James D. Hagy

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A new suite of multiple regression models was developed that describes relationships between the area of bottom water hypoxia along the northern Gulf of Mexico and Mississippi-Atchafalaya River nitrate concentration, total phosphorus (TP) concentration, and discharge. Model input variables were derived from two load estimation methods, the adjusted maximum(More)
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(More)
Both fisheries exploitation and increased nutrient loadings strongly affect fish and shellfish abundance and production in estuaries. These stressors do not act independently; instead, they jointly influence food webs, and each affects the sensitivity of species and ecosystems to the other. Nutrient enrichment and the habitat degradation it sometimes causes(More)
The environmental fate of herbicides in estuaries is poorly understood. Estuarine physical transport processes and the episodic nature of herbicide release into surface waters complicate interpretation of water concentration measurements and allocation of sources. Water concentrations of herbicides and two triazine degradation products (CIAT(More)
The often-rapid deposition of phytoplankton to sediments at the end of the spring phytoplankton bloom is an important component of benthic–pelagic coupling in temperate and high latitude estuaries and other aquatic systems. However, quantifying the flux is difficult, particularly in spatially heterogeneous environments. Surficial sediment chlorophyll-a,(More)
The incidence and intensity of hypoxic waters in coastal aquatic ecosystems has been expanding in recent decades coincident with eutrophication of the coastal zone. Worldwide, there is strong interest in reducing the size and duration of hypoxia in coastal waters, because hypoxia causes negative effects for many organisms and ecosystem processes. Although(More)
[1] Physical and biogeochemical processes determining the distribution, transport, and fate of nutrients delivered by the Mississippi and Atchafalaya river basin (MARB) to the inner Louisiana continental shelf (LCS) were examined using a three-dimensional hydrodynamic model and observations of hydrography, nutrients, and organic carbon collected during 12(More)
Pomeroy et al. (2006) proposed that temporal and spatial mismatches between eastern oyster filtration and phytoplankton abundance will preclude restored stocks of eastern oysters from reducing the severity of hypoxia in the deep channel of central Chesapeake Bay. We refute this contention by presenting arguments, data, and model results, overlooked by these(More)
Human activities on land increase nutrient loads to coastal waters, which can increase phytoplankton production and biomass and associated ecological impacts. Numeric nutrient water quality standards are needed to protect coastal waters from eutrophication impacts. The Environmental Protection Agency determined that numeric nutrient criteria were necessary(More)