Primary production Mississippi River

Figure 16.3 Relationship between primary production and salinity in the Mississippi River plume in July 1990 and March 1991. (Modified from Lohrenz et al., 1999.)...

Lohrenz, S.E., Dagg, M.J., and Whitledge, T.E. (1990) Enhanced primary production at the plume oceanic interface of the Mississippi River. Cont. Shelf Res. 10, 639-664. 

Much of the coastal sedimentation accretion work has been conducted in the Mississippi River deltaic plain, where vertical accretion rates are large, and where there are also very high rates of subsidence and coastal land loss. In other coastal areas of the United States and Europe, a wide range of results have been found, with sedimentation rates varying from 0 to 1.5 cm year". Many coastal marshes are not accreting at a rate sufficient to compensate for the present rates of sea level rise. Many factors affect accretion rates in wetlands. These include plant community, density of vegetation, tidal elevation, sediment input from riverine, estuarine and marine sources, proximity to sediment sources, total organic matter input from primary productivity of wetland, and relative sea level rise. 

Soil erosion can occur by the action of both water and wind, although water is the primary source of erosion. Millions of tons of topsoil are carried by the Mississippi River and swept fi om its mouth each year. About one-third of U.S. topsoil has been lost since cultivation began on the eontinent. At the present time, approximately one-third of U.S. eultivated land is eroding at a rate sufficient to reduce soil productivity. It is estimated that 48 million acres of land, somewhat more than 10 percent of that under cultivation, is eroding at unacceptable levels, taken to mean a loss of more than 14 tons of topsoil per aere each year. Specific areas in which the greatest erosion is occurring include northern Missouri, southern Iowa, west Texas, western Tennessee, and the Mississippi Basin. Figure 18.6 shows the pattern of soil erosion in the continental U.S. in 1977. 

Mississippi river for agricultural products. Trucks have a significant advantage for goods that need to be moved fast, over short distances, or have a low weight-to-volume ratio. Railroads face less competition for bulky, heavy products such as coal and other primary materials. 

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