Salt marshes sediment accumulation

Zwolsman, J.J.G., Berger, G.W. Van Eck, G.T.M. (1993) Sediment accumulation rates, historical input, postdepositioned mobility and retention of major elements and trace metals in salt marsh sediments of the Scheldt estuary, SW Netherlands. Marine Chemistry 44, 73-94. 

Salt marsh plants, in turn, reflect mainly sediment contaminant loads rather than the dissolved fraction, given their uptake route via the root system. Some research has been performed on the genera Spartina and Phragmites,29-33 which accumulate metals essentially in the underground... 

Bricker-Urso, S., Nixon, S.W., Cochran, J.K., Hirschberg, D.J., and Hunt, C. (1989) Accretion rates and sediment accumulation in Rhode Island salt marshes. Estuaries 12, 300-317. 

Delaune, M.L., Reddy, C.N., and Patrick, W.H. (1981) Accumulation of plant nutrients and heavy metals through sedimentation processes and accretion in a Louisiana salt marsh. Estuaries 4, 328-334. 

McCaffrey, R.J., and Thomson, J. (1980) A record of the accumulation of sediments and trace metals in a Connecticut salt marsh. In Advances in Geophysics, Estuarine Physics and Chemistry Studies in Long Island Sound (Saltzman, B., ed.), pp. 165-236, Academic Press, New York. 

The rates of accumulation in coastal deposits are commonly greater than deep-sea deposits. This disparity is not true everywhere since coastal areas can be dehcient in sediment supply or may be subject to efficient erosive processes. Accumulations can occur in estuaries, coastal depressions, and salt marshes. Attempts at geochronometry with a number of nuclides have been made in all of these areas. Confounding the record for both coastal and deep-sea sediments is the effect of bioturbation. Sediments deposited under anoxic conditions are free of this effect but all other sediments are subject to a variety of scales of bioturbation. 

Aside from anoxic or suboxic basins, the other marine environment suitable for radioactive geochronometry is salt-marsh deposits. As sea level has risen over the past 100 years, salt marshes have kept up by vertical growth of a vegetated framework that supports sediment accumulation. In addition, since high salt marshes are inundated by seawater only —5% of the year, the surface becomes an accumulator of atmospherically derived species including °Pb. The radioactive decay of °Pb can then be used to determine the age of levels in the salt marsh and thereby the accumulation rate of the salt marsh and its components. Since the salt-marsh vertical growth depends on the rise in sea level, the °Pb chronometer becomes a proxy for the rate of rise... 

Among the most prolific primary producers are mangrove swamp and salt marsh communities (see Table 3.2), and anoxicity can develop in the sediments trapped by the root systems of the macrophyte stands. However, the formation of organic-rich sediments in these environments is hindered by dilution with clastic material, a limited vertical extent of accumulation (if sea level remains constant) and subaerial exposure. Similar limitations can apply to the preservation of organic-rich sediments in freshwater swamps and marshes. Accumulation of significant thicknesses of organic-rich sediments in these areas requires a gradual rise in water level (see Section 3.4.2). 

A RECORD OF THE ACCUMULATION OF SEDIMENT AND TRACE METALS IN A CONNECTICUT SALT MARSH... 

McCaffrey, R. J. (1977). A record of the accumulation of sediment and trace metals in a Connecticut, U.S.A., salt marsh. Ph.D. Thesis, Yale University, New Haven, Connecticut. 

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