Tampa Bay Nitrogen Management Consortium Releases 2011 Report

The Tampa Bay Nitrogen Management Consortium has released its 2011 update on water quality and seagrass resources in the Tampa Bay estuary. The update was developed in response to, and in accordance with, the regulatory requirements of the Florida Department of Environmental Protection. The formal annual compliance assessment utilized by the Consortium is detailed in Section VIII.B. of the Final 2009 Reasonable Assurance Addendum: Allocation and Assessment Report.

In summary, chlorophyll-a concentrations in three of the four major bay segments of the Tampa Bay estuary were below FDEP-approved thresholds. Old Tampa Bay chl-a concentrations exceeded FDEP-approved annual average thresholds in 2011; however, this is considered a short duration exceedence as chl-a levels were below thresholds in 2010.

Chlorophyll-a is the most common type of chlorophyll, and its concentration in bay water is used to estimate the relative abundance of phytoplankton. When water contains excess nutrients, it may cause an overgrowth of phytoplankton, reducing the clarity of the water and inhibiting the penetration of sunlight to the bay bottom, thereby adversely affecting seagrass growth.

Original thresholds were adopted as part of FDEP’s 2002 Reasonable Assurance determination for Tampa Bay and, at that time, it was determined that Tampa Bay’s seagrass restoration goals could be achieved if annual chl-a concentrations remained below these thresholds. Additional RA compliance assessment steps are only necessary when thresholds are exceeded for two concurrent years in any particular bay segment. This nutrient management strategy has been utilized by the TBEP and Consortium and incorporated into an Annual Decision Matrix report for Tampa Bay, as well as this report to regulators. Additionally, the most recent seagrass estimates from the Southwest Florida Water Management District indicate that baywide seagrass coverage increased by 3,250 acres from 2008 to 2010. The SWFWMD will be providing an updated seagrass acreage estimate for Tampa Bay by the end of 2012.