Adam Blalock, FDEP

Daniel Blackman, US EPA Region 4


Ed Sherwood, TBEP Executive Director (NMC Facilitator)


Jan. 19, 2024


2023 Tampa Bay Nutrient Management Compliance Assessment Results


Ken Weaver, Jessica Mostyn, Ben Ralys, Kevin O’Donnell, Kimberly Shugar (FDEP Tallahssee)

Ramandeep Kaur, Jorge Perez, Lance Kautz, Jessica Pein, Erica Peck (FDEP Tampa)

Jeaneanne M. Gettle, Wade Lehmann, Cindy Barger, Nancy Laurson, Felicia Burks, Tom McGill (EPA Region 4/HQ)

Jeff Greenwell, Santino Provenzano (TBNMC)

Ed Sherwood, Maya Burke, Marcus Beck (TBEP)

Source content: here

On behalf of the Tampa Bay Nitrogen Management Consortium, please find attached the 2023 update on water quality and seagrass resources in the Tampa Bay estuary. This update has been developed in accordance with the compliance assessment adopted through FDEP’s Tampa Bay Reasonable Assurance determination on December 22, 2010, FDEP’s subsequent approval of the 2022 RA Update, and the federally-recognized TMDL for Tampa Bay. 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.

Chlorophyll-a concentrations for all four major bay segments were below FDEP-approved numeric nutrient criteria thresholds in 2023. Additionally, concentrations for the Remainder Lower Tampa Bay segment that includes Boca Ciega Bay South, Terra Ceia Bay, and Manatee River were also below the criteria. The approved chlorophyll-a 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, uncorrected chlorophyll-a concentrations remained below these thresholds. If a bay segment’s chlorophyll-a concentration remains above thresholds for 2 concurrent years, additional compliance assessment steps are required by the Consortium. This nutrient management strategy has been consistently used by the TBEP and Consortium in their Annual Decision Matrix and Assessment reports (Beck, Burke, and Sherwood 2024).

Seagrass coverage in Tampa Bay decreased between 2020 and 2022, prior to the reported chlorophyll-a conditions detailed above. The Southwest Florida Water Management District’s (SWFWMD) 2022 baywide seagrass coverage estimate is 30,137 acres, remaining below the baywide target of 40,000 acres (Figure 3.4). The 2022 estimate marks the third consecutive reporting period with a reduction of seagrass coverage in Tampa Bay. Losses were primarily observed in upper bay segments and additional research, assimilative capacity assessments, and restoration initiatives are being conducted in response to these trends. Notwithstanding these setbacks, the Consortium’s approved nutrient management strategy is still required to adaptively manage and address nutrient loading to the Tampa Bay estuary. For all Tampa Bay segments, water quality remained supportive of seagrass resources in 2023, though baywide seagrass losses continue to be examined. Annual seagrass transect surveys in 2023 suggest a slight increase in total frequency occurrence since 2021, although rainfall has been below annual averages and the TBEP remains cautiously optimistic that these trends will continue in future years.

Thank you again for your continued participation in the Consortium’s process. Please contact Ed Sherwood (esherwood@tbep.org) with any questions about the Consortium’s Annual Compliance Assessment.