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Tampa Bay program: wet 2024, storm runoff and river flows drove algae spikes despite long-term nitrogen gains
Summary
The Tampa Bay Estuary Program reported that 2024’s heavy rainfall and multiple hurricanes produced elevated algae and sanitary sewer overflows that worsened water-quality conditions in parts of the bay, even as long-term nitrogen loads have fallen since the 1970s.
Maya Burke, assistant director of the Tampa Bay Estuary Program, told the Hillsborough County City-County Planning Commission on March 10 that 2024 was one of the wettest years on record and that the extreme storms drove unusually large stormwater and river discharges into Tampa Bay.
Burke said the region has made substantial long-term progress cutting nitrogen inputs — from more than 9,000 tons in the 1970s–80s to roughly 3,000 tons today — largely by upgrading wastewater treatment, but that the top remaining sources are stormwater runoff and atmospheric deposition from mobile sources and power generation. "2024 is actually one of the wettest years on record," Burke said, and that rainfall pattern, plus several tropical storms and hurricanes, shifted the bay’s conditions.
The report the program presented uses a stoplight-style assessment of bay segments tied to management goals for seagrass. Burke said most bay segments remained in acceptable condition for seagrass after 2024, but Lower Tampa Bay moved into a cautionary state because it exceeded both chlorophyll (algae) and light-attenuation targets. Old Tampa Bay continued to show persistent seagrass losses, the program reported.
Burke emphasized that the peak impacts in 2024 were driven by surface-water flows: "Over the course of those three major hurricanes, we really saw about 250 times more volume being pumped over the land and out those rivers into the bay than anything that I'll talk about on the wastewater side." She said that the region recorded about 90,000,000 gallons of partially treated or untreated sanitary sewer discharges to the bay in 2024, concentrated around storm events and power outages that stressed aging facilities.
The presentation outlined priority actions tied to the stoplight conditions: continued wastewater investments to prevent overflows; stormwater control through low-impact design and fertilizer management; and measures to reduce atmospheric nitrogen, including transportation investments and cleaner vehicles. Burke noted circulation projects (causeway or bridge modifications) can improve local salinity and temperature conditions and thereby support seagrass, but cautioned that circulation changes do not remove nitrogen loads and should be evaluated on expected ecological benefits.
Commissioners asked about local signals, heavy metals, and airport contributions to atmospheric deposition. Burke said benthic monitoring and targeted research with local universities track heavy metals and microplastics; depositional areas such as Old Tampa Bay show hotspots of metals and tire fragments among microplastics. On air sources, she said current regional atmospheric deposition estimates are coarse and that more focused monitoring near Old Tampa Bay and other urban hotspots is a research priority.
The Estuary Program made its data and dashboards available publicly and highlighted an upcoming seagrass aerial mapping release by the South Florida Water Management District later in the month. Burke closed by urging investments that increase the bay’s capacity to absorb shocks from storms and sustain seagrass over the long term.
