The ability to predict and mitigate the ecological and health impacts of global climate change depends upon the availability of integrated models. In this project, researchers at the Rosenstiel School of Marine and Atmospheric Sciences of the University of Miami will compile and begin synthesis of archived Gulf of Mexico environmental datasets related to harmful algal blooms (HAB) and microbial pathogens. The research team is capitalizing on six years of interdisciplinary HAB and pollution-associated pathogen research. The primary research focus will be the role of low-mixing areas combined with anthropogenic influences from nutrient-rich freshwater runoff. The goal is to build the database necessary to assess the tole of global climatic change upon the occurrence and spread of HABs and human pathogen in the zone extending from beaches to the open waters of the Gulf of Mexico.

Broader Impacts: The study has high societal relevance and importance because of the well-known and increasing occurrences disease attributable to HABs and human pathogens in coastal Florida and the Gulf of Mexico region. It will also serve as an important resource for further research and public education in the ecology of HABs and human enteropathogens in tropical and subtropical marine waters and their impacts on human health at a time of global climatic change.

Project Report

The beaches along the Gulf of Mexico are frequently exposed to harmful algal blooms (HABs) and loadings from fecal indicator microbes. For both the HABs and the microbes, the primary focus of the study is the importance of the role of low mixing areas (both near shore and in the open Gulf) combined with anthropogenic influences from nutrient-rich freshwater runoff. We have synthesized historical (physical and biological) oceanographic data collected from throughout the Gulf of Mexico (both near shore and shelf water) to create predictive models of HABs and microbe distribution and abundance. We analyzed decade-long weekly monitoring records of the fecal indicator microbes, enterococci and fecal coliform, at more than 300 Florida recreational beaches. Results showed that exposed beaches exceed the EPA threshold much less frequently than sheltered beaches, suggesting that local hydrodynamic mixing is an important factor in determining beach water quality. In addition, we found different behavior for Atlantic coast beaches versus Gulf coast beaches. We hypothesize that the microbe abundance at the Atlantic coast is controlled by waves and water temperature, whereas runoff is more important along the Gulf coast. Finally, hurricanes may remove or bury the microbial communities in the beach face, which result in low microbe levels after major storms. Several months are usually needed for the levels to recover to pre-storm conditions. We have developed a survey, which has been distributed to all county health departments throughout the State of Florida with follow up to local beach managers. The results of this survey are being consolidated into an Access database from which information will be pulled for statistical analyses. Of the 300+ beaches in Florida, we have received responses for 100+. In addition we have developed a simple microbial balance model to predict spatiotemporal variations of indicator bacteria levels at nonpoint source beaches. The model predicts the release and transport of sediment-attached enterococci at beaches and has successfully been compared with observations. The primary mechanism of release is related to the hydraulic exposure by tides and waves of the bacteria-laden sediment within the inter-tidal zone at the upper beach face where enterococci can survive and even grow. We anticipate these efforts will help beach managers in making advisory decisions by integrating information about beach management practices and their influence on marine water quality and knowledge provided by model simulations. We have also analyzed a decade-long record of HABs occurrence on the West Florida Shelf along with archived environmental datasets (including wind, river outflow and the Loop Current position). We found that the river runoff is statistically larger during times of large blooms and that the Loop Current is southern than averaged position during times of no bloom. The Loop Current intrusion on the Shelf favors the retention along the coast. On the other hand, the movement of the Loop Current to the south favors the flush out of the Shelf. No correlation was found with wind intensity and direction for various locations on the west Florida coast and HAB occurrences.

National Science Foundation (NSF)
Division of Ocean Sciences (OCE)
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Donald L. Rice
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University of Miami Rosenstiel School of Marine&Atmospheric Sci
Key Biscayne
United States
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