Elkhorn coral suffering from bleaching in Dry Tortugas National Park, Pulaski Shoal

Shown here is a colony of the threatened Elkhorn coral, Acropora palmata, that has succumbed to "bleaching," that is, lost all its algal symbionts (also called zooxanthellae) because of the summer 2023 ocean-heat wave. The coral is attached to a cement block as part of the U.S. Geological Survey’s Coral Assessment Network (USGS-CAN) that provides data on coral-growth (calcification) rates throughout the western Atlantic. Data like these are collected to document seasonal and spatial patterns in coral growth that correlate with ocean conditions and are used to guide the management and restoration of coral species that have experienced population declines across the region, and pictured here is one of calcification stations located in in Dry Tortugas National Park. Unfortunately, this colony was already completely dead when photographed on August 15, 2023.