[Coral-List] Bleaching in Florida Keys

Lewis, Cindy Cindy.Lewis at MyFWC.com
Sat Oct 10 10:41:51 EDT 2015


In response to your question about temperature data and bleaching in the Keys 2015:

We are in the 2nd year of a Dendrogyra monitoring project on the Florida Reef Tract, with data loggers placed at multiple sites from Biscayne Bay to the Dry Tortugas. We assess these sites May/Sept/Jan and some sites monthly. We have been closely following temperature data at our sites from April to the present. Mean daily water temperatures in the Upper Keys in July were 30C but exceeded 31C in the Middle Keys in early July. We were noticing some paling of several species of coral at that time.

By Aug both Upper & Middle Keys were experiencing mean daily temperature exceeding 31C with more pronounced paling and partial bleaching observed.  (maximum temps recorded: 8/2 Middle Keys 32.4C; 8/24 Upper Keys 31.9C). Multiple observations of a warmer, murky layer on the bottom in the Middle and Lower Keys were also noted, even on the deeper reefs. By late August and early Sept, most species of coral were severely bleached throughout the Keys, including many octocoral, although not quite as badly as 2014.

Of note: our data loggers in the Upper & Middle Keys Sept 13-17 recorded a nearly 2C drop in temperatures (32.1C to 30.4C), coinciding with the wind and rain event from the remnants of Tropical Storm Grace over the Keys. Water temps have continued to slowly decline since then and we are beginning to see signs of recovery in some species, at some sites. Black band disease has been rampant, rapidly overtaking many large coral heads, including M cavernosa, C natans,  and others.

We just pulled data loggers from our Lower Keys sites with data from April to Oct but have not had a chance to look at them yet. I'm sure it will tell a similar story, although the Lower Keys seems to be more severely bleached.

These observations have been reported to Coral Bleach Watch (Mote) and NOAA Coral Monitoring Program.


Cindy Lewis

Keys Marine Laboratory


US #1, mile marker 68.5

Long Key, FL


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