Coral collection
Corals were collected in 2015 from each of the six study sites (See Supplemental File “coral_collection_location_list.csv). Unsafe weather conditions lead to several delays during sampling which caused coral collection to span an 11-week period (between 17 August and 13 November). Eight species of coral, from three genera were sampled: Montipora capitata (branching and encrusting), Montipora flabellata (encrusting), Montipora patula (encrusting), Porites compressa (branching), Porites lobata (massive), Porites evermanni (massive), Pocillopora meandrina (branching), and Pocillopora acuta (branching) (McLachlan et al. submitted, Fig. 1). The Y and B morphs of P. damicornis that were historically common in Kāne'ohe Bay (Richmond and Jokiel 1984), appear to correspond to the cryptic species P. damicornis and P. acuta (Johnston et al. 2018). Recent studies have found that P. acuta has become the dominant species and that P. damicornis is now rare in Kāne'ohe Bay (Gorospe et al. 2015; Johnston et al. 2018), so we focus on P. acuta in this study. Due to the natural zonation in coral species distributions, not all eight species were found in all six locations. To minimize the impact of collection, only the most commonly available species were sampled at each site. From each site, between nine and fifteen coral ramets (each from a different genet) of each commonly available species were collected from 0.5–5 m depth yielding a total of 422 samples (McLachlan et al. submitted, Table 1). Genets were confirmed by genotyping about half of the colonies (232 of the 422 colonies sampled) using available species-specific microsatellite markers (Concepcion et al. 2010; Gorospe and Karl 2013), and no identical multilocus genotypes were found within a site, suggesting very low probability that any were clonally derived. Each coral ramet was 5–10 cm in size and was removed from larger parent genets using a hammer and chisel. None of the coral ramets included in this study were visibly pale or severely bleached. Samples were immediately frozen at -20 °C, stored at HIMB, and later shipped to The Ohio State University, Ohio, USA, where they were stored at -80 °C.
Physiological data
Encrusting algae and boring organisms were removed from the surface of each coral ramet using a Dremel tool fitted with a diamond tipped bit (Dremel Inc., Racine, WI). Each coral ramet was split into two pieces: one for biochemical and one for isotopic analysis.
The coral pieces designated for biochemical physiological analyses were photographed from all sides and the photographs processed in the software ImageJ (Rasband 1997) to estimate surface area using the geometric method (Naumann et al. 2009). Each coral piece was then individually ground into a fine homogenous paste using a chilled mortar and pestle, partitioned into subsamples designated for each biochemical analysis, and stored at -80 °C. Analyses of total chlorophyll a and c2 concentration, total soluble protein, total tissue biomass, and total soluble lipid concentration (henceforth referred to as chlorophyll, protein, biomass, and lipid, respectively) were conducted based on methods modified from Jeffrey and Humphrey (1975), Bradford (1976), Grottoli et al. (2004), and Rodrigues and Grottoli (2007). Briefly, chlorophyll was extracted from ground coral samples using a double extraction in 100 % acetone, and the absorbance at 630, 663, and 750 nm wavelengths was measured using a spectrophotometer.
Detailed protocols for each of the other analyses are deposited in Protocols.io. See:
McLachlan et al. 2020; doi:10.17504/protocols.io.bdyai7se
McLachlan et al. 2020; doi:10.17504/protocols.io.bc4qiyvw
McLachlan et al. 2020; doi:10.17504/protocols.io.bdc8i2zw
The coral pieces designated for stable isotope analyses were prepared using methods modified from Hughes et al. (2010) and a detailed protocol is deposited in Protocols.io (Price et al. 2020). All isotope 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 Davis Stable Isotope Facility. The carbon isotopic signature of the animal host (δ13Ch), and algal endosymbiont (δ13Ce), were reported as the per mil deviation of the stable isotopes 13C:12C relative to Vienna Peedee Belemnite Limestone Standard. The nitrogen isotopic signature of the animal host (δ15Nh), and algal endosymbiont (δ15Ne), were reported as the per mil deviation of the stable isotopes 14N:15N relative to air. At least 10 % of all measurements were made in duplicate, and the standard deviation of duplicate sample analyses were ±0.09 ‰ for δ13Ch, ±0.21 ‰ for δ13Ce, ±0.06 ‰ for δ15Nh, and ±0.12 ‰ for δ15Ne. Differences between δ13Ch and δ13Ce of each ramet were used to assess the relative contribution of photosynthetically and heterotrophically derived C in coral tissues [sensu Muscatine et al. (1989) and Rodrigues and Grottoli (2006)]. The lower the δ13Ch - δ13Ce value, the greater the relative contribution of heterotrophically versus photoautotrophically derived carbon to coral tissues, and vice versa for larger δ13Ch - δ13Ce values (Muscatine et al. 1989; Rodrigues and Grottoli 2006; Levas et al. 2013; Schoepf et al. 2015; Grottoli et al. 2017). Conversely, the lower the δ15Nh-e – δ15Nh-e value, the lower the relative contribution of heterotrophically derived nitrogen to coral tissues (Conti-Jerpe et al. 2020).
Species list:
ScientificName,AphiaID
Montipora capitata,287697
Montipora flabellata,207174
Montipora patula,207149
Pocillopora acuta,759099
Pocillopora meandrina,206964
Porites compressa,207236
Porites evermanni,288900
Porites lobata,207225
