Impacts of coastal and watershed changes on upper estuaries: causes and implications of wetland ecosystem transitions along the US Atlantic and Gulf Coasts Active
Estuaries and their surrounding wetlands are coastal transition zones where freshwater rivers meet tidal seawater. As sea levels rise, tidal forces move saltier water farther upstream, extending into freshwater wetland areas. Human changes to the surrounding landscape may amplify the effects of this tidal extension, impacting the resiliency and function of the upper estuarine wetlands. One visible indicator is the rapid conversion of some Southeast and mid-Atlantic tidal freshwater forested wetlands to ‘Ghost Forests’ in which trees die from increases in salinity. Because data on the complex causes and impacts of tidal extension are limited, this project takes an integrated, large-scale approach to research and monitoring to expand our ability to model these processes and apply them to other coastal areas along the Atlantic Coast, Gulf Coast, and internationally. Results of this effort will provide critical data to guide future decisions regarding the fate of carbon, water quality, coastal resilience, wildlife and fisheries, and effective allocation of taxpayer dollars for ecosystem restoration.
Statement of Problem: Throughout the southeastern United States, tidal freshwater forested wetlands (TFFW) found along the upper tidal estuary (where freshwater watersheds and estuaries meet), are converting to ‘Ghost Forests’ (dead trees) and then to oligohaline (low salinity) marsh. Nontidal floodplains are also converting into TFFW as tides extend farther upstream along rivers, and little scientific research has been directed toward describing or understanding the effects of this tidal extension.
Conversion is related to both changing sea level and associated salt-water intrusion and to human influences (e.g., land use change, coastal development, construction of dams, river dredging, etc). All these factors affect the resiliency and ecosystem services provided by wetlands of the upper estuary. Watershed inputs to the upper estuary (water, sediment, nutrients) also may determine the response of TFFW through complex interactions between the ecosystem, water, and landscape. Further, TFFW itself influences delivery of watershed sediment to lower tidal estuaries that are targets of restoration projects, making their function critical to ecosystem health.
Why this Research is Important: This project fills a large gap in integrative ecosystem research and monitoring of different coastal areas which vary in land use activity, tidal range, relative sea-level rise, watershed characteristics and changes, and delivery of ecosystem services for taxpayers. A primary outcome thus far has been the value assigned to TFFW in terms of carbon storage, sequestration, and conveyance; adding them to the list of important "blue carbon" wetlands globally.
“Blue Carbon” refers to carbon that is stored in coastal or marine ecosystems. In addition to the monetary value of the ecosystem services, these coastal wetland areas are crucial for protecting the coast from storm surge, mitigating downstream eutrophication (when a water body becomes overly enriched in nutrients), and providing wildlife and fishery habitat. By improving understanding of the processes and services provided by both healthy TFFW and those transitioned to marshes, managers and coastal inhabitants (and taxpayers) will be able to anticipate how past and current changes will affect the ecosystems in the future.
The TFFW transition/conversion phenomenon is not unique to the southeast and mid-Atlantic United States, and expansion of the project enhances our ability to (1) apply this research to other domestic and international coastal areas undergoing similar changes, and (2) add to critical information gaps on carbon sequestration to better understand the role of coastal ecosystems in the cycling of carbon and nutrients).
Objective(s): We hypothesize that ecosystem functions, sediment and nutrient processes, and carbon sequestration vary in predictable ways in different coastal environments as nontidal floodplains convert to TFFW and TFFW convert to marshes. Through extensive data collection over 15 years, we have quantified several processes and changes to sedimentation, nutrient uptake and release, forest condition, and balance of habitat. From analyses of these data we developed an understanding of emergent processes at multiple scales that are critical to future investigation, culminating in predictive models and advancements to ecological theory of coastal wetland change. In order to further expand our focus from TFFW stresses and degradation, our focus moves to the larger scale of the entire upper estuary landscape, guiding a series of new goals and objectives:
- Maintain repeated measurements at existing field sites in order to reach a full 20-year-record of change, while also incorporating new site locations farther inland, upriver, and into non-tidal zones
- Incorporate new studies to determine where sediment is coming from and what potential land use and management practices may influence sedimentation
- Continue documenting how biogeochemical cycles are affected by changes in the watershed and estuary
- Perform comparative carbon studies between regions to determine generality
- Map and describe tidal extension and landward habitat conversion to develop accurate land cover maps of tidal wetland habitat distribution
- Advance dynamic models to predict upper estuarine habitat change, coupled with elevated CO2 experiments simulating environmental stress to support future modeling
- Begin proactive efforts to compare upper estuarine wetlands of the US Atlantic and Gulf Coasts to similarly positioned habitat conditions globally (e.g., Pacific Northwest, Australia, New Zealand)
Methods: We use a combination of complementary field, laboratory, modeling, and remote sensing techniques to achieve our objectives. Changes in vegetation, tidal extent, surface elevation, and microtopography are measured using field data collection. For example, plots of trees and herbaceous vegetation are surveyed over time to document a record of habitat change, while direct measurements of growth records inform contemporary and historic productivity.
Water level and salinity are measured continuously with logging devices. Surfaces of hummocks and hollows are measured annually to assess changes in elevation, accretion, subsidence and general resilience to sea-level rise. More complex methods that involve both field collection and laboratory analyses are required to measure soil biogeochemistry, nutrients, and carbon (C) storage and flux.
We collect and analyze shallow soil cores (up to 1-meter in depth), for total organic carbon and nitrogen, and date them using Pb-210 activity to determine rates of soil C burial. In analyses of deeper cores (up to 6-7 meters depth), macrofossils, pollen, C-14, and carbon and nutrient sequestration are used to develop historic baselines prior to rising sea-level conditions. Further soil and vegetation analyses assess ground carbon stocks, belowground net ecosystem productivity, greenhouse gas production (CO2, CH4, N2O) in soils of hummocks and hollows, and transpirational demand on soils in forests vs. newly converted marsh.
Finally, river channel bathymetry, longitudinal sampling of suspended and bed sediment, and analysis of sediment stable isotopes and metals to determine changes in mineral and organic sediment sources (“sediment fingerprinting”) are used together to determine how channels and floodplains have changed and have impacted sediment transport. We will use remote sensing techniques to gather information on the extent of tidal flooding along upper estuarine reaches in our study areas. Using our data, we will validate remote sensing results and apply it to regional and national mapping efforts, as well as model development. Synthesizing the various data streams is accomplished through development and application of both statistical and dynamic process models to generate new understanding and tools to predict ecosystem change in new coastal areas.
Below are other science projects associated with this project.
Below are data or web applications associated with this project.
Below are publications associated with this project.
Direct and indirect controls on organic matter decomposition in four coastal wetland communities along a landscape salinity gradient
Linear and nonlinear effects of temperature and precipitation on ecosystem properties in tidal saline wetlands
Assessing coastal wetland vulnerability to sea-level rise along the northern Gulf of Mexico coast: Gaps and opportunities for developing a coordinated regional sampling network
Performance measures for a Mississippi River reintroduction into the forested wetlands of Maurepas Swamp
Causal mechanisms of soil organic matter decomposition: Deconstructing salinity and flooding impacts in coastal wetlands
Created mangrove wetlands store belowground carbon and surface elevation change enables them to adjust to sea-level rise
Relationships between salinity and short-term soil carbon accumulation rates form marsh types across a landscape in the Mississippi River Delta
Delta-Flux: An eddy covariance network for a climate-smart Lower Mississippi Basin
Forested floristic quality index: An assessment tool for forested wetland habitats using the quality and quantity of woody vegetation at Coastwide Reference Monitoring System (CRMS) vegetation monitoring stations
Salinity influences on aboveground and belowground net primary productivity in tidal wetlands
A landscape-scale assessment of above- and belowground primary production in coastal wetlands: Implications for climate change-induced community shifts
Contemporary deposition and long-term accumulation of sediment and nutrients by tidal freshwater forested wetlands impacted by sea level rise
Below are partners associated with this project.
- Overview
Estuaries and their surrounding wetlands are coastal transition zones where freshwater rivers meet tidal seawater. As sea levels rise, tidal forces move saltier water farther upstream, extending into freshwater wetland areas. Human changes to the surrounding landscape may amplify the effects of this tidal extension, impacting the resiliency and function of the upper estuarine wetlands. One visible indicator is the rapid conversion of some Southeast and mid-Atlantic tidal freshwater forested wetlands to ‘Ghost Forests’ in which trees die from increases in salinity. Because data on the complex causes and impacts of tidal extension are limited, this project takes an integrated, large-scale approach to research and monitoring to expand our ability to model these processes and apply them to other coastal areas along the Atlantic Coast, Gulf Coast, and internationally. Results of this effort will provide critical data to guide future decisions regarding the fate of carbon, water quality, coastal resilience, wildlife and fisheries, and effective allocation of taxpayer dollars for ecosystem restoration.
Statement of Problem: Throughout the southeastern United States, tidal freshwater forested wetlands (TFFW) found along the upper tidal estuary (where freshwater watersheds and estuaries meet), are converting to ‘Ghost Forests’ (dead trees) and then to oligohaline (low salinity) marsh. Nontidal floodplains are also converting into TFFW as tides extend farther upstream along rivers, and little scientific research has been directed toward describing or understanding the effects of this tidal extension.
Conversion is related to both changing sea level and associated salt-water intrusion and to human influences (e.g., land use change, coastal development, construction of dams, river dredging, etc). All these factors affect the resiliency and ecosystem services provided by wetlands of the upper estuary. Watershed inputs to the upper estuary (water, sediment, nutrients) also may determine the response of TFFW through complex interactions between the ecosystem, water, and landscape. Further, TFFW itself influences delivery of watershed sediment to lower tidal estuaries that are targets of restoration projects, making their function critical to ecosystem health.
Why this Research is Important: This project fills a large gap in integrative ecosystem research and monitoring of different coastal areas which vary in land use activity, tidal range, relative sea-level rise, watershed characteristics and changes, and delivery of ecosystem services for taxpayers. A primary outcome thus far has been the value assigned to TFFW in terms of carbon storage, sequestration, and conveyance; adding them to the list of important "blue carbon" wetlands globally.
“Blue Carbon” refers to carbon that is stored in coastal or marine ecosystems. In addition to the monetary value of the ecosystem services, these coastal wetland areas are crucial for protecting the coast from storm surge, mitigating downstream eutrophication (when a water body becomes overly enriched in nutrients), and providing wildlife and fishery habitat. By improving understanding of the processes and services provided by both healthy TFFW and those transitioned to marshes, managers and coastal inhabitants (and taxpayers) will be able to anticipate how past and current changes will affect the ecosystems in the future.
The TFFW transition/conversion phenomenon is not unique to the southeast and mid-Atlantic United States, and expansion of the project enhances our ability to (1) apply this research to other domestic and international coastal areas undergoing similar changes, and (2) add to critical information gaps on carbon sequestration to better understand the role of coastal ecosystems in the cycling of carbon and nutrients).
Objective(s): We hypothesize that ecosystem functions, sediment and nutrient processes, and carbon sequestration vary in predictable ways in different coastal environments as nontidal floodplains convert to TFFW and TFFW convert to marshes. Through extensive data collection over 15 years, we have quantified several processes and changes to sedimentation, nutrient uptake and release, forest condition, and balance of habitat. From analyses of these data we developed an understanding of emergent processes at multiple scales that are critical to future investigation, culminating in predictive models and advancements to ecological theory of coastal wetland change. In order to further expand our focus from TFFW stresses and degradation, our focus moves to the larger scale of the entire upper estuary landscape, guiding a series of new goals and objectives:
- Maintain repeated measurements at existing field sites in order to reach a full 20-year-record of change, while also incorporating new site locations farther inland, upriver, and into non-tidal zones
- Incorporate new studies to determine where sediment is coming from and what potential land use and management practices may influence sedimentation
- Continue documenting how biogeochemical cycles are affected by changes in the watershed and estuary
- Perform comparative carbon studies between regions to determine generality
- Map and describe tidal extension and landward habitat conversion to develop accurate land cover maps of tidal wetland habitat distribution
- Advance dynamic models to predict upper estuarine habitat change, coupled with elevated CO2 experiments simulating environmental stress to support future modeling
- Begin proactive efforts to compare upper estuarine wetlands of the US Atlantic and Gulf Coasts to similarly positioned habitat conditions globally (e.g., Pacific Northwest, Australia, New Zealand)
Methods: We use a combination of complementary field, laboratory, modeling, and remote sensing techniques to achieve our objectives. Changes in vegetation, tidal extent, surface elevation, and microtopography are measured using field data collection. For example, plots of trees and herbaceous vegetation are surveyed over time to document a record of habitat change, while direct measurements of growth records inform contemporary and historic productivity.
Water level and salinity are measured continuously with logging devices. Surfaces of hummocks and hollows are measured annually to assess changes in elevation, accretion, subsidence and general resilience to sea-level rise. More complex methods that involve both field collection and laboratory analyses are required to measure soil biogeochemistry, nutrients, and carbon (C) storage and flux.
We collect and analyze shallow soil cores (up to 1-meter in depth), for total organic carbon and nitrogen, and date them using Pb-210 activity to determine rates of soil C burial. In analyses of deeper cores (up to 6-7 meters depth), macrofossils, pollen, C-14, and carbon and nutrient sequestration are used to develop historic baselines prior to rising sea-level conditions. Further soil and vegetation analyses assess ground carbon stocks, belowground net ecosystem productivity, greenhouse gas production (CO2, CH4, N2O) in soils of hummocks and hollows, and transpirational demand on soils in forests vs. newly converted marsh.
Finally, river channel bathymetry, longitudinal sampling of suspended and bed sediment, and analysis of sediment stable isotopes and metals to determine changes in mineral and organic sediment sources (“sediment fingerprinting”) are used together to determine how channels and floodplains have changed and have impacted sediment transport. We will use remote sensing techniques to gather information on the extent of tidal flooding along upper estuarine reaches in our study areas. Using our data, we will validate remote sensing results and apply it to regional and national mapping efforts, as well as model development. Synthesizing the various data streams is accomplished through development and application of both statistical and dynamic process models to generate new understanding and tools to predict ecosystem change in new coastal areas.
- Science
Below are other science projects associated with this project.
- Data
Below are data or web applications associated with this project.
- Publications
Below are publications associated with this project.
Filter Total Items: 56Direct and indirect controls on organic matter decomposition in four coastal wetland communities along a landscape salinity gradient
Coastal wetlands store more carbon than most ecosystems globally. As sea level rises, changes in flooding and salinity will potentially impact ecological functions, such as organic matter decomposition, that influence carbon storage. However, little is known about the mechanisms that control organic matter loss in coastal wetlands at the landscape scale. As sea level rises, how will the shift fromAuthorsCamille L. Stagg, Melissa M. Baustian, Carey L. Perry, Tim J. B. Carruthers, Courtney T. HallLinear and nonlinear effects of temperature and precipitation on ecosystem properties in tidal saline wetlands
Climate greatly influences the structure and functioning of tidal saline wetland ecosystems. However, there is a need to better quantify the effects of climatic drivers on ecosystem properties, particularly near climate-sensitive ecological transition zones. Here, we used climate- and literature-derived ecological data from tidal saline wetlands to test hypotheses regarding the influence of climatAuthorsLaura C. Feher, Michael J. Osland, Kereen T. Griffith, James B. Grace, Rebecca J. Howard, Camille L. Stagg, Nicholas M. Enwright, Ken W. Krauss, Christopher A. Gabler, Richard H. Day, Kerrylee RogersAssessing coastal wetland vulnerability to sea-level rise along the northern Gulf of Mexico coast: Gaps and opportunities for developing a coordinated regional sampling network
Coastal wetland responses to sea-level rise are greatly influenced by biogeomorphic processes that affect wetland surface elevation. Small changes in elevation relative to sea level can lead to comparatively large changes in ecosystem structure, function, and stability. The surface elevation table-marker horizon (SET-MH) approach is being used globally to quantify the relative contributions of proAuthorsMichael J. Osland, Kereen T. Griffith, Jack C. Larriviere, Laura C. Feher, Donald R. Cahoon, Nicholas M. Enwright, David A. Oster, John M. Tirpak, Mark S. Woodrey, Renee C. Collini, Joseph J. Baustian, Joshua L. Breithaupt, Julia A Cherry, Jeremy R. Conrad, Nicole Cormier, Carlos A. Coronado-Molina, Joseph F. Donoghue, Sean A. Graham, Jennifer W. Harper, Mark W. Hester, Rebecca J. Howard, Ken W. Krauss, Daniel Kroes, Robert R. Lane, Karen L. McKee, Irving A. Mendelssohn, Beth A. Middleton, Jena A. Moon, Sarai Piazza, Nicole M. Rankin, Fred H. Sklar, Gregory D. Steyer, Kathleen M. Swanson, Christopher M. Swarzenski, William Vervaeke, Jonathan M Willis, K. Van WilsonPerformance measures for a Mississippi River reintroduction into the forested wetlands of Maurepas Swamp
The use of freshwater diversions (river reintroductions) from the Mississippi River as a restoration tool to rehabilitate Louisiana coastal wetlands has been promoted widely since the first such diversion at Caernarvon became operational in the early 1990s. To date, aside from the Bonnet Carré Spillway (which is designed and operated for flood control), there are only four operational MississippiAuthorsKen W. Krauss, Gary P. Shaffer, Richard F. Keim, Jim L. Chambers, William B. Wood, Stephen B. HartleyCausal mechanisms of soil organic matter decomposition: Deconstructing salinity and flooding impacts in coastal wetlands
Coastal wetlands significantly contribute to global carbon storage potential. Sea-level rise and other climate change-induced disturbances threaten coastal wetland sustainability and carbon storage capacity. It is critical that we understand the mechanisms controlling wetland carbon loss so that we can predict and manage these resources in anticipation of climate change. However, our current underAuthorsCamille L. Stagg, Donald Schoolmaster, Ken W. Krauss, Nicole Cormier, William H. ConnerCreated mangrove wetlands store belowground carbon and surface elevation change enables them to adjust to sea-level rise
Mangrove wetlands provide ecosystem services for millions of people, most prominently by providing storm protection, food and fodder. Mangrove wetlands are also valuable ecosystems for promoting carbon (C) sequestration and storage. However, loss of mangrove wetlands and these ecosystem services are a global concern, prompting the restoration and creation of mangrove wetlands as a potential solutiAuthorsKen W. Krauss, Nicole Cormier, Michael J. Osland, Matthew L. Kirwan, Camille L. Stagg, Janet A. Nestlerode, Marc J. Russell, Andrew From, Amanda C. Spivak, Darrin D. Dantin, James E. Harvey, Alejandro E. AlmarioRelationships between salinity and short-term soil carbon accumulation rates form marsh types across a landscape in the Mississippi River Delta
Salinity alterations will likely change the plant and environmental characteristics in coastal marshes thereby influencing soil carbon accumulation rates. Coastal Louisiana marshes have been historically classified as fresh, intermediate, brackish, or saline based on resident plant community and position along a salinity gradient. Short-term total carbon accumulation rates were assessed by collectAuthorsMelissa M. Baustian, Camille L. Stagg, Carey L. Perry, Leland C Moss, Tim J. B. Carruthers, Mead AllisonDelta-Flux: An eddy covariance network for a climate-smart Lower Mississippi Basin
Networks of remotely monitored research sites are increasingly the tool used to study regional agricultural impacts on carbon and water fluxes. However, key national networks such as the National Ecological Observatory Network and AmeriFlux lack contributions from the Lower Mississippi River Basin (LMRB), a highly productive agricultural area with opportunities for soil carbon sequestration througAuthorsBenjamin R. K. Runkle, James R. Rigby, Michele L. Reba, Saseendran S. Anapalli, Joydeep Bhattacharjee, Ken W. Krauss, Lu Liang, Martin A. Locke, Kimberly A. Novick, Ruixiu Sui, Kosana Suvočarev, Paul M. WhiteForested floristic quality index: An assessment tool for forested wetland habitats using the quality and quantity of woody vegetation at Coastwide Reference Monitoring System (CRMS) vegetation monitoring stations
The U.S. Geological Survey, in cooperation with the Coastal Protection and Restoration Authority of Louisiana and the Coastal Wetlands Planning, Protection and Restoration Act, developed the Forested Floristic Quality Index (FFQI) for the Coastwide Reference Monitoring System (CRMS). The FFQI will help evaluate forested wetland sites on a continuum from severely degraded to healthy and will assistAuthorsWilliam B. Wood, Gary P. Shaffer, Jenneke M. Visser, Ken W. Krauss, Sarai C. Piazza, Leigh Anne Sharp, Kari F. CretiniSalinity influences on aboveground and belowground net primary productivity in tidal wetlands
Tidal freshwater wetlands are one of the most vulnerable ecosystems to climate change and rising sea levels. However salinification within these systems is poorly understood, therefore, productivity (litterfall, woody biomass, and fine roots) were investigated on three forested tidal wetlands [(1) freshwater, (2) moderately saline, and (3) heavily salt-impacted] and a marsh along the Waccamaw andAuthorsKathryn N. Pierfelice, B. Graeme Lockaby, Ken W. Krauss, William H. Conner, Gregory B. Noe, Matthew C. RickerA landscape-scale assessment of above- and belowground primary production in coastal wetlands: Implications for climate change-induced community shifts
Above- and belowground production in coastal wetlands are important contributors to carbon accumulation and ecosystem sustainability. As sea level rises, we can expect shifts to more salt-tolerant communities, which may alter these ecosystem functions and services. Although the direct influence of salinity on species-level primary production has been documented, we lack an understanding of the lanAuthorsCamille L. Stagg, Donald R. Schoolmaster, Sarai C. Piazza, Gregg Snedden, Gregory D. Steyer, Craig J Fischenich, Robert W. McComasContemporary deposition and long-term accumulation of sediment and nutrients by tidal freshwater forested wetlands impacted by sea level rise
Contemporary deposition (artificial marker horizon, 3.5 years) and long-term accumulation rates (210Pb profiles, ~150 years) of sediment and associated carbon (C), nitrogen (N), and phosphorus (P) were measured in wetlands along the tidal Savannah and Waccamaw rivers in the southeastern USA. Four sites along each river spanned an upstream-to-downstream salinification gradient, from upriver tidal fAuthorsGregory B. Noe, Cliff R. Hupp, Christopher E. Bernhardt, Ken W. Krauss - Partners
Below are partners associated with this project.