Human Health
Florida Keys

This beach is monitored as part of the healthy beaches program
The Florida Department of Health posts swimming advisories at beaches throughout the Florida Keys. This sign indicates if it is advisable or not to swim due to water quality issues such as fecal coliform levels. Credit: NOAA/FKNMS

Why is it a concern?

Human health can be affected by different factors found in Florida Keys National Marine Sanctuary. For example, fecal coliform and enterococci bacteria, harmful algal blooms (e.g., red tides), and ciguatera fish poisoning all have the potential to affect human health.

Runoff and spills have periodically resulted in high levels of fecal coliform and enterococci bacteria in the Florida Keys, resulting in swimming advisories for nearshore waters and beaches. Enterococci bacteria and fecal coliform bacteria are often used as indicator organisms in nearshore water quality monitoring, and while they may not cause diseases in humans, their presence can indicate that water may be contaminated with organisms that cause human health impacts such as fever, flu-like symptoms, ear infection, respiratory illness, rashes, gastroenteritis, cryptosporidiosis, and hepatitis. Sources of polluted and contaminated water include runoff from urban, suburban and rural areas, aging sewer infrastructure systems pressed to meet increasing demands, and contaminated flows from other upland sources.

Human health can also be impacted by Harmful Algal Blooms (HABs) which occur when certain types of microscopic algae grow quickly in water. HABs are attributed to two primary factors: natural processes such as warm water and poor water circulation and flow, and anthropogenic causes such as nutrient loading leading to eutrophication. HABs can lead to discoloration (red, brown or green tides) of the water as large numbers of algae accumulate. Some HAB-causing algae can release toxins that can lead to fish kills, coral stress and mortality and skin and respiratory problems in humans.

Ciguatera fish poisoning (CFP), found throughout the tropical Pacific and the Caribbean, is rare in the Keys, with the most recent case occurring in 2006. However, it is well documented that certain fishes such as grouper, moray eel, jacks, kingfish, snapper, hogfish, and barracuda are more prone to be ciguatoxic due to their position in the food chain and large adult size. While CFP is an issue regionally and has been reported locally in the Florida Keys, there is no evidence that the incidence of ciguatera is increasing in the sanctuary.

Overview of Research

Science Needs and Questions

  • Are there increasing incidents of swim advisories?
  • Are there increasing incidents of ciguatera fish poisoning?

Education and Outreach Material


Abbott, G.M., J.H. Landsberg, A.R. Reich, K.A. Steidinger, S. Ketchen, C. Blackmore. 2009a. Resource guide for public health response to harmful algal blooms in Florida. Fish and Wildlife Research Institute Technical Report TR-14. viii + 132 p.

Abbott, J.P., L.J. Flewelling, J.H. Landsberg. 2009b. Saxitoxin monitoring in three species of Florida puffer fish. Harmful Algae 8:343-348.

de Sylva, D. P. 1994. Distribution and ecology of ciguatera fish poisoning in Florida, with emphasis on the Florida Keys. Bull. Mar. Sci. 54(3): 944—954.

Florida Keys National Marine Sanctuary (FKNMS) Comprehensive Science Plan, November 2002 Final Draft.

Harvell, C.D., K. Kim, J.M. Burkholder, R.R. Colwell, P.R. Epstein, D.J. Grimes, E.E. Hofmann, E.K. Lipp, A.D.M.E. Osterhaus, R.M. Overstreet, J.W. Porter, G.W. Smith, G.R. Vasta. 1999. Emerging Marine Diseases - Climate Links and Anthropogenic Factors.Marine Ecology
285:1505-1510. Electronic document available from:

Marine Ecosystem Event Response and Assessment (MEERA) Project.  Mote Marine Laboratory. We Nobles, R.E., P. Brown, J. Rose, E. Lipp. 2000. The investigation and analysis of swimming associated illness using the fecal indicator Enterococcus in Southern Florida's marine water. Fla. J. Environ. Health 169:13-19.

Office of National Marine Sanctuaries. 2011. Florida Keys National Marine Sanctuary Condition Report 2011. U.S. Department of Commerce, National Oceanic and Atmospheric Administration, Office of National Marine Sanctuaries, Silver Spring, MD. 105 pp.