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Category: Project

Description: Predicting if reefs can keep pace with future sea-level (SL) rise is problematic because accretion occurs over geological timescales. For example, although meltwater pulses drowned reefs during postglacial SL rise, drowning has also been reported during the mid Holocene, when SL rise was slower and meltwater pulses unlikely. Here we report the discovery of a drowned incipient reef-crest on the widest part of northeast Yucatan shelf. Our data show the reef is an array of closely-spaced patches that crest at -14 m. These patches consist of 3 m-thick stands of Acropora palmata that grew over a Pleistocene dune ridge ~8 ka ago, but subsequently failed to keep pace with rising SL. We hypothesize that this failure is due to the suppression of coral recruitment by high sediment flux on wide shelves. Although recruitment does occur as the surf zone crosses topographic residuals during the transgression, suppression in sandy reef-fronts and back-reefs limits accretion of these incipient crests, causing their slow drowning during SL rise. We conclude that although reefs can slowly develop breakwaters in such settings, they may be incapable of vertical accretion and thus vulnerable to drowning. Identifying reefs with this vulnerability will be key to managing future SL rise.