Effects of Red Tide (Karenia brevis) on Piscivorous Birds in Sarasota Bay, Florida

EPA Grant Number: FP916934
Title: Effects of Red Tide (Karenia brevis) on Piscivorous Birds in Sarasota Bay, Florida
Investigators: Deborah, Fauquier Ann
Institution: University of California - Santa Cruz
EPA Project Officer: Michaud, Jayne
Project Period: September 1, 2008 through August 31, 2011
RFA: STAR Graduate Fellowships (2008) RFA Text |  Recipients Lists
Research Category: Academic Fellowships


Estuaries are highly productive and ecologically rich areas that are important habitats for fish and bird species. Over the past few decades, the frequency and duration of harmful algal blooms (HABs) have been increasing globally in coastal areas. HABs, especially those caused by the red tide organism, Karenia brevis, occur frequently along Florida’s west coast, causing episodes of high mortality in fish, sea turtles, birds, bottlenose dolphins and manatees. Although red tide is known to cause episodes of mass mortality among marine vertebrates, it is not know whether this disturbance results in significant declines in vertebrate populations or changes in community structure. This project will determine how red tide influences the abundance, habitat use and behavior of piscivorous birds in the Sarasota Bay estuary. In addition, the extent that brevetoxin intoxication contributes to morbidity and mortality in stranded piscivorous birds from the Sarasota Bay area will be investigated.


Field sampling will examine the effects of K. brevis blooms on the densities, distributions and behaviors of piscivorous birds in Sarasota Bay, Florida. Four habitat types within this region will be investigated: sand/mud flats, mangrove fringe, seagrass and open bay. Each of these habitats has its own characteristic vertebrate community that is distinct from those of the other habitats. Concurrent surveys of (1) K. brevis cell densities; (2) water quality (temperature, salinity, dissolved oxygen and turbidity); (3) distribution and abundance of phytoplankton; (4) distribution and abundances of fishes and birds; (5) stomach content analyses of planktivorous fish; and (6) brevetoxin concentrations in tissues of stranded birds during summer (June – September) and winter (January - March) for three years, will be conducted. Serial blood (1-2 ml) and/or fecal samples will be collected from live sea birds admitted to a local rehabilitation hospital. Tissues will also be collected from dead animals for brevetoxin analysis and may include liver, kidney, stomach contents, feces, and bile. A competitive ELISA to detect brevetoxins (PbTx) will be performed according to Naar et al. (2002) for both live and dead animal samples.

Expected Results:

Red tide will cause changes in the abundance and distribution of fishes, which will be accompanied by changes in the patterns of habitat use by birds. Birds will be affected by exposure to brevetoxin via their prey and they will also face decreased availability of prey during and following red tides. Additionally, preliminary findings from initial testing of stranded birds (n=25) have found that birds can clear the red tide toxin from their bodies within 10 days of rehabilitation. This initial metabolism data can be used by rehabilitators to modify treatment plans for animals suspected of suffering from red tide intoxication. If endangered or threatened bird species become impacted by red tides in the future this data could prove useful to increasing treatment success for these species. Estuaries are ecologically and economically important systems that are subject to intense disturbance by HABs. However, the consequences of HABs to estuarine communities are not well known. Despite this lack of knowledge, natural resource managers are required to make regulatory decisions that reflect societal concerns regarding these important estuarine resources. Our research will address this knowledge gap by examining the nature of disturbances to the estuarine bird community caused by K. brevis blooms.

Supplemental Keywords:

Red tide, Karenia brevis, brevetoxin, HABs, harmful algal blooms, piscivorous birds, estuary, Florida,, RFA, Scientific Discipline, Water, ECOSYSTEMS, Ecosystem Protection/Environmental Exposure & Risk, Aquatic Ecosystems, algal blooms, Environmental Monitoring, Ecology and Ecosystems, bloom dynamics, estuaries, coastal habitats, bird habitat, HAB ecology, red tide bloom, water quality, algal bloom detection, K. brevis

Progress and Final Reports:

  • 2009
  • 2010
  • Final