How a Massachusetts salt marsh is changing what we know about New
England's coast
New research shows that salt marshes grow from marine sediment washed
ashore during storms, reversing commonly held assumptions

Date:
March 14, 2022
Source:
University of Massachusetts Amherst
Summary:
New research into the life and times of a New England salt marsh
fundamentally changes our understanding of how salt marshes
acquire the sediment that keeps them viable. This research has
wide-ranging implications for managing New England's coastline
as it struggles to keep up with development, sea-level rise and
other environmental impacts.



FULL STORY ==========================================================================
New research led by the University of Massachusetts Amherst into the
life and times of a New England salt marsh fundamentally changes our understanding of how salt marshes acquire the sediment that keeps them
viable. This research, published recently in the Journal of Geophysical Research: Earth Surface, has wide-ranging implications for managing
New England's coastline as it struggles to keep up with development,
sea-level rise and other environmental impacts.


==========================================================================
Salt marshes are critically important because they buffer against erosion
and flooding, sequester carbon, provide habitat to juvenile species
and migratory birds, and filter pollutants and excess nutrients,but a
marsh can only survive when its surface sits high enough above sea level
to drain at low tide, which means that marshes need to import mineral
sediment to build volume and survive.

For decades, the standard model of how a salt marsh developed went like
this: as a river wound its way to the sea, it picked up sediment as
it flowed through hill and field. Once the river arrived at the coast,
it slowed down and dropped its sediment load, which salt marshes have incorporated and grown upon over the years to form the salt marsh
platforms at river and stream mouths throughout New England. The only
problem with this model is that it might not be the way that New England's
salt marshes actually work.

"We've been looking in the wrong direction," says Jon Woodruff, professor
of geosciences at UMass Amherst and one of the paper's co-authors. "These sediments are mostly coming from the ocean, not rivers." "If we're
going to manage and protect salt marshes efficiently and effectively,
we need to know where their sediment comes from," says Hannah Baranes,
the paper's lead author and a postdoctoral researcher at the Gulf of
Maine Research Institute (GMRI) who completed this research as part of
her Ph.D. in geosciences at UMass. "But a great deal of previous work has focused on large, complex marsh systems, which has made it difficult to pinpoint where exactly sediment comes from." Baranes and her colleagues focused their research on the North/South River estuary, a typical
New England salt marsh system near Marshfield, Massachusetts. They
combined long, medium and short-term experiments, which ranged from
taking sediment cores that record a 200-year history of the marsh, to
placing instruments in the channel and on the surface of the marsh to
track sediment transport and deposition in real time.

It was dirty work: "we had to navigate these salt marshes on foot and
figure out how to get our equipment in and out while wading through
waist-deep mud in all seasons," says Baranes. Then there were the
mosquitoes and other bugs to deal with. And don't even get Baranes
started on the crabs that fell into some of the sediment traps. But
over the course of two years, Baranes and her colleagues, including undergraduates from UMass Amherst, were able to stitch together an unprecedented look at the life of salt marshes in New England.

It turns out that the vast majority of sediment is delivered by the ocean during the storms that batter the coast. This has important implications
for the health of New England's coasts. "Salt marshes are expensive
to protect and we have limited resources to figure out this problem,"
says Baranes. "We need to understand any natural process that can help
us out." Furthermore, as Woodruff points out, beaches and marshes are
paired systems, and any effort to protect beaches against erosion can
affect the health of the salt marshes in unforeseen ways. Unfortunately,
there is very little work to date that does so, and so we don't really
know what unforeseen consequences "coastal armoring" -- including the
creation of sea walls, jetties, etc. - - might have on neighboring
salt marshes.

Both researchers plan to continue exploring the interactions between
salt marshes and other coastal features, such as Maine's bluffs and Massachusetts's beaches.

The research, funded by the DOI/USGS Northeast Climate Adaptation
Science Center, also benefitted immensely from the work of UMass Amherst undergraduate researchers. "This has been a fantastic opportunity to
bring undergrads into the project and show them what actual in-the-field science research looks like," says Baranes, and Woodruff agrees. "We
always have students who grew up on the coast, and they love bringing
that personal history to their scientific research."

========================================================================== Story Source: Materials provided by
University_of_Massachusetts_Amherst. Note: Content may be edited for
style and length.


========================================================================== Journal Reference:
1. H. E. Baranes, J. D. Woodruff, W. R. Geyer, B. C. Yellen, J. B.

Richardson. Sources, Mechanisms, and Timescales of Sediment Delivery
to a New England Salt Marsh. Journal of Geophysical Research:
Earth Surface, 2022; DOI: 10.1029/2021JF006478 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/03/220314154417.htm

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