Old Tampa Bay (OTB) had consistent losses in seagrass coverage from 2016-2024 due, in part, to persistent algal blooms caused by the dinoflagellate Pyrodinium bahamense var. bahamense. Elevated algal biomass resulted in non-attainment of the management target and regulatory threshold for chlorophyll-a concentrations during most of this period, prompting an evaluation of the OTB nutrient management paradigm by the Tampa Bay Estuary Program. Empirical approaches including regressions, probability distributions, and causality analyses were used to evaluate nitrogen loading dynamics and associated chlorophyll-a seasonal changes driven mainly by P. bahamense blooms. Updated analyses indicated that reducing pulsed freshwater discharges (thus managing large rainy season nitrogen loading), expanding oyster restoration, and additional nitrogen load reduction projects for wastewater and stormwater sources to achieve total nitrogen loadings commensurate with a federally-recognized TMDL could  increase the probability of consistently meeting water quality regulatory criteria. As a complement to the empirical analyses, the mechanistic Comprehensive Aquatic Ecosystem Model (CASM) was adapted for OTB. The CASM-OTB simulations indicated  chlorophyll-a reductions ranged from 12% - 17% when nitrogen loading and pulsed freshwater discharges were constrained, and up to 53% reductions with oyster restoration. Combining results from all three simulated interventions suggested an average 17% decline in chlorophyll-a concentrations compared to baseline conditions, although the magnitude of the reductions varied throughout the entire simulated period. This  project underscored the importance of using a variety of tools to build sufficient evidence to recommend modifications to existing management approaches and regulatory criteria. By developing several lines of evidence, this project provides resource managers reasonable options for managing water quality within this urbanized ecosystem.