Cultural Eutrophication in the Choptank and Patuxent Estuaries of Chesapeake Bay

• Published in: Limnology and oceanography 2006-01, Vol.51 (1), p.435-447
• Main Authors: Fisher, T. R., J. D. Hagy III, Boynton, W. R., Williams, M. R.
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Brackish; Brackish water ecosystems; Earth sciences; Earth, ocean, space; Estuaries; Eutrophication; Exact sciences and technology; Fertilizers; Freshwater; Fundamental and applied biological sciences. Psychology; Geochemistry; Groundwater; Hypoxia; Land use; Marine and continental quaternary; Mineralogy; Nitrates; Silicates; Surface water; Surficial geology; Synecology; Wastewater; Water geochemistry; Watersheds
• ISSN: 0024-3590; 1939-5590
• DOI: 10.4319/lo.2006.51.1_part_2.0435

The Choptank and Patuxent tributaries of Chesapeake Bay have become eutrophic over the last 50-100 years. Systematic monitoring of nutrient inputs began in ~1970, and there have been 2-5-fold increases in nitrogen (N) and phosphorus (P) inputs during 1970-2004 due to sewage discharges, fertilizer applications, atmospheric deposition, and changes in land use. Hydrochemical modeling and land-use yield coefficients suggest that current input rates are 4-20 times higher for N and P than under forested conditions existing 350 yr ago. Sewage is a major cause of increased nutrients in the Patuxent; agricultural inputs dominate in the Choptank. These loading increases have caused three major water-quality problems: (1) increased nutrients, phytoplankton, and turbidity; (2) decreased submerged grasses due to higher turbidity and epiphyton shading; and (3) bottom-water hypoxia due to respiration of excess organic matter. Oxygen in the Patuxent is consistently $