Study finds Tampa Bay seagrass growth, bottom health improving

In any body of water, the benthic zone, or bottom layer, can be considered a good indicator of the water body’s overall health.

A 20-year study of Tampa Bay’s benthic ecological region shows that as a whole, Tampa Bay's waters are in fair-to-good condition. 

Middle and Lower Tampa Bay, which comprise over 50 percent of Tampa Bay’s surface area, were rated “Good.”

Hillsborough Bay and some of the smaller or more heavily urbanized bodies of water within Tampa Bay (including Boca Ciega Bay, Terra Ceia Bay and Manatee River) were ranked “Poor.” Old Tampa Bay was rated “Fair.”

The 20-Year Tampa Bay Benthic Community Trends Study, released by the Environmental Protection Commission of Hillsborough County, was conducted from 1993-2012. Ratings were determined using criteria from the EPA’s National Coastal Assessment program and the Tampa Bay Benthic Index.

For two decades, random samples were collected at more than 1,500 sites across Tampa Bay’s main segments, which total just shy of 400 square miles. The samples were taken in late summer and then processed in the EPC’s labs.

Sampling data monitored animal communities in the Bay (over 1,500 invertebrate animal species were identified); sediment composition and contaminants (heavy metals, pesticides, etc.); salinity; temperature; pH levels, and more.

The study found that the majority of Tampa Bay sediments at the bottom layer do not contain high levels of contaminants; exceptional sites with higher contaminant levels were primarily found in Hillsborough Bay. 

The collection and processing of data for the study was initiated two decades ago by the Tampa Bay National Estuary Program (TBEP), and continues today as a cooperative effort between Hillsborough, Manatee and Pinellas counties.

Study results reveal continued improvement in Tampa Bay’s “fair to good” regions, Dr. David Karlen, the EPC Chief Environmental Scientist who authored the report, explained in a news release.

“Baywide, we’ve seen improvement in the benthic index, which is an overall summary of all species,” Karlen says.

Along with Karlen, report authors include Kevin W. Campbell; Dr. Thomas L. Dix; Barbara K. Goetting; Joette M. Jernigan; and Sara E. Markham.

The report includes recommendations for the future monitoring of benthic communities in Tampa Bay, although additional funding is required to support continued analysis and monitoring programs.

Recommendations include:

• Special study of some sites within Tampa Bay, including Port Tampa Bay (which contains Ybor and Sparkman Channels and Garrison Channel), East Bay, Clam Bayou and Bayboro Harbor.
• Increased monitoring of river and tidal tributary systems, low salinity areas that serve as nursery areas for many species. These include the Hillsborough, Palm, Alafia and Little Manatee Rivers. Known high sediment contaminants in several rivers could have potential impacts.
• Expanding lab analysis to include newer sediment contaminants, such as microplastics.

"The benthic report gives us insight into the legacy (longterm) contaminants that can be found in the sediment," TBEP senior scientist Ed Sherwood says in a news release.

Problem areas indicated by the benthic report will help to guide the estuary program, determine the next step in special studies, track long-term trends in the benthic community and form management policy, Sherwood says.

Another indicator that Tampa Bay is in good shape: seagrass is flourishing. Like a benthic ecological region, seagrasses can be a good measure of a body of water’s overall health. In the case of Tampa Bay, it's on the rise.