.F., Zhao J.X., Shi Q., Chen T.G., Wang P.X., Collerson K.D., Liu T.S. 2006 U-series dating of dead Porites corals in the South China sea: Evidence for episodic coral mortality over the past two centuries. Quaternary Geochronology 1(2), 129-141. (doi:10.1016/j.quageo.2006.06.005). 3. Edwards R.L., Chen J.H., Ku T.L., Wasserburg G.J. 1987 Precise timing of the last interglacial period from mass spectrometric determination of thorium-230 in corals. Science 236(4808), 1547-1553. 4. Zhao J.X., Yu K.F., Feng Y.X. 2009 High-precision U-238-U-234-Th-230 disequilibrium dating of the recent past: a review. Quaternary Geochronology 4(5), 423-433. (doi:Doi 10.1016/J.Quageo.2009.01.012). 5. Ludwig K.R. 2003 User's manual for Isoplot Version 3.0, A geochronological toolkit for Microsoft Excel. In Berkeley Geochronology Center Special Publication No 4 ( 6. Cheng H., Edwards R.L., Hoff J., Gallup C.D., Richards D.A., Asmerom Y. 2000 The half- lives of uranium-234 and thorium-230. Chemical Geology 169(1-2), 17-33. 7. Hellstrom J. 2003 Rapid and accurate U/Th dating using parallel ion-counting multi- collector ICP-MS. Journal of Analytical Atomic Spectrometry 18, 1346-1351. 8. McCulloch M.T., Mortimer G.E. 2008 Applications of the U-238-Th-230 decay series to dating of fossil and modern corals using MC-ICPMS. Australian Journal of Earth Sciences 55(6- 7), 955-965. (doi:10.1080/08120090802097435). 9. Jaffey A.H., Flynn K.F., Glendenin L.E., Bentley W.C., Essling A.M. 1971 Precision measurement of half-lives and specific activities of 235U and 238U. Physical Review 4, 1889– 1906.