Assessing water quality in the impounded Guana Estuary: A baseline with implications for future management.

Assessing water quality is an important undertaking in environmental management, particularly along coasts where human development is concentrated. This study assessed waters of the Guana Estuary, an impounded estuary in Northeast Florida with an urbanized watershed. Discrete monthly samples collected from 2017 to 2023 were analyzed for chlorophyll a, nitrogen species, total phosphorus, fecal indicator bacteria (Enterococcus), and other parameters. Results indicated elevated nutrients and chlorophyll a throughout the entire estuary, but more so in the upper-middle portions. A spatial separation of nutrient sources and peak concentrations suggests that internal processes like sediment recycling and vegetation growth/senescence are important drivers of nutrient availability. A flood control project in the headwaters also introduced a pulse of nutrients and algae to the system. This baseline assessment will inform management strategies to restore water quality in this high value system, and the overall approach can serve as a model for other place-based studies.