Dataset: Carbon and nitrogen stable isotopes of Hawaiian corals collected from August to November 2015

A complete description of the collection and experimental methods is available in Price et al. (in review). In brief, corals were collected between 17 August and 13 November 2015 from six sites (Electric Beach, Hale'iwa, Hawai'i Institute of Marine Biology [HIMB], Magic Island, Sampan Channel, and Waimanalo) surrounding the island of O'ahu, Hawai'i, USA. Ramets of seven coral species (Montipora capitata, Montipora patula, Pocillopora acuta, Pocillopora meandrina, Porites compressa, Porites evermanni, and Porites lobata) were collected at a depth of 0.5 to 5 m. A 5 to 10 cm coral ramet (branch or mound) was removed underwater via hammer and chisel from visually healthy parent colonies separated by at least 5 m on the reef to minimize the possibility of selecting corals of the same genet.

Sample Solutions and Standards: All solutions were made with MilliQ water (18 MΩ; Millipore, MA) and ultrapure reagents unless otherwise noted. All labware was pre-cleaned with 10% v/v HCl and MilliQ water.

Sample Preparation: Methods for the processing and separating coral host tissue and algal endosymbionts tissues for isotopic analyses are described in Price et al. (2020). Briefly, a small subsample (approximately 4 to 6 cm²) of each collected coral ramet was removed via hammer and a sterile chisel, the bulk coral tissue removed from the skeleton by airbrushing, and the resulting slurry was homogenized. A 0.5 ml sub-sample was removed, dried into silver capsules, and acidified via fumigation with 1N HCl for whole coral isotopic analysis. The remaining slurry was separated into animal host and endosymbiotic algal fractions via centrifugation and filtering steps. Overall, this process resulted in a whole coral sample, a host tissue sample, and an isolated algal endosymbiont sample for each coral collected.

Elemental Analyses: All samples were combusted using a PDZ Europa ANCA-GSL elemental analyzer interfaced to a PDZ Europa 20-20 isotope ratio mass spectrometer (Sercon Ltd., Cheshire, UK) at the University of California (UC) Davis Stable Isotope Facility. The carbon isotopic signature of the animal host (δ¹³Ch), algal endosymbiont (δ¹³Ce), and whole coral (δ¹³Cw) are reported as the per mil deviation of the stable isotopes ¹³C:¹²C relative to Vienna Peedee Belemnite Limestone Standard (v-PDB). Repeated measures of internal standards had a standard deviation of ± 0.2‰ for δ¹³C. The nitrogen isotopic signature of the animal host (δ¹⁵Nh), algal endosymbiont (δ¹⁵Ne), and whole coral (δ¹⁵Nw) are reported as the per mil deviation of the stable isotopes ¹⁵N:¹⁴N relative to air. Repeated measures of internal standard had a standard deviation of ± 0.2‰ for δ¹⁵N. At least 10% of all coral measurements were made in duplicate. The standard deviation of duplicate sample analyses was ± 0.14‰ for δ¹³Ch, ± 0.26‰ for δ¹³Ce, ± 0.12‰ for the δ¹³Cw, ± 0.07‰ for δ¹⁵Nh, ± 0.22‰ for δ¹⁵Ne, and ± 0.06‰ for the δ¹⁵Nw.