Taxonomic, Spatial and Temporal Patterns of Bleaching in Anemones Inhabited by Anemonefishes

Jean-Paul A. Hobbs,Michele Thums,Pablo Saenz-Agudelo,Kathryn A. Furby,Michael L. Berumen,Benjamin M. Ford,Ashley J. Frisch,Sebastian C. A. Ferse

doi:10.1371/journal.pone.0070966

Abstract

BackgroundRising sea temperatures are causing significant destruction to coral reef ecosystems due to coral mortality from thermally-induced bleaching (loss of symbiotic algae and/or their photosynthetic pigments). Although bleaching has been intensively studied in corals, little is known about the causes and consequences of bleaching in other tropical symbiotic organisms.Methodology/Principal FindingsThis study used underwater visual surveys to investigate bleaching in the 10 species of anemones that host anemonefishes. Bleaching was confirmed in seven anemone species (with anecdotal reports of bleaching in the other three species) at 10 of 19 survey locations spanning the Indo-Pacific and Red Sea, indicating that anemone bleaching is taxonomically and geographically widespread. In total, bleaching was observed in 490 of the 13,896 surveyed anemones (3.5%); however, this percentage was much higher (19–100%) during five major bleaching events that were associated with periods of elevated water temperatures and coral bleaching. There was considerable spatial variation in anemone bleaching during most of these events, suggesting that certain sites and deeper waters might act as refuges. Susceptibility to bleaching varied between species, and in some species, bleaching caused reductions in size and abundance.Conclusions/SignificanceAnemones are long-lived with low natural mortality, which makes them particularly vulnerable to predicted increases in severity and frequency of bleaching events. Population viability will be severely compromised if anemones and their symbionts cannot acclimate or adapt to rising sea temperatures. Anemone bleaching also has negative effects to other species, particularly those that have an obligate relationship with anemones. These effects include reductions in abundance and reproductive output of anemonefishes. Therefore, the future of these iconic and commercially valuable coral reef fishes is inextricably linked to the ability of host anemones to cope with rising sea temperatures associated with climate change.

Highlights

Increasing sea temperatures associated with global warming are having a profound effect on coral reef ecosystems, largely due to coral bleaching [1]
Sea Temperatures and Anemone Bleaching To determine if anemone bleaching was associated with elevated sea temperatures we examined sea temperatures during major bleaching events
Sea Temperature and Bleaching Archival sea surface temperature (SST) data and in situ water measurements confirmed that all five of the major anemone bleaching events were associated with elevated water temperatures (Figure 2, [38,43])

Summary

Introduction

Increasing sea temperatures associated with global warming are having a profound effect on coral reef ecosystems, largely due to coral bleaching [1]. Bleaching can lead to partial or total mortality of corals and can reduce future reproduction and compromise immunity [2,3,4]. To predict how rising sea temperature will affect the community composition and spatial distribution of coral reefs in the future, much research effort has focused on determining spatial, temporal and taxonomic patterns of coral bleaching. In addition to the direct effects on corals, bleaching can have significant impact to other organisms (e.g. fish) that rely on corals for food and/or shelter [16,17]. Rising sea temperatures are causing significant destruction to coral reef ecosystems due to coral mortality from thermally-induced bleaching (loss of symbiotic algae and/or their photosynthetic pigments). Bleaching has been intensively studied in corals, little is known about the causes and consequences of bleaching in other tropical symbiotic organisms

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