Dataset: coral - carbon oxygen boron isotopes

Full details of the experimental design and analytical methods are in:
Schoepf V, McCulloch MT, Warner ME, Levas SJ, Matsui Y, Aschaffenburg MD, Grottoli AG. 2014. Short-term coral bleaching is not recorded by skeletal boron isotopes. PLOS ONE 9(11): e112011. doi:10.1371/journal.pone.0112011

A brief description of the methods follows:

Coral Bleaching Experiment
The corals used for this study were taken from an experiment where three species of Caribbean corals were experimentally bleached in two consecutive summers. These corals were physiologically fully recovered (i.e., there were no significant differences between treatment and control corals in any of the measured variables) after a year on the reef prior to exposure to the elevated temperature stress for a second time. The coral fragments were collected from 9 healthy colonies of Porites divaricata (branching morphology), Porites astreoides (mounding/encrusting morphology), and mounding Orbicella faveolata (formerly Montastraea faveolata) (large mounding morphology) in July 2009 from reefs near Puerto Morelos, Yucatan Peninsula, Mexico (20 deg 50' N, 86 deg 52' W). Half of the coral fragments from each parent colony were randomly assigned to each treatment: (1) ambient control fragments were maintained in tanks with ambient seawater temperature (30.66 +/- 0.24 degrees C), and (2) treatment fragments were placed in tanks with elevated seawater temperature (31.48 +/- 0.20 degrees C). Seawater temperature in the treatment tanks was gradually elevated over the course of a week. Corals were not fed but had access to unfiltered seawater. After a total of 15 days, temperature in all tanks was returned to ambient levels, and all coral fragments were placed back in situ on the reef for one year.

The experiment was repeated in July 2010. All corals that had served as ambient control fragments the previous summer were placed in tanks with ambient seawater, whereas all corals that had been used as treatment fragments were maintained in tanks with elevated temperature. After 17 days, all tanks were returned to ambient temperature levels and one control and one treatment fragment per colony of each species were then frozen for geochemical analyses (0 weeks on the reef). All remaining fragments were placed on the back reef. All remaining corals were recollected from the reef after 6 weeks and frozen for geochemical analyses.

Chlorophyll a
Coral tissue was removed from the skeleton of a portion of each fragment with a WaterPik, homogenized and centrifuged. Chlorophyll a was determined using a Shimadzu UV-VIS spectrophotometer and the equations of Jeffrey and Humphrey. Chlorophyll a content was standardized to surface area, which was determined using the aluminium foil method.

Calcification
Published calcification rates determined using the buoyant weight technique were reproduced from Grottoli
et al.

Isotopic Analyses
Coral tissue was removed from the skeleton using a dental hygiene tool. The uppermost layer of the dried skeleton was then gently shaved with a diamond-tipped Dremel tool and ground to fine powder using agate mortar and pestles.

Boron isotopes: Refer to Schoepf et al. 2014 PLOS ONE for the boron extraction methods. The extracted boron was analysed at the University of Western Australia using either a Neptune Plus Multi-Collector Inductively Coupled Plasma Mass Spectrometer (MC-ICP-MS; Thermo Fisher Scientific) fitted with a PFA nebulizer and a cyclonic quartz spray chamber or a NU Plasma II MC-ICP-MS (NU Instruments). The boron isotopic composition of the skeleton (delta 11B) was reported as the per mil deviation of the stable isotopes 11B:10B relative to SRM-951.

Carbon and oxygen isotopes: An aliquot of the dried and ground skeletal powder was analysed for d13C and d18O using an automated Kiel Carbonate Device coupled to a Stable Isotope Ratio Mass Spectrometer (SIRMS; Finnigan Delta IV) at The Ohio State University. Samples were not pre-treated. Samples were acidified under vacuum with 100% ortho-phosphoric acid. The carbon isotopic composition of the skeleton (d13C) was reported as the per mil deviation of the stable isotopes 13C:12C relative to Vienna-Peedee Belemnite Limestone standard (v-PDB). Skeletal oxygen isotopes (d18O) were reported as the per mil deviation of the stable isotopes 18O:16O relative to v-PDB.

Trace Element Analyses
From the solution used for d11B analysis, a 2-7 uL aliquot was diluted to a final concentration of 10 ppm Ca in 2% HNO3 spiked with ~19 ppb Sc, 19 ppb Y, 0.19 ppb Pr, 0.095 ppb Bi, and 19 ppb V. Samples were then analysed for Sr/Ca, Mg/Ca, U/Ca, and Ba/Ca on an X-Series 2 Quadrupole Inductively Coupled Plasma Mass Spectrometer (Q-ICPMS; Thermo Fisher Scientific) at the University of Western Australia using the standard Xt interface and the plasma screen fitted.