http://sanctuaries.noaa.gov

Coral Reef Evaluation & Monitoring

Sanctuary Managers Rely on Research Results to Protect Coral Reef

North America’s only barrier coral reef is adjacent to the Florida Keys within the 

Florida Keys National Marine Sanctuary. Located on the ocean side of the 

island chain, the reef is bathed by the warm, clear waters of the Florida Current 

fl owing from the south. The coral reef of the Florida Keys lies only a few 

miles from shore and experiences both natural and human impacts. 

Hurricanes and storms overturn large coral colonies and wastewater and 

stormwater degrades nearshore waters, potentially affecting corals and 

other marine life. Keys reefs, along with reefs throughout the Caribbean, 

have also experienced bleaching events and disease outbreaks over the 

years. Sanctuary managers rely on the fi ndings from research and monitoring 

programs to aid them in protecting and managing this world-renowned coral 

reef for future generations.

To collect valuable information about the reef ecosystem, scientists from 

Florida’s Fish and Wildlife Conservation Commission began systematically 

monitoring coral reefs throughout the sanctuary in 1996. This research program, 

called the Coral Reef Evaluation & Monitoring Program (CREMP), studies various 

aspects of reef ecology and health and employs numerous survey methods and 

analyses. CREMP is part of the Water Quality Protection Program, which 

was established by Congress to track the status of natural resources within 

sanctuary waters and is jointly managed by the U.S. Environmental Protection 

Agency and the state of Florida. 

Systematic Monitoring of Coral Reef Ecosystem Reveals Trends

CREMP scientists have conducted systematic inventories of species and recorded digital video at sampling stations throughout 

the Keys since 1996. The sampling stations fall into four habitat types: hardbottom, patch reef, offshore shallow and 

offshore deep, and cover four regional areas: Upper Keys, Middle Keys, Lower Keys and Dry Tortugas. The species inventory data 

allow scientists to determine species richness, or the 

number of different coral species present at each station, 

and the digital video data is used to quantify coral cover and 

species composition of the benthic (bottom) community. 

Since monitoring began, an average of 3.3 species have 

been lost per station throughout the sanctuary, with 76% 

of all stations showing a decrease in the species richness. 

Declines in 13 of the 43 species account for most of the 

losses observed. However, between the years 2006 and 

2007, there was a slight increase in species richness 

observed in some regions and habitats, with the greatest 

increase seen at the patch reefs and Tortugas stations. Trends 

in coral cover, a measure of how much living coral exists in an 

area, have also been analyzed. Cover for stony corals declined 

in the late 1990s, but increased slightly from 2006 to 2007 in 

the Upper Keys and Dry Tortugas. 

A scientist digitally records benthic species. 

Photo: Florida Fish and Wildlife Conservation Commission

All regions in the Keys showed declines in coral cover. 

Image: Florida Fish and Wildlife Conservation Commission 

Florida Keys National Marine Sanctuary

http://fl oridakeys.noaa.gov/
To learn more about these and other accomplishments, 

visit sanctuaries.noaa.gov

Coral diseases have been tracked since 1996 by CREMP. 

Image: Florida Fish and Wildlife Conservation Commission

Principal Investigator: Mr. Rob Ruzicka, Florida Fish and Wildlife Conservation Commission

Written by: Nancy Diersing, Florida Keys National Marine Sanctuary

Published: May 2009

Bleaching and Disease Impact Caribbean Corals

Bleaching impacted corals in the Caribbean, including 

those in the Keys, in 1997 and 1998 and is a likely 

contributor to the declines in coral cover recorded in the 

late 1990s. Bleaching is a stress response to high seawater 

temperatures that takes place when corals expel the 

benefi cial microscopic algae living within their coral 

polyps. These microscopic algae, known as zooxanthellae, 

provide nutrition for the coral colony and give the coral its 

characteristic color. Without zooxanthellae, stony corals 

appear white, or “bleached.” Corals that have bleached 

are more susceptible to disease, but some do regain their 

zooxanthellae and recover from bleaching.

Diseases also contributed to declines seen in coral 

cover and species richness. CREMP scientists record the 

presence or absence of disease for each species at each 

station during fi eld sampling. In general, from 1996 to 

2002, increases were documented in the number of 

diseased corals per station, the number of stations with diseased corals, and the different types of diseases recorded. Blackband, 

a disease that attacks many species of corals worldwide, peaked in 1998, but has remained relatively stable during the study. 

“White” diseases, such as white plague, affected the major reef-building corals like boulder star coral (Montastrea annularis), while 

white-band disease targeted elkhorn (Acropora palmata) and staghorn (Acropora cervicornis) corals. The category of diseases 

grouped as “white” peaked in 2002. 

Multiple Stressors Affect Coral Cover and Species Richness

In 2007, staghorn coral and elkhorn coral were listed as threatened 

species under the Endangered Species Act and awarded new 

protections. Based on CREMP surveys, staghorn cover has been 

historically low throughout the sanctuary, but elkhorn coral cover was 

much higher at the inception of the study than it is today. After 1999, 

elkhorn cover declined signifi cantly as a result of disease, but in recent 

years has remained relatively stable. The heavy losses of staghorn corals 

seen in the Tortugas between 2002 and 2004 were brought about by 

multiple disease and thermal stress events.

Reductions in coral cover and species richness in the Florida Keys have 

been largely attributed to multiple recurring stressors, including disease 

outbreaks, hurricanes and fl uctuations in major weather patterns, all of which cause coral mortality. For example, the El Niño 

weather pattern of 1997-1998 caused high sea surface temperatures, which brought about widespread coral bleaching, followed 

by severe losses of coral cover in 1998 and 1999. Subsequent bleaching events have occurred during warmer summers when 

high seawater temperatures and calm seas have prevailed (for example, in 2005). Diseases were also highly prevalent from 1999 

through 2003, with different diseases targeting different species of coral. Hurricanes and intense storms like those of the 2004 

storm season have had detrimental effects on sanctuary reefs by causing direct physical damage to corals. 

Research and Monitoring are Critical to Managing Reefs for the Future 

The health of the coral reef ecosystem in the Florida Keys depends on the quality of water in which the corals live. Because of the 

nature of corals, even slight deterioration in water quality can be stressful to the reef. CREMP scientists have begun to analyze water 

quality data in conjunction with coral data to tease out connections and correlations between water quality and 

coral health whenever possible. Continued study into the causes and nature of disease outbreaks, along with rigorous 

monitoring of coral reefs and their inhabitants, will facilitate in managing coral reefs for the future. Coral reef research and 

monitoring are especially important for tracking the effects of increasing seawater temperatures and sea level rise 

associated with the Earth’s changing climate. They are also critical in evaluating the impacts of changing freshwater 

fl ows on the Florida mainland as part of the Comprehensive Everglades Restoration Plan. For more CREMP results, visit 

http://ocean.fl oridamarine.org/fknms_wqpp/pages/cremp.html.

Unbleached elkhorn coral growing next to bleached fi re coral.

Photo: FKNMS