Studying Nutrient Sources in the Hillsborough River 

In partnership with local scientists and community groups, Ocean Conservancy is conducting a two-year study to identify sources of nutrient pollution in the Hillsborough River and Tampa Bay. Excess nitrogen and phosphorus contribute to harmful algal blooms that damage seagrass, harm wildlife, and reduce water quality. 

The Nutrient Fingerprinting Project uses a range of chemical tracers such as caffeine, artificial sweeteners, and pesticide residues to determine whether nutrients originate from septic systems, leaking sewer lines, stormwater runoff, or other pathways. Researchers have collected water samples from more than 20 locations across the watershed. Preliminary results reveal that nitrogen levels in these waters rise significantly during the wet season when runoff is at its peak. Chemical tracers, which act like “markers” for pollution sources, suggest that treated wastewater (reclaimed water), stormwater, and agriculture contribute to nitrogen sources in the waterway.

Within the Hillsborough River watershed, nitrogen levels show distinct patterns (i.e., “fingerprints”) linked to various sources. Reclaimed water and agricultural activities are prominent in the upper watershed, while urban stormwater runoff and wastewater inputs are notable near the river’s mouth. Potential contributions from other sources, such as septic systems, are still under investigation. By comparing chemical “fingerprints” at each site, the project can pinpoint high-loading areas, often down to a neighborhood level. These findings will help local governments prioritize infrastructure repairs, stormwater upgrades, and other targeted measures to reduce nutrient inputs. 

The study began in 2023 and is supported by the region’s universities, nonprofits, and environmental programs. Its results will inform management strategies for improving the health of the river and bay. An update of the study was presented to the Hillsborough River Technical Advisory Council at its August meeting and can be found under the Plan Hillsborough’s YouTube channel here.