Nonpoint Pollution of Surface Waters with Phosphorus and Nitrogen

Abstract

Abstract. Agriculture and urban activities are major sources of phosphorus and nitrogen to aquatic ecosystems. Atmospheric deposition further contributes as a source of N. These nonpoint inputs of nutrients are difficult to measure and regulate because they derive from activities dispersed over wide areas of land and are variable in time due to effects of weather. In aquatic ecosystems, these nutrients cause diverse problems such as toxic algal blooms, loss of oxygen, fish kills, loss of biodiversity (including species important for commerce and recreation), loss of aquatic plant beds and coral reefs, and other problems. Nutrient enrichment seriously degrades aquatic ecosystems and impairs the use of water for drinking, industry, agriculture, recreation, and other purposes.Based on our review of the scientific literature, we are certain that (1) eutrophication is a widespread problem in rivers, lakes, estuaries, and coastal oceans, caused by overenrichment with P and N; (2) nonpoint pollution, a major source of P and N to surface waters of the United States, results primarily from agriculture and urban activity, including industry; (3) inputs of P and N to agriculture in the form of fertilizers exceed outputs in produce in the United States and many other nations; (4) nutrient flows to aquatic ecosystems are directly related to animal stocking densities, and under high livestock densities, manure production exceeds the needs of crops to which the manure is applied; (5) excess fertilization and manure production cause a P surplus to accumulate in soil, some of which is transported to aquatic ecosystems; and (6) excess fertilization and manure production on agricultural lands create surplus N, which is mobile in many soils and often leaches to downstream aquatic ecosystems, and which can also volatilize to the atmosphere, redepositing elsewhere and eventually reaching aquatic ecosystems.If current practices continue, nonpoint pollution of surface waters is virtually certain to increase in the future. Such an outcome is not inevitable, however, because a number of technologies, land use practices, and conservation measures are capable of decreasing the flow of nonpoint P and N into surface waters.From our review of the available scientific information, we are confident that: (1) nonpoint pollution of surface waters with P and N could be reduced by reducing surplus nutrient flows in agricultural systems and processes, reducing agricultural and urban runoff by diverse methods, and reducing N emissions from fossil fuel burning; and (2) eutrophication can be reversed by decreasing input rates of P and N to aquatic ecosystems, but rates of recovery are highly variable among water bodies. Often, the eutrophic state is persistent, and recovery is slow.

Identifying multiple stressor controls on phytoplankton dynamics in the River Thames (UK) using high-frequency water quality data

“…Phytoplankton blooms can pose a serious risk to water quality, and may result in major disruptions to the structure and function of aquatic ecosystems. Excessive algal growth can result in shifts in species composition, including the loss of macrophyte and macroinvertebrate communities, and the low dissolved oxygen concentrations that often accompany the cessation of blooms can lead to fish kills (Carpenter et al, 1998;Hilton et al, 2006). They can cause significant financial loses to the water industry, due to filter blockages at water abstraction points and toxin, taint and odour problems produced by cyanobacterial communities, and can greatly affect the leisure and tourism industry (Dodds et al, 2009;Pretty et al, 2003;Whitehead et al, 2013).…”

Has eutrophication promoted forage fish production in the Baltic Sea?

“…Carpenter et al 1998;Smith et al 1999). Eutrophication is generally associated with negative impacts on the environment, such as toxic algal blooms, degradation of habitats, oxygen deficiency and fish kills (e.g.…”

Atmospheric nitrogen deposition to the Mullica River-Great Bay Estuary

“…Excessive fluxes of nitrogen from atmospheric sources result in the eutrophication of many coastal waters in the United States, which is now considered the most widespread water quality problem (Nixon, 1995;Carpenter et al, 1998 (Psuty et al, 1993;Zampella et al, 2001). This estuary, therefore, can serve as an excellent reference location to assess the health of impacted coastal ecosystems in New Jersey.…”