Rate of Sedimentation and Its Role in Nutrient Cycling in a Louisiana Salt Marsh
The Gulf Coast salt marshes in the deltaic plain of the Mississippi River are in a rapidly subsiding zone where accretion processes are important for maintenance of the marsh surface within the intertidal range. Incoming sediment is essential for maintaining the marsh surface and for supplying nutrients for plant growth. In an area that is apparently maintaining its surface with respect to sea level, 137Cs dating shows an accretion rate of 1.35 cm/yr. In an adjacent deteriorating marsh the sedimentation rate is 0.75 cm/yr, not enough to compensate for subsidence. The incoming sediment also is a major source of plant nutrients for Spartina alterniflora, with inputs as great as 231, 23.1 and 991 kg/ha of nitrogen, phosphorus and potassium, respectively. Mineralization of these nutrients in the sediment provides a significant portion of the plant’s requirements, but growth of salt marsh plants is still limited by available nitrogen, as addition of nitrogen fertilizer confirms.
KeywordsSalt Marsh Nutrient Cycling Accretion Rate Baton Rouge Marsh Surface
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