Coral bleaching: the winners and the losers

TLDR

Sea surface temperatures were warmer throughout 1998 at Sesoko Island, Japan, than in the 10 preceding years. The study proposes that preferential survival of thick‑tissued species and shape‑dependent differences in colony mass‑transfer efficiency together explain observed mortality patterns. The authors used random quadrat surveys to quantify coral community structure one year before and after the bleaching event. The 1998 bleaching event, driven by temperatures 2.8 °C above average, reduced coral species richness by 61 % and cover by 85 %, with finely branched corals most vulnerable, while massive and encrusting species survived and the reef community shifted toward these more resistant forms.

Abstract

Sea surface temperatures were warmer throughout 1998 at Sesoko Island, Japan, than in the 10 preceding years. Temperatures peaked at 2.8 °C above average, resulting in extensive coral bleaching and subsequent coral mortality. Using random quadrat surveys, we quantitatively documented the coral community structure one year before and one year after the bleaching event. The 1998 bleaching event reduced coral species richness by 61% and reduced coral cover by 85%. Colony morphology affected bleaching vulnerability and subsequent coral mortality. Finely branched corals were most susceptible, while massive and encrusting colonies survived. Most heavily impacted were the branched Acropora and pocilloporid corals, some of which showed local extinction. We suggest two hypotheses whose synergistic effect may partially explain observed mortality patterns (i.e. preferential survival of thick‐tissued species, and shape‐dependent differences in colony mass‐transfer efficiency). A community‐structural shift occurred on Okinawan reefs, resulting in an increase in the relative abundance of massive and encrusting coral species.