Crumbling Reefs and Cold-Water Coral Habitat Loss in a Future Ocean: Evidence of "Coralporosis" as an Indicator of Habitat Integrity

Ocean acidification is a threat to the net growth of tropical and deep-sea coral reefs, due
to gradual changes in the balance between reef growth and loss processes. Here we
go beyond identification of coral dissolution induced by ocean acidification and identify
a mechanism that will lead to a loss of habitat in cold-water coral reef habitats on an
ecosystem-scale. To quantify this, we present in situ and year-long laboratory evidence
detailing the type of habitat shift that can be expected (in situ evidence), the mechanisms
underlying this (in situ and laboratory evidence), and the timescale within which the
process begins (laboratory evidence). Through application of engineering principals, we
detail how increased porosity in structurally critical sections of coral framework will lead
to crumbling of load-bearing material, and a potential collapse and loss of complexity
of the larger habitat. Importantly, in situ evidence highlights that cold-water corals can
survive beneath the aragonite saturation horizon, but in a fundamentally different way to
what is currently considered a biogenic cold-water coral reef, with a loss of the majority
of reef habitat. The shift from a habitat with high 3-dimensional complexity provided
by both live and dead coral framework, to a habitat restricted primarily to live coral
colonies with lower 3-dimensional complexity represents the main threat to cold-water
coral reefs of the future and the biodiversity they support. Ocean acidification can cause
ecosystem-scale habitat loss for the majority of cold-water coral reefs.