Abstract
Freshwater discharge significantly impacts coastal water quality, yet comprehensive multi-indicator assessments remain limited in urbanized estuarine systems. This study employed an integrated approach to examine seasonal and spatial water quality variation in Mobile Bay, Alabama, using salinity, nutrients (NO₃⁻, NH₄⁺), stable isotopes (δ¹³C, δ¹⁵N), microbial indicators (fecal coliforms, Escherichia coli, male-specific coliphage), and pathogens (Toxoplasma gondii, Erysipelothrix rhusiopathiae). Over 13 months (September 2022-2023), water samples were collected from 13 sites representing diverse contamination sources across the estuary. Results revealed a complex system in which drivers of water quality operated at multiple scales. Mobile River discharge controlled system-wide trends while local precipitation and land use influenced site-specific patterns. This research establishes salinity as a reliable proxy for discharge conditions and validates strontium-to-barium ratios as freshwater tracers. Peak freshwater discharge during winter-spring months (December-June) corresponded with lowest salinities, most depleted δ¹³C values, and highest microbial indicator and E. rhusiopathiae concentrations. E. rhusiopathiae detection correlated strongly with precipitation, demonstrating terrestrial pathogen transport pathways. Spatial analysis identified distinct regional patterns with North and East regions exhibiting greater freshwater influence and higher microbial and pathogen concentrations compared to sites in the South. The multi-indicator framework provides essential baseline data for freshwater-related impacts and offers a transferable approach for monitoring urbanized coastal systems more widely. The findings support enhanced surveillance during high-discharge periods and can inform policy development for coastal water resource management.
Purpose
DOI: 10.57778/8bf3-rs27
Suggested Citation
Brown, A. (2026). Mobile Bay Multi-Indicator Water Quality Dataset (2022-2023) [Data set]. Dauphin Island Sea Lab. https://doi.org/10.57778/8BF3-RS27
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