| Summary: | As the aragonite saturation horizon shoals globally, cold-water corals may be among the first organisms affected by an acidifying ocean. The current study evaluated the effect of low aragonite saturation states (Ω arag) on the cosmopolitan cold-water reef-forming coral, Lophelia pertusa. Part I employed laboratory experiments to identify threshold Ω arag below which the skeleton begins to dissolve and to quantify the dissolution rate of L. pertusa skeleton in acidified water. Aside from the lowest treatment (Ωarag =0.5) dissolution rates were lower than many published growth rates. The critical Ω arag was near 0.80, indicating that skeletal fragments not covered by tissue, such as hold-fasts and dead coral matrix, would be vulnerable to dissolution at Ωarag <0.80. Part II examined the distribution of L. pertusa in the naturally acidified conditions of the Southern California Bight (SCB) using 2003-2012 fishery surveys. While L. pertusa was widespread, only 8% occurrences (n=131) included reef-framework. Large, intact live aggregations were generally limited to depths <160 m (mean Ωarag >0.9). Total area of L. pertusa was not correlated with depth, but proportion of live coral decreased with increasing depth. Oxygen concentrations and Ωarag near aggregations were lower than reported for L. pertusa in other ocean basins. The SCB reflects marginal habitat for L. pertusa and provides insight to the future of cold-water coral reefs as the ocean acidifies globally.
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