Accumulation in the Sediments 



Surprisingly, few studies of the 

 sedinients and peat found on New 

 England high marshes have been 

 conducted. With the notable exception 

 of McCaffrey's (1977; McCaffrey and 

 Thomson 1980) analysis of Spartina 

 patens peat at Farm Creek Marsh in 

 Connecticut, the limited information 

 available is based largely on studies 

 of the stunted S^. alterni flora zones 

 of two marshes on Cape Cod. Because 

 the composition of marsh sediment 

 appears to be somewhat higher in 

 organic carbon and nitrogen than 

 nearshore subtidal sediments (Table 

 12), some fraction of the biologically 

 accumulated carbon and nitrogen on 

 the marsh must also be buried along 

 with the mineral and organic material 

 deposited by the tidal waters. The 

 role of phosphorus is not as clear 

 because there is some suggestion that 

 this element may be released by anoxic 

 marsh sediments. The remobilized 

 phosphorus may then be exchanged 

 across the sediment-water interface 



and removed from 

 tides (Nixon 1980), 



the marsh on ebb 



Based on a reasonable range in 

 density and chemical composition of 

 salt marsh sediment, and the range of 

 accretion rates summarized in Table 2, 

 somewhere between 75 to 400 g C/m^ /yr 

 and 5 to 20 g N/m ^/yr may be 

 accumulated in marsh peat (Figure 20). 

 A consideration of the composition of 

 estuarine sediment suggests that some 

 35 to 75 g of the carbon and 2 to 4 g 

 of the nitrogen may be associated with 

 the material that is removed from the 

 tidal water. The remaining to 

 365 g C/mVyr and 1 to 18 g M/mVyr 

 would then be due to the burial of 

 Spartina and marsh algae, though the 

 contribution of the latter must be 

 \/ery small. 



It seems apparent that the 

 source of this organic matter is 

 the large amount of belowground 

 production of roots and rhizomes, 

 although it is still not clear what 

 is happening below the marsh surface. 



Table 12. Comparison of sediments found on the high marsh at Farm 

 Creek, Connecticut, with those of Long Island Sound and a short 

 S^. alterniflora marsh at Barnstable, Massachusetts. Data from 

 McCaffrey (1977) and Redfield (1965). 



S. patens 

 marsh. Conn. 



L.I .Sound 



S. alterniflora 

 marsh, Mass. 



Wet bulk density g/cm,^ 



Dry bulk density g/cm. 



Inorganic matter g/cm,. 



Organic content g/cm 



Organic content, % dw 



1.011 

 0.2 

 0.135 

 0.056 

 28 



0.65 

 0.624 

 0.04 

 6 



1.15 

 0.25 

 0.19 

 0.06 

 5.2 



Averaged over 1 m. 

 Averaged over 5 m. 



42 



