EFFECT OF IMPOUNDING WATER ON SALT MARSHES

Susan Adamowicz

Rachel Carson National Wildlife Refuge

321 Port Rd.

Wells, ME 04090

Susan_Adamowicz@fws.gov

ABSTRACT

Ditch plugging has been employed widely in East Coast Spartina marshes as a means of increasing surface water habitat on previously ditched marshes. Ditch plugs are formed by excavating peat from the surface of a salt marsh and packing it in a narrow portion of a ditch. Water then is impounded in the ditch channel on the upstream side of the plug. Small u-shaped berms or “wings” have also been employed to increase a plug’s holding capacity and area of impounded water.

We examined 2 physical soil parameters (bulk density, percent organic matter), interstitial hydrogen sulfide concentrations, groundwater levels, vegetation community, and above-ground biomass at ditched and unditched marshes at 2 sites each in Maine, Massachusetts and Connecticut in 2005. The study was repeated in 2009 with the addition of 1 unditched marsh (with natural creeks) in southern Maine. Ditch plugs were installed from 1 to 11 years prior to the study except at 1 Connecticut site where ditches had filled in naturally over a period of decades.

Results are given in light of long-term consequences for maintaining peat integrity and salt marsh accretion processes in the face of sea level rise.