Caribbean Corals in Crisis: Record Thermal Stress, Bleaching, and Mortality in 2005

TLDR

Rising ocean temperatures threaten coral reefs worldwide, and in 2005 the tropical Atlantic and Caribbean experienced the most severe bleaching event ever recorded, coinciding with waters near a western Atlantic warm pool off the Lesser Antilles. The study used satellite‑based heat‑stress monitoring to guide detailed field surveys of bleaching and mortality across the Caribbean from June to October 2005, establishing a new standard for documenting bleaching effects and testing nowcast/forecast products. The 2005 Caribbean bleaching event caused over 80 % of corals to bleach and more than 40 % to die at many sites, with thermal stress exceeding all Caribbean events in the past 20 years and regionally the warmest in 150 years; satellite heat‑stress metrics predicted bleaching intensity, and the widespread mortality is expected to have long‑term detrimental effects on reef ecosystems.

Abstract

Background The rising temperature of the world's oceans has become a major threat to coral reefs globally as the severity and frequency of mass coral bleaching and mortality events increase. In 2005, high ocean temperatures in the tropical Atlantic and Caribbean resulted in the most severe bleaching event ever recorded in the basin. Methodology/Principal Findings Satellite-based tools provided warnings for coral reef managers and scientists, guiding both the timing and location of researchers' field observations as anomalously warm conditions developed and spread across the greater Caribbean region from June to October 2005. Field surveys of bleaching and mortality exceeded prior efforts in detail and extent, and provided a new standard for documenting the effects of bleaching and for testing nowcast and forecast products. Collaborators from 22 countries undertook the most comprehensive documentation of basin-scale bleaching to date and found that over 80% of corals bleached and over 40% died at many sites. The most severe bleaching coincided with waters nearest a western Atlantic warm pool that was centered off the northern end of the Lesser Antilles. Conclusions/Significance Thermal stress during the 2005 event exceeded any observed from the Caribbean in the prior 20 years, and regionally-averaged temperatures were the warmest in over 150 years. Comparison of satellite data against field surveys demonstrated a significant predictive relationship between accumulated heat stress (measured using NOAA Coral Reef Watch's Degree Heating Weeks) and bleaching intensity. This severe, widespread bleaching and mortality will undoubtedly have long-term consequences for reef ecosystems and suggests a troubled future for tropical marine ecosystems under a warming climate.