Linking Landscape and Water Quality in the Mississippi River Basin for 200 Years

Abstract Two centuries of land use in the Mississippi River watershed are reflected in the water quality of its streams and in the continental shelf ecosystem receiving its discharge. The most recent influence on nutrient loading—intense and widespread farming and especially fertilizer use—has had a more significant effect on water quality than has land drainage or the conversion of native vegetation to cropland and grazing pastures. The 200-year record of nutrient loading to offshore water is reflected in the paleoreconstructed record of plankton in dated sediments. This record illustrates that the development of fair, sustained management of inland ecosystems is linked to the management of offshore systems. Land use in this fully occupied watershed is under the strong influence of national policies affecting all aspects of the human ecosphere. These policies can be modified for better or worse, but water quality will probably change only gradually because of the strong buffering capacity of the soil ecosystem.