# Coral tissue depth reconstructed using skeletal microstructural offsets is driven by environmental stress

## TL;DR

This study shows how coral tissue depth can be used to track environmental stress over time by analyzing skeletal microstructural offsets in a coral core from Barbados.

## Contribution

The study introduces a novel method to reconstruct seasonal tissue depth using skeletal microstructural offsets as a proxy for coral health.

## Key findings

- Tissue depth varies systematically over multiyear timescales and decreases under thermal stress.
- Environmental disturbances like volcanic eruptions affect tissue depth through the release of bioactive metals.
- The offset signal is robust within a single coral colony and could be validated across multiple colonies.

## Abstract

Coral tissue depth reflects organismal health and is influenced by environmental stressors. Reconstructing its past variability on inter- and intra-annual timescales, however, is not yet possible. Here we reconstructed seasonal tissue depth by measuring spatial offsets between growth cycles in corallite porosity and theca geochemistry (Lithium/Magnesium and Barium/Calcium ratios) of a single Siderastrea siderea core collected in Barbados. We show spatial offsets and thus tissue depth vary systematically over multiyear timescales, with decreasing values associated with thermal stress that impact extension rate and calcification in subsequent growth cycles. Large environmental disturbances such as the 2021 volcanic eruption of La Soufrière (St. Vincent) also impact tissue depth, in this case likely due to the release of bioactive metals upon ash deposition. This study investigates the robustness of the offset signal within a single colony and with further validation across multiple colonies could help reconstruct regional to global environmental and ecological stressors.

Coral tissue depth is influenced by environmental stressors, directly impacting skeletal extension and calcification; it may therefore be used as a proxy for past coral health, according to analysis of a coral core from Barbados.