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New England Marsh Dieback

(Nov 2008) Link to a website summarizing the state of knowledge about salt marsh dieback on Cape Cod. The link is: http://www.nps.gov/caco/naturescience/salt-marsh-dieback.htm

Ron Rozsa (Coastal Ecologist with the Connecticut Department of Environmental Protection - Coastal Management Program) contacted the GCRC some years ago to alert us to some interesting observations concerning marsh dieback in Connecticut and Massachusetts. What follows are a powerpoint "poster" including some photos of dieback areas in Harwich (MA), a link to more of Ron's photos, and notes from our correspondance with him.

Link to webpage "New England Sudden Wetland Dieback" hosted by the New England Estuarine Research Society.

Powerpoint, "Are Cape Cod/Nantucket Sound marshes downing?"
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Link to 2002 photos Herring River, MA
Link to 2004 photos Herring River, MA
Link to 2000 & 2004 photos near Branford, CT
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Ron wrote (JF editted):

I just discovered your documentation of wetland losses in Georgia beginning in 2002* - what a coincidence for the same (?) type of vegetation losses began suddenly on the southern shore of Cape Cod, Mass.  These losses continued in 2003.      *The Cape was well into a drought in 2002 - the Cape is one large glacial sandplain - not bedrock. I assume that geology is a contributing factor to where the wetland die-backs are occurring.

This dieoff was first notice by a colleague of mine, Scott Warren at Connecticut College in the fall of 2002 when he took his wetlands ecology class to Cape Cod for a field trip - Scott and I have been visiting these sites for years - Scott longer than I. Some photographic evidence for 2000 sudden dieback in CT has been found.

When he mentioned that - I remember seeing similar dieback on a nearby but much larger system on the south shore of the Cape that summer. I then toured several sites and took photographs - In general, most of the dieoff was in the mid-estuary section of these tidal rivers/systems. We are beginning to think that it is the mid-estuary that is most sensitive to changes in hydrology.

In 2003, I toured several more marshes - dieoff still present and present in the new wetlands that I examined. I am attempting to have the EPA Narragansett Bay lab fly the south shore of the Cape with their digital video camera so that someone can record/map the extent of this problem.

In Connecticut, we have occurrence of low marsh vegetation losses in western Long Island Sound that began pre- 1970's - and again most of the losses are in the mid-estuary of our tidal rivers and coves - the same for New York state losses.

Take a look at your losses and see if there is some common geographic pattern - I would bet there is.

Would be interesting to know if this is occurring anywhere else along the eastern seaboard on this time frame!
A colleague in New Hampshire claims this phenomenon is in their coastal wetlands as well.

-----(RE: some correspondance he had with colleagues in Louisiana):

If memory serves me the shallow SET (sediment elevation table) revealed no changes but the deep SET revealed that the marsh was floating on the ground water and elevation decreased with drought and restored when the groundwater recharged.

If in these cases, the rhizomes die - there is likely to soil collapse/subsidence making the sites even wetter and less likely to support Spartina alterniflora. What was different about the Cape Cod loss (compared to the Connecticut multidecadal declines) was that is appears to affect both low marsh and high marsh (we presently see no long term losses of high marsh vegetation in CT).




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