Henry Allen Walker

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This paper assesses the potential impacts of climate change on the mid-Atlantic coastal (MAC) region of the United States. In order of increasing uncertainty, it is projected that sea level, temperature and streamflow will increase in the MAC region in response to higher levels of atmospheric CO2. A case study for Delaware based on digital elevation models(More)
Conditional probability is the probability of observing one event given that another event has occurred. In an environmental context, conditional probability helps to assess the association between an environmental contaminant (i.e., the stressor) and the ecological condition of a resource (i.e., the response). These analyses, when combined with controlled(More)
*Correspondence: Daniel Elliott Campbell , Atlantic Ecology Division, National Health and Environmental Effects Research Laboratory, Office of Research and Development, United States Environmental Protection Agency, 27 Tarzwell Drive, Narragansett, RI 02882, USA e-mail: campbell.dan@epa.gov Energy Systems Language models of the resource base for the U.S.(More)
Empirically derived relationships associating sediment metal concentrations with degraded ecological conditions provide important information to assess estuarine condition. Resources limit the number, magnitude, and frequency of monitoring activities to acquire these data. Models that use available information and simple statistical relationships to predict(More)
Social network analysis (SNA) is based on a conceptual network representation of social interactions and is an invaluable tool for conservation professionals to increase collaboration, improve information flow, and increase efficiency. We present two approaches to constructing internet-based social networks, and use an existing traditional (survey-based)(More)
U.S. Environmental Protection Agency’s (EPA’s) National Coastal Assessment was envisioned as a research effort led by EPA’s Office of Research and Development to evaluate assessment methods for ecosystem condition monitoring. The program was conducted through strategic partnerships with the coastal states. These states conducted the survey in their waters(More)
An experiment was conducted with six 13-m3 land-based mesocosms (5 m deep) in December 1996/February 1997 to address the impact of increased temperature on the trophic structure of nutrient-rich coastal systems. All mesocosms were exposed to a high nutrient loading rate (2.31 mmol N m23 d21 : 0.18 mmol P m23 d21 : 0.165 mmol Si m23 d21). Three treatment(More)
U.S. Environmental Protection Agency’s (EPA’s) National Coastal Assessment was envisioned as a research effort led by EPA’s Office of Research and Development to evaluate assessment methods for ecosystem condition monitoring. The program was conducted through strategic partnerships with the coastal states. These states conducted the survey in their waters(More)
Global nutrient cycles have been altered by the use of fossil fuels and fertilizers resulting in increases in nutrient loads to aquatic systems. In the United States, excess nutrients have been repeatedly reported as the primary cause of lake water quality impairments. Setting nutrient criteria that are protective of a lakes ecological condition is one(More)
Often when various estuarine benthic indices disagree in their assessments of benthic condition, they are reflecting different aspects of benthic condition. We describe a process to screen indices for associations and, after identifying candidate metrics, evaluate metrics individually against the indices. We utilize radar plots as a multi-metric(More)
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