Geography,\nTrajectories, and Controls of Coastal Water\nQuality: More Rapid Improvement in the Shallow Zone of the Chesapeake\nBay

Many coastal ecosystems\nhave suffered from cultural eutrophication\nand dead zones. In the Chesapeake Bay, water quality degradation is\nmanifested in low dissolved oxygen, poor water clarity, and decreased\nsubmerged aquatic vegetation acreage. This research combines long-term\nmonitoring data, science-based assessment methods, and novel data\nanalysis approaches (i.e., machine learning) toward understanding\nthe geography, trajectories, and controls of water quality in the\nChesapeake Bay, which provides an example for the assessment and management\nof complex coastal ecosystems. Results showed that the attainment\nof water quality standards has improved in both the deep zone and\nthe shallow zone since 1985, but the shallow zone has improved more\nrapidly. In addition, the attainment trajectory has been affected\nby mainly external drivers (i.e., nutrient reductions) and, to a lesser\nextent, internal drivers (i.e., water temperature and stratification).\nReductions in nutrient loads would improve attainment, whereas warming\nand stratification would decrease attainment. Furthermore, scenario\nanalyses demonstrated the importance of managing both nitrogen and\nphosphorus loads. Overall, the deep zone and the shallow zone showed\ndifferent trajectories and controls, emphasizing the importance of\ngeographical targeting with management actions.