Nutrient cycling in the Columbia River Basin eutrophication in part due to the use of the river and its tributaries to irrigate over seven million acres of farmland, an extraction that comprises an average of 93 percent of daily water use in the basin. Natural run-off caused by precipitation and snowpack melt across agricultural lands further transports more of these nutrients into the river. In the late 1990s, the nitrogen load in the Columbia river was over twice the concentration historically observed. Forests are important terrestrial sinks for nutrients due to the ability of vegetation to sequester excess nutrients into their biomass. Additionally, plant roots stabilize soils
Marine pollution is a primary cause of eutrophication of surface waters, in which excess nutrients, usually nitrates or phosphates, stimulate algae growth. Many potentially toxic chemicals adhere to tiny particles which are then taken up by plankton and benthic animals, most of which are either deposit feeders or filter feeders. In this way, the toxins are concentrated upward within ocean food chains. Many particles combine chemically in a manner highly depletive of oxygen, causing estuaries to become anoxic. When pesticides are incorporated into the marine ecosystem, they quickly become absorbed into marine food webs. Once in the food webs, these pesticides can