Award Abstract # 1458633
Collaborative Research: Impact of saltwater intrusion on C storage in tidal freshwater wetlands: Assessing the amount, age, and fate of mobilized C

NSF Org: DEB
Division Of Environmental Biology
Recipient: VIRGINIA COMMONWEALTH UNIVERSITY
Initial Amendment Date: September 2, 2014
Latest Amendment Date: September 2, 2014
Award Number: 1458633
Award Instrument: Continuing Grant
Program Manager: Elizabeth Blood
DEB
 Division Of Environmental Biology
BIO
 Directorate for Biological Sciences
Start Date: March 21, 2014
End Date: February 28, 2017 (Estimated)
Total Intended Award Amount: $255,031.00
Total Awarded Amount to Date: $255,031.00
Funds Obligated to Date: FY 2011 = $144,418.00
FY 2013 = $110,613.00
History of Investigator:
  • Scott Neubauer (Principal Investigator)
    sneubauer@vcu.edu
Recipient Sponsored Research Office: Virginia Commonwealth University
910 WEST FRANKLIN ST
RICHMOND
VA  US  23284-9005
(804)828-6772
Sponsor Congressional District: 04
Primary Place of Performance: Virginia Commonwealth University
VA  US  23284-9067
Primary Place of Performance
Congressional District:
Unique Entity Identifier (UEI): MLQFL4JSSAA9
Parent UEI: WXQLZ1PA6XP3
NSF Program(s): ECOSYSTEM STUDIES
Primary Program Source: 01001112DB NSF RESEARCH & RELATED ACTIVIT
01001314DB NSF RESEARCH & RELATED ACTIVIT
Program Reference Code(s): 1181, 9150, 9169, EGCH
Program Element Code(s): 118100
Award Agency Code: 4900
Fund Agency Code: 4900
Assistance Listing Number(s): 47.074

ABSTRACT

Rising sea levels, reduced precipitation in watersheds, and global increases in water consumption are resulting in widespread saltwater intrusion into tidal freshwater wetlands. The movement of saline water into these historically freshwater ecosystems is likely to impact plant productivity, the decomposition of roots and litter, the metabolism of soil microbial communities, and, as a result, the rate of organic matter accumulation. Organic matter accumulation is an important factor determining the rate of vertical accretion in tidal freshwater wetlands, and whether these wetlands will be able to "keep up" with rising sea levels. The overall goal of this project is to understand how saltwater intrusion will impact the fate of organic carbon in tidal freshwater wetlands. Several tidal freshwater wetlands in Virginia and South Carolina that cover a range of soil types, plant communities, and potential responses to saltwater intrusion will be studied.

Coastal marshes supply a number of important ecosystem goods and services, including water quality improvement, floodwater buffering, and habitat for economically and ecologically important plants and animals. As sea level rises, it is critical to understand whether and how freshwater tidal wetlands will be able to keep pace by building soil volume. This research will allow us to understand and perhaps respond to the effects of climate change on tidal freshwater wetlands.

PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH

Note:  When clicking on a Digital Object Identifier (DOI) number, you will be taken to an external site maintained by the publisher. Some full text articles may not yet be available without a charge during the embargo (administrative interval).

Some links on this page may take you to non-federal websites. Their policies may differ from this site.

Ellen R. Herbert, Paul Boon, Amy J. Burgin, Scott C. Neubauer, Rima B. Franklin, Marcelo Ardón, Kristine N. Hopfensperger, Leon P. M. Lamers, and Peter Gell "A global perspective on wetland salinization: Ecological consequences of a growing threat to freshwater wetlands" Ecosphere , v.6 , 2015 , p.206 10.1890/ES14-00534.1
Morris, J.T., D.C. Barber, J. Callaway, R. Chambers, S.C. Hagen, C. Hopkinson, B.J. Johnson, J.P. Megonigal, S.C. Neubauer, T. Troxler, C. Wigand "Contributions of organic and inorganic matter to volume and accretion in tidal wetlands at steady state." Earth's Future , v.4 , 2016 10.1002/2015EF000334

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.

Collaborative Research: Impact of salt water intrusion on C storage in temperate tidal freshwater wetlands: Assessing the amount, age, and fate of mobilized C

Scott C. Neubauer1,2, S. Leigh McCallister1

1 Virginia Commonwealth University; 2 University of South Carolina, Baruch Marine Field Laboratory

 

Summary

Soil in wetlands is a mixture of organic materials (largely derived from dead plants) and inorganic materials (for example, sand, silt, and clay). By building soil, tidal wetlands are able to grow vertically and can avoid being permanently submerged by rising sea levels. Because organic matter accumulation is important in building soil volume, changes in organic matter storage have implications for the ability of these wetlands to track rising sea levels and will ultimately play a role in determining the long-term stability and persistence of these valuable coastal ecosystems. In order to better understand how sea level rise and the associated stressor of saltwater intrusion will impact the fate of organic matter in tidal freshwater wetlands, we conducted a series of experiments on soils collected from a variety of wetlands that differ in factors including the dominant vegetation and soil characteristics. Despite our expectations to the contrary, we did not find that salinity was the major control on the fate of soil organic matter in tidal freshwater wetlands. Instead, other factors including vegetation type and soil age appear to play a controlling role in determining the reactivity and preservation of soil organic matter.

Introduction, Hypothesis and Objectives 

Wetlands are important ecosystems that provide a multitude of services for humanity such as serving as a reservoir for freshwater, controlling floods on the landscape, and serving as key nursery habitat for inland and coastal fisheries. Importantly, wetlands store almost one-third of the world’s carbon while covering a mere 3-4% of the terrestrial land area. Vertical accretion in tidal wetlands is governed by net input of organic matter (a function of both production and decomposition) and inorganic matter; any factor that changes either organic or inorganic accumulation rates will impact the ability of these systems to grow vertically and keep up with rising sea levels. The goal of this project was to determine how saltwater intrusion impacts the fate of organic carbon in coastal freshwater wetlands by examining factors that affect the decomposition of soil organic matter.

Experimental Design, Research Sites and Methods

We established a suite of twelve tidal freshwater wetland sites, six sites in South Carolina and six in Virginia, that collectively span gradients of dominant vegetation (herbaceous marsh vs. forested swamp versus scrub-shrub wetland), soil characteristics (e.g., high versus low organic matter content), and hydrology. We exposed the soils from these sites to either freshwater or low salinity brackish water and measured rates of total decomposition (as production of carbon dioxide and methane), quantified the desorption of organic carbon from soils, and assessed how quickly that desorbed material was broken down by microbial processes. We collected baseline data on soil properties, plants, and porewater, and used spectroscopic techniques to examine the chemical composition of desorbed soil organic carbon. We related our indices of organic matter preservation and decomposition to various environmental drivers.

We provided training to multiple technicians and undergraduate students, each of whom helped with field sample collection, laboratory analyses, and data processing. All of these individuals also received training in concepts relating to wetland science, biogeochemistry, and ecosystem ecology. The Carbon Awareness Partnership (CAP) was created as part of the outreach component of this grant and has now been active in the greater Richmond area since 2011. The primary goals of our CAP program were 1) to provide Virginia high school teachers with strong lesson plans and hands-on activities that focus on C cycle, and 2) to expand scientific literacy and competency at the secondary school level.

Results

Our results show very interesting trends in responses of freshwater wetland soils to saltwater intrusion. In the low organic soils of the Virginia wetlands, increasing salinity caused a decrease in pathways of decomposition that result in the production of methane but did not affect the production of carbon dioxide through decomposition. In contrast, neither carbon dioxide nor methane production of the wetland soils was affected by salinity at the South Carolina sites. There were differences in the desorption of soil carbon from different wetland soils, although our results indicate that salinity does not significantly affect the amount of carbon desorbed from any of our forested swamps, herbaceous marshes, or scrub-shrub wetlands. Instead, vegetation type and soil age play a larger role in determining carbon availability in wetland soils. This work raises interesting questions about the effects of saltwater intrusion, suggesting the decrease in organic matter inputs caused by plant stress in response to rising salinity is more important than changes in decomposition in influencing how much organic matter can be stored in wetland soils. 

 


Last Modified: 11/22/2017
Modified by: Scott C Neubauer

Please report errors in award information by writing to: awardsearch@nsf.gov.

Print this page

Back to Top of page