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Bleached Elkhorn coral under a shade in Dry Tortugas National Park, Garden Key

Detailed Description

Shown here is a colony of the threatened Elkhorn coral, Acropora palmata, that has become "bleached," 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. Pictured here is one of calcification stations located in Dry Tortugas National Park. The shade structure could help to reduce light stress that is problematic when corals are in a bleached state (see for more information). A pink "glow stick" can be seen attached to the front, right support rod of the shade structure. We are testing whether the glow stick could be effective in attracting extra zooplankton for the coral to feed on during nighttime when corals typically catch prey with their tentacles. While the glow stick will only emit light for a night or two, we are hoping to give the bleached corals a head start on their recovery with a night of extra food.


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