Salt marsh plants may signal carbon capture capacity
Learning how the composition of salt marshes can predict their ability to serve as reservoirs for carbon

Date:
June 22, 2021
Source:
University of Connecticut
Summary:
Coastal wetlands like seagrass meadows, mangroves, and salt marshes
play vital roles along the shoreline, from providing a buffer
against storm surges, to providing critical habitat for animals,
to capturing atmospheric carbon. We are still just beginning
to comprehend the intricate workings of these highly productive
ecosystems and their role in mitigating the climate crisis, but
researchers are one step closer to understanding how salt marsh
vegetation, their bacterial communities, and vegetation can help
predict a marsh's potential to be a blue carbon reservoir.



FULL STORY ========================================================================== Coastal wetlands like seagrass meadows, mangroves, and salt marshes
play vital roles along the shoreline, from providing a buffer against
storm surges, to providing critical habitat for animals, to capturing atmospheric carbon.


==========================================================================
We are still just beginning to comprehend the intricate workings of these highly productive ecosystems and their role in mitigating the climate
crisis, but UConn researchers are one step closer to understanding how
salt marsh vegetation, their bacterial communities, and vegetation can
help predict a marsh's potential to be a blue carbon reservoir. The
research was recently published in the journal Estuaries and Coasts.

"Coastal marshes are increasingly recognized as important ecosystems
because they sequester and store a lot of carbon. There is increasing
interest in understanding these blue carbon ecosystems because of our
current climate crisis," says Beth Lawrence, co-author and College
of Agriculture, Health, and Natural Resources Assistant Professor of
Wetland and Plant Ecology in the Department of Natural Resources and
the Environment and Center for Environmental Science and Engineering.

Lawrence explains how salt marshes serve as focal ecosystems in
conservation and restoration. They are habitat for a wide range of
species, including endangered species like the salt marsh sparrow. Located
at the interface between land and sea, these ecosystems buffer storm
energy and perform other important functions, like the removal of excess nitrogen from water making its way to estuaries where it may otherwise
lead to algal blooms and oxygen- deprived "dead zones." Development
leads to changes in the movement of water (see side bar) and Lawrence
says that, often, tide-restricted salt marshes become less salty and
wet, leading to shifts in what plants grow there. Plants that thrive in
these brackish conditions can be invasive, like Phragmites australis,
which has become the bane of coastal managers, Lawrence says.

Tidal restoration aims to reconnect marshes cut off from the ocean
to improve habitat. Increasing the size of culverts underneath roads,
railroads or bridges or removing tide gates can restore tidal flow and
the organisms that rely on it.



==========================================================================
To observe how tidal restoration may alter carbon cycling and soil
microbes, the researchers sampled from several marsh locations in
Connecticut, including less-disturbed "reference" marshes, and formerly restricted marshes that have since undergone restoration.

"Tidally restored and the unrestored references differed in carbon density
and how much carbon is in the soil. Highly restricted sites presumably
had dried out to some degree and lost some carbon," says Lawrence.

This makes sense, Lawrence says, because in wetter soils, microbes do
not break down carbon-rich plant material as efficiently as in dry soil, therefore the material and the carbon within it remains. When microbes
can feast away on the plant matter in drier, more oxygenated conditions,
the carbon is lost to the atmosphere in the form of carbon gas, in a
process called mineralization.

Other measurements between tidally restored and undisturbed marshes
were the same across the suite of parameters used in the researchers' measurements, including soil chemistry, plant biomass, and microbial communities. However, there were large differences across vegetation
zones.

"The key difference we saw were across plant communities," Lawrence
says. "We saw differences in microbial respiration as well as the
microbial communities living in the soils in different vegetation
zones. These findings suggest that both plants and microbes are responding
to differences in environmental conditions." With the knowledge of which plants thrive where, the researchers can get a glimpse into the biological processes at play within the marsh by noting which plants are present.

"I think one of the key takeaways from our study is that these bands
of vegetation are good indicators of what's going on hydrologically and biogeochemically," says Lawrence. "For example, if we see native Spartina alterniflora growing, we know the environment is saltier than where
Phragmites is growing. These soils are likely to have different bacterial community composition and process carbon and nitrogen differently than in
a higher, drier community." Considering the importance of salt marshes
and the need for further restoration work, Lawrence says managers could
use satellite imagery or drones to look at the vegetation at greater
spatial scales to get an indication of growing conditions as well as a
system's carbon capture capacity. This could help in focusing restoration efforts and monitoring.

"Managers are really interested in scaling up," Lawrence
says. "Quantifying carbon and nutrient cycling is very
time-consuming and detailed so an important implication of this
work is that the dominant vegetation in salt marshes can be used
as a proxy for some biogeochemical processes. We have to carefully
consider how we're spending our limited conservation dollars." ========================================================================== Story Source: Materials provided by University_of_Connecticut. Original
written by Elaina Hancock. Note: Content may be edited for style and
length.


========================================================================== Journal Reference:
1. A. Barry, S. K. Ooi, A. M. Helton, B. Steven, C. S. Elphick, B. A.

Lawrence. Vegetation Zonation Predicts Soil Carbon Mineralization
and Microbial Communities in Southern New England Salt
Marshes. Estuaries and Coasts, 2021; DOI: 10.1007/s12237-021-00943-0 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/06/210622123335.htm

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