Linear extension, skeletal density, and calcification rates of the blue coral Heliopora coerulea

Travis A Courtney,Romeo M Dizon,James R Guest,Alasdair J Edwards

doi:10.1007/s00338-021-02137-3

Abstract

The brooding reef-building octocoral Heliopora is widespread on Indo-West Pacific reefs and appears to be relatively resistant to thermal stress, which may enable it to persist locally while scleractinians diminish under Anthropocene conditions. However, basic physiological measurements of “blue corals” are lacking and prevent their inclusion in trait-based studies. We address this by quantifying rates (mean ± SE) of linear extension (0.86 ± 0.05 cm yr−1) and skeletal density (2.01 ± 0.06 g cm−3) to estimate calcification rates (0.87 ± 0.08 g cm−2 yr−1) for the small branching/columnar morphology of Heliopora coerulea. We postulate that H. coerulea may become an increasingly important reef-builder under ocean warming due to its relative resistance to thermal stress and high skeletal density that make colonies less vulnerable to storm damage under ocean acidification. Moreover, Heliopora corals are likely dispersal limited suggesting they may be an underappreciated genus for restoration of stress-tolerant reef-building capacity on degraded reefs.

Highlights

Calcium carbonate production represents one of the core functions of coral reef ecosystems (Brandl et al 2019) and can be approximated from estimates of benthic cover and taxa-specific calcification rates as part of census-based coral reef carbonate production budgets (Perry et al 2012)
Basic physiological measurements of ‘‘blue corals’’ are lacking and prevent their inclusion in trait-based studies. We address this by quantifying rates of linear extension (0.86 ± 0.05 cm yr-1) and skeletal density (2.01 ± 0.06 g cm-3) to estimate calcification rates (0.87 ± 0.08 g cm-2 yr-1) for the small branching/columnar morphology of Heliopora coerulea
Mean ( ± SE) linear extension did not differ significantly between the large (0.88 ± 0.08 cm yr-1) and small (0.83 ± 0.06 cm yr-1) fragments, so we calculated the mean ( ± SE) linear extension rate for all H. coerulea fragments (n = 100). This rate (0.86 ± 0.05 cm yr-1) was lower than the extension rates of 2.1 ± 0.9 cm yr-1 reported for H. coerulea laterally overgrowing massive Porites spp. by Guzman et al (2019)

Summary

Introduction

Calcium carbonate production represents one of the core functions of coral reef ecosystems (Brandl et al 2019) and can be approximated from estimates of benthic cover and taxa-specific calcification rates as part of census-based coral reef carbonate production budgets (Perry et al 2012). We address this by quantifying rates (mean ± SE) of linear extension (0.86 ± 0.05 cm yr-1) and skeletal density (2.01 ± 0.06 g cm-3) to estimate calcification rates (0.87 ± 0.08 g cm-2 yr-1) for the small branching/columnar morphology of Heliopora coerulea.

Results

Conclusion