The status of coral reef communities has been monitored annually since 1996 at two sites north of Key West, Florida, . Percent cover of selected benthic community categories and stony (hermatypic) coral species number at these sites were relatively stable from 1996 to 2001, but decreased by >70% and >40%, respectively, from 2001 to 2002. Clionid sponges ranged from 12--16 colonies in 2001, but none were observed in 2002. Satellite ocean color imagery showed the transit of water with abnormally low water-leaving radiance values between March and May 2002 over these sites. Field observations showed that this black water contained the red tide organism Karenia brevis and high diatom concentrations. The observations from satellite ocean color data suggested that the decline in the benthic communities was related to the passage of the water patch over the reef sites.