Kevin Kroeger has studied coastal ecosystems since 1990, with focus on a range of topics including fluxes and biogeochemistry of nitrogen in groundwater discharge to estuaries and wetlands, estuarine water quality, and carbon and greenhouse gas cycling and fluxes in coastal wetlands.
Kroeger is lead of the Biogeochemical Processes group at Woods Hole Coastal and Marine Science Center, and lead of a new project titled: Biogeochemical Drivers of Wetland Persistence and Feedbacks on Coastal Hazards The objectives of this Project are to provide guidance to federal (National Park Service, Fish & Wildlife Service, Army Corp of Engineers), state, local and private land owners and managers regarding stability and persistence of coastal wetlands under a range of hydrological management conditions and changing environmental conditions. Tidal wetlands provide critical services to society, including protection of infrastructure from coastal hazards, and habitat provision for economically important species. A large fraction of U.S. tidal wetlands, however, has been lost or degraded during recent centuries due to human actions, largely related to development and utilization of coastal lands. Feedbacks and interactions among natural and anthropogenic drivers have altered the stability and persistence of coastal wetlands. Decisions regarding hydrological management can alter the balance of organic matter production, retention and preservation, and thus management actions can either promote wetland persistence and resilience, or cause catastrophic loss of elevation, putting coastal infrastructure at increased risk of flooding or storm damage. This project impacts wetland management decisions. The contiguous U.S. has close to 2 million hectares of estuarine and marine wetlands. Nearly all of that area is under some level of management, with the federal government being the largest single manager. Land managers at FWS and NPS, and flood managers at ACOE, must make decisions regarding whether to spend substantial funds to maintain, repair and enhance water control structures under increasing rates of sea level change, or alternatively whether to reduce or remove hydrological management, to restore managed wetlands to more natural hydrology and enhance the capability of wetlands to build elevation over time, and to migrate landward. Society needs guidance and predictions regarding the result of those decisions for continued elevation gain, migration, and ongoing persistence of the wetlands.
Professional Experience
Present: Research Chemist, USGS Coastal and Marine Geology Program, Woods Hole Science Center, Woods Hole, MA
2004-2006: Mendenhall Fellow, US Geological Survey Geologic Division, St Petersburg, FL
2003-2004: Postdoctoral Scholar, Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA
1997-2003: Research Fellow and Teaching Fellow, Bos
Education and Certifications
PhD Boston University Marine Program (Biogeochemistry)
M.S. University of Connecticut (Marine Science)
B.A. University of Tennessee (Ecology)
Affiliations and Memberships
Contributing Author: 2nd State of the Carbon Cycle Report (SOCCR-2), Chapter 15 Tidal Wetlands and Estuaries
Lead, USGS Woods Hole Coastal Biogeochemical Processes Project
Participant, 2017 EPA AFOL
Science and Products
Wetland Carbon Working Group: Improving Methodologies and Estimates of Carbon and Greenhouse Gas Flux in Wetlands
Submarine Groundwater Discharge
Global Science and Data Network for Coastal Blue Carbon (SBC)
NASA-USGS National Blue Carbon Monitoring System
Environmental Geochemistry
Advancing understanding of ecosystem responses to climate change with warming experiments: what we have learned and what is unknown?
Carbon dioxide and methane fluxes with supporting environmental data from coastal wetlands across Cape Cod, Massachusetts
Geochemical data supporting analysis of fate and transport of nitrogen in the near shore groundwater and subterranean estuary near East Falmouth, Massachusetts, 2015
Collection, analysis, and age-dating of sediment cores from Herring River wetlands and other nearby wetlands in Wellfleet, Massachusetts, 2015-17
Collection, Analysis, and Age-Dating of Sediment Cores from Salt Marshes, Rhode Island, 2016
Collection, analysis, and age-dating of sediment cores from natural and restored salt marshes on Cape Cod, Massachusetts, 2015-16
Collection, analysis, and age-dating of sediment cores from mangrove and salt marsh ecosystems in Tampa Bay, Florida, 2015
Geochemical data supporting investigation of solute and particle cycling and fluxes from two tidal wetlands on the south shore of Cape Cod, Massachusetts, 2012-19
Continuous Monitoring Data From Herring River Wetlands Cape Cod, Massachusetts, 2015-Jan2020
Continuous Monitoring Data From Great Barnstable Marsh on Cape Cod, Massachusetts, 2017-19
Tidal marsh biomass field plot and remote sensing datasets for six regions in the conterminous United States (ver. 2.0, June 2020)
Continuous monitoring data from natural and restored salt marshes on Cape Cod, Massachusetts, 2016-17
Time-series biogeochemical and flow data from a tidal salt-marsh creek, Sage Lot Pond, Waquoit Bay, Massachusetts, 2012-2016
Detection and characterization of coastal tidal wetland change in the northeastern US using Landsat time series
Estimating the aboveground biomass and carbon stocks of tall shrubs in a prerestoration degraded salt marsh
Oxygen-controlled recirculating seepage meter reveals extent of nitrogen transformation in discharging coastal groundwater at the aquifer–estuary interface
Assessment of water quality and discharge in the Herring River, Wellfleet, Massachusetts, November 2015 to September 2017
Pore water exchange-driven inorganic carbon export from intertidal salt marshes
Plant biomass and rates of carbon dioxide uptake are enhanced by successful restoration of tidal connectivity in salt marshes
An important biogeochemical link between organic and inorganic carbon cycling: Effects of organic alkalinity on carbonate chemistry in coastal waters influenced by intertidal salt marshes
Tidal wetland gross primary production across the continental United States, 2000–2019
Phytoplankton community structure response to groundwater-borne nutrients in the inland bays, Delaware
Water salinity and inundation control soil carbon decomposition during salt marsh restoration: An incubation experiment
Salt marsh ecosystem restructuring enhances elevation resilience and carbon storage during accelerating relative sea-level rise
Uncertainty in United States coastal wetland greenhouse gas inventorying
Science and Products
- Science
Wetland Carbon Working Group: Improving Methodologies and Estimates of Carbon and Greenhouse Gas Flux in Wetlands
WARC researchers are working to quantify the impacts of future climate and land use/land cover change on greenhouse gas emissions and reductions.Submarine Groundwater Discharge
We define submarine groundwater discharge (SGD) to consist either of fresh groundwater, re-circulated seawater, or a composite thereof. We evaluate and present SGD in terms of a vector for nutrient delivery to coastal waters.Global Science and Data Network for Coastal Blue Carbon (SBC)
The Global Science and Data Network for Coastal Blue Carbon (SBC) brings together scientists from a wide range of disciplines. Our goal is to increase the accuracy of and confidence in local, regional, and global estimates of carbon cycle processes, fluxes, and storage as well as greenhouse gas emissions from coastal ecosystems, and to allow global access to quality controlled coastal ecosystem...NASA-USGS National Blue Carbon Monitoring System
The NASA-USGS National Blue Carbon Monitoring System project will evaluate the relative uncertainty of iterative modeling approaches to estimate coastal wetland (marsh and mangrove) C stocks and fluxes based on changes in wetland distributions, using nationally available datasets (Landsat) and as well as finer scale satellite and field derived data in six sentinel sites.Environmental Geochemistry
Coastal Environmental Geochemistry research at the Woods Hole Coastal and Marine Science Center spans multiple ecosystems and topics, including coastal wetlands, aquifers, and estuaries, with the goal of providing data and guidance to federal, state, local, and private land owners and managers on these vital ecosystems.Advancing understanding of ecosystem responses to climate change with warming experiments: what we have learned and what is unknown?
Advancing our mechanistic understanding of ecosystem responses to climate change is critical to improve ecological theories, develop predictive models to simulate ecosystem processes, and inform sound policies to manage ecosystems and human activities. Manipulation of temperature in the field, or the “ecosystem warming experiment,” has proved to be a powerful tool to understand ecosystem responses... - Data
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Carbon dioxide and methane fluxes with supporting environmental data from coastal wetlands across Cape Cod, Massachusetts
Saline tidal wetlands are important sites of carbon sequestration and produce negligible methane (CH4) emissions due to regular inundation with sulfate-rich seawater. Yet, widespread management of coastal hydrology has restricted vast areas of coastal wetlands to tidal exchange. These ecosystems often undergo impoundment and freshening, which in turn cause vegetation shifts like invasion by PhragmGeochemical data supporting analysis of fate and transport of nitrogen in the near shore groundwater and subterranean estuary near East Falmouth, Massachusetts, 2015
Geochemical data were obtained to investigate the fate and transport of nitrogen in a subterranean estuary near East Falmouth, Massachusetts. The goal of this investigation was to assess nitrogen attenuation in the aquifer under the Eel River Estuary and the adjacent peninsula that was densely populated with residences having septic systems and legacy cesspool inputs of inorganic nitrogen. This esCollection, analysis, and age-dating of sediment cores from Herring River wetlands and other nearby wetlands in Wellfleet, Massachusetts, 2015-17
The Herring River estuary in Wellfleet, Cape Cod, Massachusetts, has been tidally restricted for more than a century by a dike constructed near the mouth of the river. Upstream from the dike, the tidal restriction has caused the conversion of salt marsh wetlands to various other ecosystems including impounded freshwater marshes, flooded shrub land, drained forested upland, and brackish wetlands doCollection, Analysis, and Age-Dating of Sediment Cores from Salt Marshes, Rhode Island, 2016
The accretion history of fringing salt marshes in Narragansett Bay, Rhode Island, was reconstructed from sediment cores. Age models, based on excess lead-210 and cesium-137 radionuclide analysis, were constructed to evaluate how vertical accretion and carbon burial rates have changed during the past century. The Constant Rate of Supply (CRS) age model was used to date six cores collected from threCollection, analysis, and age-dating of sediment cores from natural and restored salt marshes on Cape Cod, Massachusetts, 2015-16
Nineteen sediment cores were collected from five salt marshes on the northern shore of Cape Cod where previously restricted tidal exchange was restored to part of the marshes. Cores were collected in duplicate from two locations within each marsh complex: one upstream and one downstream from the former tidal restriction (typically caused by an undersized culvert or a berm). The unaltered, naturalCollection, analysis, and age-dating of sediment cores from mangrove and salt marsh ecosystems in Tampa Bay, Florida, 2015
Coastal wetlands in Tampa Bay, Florida, are important ecosystems that deliver a variety of ecosystem services. Key to ecosystem functioning is wetland response to sea-level rise through accumulation of mineral and organic sediment. The organic sediment within coastal wetlands is composed of carbon sequestered over the time scale of the wetland’s existence. This study was conducted to provide inforGeochemical data supporting investigation of solute and particle cycling and fluxes from two tidal wetlands on the south shore of Cape Cod, Massachusetts, 2012-19
Assessment of geochemical cycling within tidal wetlands and measurement of fluxes of dissolved and particulate constituents between wetlands and coastal water bodies are critical to evaluating ecosystem function, service, and status. The U.S. Geological Survey and collaborators collected surface water and porewater geochemical data from a tidal wetland located on the eastern shore of Sage Lot PondContinuous Monitoring Data From Herring River Wetlands Cape Cod, Massachusetts, 2015-Jan2020
The Herring River estuary (Wellfleet, Cape Cod, Massachusetts) has been tidally restricted for over a century by a dike constructed near the mouth of the river. Behind the dike, the tidal restriction has caused the conversion of salt marsh wetlands to various other ecosystems including impounded freshwater marshes, flooded shrub land, drained forested upland, and wetlands dominated by Phragmites aContinuous Monitoring Data From Great Barnstable Marsh on Cape Cod, Massachusetts, 2017-19
Salt marshes are environmental ecosystems that contribute to coastal landscape resiliency to storms and rising sea level. Ninety percent of mid-Atlantic and New England salt marshes have been impacted by parallel grid ditching that began in the 1920s–40s to control mosquito populations and to provide employment opportunities during the Great Depression (James-Pirri and others, 2009; Kennish,Tidal marsh biomass field plot and remote sensing datasets for six regions in the conterminous United States (ver. 2.0, June 2020)
Remote sensing based maps of tidal marshes, both of their extents and carbon stocks, have the potential to play a key role in conducting greenhouse gas inventories and implementing climate mitigation policies. Our objective was to generate a single remote sensing model of tidal marsh aboveground biomass and carbon that represents nationally diverse tidal marshes within the conterminous United StatContinuous monitoring data from natural and restored salt marshes on Cape Cod, Massachusetts, 2016-17
Continuous monitoring data reported are a portion of data from a larger study investigating changes in soil properties, carbon accumulation, and greenhouse gas fluxes in four recently restored salt marsh sites and nearby natural salt marshes. For several decades, local towns, conservation groups, and government organizations have worked to identify, replace, repair, and enlarge culverts to restoreTime-series biogeochemical and flow data from a tidal salt-marsh creek, Sage Lot Pond, Waquoit Bay, Massachusetts, 2012-2016
Extended time-series sensor data were collected between 2012 and 2016 in surface water of a tidal salt-marsh creek on Cape Cod, Massachusetts. The objective of this field study was to measure water chemical characteristics and flows, as part of a study to quantify lateral fluxes of dissolved carbon species between the salt marsh and estuary. Data consist of in-situ measurements including: salinity - Publications
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Detection and characterization of coastal tidal wetland change in the northeastern US using Landsat time series
Coastal tidal wetlands are highly altered ecosystems exposed to substantial risk due to widespread and frequent land-use change coupled with sea-level rise, leading to disrupted hydrologic and ecologic functions and ultimately, significant reduction in climate resiliency. Knowing where and when the changes have occurred, and the nature of those changes, is important for coastal communities and natEstimating the aboveground biomass and carbon stocks of tall shrubs in a prerestoration degraded salt marsh
Wetlands play a vital role in Earth's carbon cycle and provide important ecosystem services. Their ability to perform their roles can be compromised by human activities that destroy or impair their functioning. The restoration of degraded wetlands may allow carbon cycle functioning, as well as other services, to be recovered. Predicting the potential outcomes from any restoration project requiresOxygen-controlled recirculating seepage meter reveals extent of nitrogen transformation in discharging coastal groundwater at the aquifer–estuary interface
Nutrient loads delivered to estuaries via submarine groundwater discharge (SGD) play an important role in the nitrogen (N) budget and eutrophication status. However, accurate and reliable quantification of the chemical flux across the final decimeters and centimeters at the sediment–estuary interface remains a challenge, because there is significant potential for biogeochemical alteration due to cAssessment of water quality and discharge in the Herring River, Wellfleet, Massachusetts, November 2015 to September 2017
The U.S. Geological Survey, Cape Cod National Seashore of the National Park Service, and Friends of Herring River cooperated from 2015 to 2017 to assess nutrient concentrations and fluxes across the ocean-estuary boundary at a dike on the Herring River in Wellfleet, Massachusetts. The purpose of this assessment was to characterize environmental conditions prior to a future removal of the dike, whiPore water exchange-driven inorganic carbon export from intertidal salt marshes
Respiration in intertidal salt marshes generates dissolved inorganic carbon (DIC) that is exported to the coastal ocean by tidal exchange with the marsh platform. Understanding the link between physical drivers of water exchange and chemical flux is a key to constraining coastal wetland contributions to regional carbon budgets. The spatial and temporal (seasonal, annual) variability of marsh porePlant biomass and rates of carbon dioxide uptake are enhanced by successful restoration of tidal connectivity in salt marshes
Salt marshes, due to their capability to bury soil carbon (C), are potentially important regional C sinks. Efforts to restore tidal flow to former salt marshes have increased in recent decades in New England (USA), as well as in some other parts of the world. In this study, we investigated plant biomass and carbon dioxide (CO2) fluxes at four sites where restoration of tidal flow occurred five toAn important biogeochemical link between organic and inorganic carbon cycling: Effects of organic alkalinity on carbonate chemistry in coastal waters influenced by intertidal salt marshes
Organic acid charge groups in dissolved organic carbon (DOC) contribute to total alkalinity (TA), i.e. organic alkalinity (OrgAlk). Its effect is often ignored or treated as a calculation uncertainty in many aquatic CO2 studies. This study evaluated the variability, sources, and characteristics of OrgAlk in estuarine waters exchanged tidally with a groundwater-influenced salt marsh in the northeasTidal wetland gross primary production across the continental United States, 2000–2019
We mapped tidal wetland gross primary production (GPP) with unprecedented detail for multiple wetland types across the continental United States (CONUS) at 16‐day intervals for the years 2000–2019. To accomplish this task, we developed the spatially explicit Blue Carbon (BC) model, which combined tidal wetland cover and field‐based eddy covariance tower data into a single Bayesian framework, and uPhytoplankton community structure response to groundwater-borne nutrients in the inland bays, Delaware
To determine the impacts of groundwater-borne nutrients on phytoplankton biomass and community structure, we conducted a series of mesocosm experiments in the Inland Bays of Delaware. Four treatments were tested, including mesocosms coupled directly to submarine groundwater seepage, mesocosms with the addition of pumped submarine groundwater, mesocosms with the addition of phosphate, and control mWater salinity and inundation control soil carbon decomposition during salt marsh restoration: An incubation experiment
Coastal wetlands are a significant carbon (C) sink since they store carbon in anoxic soils. This ecosystem service is impacted by hydrologic alteration and management of these coastal habitats. Efforts to restore tidal flow to former salt marshes have increased in recent decades and are generally associated with alteration of water inundation levels and salinity. This study examined the effect ofSalt marsh ecosystem restructuring enhances elevation resilience and carbon storage during accelerating relative sea-level rise
Salt marshes respond to sea-level rise through a series of complex and dynamic bio-physical feedbacks. In this study, we found that sea-level rise triggered salt marsh habitat restructuring, with the associated vegetation changes enhancing salt marsh elevation resilience. A continuous record of marsh elevation relative to sea level that includes reconstruction of high-resolution, sub-decadal, marsUncertainty in United States coastal wetland greenhouse gas inventorying
Coastal wetlands store carbon dioxide (CO2) and emit CO2 and methane (CH4) making them an important part of greenhouse gas (GHG) inventorying. In the contiguous United States (CONUS), a coastal wetland inventory was recently calculated by combining maps of wetland type and change with soil, biomass, and CH4 flux data from a literature review. We assess uncertainty in this developing carbon monitor - News