| NSF Org: |
DEB Division Of Environmental Biology |
| Recipient: |
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| Initial Amendment Date: | July 30, 2015 |
| Latest Amendment Date: | July 30, 2015 |
| Award Number: | 1457435 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Matthew Kane
mkane@nsf.gov (703)292-7186 DEB Division Of Environmental Biology BIO Directorate for Biological Sciences |
| Start Date: | August 1, 2015 |
| End Date: | July 31, 2019 (Estimated) |
| Total Intended Award Amount: | $70,888.00 |
| Total Awarded Amount to Date: | $70,888.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
910 WEST FRANKLIN ST RICHMOND VA US 23284-9005 (804)828-6772 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
VA US 23298-0568 |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): | ECOSYSTEM STUDIES |
| Primary Program Source: |
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| Program Reference Code(s): |
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| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.074 |
ABSTRACT
Tidal marshes are productive ecosystems that provide key services to society such as storm surge buffering, and water-quality mitigation. The long-term stability of coastal wetlands is explained by interactions between sea level, plant growth, sediment supply, and wetland accretion, but coastal wetland stability is threatened by changes in environmental conditions. Sediment supply has been implicated as the ultimate control on potential vertical accretion rates in many tidal wetlands and, hence, their ability to keep pace with sea level. Human activities in watersheds have significantly altered the delivery of sediment from watersheds to the coast, and indeed there is evidence of past expansion of tidal wetlands in response to increased sediment supply. However, more recent land use change, reforestation, and dam construction have reduced sediment delivery from many watersheds to the coast. The goal of this project is to understand how past and current land use in watersheds that drain to the East Coast of the United States has altered sediment concentrations in rivers, to determine how changes in sediment supply influences sediment accumulation rates in coastal wetlands, and to project future wetland vulnerability along the East Coast under various scenarios of sea level rise and sediment supply. This information is critically needed, and will be of use to researchers, managers, and stakeholders. This collaborative project includes a strong commitment to integrate research and undergraduate education and increase diversity in the sciences. The lead institution on this project serves primarily undergraduate students, and undergraduate student summer interns and academic year thesis research students will be involved in all aspects of the project.
This project takes the novel approach of documenting temporally-variable wetland accretion rates over the past century to evaluate changing watershed-derived sediment supply in nine estuaries along the East Coast of the United States. Land use change over the same time period will be examined in these watersheds to determine the major drivers of changing sediment supply. The investigators will test the following hypotheses: H1. Suspended sediment concentrations (SSCs) have decreased in many (but not all) rivers draining to the East Coast in recent decades due to increased population densities, shifts away from agricultural land-use, and dam construction in watersheds, H2. Recent declines in fluvial SSC are reflected in lower wetland mineral accretion rates in many coastal estuarine wetlands. Geographic patterns of recent accretion rates reflect regional patterns of sediment decline, with the greatest reductions in mid-Atlantic wetlands, H3. Sediment deposition and marsh accretion will be greater in the plots with higher SSC availability and with plant trapping of SSCs. Further, due to complex ecogeomorphic feedbacks between marsh elevation, sediment deposition, and plant production, plant productivity will respond to SSC availability, and H4. Coastal wetland vulnerability to current sea level rise follows a regional pattern that reflects both the rate of relative sea level rise (highest in mid-Atlantic) and SSC (lowest in Northeast and Southeast). However, changing SSC and mineral accretion rates (greatest declines in mid-Atlantic) will alter future regional patterns of vulnerability to sea level rise. The researchers will use innovative experiments to manipulate suspended sediment concentrations in water flooding a marsh over several years in a sediment-poor marsh system to directly evaluate rates of sediment deposition, plant growth, and marsh elevation, yielding empirical evidence for the role of sediment availability on ecogeomorphic feedback processes in marshes. These data will be used to validate, parameterize, and expand an existing model (the Marsh Equilibrium Model). The model will then be used to hindcast marsh accretion rates and to forecast marsh stability under various future scenarios of sediment availability and rates of relative sea level rise. The land use change and fluvial sediment supply analyses will be coupled with measurements of temporally-variable marsh accretion rates and modeling to provide a comprehensive examination of estuarine wetland vulnerability to sea level rise. This research will provide integrated assessment of estuarine marsh response to both sea level rise and sediment availability.
PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
Coastal wetlands are highly productive systems that provide many critical ecosystem services but are thought to be at increasing risk due to sea level rise and reductions in sediment supply from the landscape that support wetland accretion. This project was focused on understanding how human activities in watersheds that drain to the U.S. East Coast have influenced sediment delivery to the coastal zone, how changing sediment supply has altered estuarine wetland accretion rates in the recent past, and to predict how current and future changes in sediment supply and sea-level will shape coastal wetland vulnerability. We combined field measurements and experiments, spatial data analyses, and modeling to better understand how tidal wetlands are responding to climate change and land-use change. We measured rates of vertical accretion in nine wetlands along the U.S. East Coast from Maine to Georgia and found that vertical accretion has accelerated over the last century in a manner that is remarkably similar to the acceleration in global sea-level rise. The overall rate of accretion, as well as the acceleration in accretion, across these nine wetland systems can be explained by variations in rates of local relative sea level rise, suspended sediment availability, and temperature. These findings indicate that systems with higher rates of sea level rise, greater sediment supply, and lower temperatures have higher accretion rates, and are experiencing more rapid accelerations in accretion. Predictions of marsh response to sea level rise based on historical estimates of accretion may overestimate the vulnerability of tidal marsh systems to future accelerations in SLR. However, further declines in sediment supply and increases in temperature along with additional acceleration in sea-level rise will likely test the ability of coastal wetlands to keep pace with rates of environmental change. These findings provide further evidence of widespread response in Earth’s biological systems to human-induced climate change. This work has helped us to better understand how human activities regulate the physical drivers of coastal wetland stability and vulnerability, and will be of use to researchers, managers, and stakeholders.
This project had strong impacts beyond the science through the training and preparation of students. Seventeen undergraduate students participated in summer independent research experiences, with many continuing their engagement in the project during academic year research and completion of independent projects. Seven graduate students participated in the project and completed theses supported by this project. Females and members of underrepresented groups in the sciences were strongly represented among these students. All of these undergraduate and graduate students gained substantial experience in the field and laboratory through completing independent research projects.
Last Modified: 05/06/2020
Modified by: Scott C Neubauer
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