Hollie Emery's Ph.D. research is focused on understanding human impacts on salt marshes in Massachusetts.
Can We Disentangle the Effects of Tidal Restriction, Invasive Species, and Tidal Restoration on the Biogeochemistry of a New England Salt Marsh System?At least three human impacts are present in many marshes within the Great Marsh system north of Boston, Massachusetts. The first is a long history of tidal restriction mainly from the construction of roads, the second is a cryptic invasion by the exotic reed Phragmites australis, and the third is the attempt to remedy these two degradations by restoring tidal flow with culverts and ditching.
All of these impacts are known to affect both the ecology and biogeochemistry of marsh ecosystems, so a change in the quantity of greenhouse gases produced and absorbed during biogeochemical processes is expected. However, it remains unclear what the effect of each individual impact is since they so often occur together. This project is working to determine the effects that these three human impacts have on the production and consumption of the three powerful greenhouse gases: carbon dioxide, methane, and nitrous oxide. |
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We have been comparing emissions from two plant types (Phragmites australis and native species) in each of three marsh types (tidally restricted, restored, and unimpacted) in sites throughout the Great Marsh North of Boston. This nested design is allowing us to quantify the effects each human impact is having, both alone and in concert. Additionally, we are measuring emissions from marshes restored at different times along with unimpacted and unrestored references, creating a tidal restriction impact gradient. This gradient is illuminating the biogeochemical path taken by restored marshes, as well as providing a means to detect non-linear patterns in the effects of tidal restriction and the timeline of recovery.
It is our hope that the results of this project will help communities to predict the effects that marsh restoration and invasive species removal projects may have on local greenhouse gas production, as well as help climate scientists and modelers predict the effects that ongoing human alterations to salt marshes will have on the global carbon budget and climate change.
It is our hope that the results of this project will help communities to predict the effects that marsh restoration and invasive species removal projects may have on local greenhouse gas production, as well as help climate scientists and modelers predict the effects that ongoing human alterations to salt marshes will have on the global carbon budget and climate change.
Video of water flow at Castle Hill - the restricted marsh site.
Below a video showing the field conditions Hollie and her team experience while they attempt to sample at Castle Hill, the restricted site, during high tide. As Hollie explains, on one side of the road the water is so high the pipe is submerged by ~6 inches of water and there is a whirlpool of water trying to get in, and on the other side of the road the pipe is not submerged by about 6 inches and water is rushing out. There is also water pouring over the road since the pipe cannot keep up with the volume of water coming in.
Thank you!
We wish to thank all of the organizations that gave us permission to sample these salt marsh sites: Essex County Greenbelt Association, The Trustees of Reservations, Massachusetts Audubon Society, Department of Fish and Game, and Plum Island Estuary LTER.
We also want to thank Robert Buchsbaum, from Mass Audubon, for his fantastic tour of impacted salt marshes in this area.
We also want to thank Robert Buchsbaum, from Mass Audubon, for his fantastic tour of impacted salt marshes in this area.