Coral Records of Variable Stress Impacts and Possible Acclimatization to Recent Marine Heat Wave Events on the Northwest Shelf of Australia

Abstract

AbstractThe ability of massive corals to record the impacts of marine heat wave events provides a unique perspective into the variable responses of corals to anthropogenic climate change. In this study, coral cores (Porites spp.) were collected from seven reef sites across the inner‐, mid‐, and outer‐NW shelf of Australia, to examine seasonal patterns of trace element (TE), Sr/Ca and Li/Mg ratios, and extension rate signatures associated with past marine heat waves in the region. TE anomalies and declines in linear extension rate were observed in the records during the late 1990s (two of five records) and more recently during the summers of 2011 (three of seven records) and 2013 (five of seven records), indicating the impacts of marine heat waves have become increasingly widespread in the region. However, for the summers of 2011 and 2013, no significant relationships were observed between the magnitude of these TE ratio anomalies in the core records and maximum thermal stresses predicted at the reef sites from high‐resolution satellite records. We show that the strongest individual reductions in linear extension rates and associated TE ratio anomalies occurred during the 2011 heat wave, rather than during the subsequent and more intense (~1 °C warmer) 2013 event. Together, these observations suggest that at the local reef scale, Porites spp. colonies and their symbionts exhibit differential responses to heat wave events, with the prior exposure to less intense events probably playing an important role in acclimatization.