Toward a standardised protocol for the stable isotope analysis of scleractinian corals

Abstract

Rationale The stable isotope analysis of carbon and nitrogen is a powerful tool in many ecological studies, but different sample treatments may affect stable isotope ratios and hamper comparisons among studies. The goal of this study was to determine whether treatments that are commonly used to prepare scleractinian coral samples for stable isotope analysis yield different δ15N and δ13C values, and to provide guidelines toward a standardised protocol. Methods The animal tissues and Symbiodiniaceae of two symbiotic scleractinian coral species (Stylophora pistillata and Porites lutea) were divided into subsamples to test the effects of the drying method, lipid extraction, acidification treatment and water washing. All the subsamples were analysed for their δ15N and δ13C values, using continuous flow elemental analyser/isotope ratio mass spectrometry. Results The drying method and lipid extraction treatment had no substantial effects on the δ15N and δ13C values of Symbiodiniaceae and animal tissues. Acid treatment did cause significant differences in δ13C values (mean differences ≤0.5‰, with individual samples becoming up to 2.0‰ more negative), whereas no ecologically significant differences were observed in δ15N values. Animal tissue δ13C values may vary depending on whether samples are washed or not. Conclusions To move towards a standardised protocol in coral research, we recommend using an available drying method (as they are equally acceptable) for the stable isotope analysis of scleractinian corals, examining the need for lipid extraction on a case‐by‐case basis, performing a direct acidification of Symbiodiniaceae and animal tissues, and avoiding washing animal tissue with distilled water.

Two offshore coral species show greater acclimatization capacity to environmental variation than nearshore counterparts in southern Belize

“…Possible nearshore sources of enriched d 15 N include sewage (* 10%; Baker et al 2010;Katz 2004), mangrove leaf detritus (* 5%; Wooller et al 2003), terrestrial sediments , and agricultural runoff. Higher d 15 N in consumer tissues is often indicative of higher tropic position (DeNiro and Epstein 1981;Sturaro et al 2019), suggesting that nearshore corals may utilize more heterotrophically acquired energy than offshore corals. However, due to tightly coupled recycling mechanisms between corals and their associated symbionts, it can be hard to tie enrichment in d 15 N to increased heterotrophy (Reynaud et al 2009).…”

The Effects of Temperature, Light, and Feeding on the Physiology of Pocillopora damicornis, Stylophora pistillata, and Turbinaria reniformis Corals

“…A subsample of coral tissue slurry was homogenized, sonicated (probe sonicator: 20% amplitude for 60 s total, 1:1 cycle), and 35 mg mL −1 NaCl added. The subsample was filtered through 20 µm nitex mesh to remove skeletal material, the algal endosymbiont isolated onto GF/F filters, and the host tissue filtrate dried down in 9 mm × 10 mm tin capsules on a heat plate (60 • C) with ultra-pure nitrogen gas (this step does not affect sample nitrogen isotope values [82]. Pocillopora damicornis and T. reniformis were prepared for isotopic analyses according to methods modified from Hughes and Grottoli [17] and described in Price et al [83].…”

Effect of removal of organic material on stable isotope ratios in skeletal carbonate from taxonomic groups with complex mineralogies

“…The pretreatment debate is also ongoing among the users of clumped isotopes, 125,126 those working in other isotope systems, 127,128 those focused on abiogenic carbonates, 113,129,130 and those measuring stable isotopes in soft tissues 131 . On‐line geochemistry list‐serves reflect the lack of consensus on what, if any, pretreatment should be used.…”