Natural thermal stress-hardening of corals through cold temperature pulses in the Thai Andaman Sea

Stress-hardening by environmental priming could increase the odds for corals to resist ocean warming. Natural environmental fluctuations, such as those observed on offshore reefs in the Andaman Sea, provide an ideal natural environment to study these effects. Here, internal waves (IW) generate short cold-water pulses that peak from January to June and are absent from August to November. Additionally, only western shores of islands are exposed to this stress-hardening stimulus of IWs, while eastern shores remain sheltered. Therefore, this study examined (1) whether exposed corals were more heat stress resistant than their sheltered conspecifics and (2) whether this trait would persist during the season of stimulus absence. We exemplify that thermal regimes featuring cold-temperature pulses successfully induced thermal stress-hardening in corals. Corals from the IW-sheltered shore responded strongly to heat stress irrespective of the season, while stress responses of IW-exposed corals wer..., Study sites and coral collection
Study sites were located at Racha Island in the Andaman Sea off the coast of Thailand, both at 15 m water depth (Figure 1 A-B). A reef on the western shore was chosen (7.595530°N, 98.354320°E, Figure 1 B) where internal wave (IW) forcing as a potential stress-hardening stimulus induced environmental variability through frequent upwelling of deep, cool, and nutrient rich water onto the shelf (Schmidt et al., 2016; Wall et al., 2012). A reef on the eastern shore, sheltered from the stimulus of IWs, was chosen to represent a low variability reef (7.598910°N, 98.373100°E, Figure 1 B). Temperature fluctuations were monitored in situ as a proxy for IW impact and environmental variability. Temperature loggers (HOBO Pendant Temperature/Light 8K Data Logger, Onset, USA) were deployed at the study sites one month before heat stress assays were performed. At each study site, visually healthy coral colonies of Pocillopora sp. and Porites sp. were permanently tagged ..., , # Natural thermal stress-hardening of corals through cold temperature pulses in the Thai Andaman Sea

## Description of the data and file structure

This dataset includes all data for the manuscript \"Natural thermal stress-hardening in corals: Cold-water pulses boost heat resistance\" by Wall M./Roik A. et al. which investigated the phenomenon of stress-hardening through environmental priming in corals during two distinct seasons. Data were collected at the Andaman Sea coast of Thailand.
This data collection contains environmental data (temperature °C, HOBO Pendant Temperature/Light 8K Data Logger, Onset, USA), coral bleaching score data (decline of coral tissue coloration, assessed as established in Siebeck et al., 2006), and the effective quantum efficiency (yield Φ PSII, pulse amplitude-modulated fluorometer Diving-PAM, Walz, Germany).
The two latter variables are metrics that capture the coral stress response and were assessed during short-term heat stress assays (the mothofology i...