USF Researchers: Dredging, Causeways in Tampa Bay Have Altered its Health

Two studies show how infrastructure interrupts nature’s “flushing” of pollutants from Tampa Bay

An algae bloom in Tampa Bay north of the Courtney Campbell Causeway. Photo courtesy of Tampa Bay Estuary Program..

By Vickie Chachere

USF News

ST. PETERSBURG, Fl. (Oct. 16, 2013) – Two new studies by University of South Florida researchers show that large scale infrastructure in Tampa Bay – such as shipping lanes and causeways – have had a significant impact on the state of the Bay, altering salinity and the exchange of water with the Gulf of Mexico.

USF Professor Mark Luther and Senior Scientist Steven Meyers of the College of Marine Science Ocean Monitoring and Prediction Laboratory found that deepening of the shipping channels in Tampa Bay has allowed for ocean water to flow farther into the bay, making the northern regions more saline. The bridges and causeways slow the exchange of water with the Gulf and the “flushing” of pollutants, the research shows.

The first study was published in journal the Estuaries and Coasts. The second study is under review in the same journal.

Luther said the research presents important observations and findings as economic and government leaders in the Tampa Bay region consider deepening and widening of the ship channel or building new causeways or expanded port facilities.

“Tampa Bay is our home and a primary economic driver for the region,” Luther said. “Our results show that construction of causeways and ship channels has altered the state of Tampa Bay but these changes are manifested in very expected ways. Some of the changes are large while others are small, and they vary over time and from place to place within the bay.

       Mark Luther.

“What we have learned here provides guidance to environmental protection and permitting agencies to assess future changes in water quality in the bay resulting from alterations in


causeways or in the shipping channels of the bay or from sea level rise.”

Using computer models, the researchers looked at three impacts on the bay: changes in salinity, changes in slow subtidal currents which are essential for flushing pollutants out of the bay and maintaining ecological health; and changes in retention time of material within the bay.

The largest changes in the time pollutants remain in the bay were found to the north of the Sunshine Skyway and north of the Courtney Campbell Causeway.

      Steven Meyers

Tampa Bay is the largest estuary in the state of Florida, encompassing nearly 400 square miles of open water and 2,300 square miles of watershed that supports industry, agriculture, and millions of residents people. The bay is also one of the most ecologically productive ecosystems in the world and in recent decades has undergone restoration and protective measures designed to balance the needs of its fragile environment with its economic importance to the region.

The scientists said their work is designed to help policy makers, government officials, environmentalists and citizens make informed decisions about future development and environmental protection investments.

“Our work supports the efforts of biologists and ecologists, as well as entities such as the Tampa Bay Estuary Program, which focus on the health and sustainability of Tampa Bay,” Meyers said.

Vickie Chachere can be reached at (813) 974-6251.