Phosphorus fertilization of a pristine tundra river for four consecutive summers dramatically changed biological processes and populations at all trophic levels. At the primary producer level, both algal biomass and productivity increased and chlorophyll accumulated on the river bottom in the first two summers. Diatom community composition changed little in spite oflarge chlorophyll changes. However, an increase in grazing insects prevented chlorophyll buildup in the third and fourth summers.Some microbial processes were also stimulated by the increased photosynthesis caused by fertilization. Total respiration of the epilithon, acetate uptake, and decomposition of lignin monomers were all stimulated but only in light-grown epilithon. When epilithon was grown in the dark in the fertilized region of the river, there was no increased respiration. Also, phosphorus did not stimulate the decomposition of Carex litter.Although insects grew more rapidly in the fertilized section of the river, there were community interactions that kept total insect production from appreciable change. The four most abundant large insects did increase their growth rates in response to phosphorus addition and there were increases in populations of Baetis lapponicus and Brachycentrus americanus. These increases were offset by the decline in abundance of the dominant species, the black fly Prosimulium martini, perhaps caused by competition for space from Brachycentrus.Growth of both young-of-the-year and adult grayling (Thymallus arcticus) was strongly stimulated by phosphorus addition in years 3 and 4 (not tested in years 1 and 2). Carbon and nitrogen stable isotope tracers indicated that the measured increases in insect and fish growth were largely attributable to increases in the production of epilithic algae. Overall, the results indicate a strong "bottom-up" response of the riverine food web to additions of the limiting nutrient, phosphorus. The response was modified in later years, however, by a strong "top-down" feedback of insects grazing on epilithic algae and by competitive exclusion of black flies by caddisflies.

An estimated 11 million people in the US have home wells with unsafe levels of hazardous metals and nitrate. The national scope of the health risk from consuming this water has not been assessed as home wells are largely unregulated and data on well water treatment and consumption are lacking. Here, we assessed health risks from consumption of contaminated well water on the Crow Reservation by conducting a community-engaged, cumulative risk assessment. Well water testing, surveys and interviews were used to collect data on contaminant concentrations, water treatment methods, well water consumption, and well and septic system protection and maintenance practices. Additive Hazard Index calculations show that the water in more than 39% of wells is unsafe due to uranium, manganese, nitrate, zinc and/or arsenic. Most families’ financial resources are limited, and 95% of participants do not employ water treatment technologies. Despite widespread high total dissolved solids, poor taste and odor, 80% of families consume their well water. Lack of environmental health literacy about well water safety, pre-existing health conditions and limited environmental enforcement also contribute to vulnerability. Ensuring access to safe drinking water and providing accompanying education are urgent public health priorities for Crow and other rural US families with low environmental health literacy and limited financial resources.

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Waterborne disease statistics only begin to estimate the global burden of infectious diseases from contaminated drinking water. Diarrheal disease is dramatically underreported and etiologies seldom diagnosed. This review examines available data on waterbome disease incidence both in the United States and globally together with its limitations. The waterborne route of transmission is examined for bacterial, protozoal, and viral pathogens that either are frequently associated with drinking water (e.g., Shigella spp.), or for which there is strong evidence implicating the waterbome route of transmission (e.g., Leptospira spp.). In addition, crucial areas of research are discussed, including risks from selection of treatment-resistant pathogens, importance of environmental reservoirs, and new methodologies for pathogen-specific monitoring. To accurately assess risks from waterborne disease, it is necessary to understand pathogen distribution and survival strategies within water distribution systems and to apply methodologies that can detect not only the presence, but also the viability and infectivity of the pathogen. -Environ Health Perspect107(Suppl 1) :191-206 (1999). http://ehpnetl.niehs.nih.gov/ docs/1999/Suppl 1/191-206ford/abstract htrl