Coral Bleaching / Looe Key Reef

Causey, B. bcausey at
Mon Sep 14 00:38:03 EDT 1998

Coral bleaching has been reported in a variety of coral habitats in the Florida Keys over the past 2 - 3 months.  This past Friday (September 11, 1998) the Sanctuary's Education Team and I snorkeled in four different coral habitats on and around Looe Key Reef.  We observed moderate coral bleaching in the intermediate reef habitat (45' depth) and in some of the shallower coral reef areas.

Most alarming was the impact to the shallow Acropora species on the reef crest and shallow backreef.  There has been a steady recruitment and growth spurt of Acropora palmata and A. cervicornis in that area since the mid to late 1980's.  Almost 100% of the Acropora colonies are severely bleached and large patches of coral tissue have died.  In some instances the entire colonies were dead.  It will be hard to tell what will survive at this point, considering many of the stark white colonies were still alive at this time.  There was a considerable amount of bleaching in the Millepora and again..... I observed a lot of mortality.  Although many of the head coral species were in various stages of stress from bleaching..... they were not in as bad a condition as they were last year.

I did not have a temperature meter with me and checked one of our thermographs on the reef flat and could not read the temp..... but the water was noticeably cooler than it was a week or 2 ago.  It may be that we are through the critical period for this year.  Historically, our coral bleaching in the Keys lessens as we start getting weather changes and cool fronts moving through the area.

This is the first year we have had back-to-back coral bleaching events (2 years in a row) in the Florida Keys.... since I moved here in the early 1970's.  It will be interesting to see what the future has in store for our reefs regarding other such trends.

Billy Causey, Superintendent
Florida Keys National Marine Sanctuary

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