Abstract
Abstract. Coral reefs serve as natural barriers that protect adjacent shorelines from coastal hazards such as storms, waves, and erosion. Projections indicate global degradation of coral reefs due to anthropogenic impacts and climate change will cause a transition to net erosion by mid-century. Here, we provide a comprehensive assessment of the combined effect of all of the processes affecting seafloor accretion and erosion by measuring changes in seafloor elevation and volume for five coral reef ecosystems in the Atlantic, Pacific, and Caribbean over the last several decades. Regional-scale mean elevation and volume losses were observed at all five study sites and in 77 % of the 60 individual habitats that we examined across all study sites. Mean seafloor elevation losses for whole coral reef ecosystems in our study ranged from −0.09 to −0.8 m, corresponding to net volume losses ranging from 3.4 × 106 to 80.5 × 106 m3 for all study sites. Erosion of both coral-dominated substrate and non-coral substrate suggests that the current rate of carbonate production is no longer sufficient to support net accretion of coral reefs or adjacent habitats. We show that regional-scale loss of seafloor elevation and volume has accelerated the rate of relative sea level rise in these regions. Current water depths have increased to levels not predicted until near the year 2100, placing these ecosystems and nearby communities at elevated and accelerating risk to coastal hazards. Our results set a new baseline for projecting future impacts to coastal communities resulting from degradation of coral reef systems and associated losses of natural and socioeconomic resources.
Highlights
Coral reef ecosystems develop over thousands of years as organisms build skeletons of calcium carbonate minerals that form complex 3-D structures and keep pace with rising sea level through continued growth and accretion of carbonate sediments
Our study examined changes in seafloor elevation within five regions characterized by extensive coral reef ecosystems that included reef flats as well as reef crest and slope habitats, adjacent habitats such as seagrass beds, sand bottom, and hard bottom communities, and deeper water habitats
We chose to perform our analyses at the coral reef ecosystem scale because accretion in non-coral-dominated habitats within these ecosystems, as well as off shore habitats, is supported by sand/sediment production from the breakdown of carbonate produced by corals and other calcifying reef organisms
Summary
Coral reef ecosystems develop over thousands of years as organisms build skeletons of calcium carbonate minerals that form complex 3-D structures and keep pace with rising sea level through continued growth and accretion of carbonate sediments. These ecosystems support up to 25 % of fisheries in tropical regions and developing nations (Garcia and Moreno, 2003) and economic and recreational services for more than 100 countries (Burke et al, 2011).
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