Trent Biggs, a geography professor at San Diego State University, presented research deploying fluorescence-based monitoring and remote sensing to detect sewage and sediment contamination in the Tijuana River and coastal plume.

Biggs explained that two fluorescence proxies — tryptophan-like fluorescence (a bacterial/sewage proxy) and CDOM (chromophoric dissolved organic matter) — were measured with a bench-top AquaLog and an in-situ Manta 3 sensor. "Fluorescence-based measurements provide useful proxies of bacteria," he said, describing lab dilution experiments that showed a linear relationship between bench-top tryptophan measures and wastewater fraction.

In field deployments at the International Boundary and Water Commission (IBWC) station and a Boca Rio floating platform, Manta 3 sensors provided telemetry for near-real-time data but required turbidity corrections and frequent maintenance to mitigate fouling and sensor degradation. Biggs said in-situ tryptophan sensors correlated with E. coli after event-by-event turbidity correction, but that the Manta sensor performance could saturate at high wastewater percentages.

On remote sensing, Biggs described near-surface hyperspectral cameras and satellite sources (Planet, Sentinel) as complementary: optical imagery helps map turbidity and CDOM when conditions permit, while Sentinel-1 radar can detect surface-roughness anomalies (useful through clouds) that sometimes identified plumes originating from Punta Bandera rather than the Tijuana River mouth. He emphasized the need for shore- and boat-based validation and integration with hydrodynamic modeling to link radar/optical signatures to contaminant concentrations.

Biggs said the team will continue deployments and boat transects, and is working to integrate remote sensing, in-situ monitoring, and modeling to improve plume mapping and near-real-time situational awareness for managers.