(Table S1) Original element/Ca data for the OGA and Tahiti corals

[1] Previous studies have demonstrated the potential for the Li content of coral aragonite to record information about environmental conditions, but no detailed study of tropical corals exists. Here we present the Li and Mg to Ca ratios at a bimonthly to monthly resolution over 25 years in two modern Porites corals, the genus most often used for paleoclimate reconstructions in the tropical Indo-Pacific. A strong relationship exists between coral Li/Ca and locally measured SST, indicating that coral Li/Ca can be used to reconstruct tropical SST variations. However, Li/Ca ratios of the skeleton deposited during 1979-1980 do not track local SST well and are anomalously high in places. The Mg/Ca ratios of this interval are also anomalously high, and we suggest Li/Ca can be used to reconstruct tropical SST only when Mg/Ca data are used to carefully screen for relatively rare biological effects. Mg/Li or Li/Mg ratios provide little advantage over Li/Ca ratios, except that the slope of the Li/Mg temperature relationship is more similar between the two corals. The Mg/Li temperature relationship for the coral that experienced a large temperature range is similar to that found for cold water corals and aragonitic benthic foraminifera in previous studies. The comparison with data from other biogenic aragonites suggests the relationship between Li/Mg and water temperature can be described by a single exponential relationship. Despite this hint at an overarching control, it is clear that biological processes strongly influence coral Li/Ca, and more calibration work is required before widely applying the proxy.

Seawater carbonate chemistry, nutrients and calcification during experiments with cold-water scleractinian corals (Lophelia pertusa, Madrepora oculata and Desmophyllum dianthus), 2011

Global environmental changes, including ocean acidification, have been identified as a major threat to scleractinian corals. General predictions are that ocean acidification will be detrimental to reef growth and that 40 to more than 80 per cent of present-day reefs will decline during the next 50 years. Cold-water corals (CWCs) are thought to be strongly affected by changes in ocean acidification owing to their distribution in deep and/or cold waters, which naturally exhibit a CaCO3 saturation state lower than in shallow/warm waters. Calcification was measured in three species of Mediterranean cold-water scleractinian corals (Lophelia pertusa, Madrepora oculata and Desmophyllum dianthus) on-board research vessels and soon after collection. Incubations were performed in ambient sea water. The species M. oculata was additionally incubated in sea water reduced or enriched in CO2. At ambient conditions, calcification rates ranged between -0.01 and 0.23% d-1. Calcification rates of M. oculata under variable partial pressure of CO2 (pCO2) were the same for ambient and elevated pCO2 (404 and 867 µatm) with 0.06 ± 0.06% d-1, while calcification was 0.12 ± 0.06% d-1 when pCO2 was reduced to its pre-industrial level (285 µatm). This suggests that present-day CWC calcification in the Mediterranean Sea has already drastically declined (by 50%) as a consequence of anthropogenic-induced ocean acidification.

U-Th, 14C and d11B results for Holocene North Atlantic deep sea corals (Lophelia pertusa), 2011

Sediment Core MD01-2454G SW Rockall BANK 747m water depth on Logatechev Mounds (Core was taken during Marion Dufresne Cruise Geosciences 2001 at 55°31'N and 15°39'W) ENAM corals from BoxCores of SW Rockall Bank and Porcupine Bank water depth 725 and 750m (Box cores ENAM 9915 and ENAM 9910 were taken from 725 m bsl on the Southwest Rockall Bank (55,32°N, 15,40°W), and ENAM 9828 from 745 m bsl on the Porcupine Bank (53,48°N, 13,54°W))

Acclimatization to high-variance habitats does not enhance physiological tolerance of two key Caribbean corals to future temperature and pH

Corals are acclimatized to populate dynamic habitats that neighbour coral reefs. Habitats such as seagrass beds exhibit broad diel changes in temperature and pH that routinely expose corals to conditions predicted for reefs over the next 50-100 years. However, whether such acclimatization effectively enhances physiological tolerance to, and hence provides refuge against, future climate scenarios remains unknown. Also, whether corals living in low-variance habitats can tolerate present-day high-variance conditions remains untested. We experimentally examined how pH and temperature predicted for the year 2100 affects the growth and physiology of two dominant Caribbean corals (Acropora palmata and Porites astreoides) native to habitats with intrinsically low (outer-reef terrace, LV) and/or high (neighbouring seagrass, HV) environmental variance. Under present-day temperature and pH, growth and metabolic rates (calcification, respiration and photosynthesis) were unchanged for HV versus LV populations. Superimposing future climate scenarios onto the HV and LV conditions did not result in any enhanced tolerance to colonies native to HV. Calcification rates were always lower for elevated temperature and/or reduced pH. Together, these results suggest that seagrass habitats may not serve as refugia against climate change if the magnitude of future temperature and pH changes is equivalent to neighbouring reef habitats.

Calcification is not the Achilles'heel of cold-water corals in an acidifying ocean

Ocean acidification is thought to be a major threat to coral reefs: laboratory evidence and CO2 seep research has shown adverse effects on many coral species, although a few are resilient. There are concerns that cold-water corals are even more vulnerable as they live in areas where aragonite saturation (Omega ara) is lower than in the tropics and is falling rapidly due to CO2 emissions. Here, we provide laboratory evidence that net (gross calcification minus dissolution) and gross calcification rates of three common cold-water corals, Caryophyllia smithii, Dendrophyllia cornigera, and Desmophyllum dianthus, are not affected by pCO2 levels expected for 2100 (pCO2 1058 µatm, Omega ara 1.29), and nor are the rates of skeletal dissolution in D. dianthus. We transplanted D. dianthus to 350 m depth (pHT 8.02; pCO2 448 µatm, Omega ara 2.58) and to a 3 m depth CO2 seep in oligotrophic waters (pHT 7.35; pCO2 2879 µatm, Omega ara 0.76) and found that the transplants calcified at the same rates regardless of the pCO2 confirming their resilience to acidification, but at significantly lower rates than corals that were fed in aquaria. Our combination of field and laboratory evidence suggests that ocean acidification will not disrupt cold-water coral calcification although falling aragonite levels may affect other organismal physiological and/or reef community processes.

Stress-tolerant corals of Florida Bay are vulnerable to ocean acidification

In situ calcification measurements tested the hypothesis that corals from environments (Florida Bay, USA) that naturally experience large swings in pCO2 and pH will be tolerant or less sensitive to ocean acidification than species from laboratory experiments with less variable carbonate chemistry. The pCO2 in Florida Bay varies from summer to winter by several hundred ppm roughly comparable to the increase predicted by the end of the century. Rates of net photosynthesis and calcification of two stress-tolerant coral species, Siderastrea radians and Solenastrea hyades, were measured under the prevailing ambient chemical conditions and under conditions amended to simulate a pH drop of 0.1-0.2 units at bimonthly intervals over a 2-yr period. Net photosynthesis was not changed by the elevation in pCO2 and drop in pH; however, calcification declined by 52 and 50 % per unit decrease in saturation state, respectively. These results indicate that the calcification rates of S. radians and S. hyades are just as sensitive to a reduction in saturation state as coral species that have been previously studied. In other words, stress tolerance to temperature and salinity extremes as well as regular exposure to large swings in pCO2 and pH did not make them any less sensitive to ocean acidification. These two species likely survive in Florida Bay in part because they devote proportionately less energy to calcification than most other species and the average saturation state is elevated relative to that of nearby offshore water due to high rates of primary production by seagrasses.