A ‘Perfect Storm’ of Cumulative and Acute Heat Stress, and a Warming Trend, Lead to Bleaching Events in Tutuila, American Samoa
July 21, 2022
To better understand vertical thermal structure of reefs at depth and identify predictors of mass bleaching events, we used long-term in situ temperature data collected at multiple reefs and depths around the island of Tutuila in American Samoa.
Coral reefs are the most diverse ecosystems on the planet despite evolving in nutrient depleted water and within a narrow range in temperature, salinity, and water quality. Corals are predominantly limited to tropical, shallow waters in the euphotic zone due to their light- dependent symbiotic relationship with photosynthetic algae called zooxanthellae. Environmental changes catalyze the breakdown of coral-symbionts by triggering corals to expel their zooxanthellae, causing coral tissue to pale and, in extreme cases, reveal their underlying skeleton and appear white. This phenomenon is called coral bleaching.
In an effort to predict future bleaching events, various temperature predictor variables have been calculated primarily from sea surface temperatures (SST) derived from satellite data. High frequency temperature data can provide informative measures to predict bleaching prevalence that may be overlooked if only satellite-derived metrics are evaluated.
The objectives of our study are to (1) conduct a time series analysis on in situ temperature data (2012–2018) and calculate heating metrics and (2) determine whether heating metrics predicted coral bleaching prevalence during the 2015 bleaching event.
Smith J, Halperin A, Barkley H. 2022. A 'perfect storm' of cumulative and acute heat stress, and a warming trend, lead to bleaching events in Tutuila, American Samoa Turn on screen reader support. U.S. Dept. of Commerce, NOAA Technical Memorandum NOAA-TM-NMFS-PIFSC-129, 52 p. https://doi.org/10.25923/yphg-pq04.