Meagan J Eagle , PhD
My research lies at the interface of land and sea and is used to build new tools to address coastal hazards. This dynamic region is experiencing rapid change, with new pressures from rising temperatures and sea level adding to those already wrought by the impacts of coastal development.
Biography
I utilize a suite of geochemical tools, including naturally occurring radioisotopes in the Uranium-Thorium decay series, to understand both the magnitude and rate of change within coastal ecosystems. In particular, I am interested in how salt marshes have responded to a century of accelerating sea level rise, with a focus on their ability to store carbon and dynamically build elevation. I combine historical ecosystem information, gleaned from analysis of salt marsh peat, with modern environmental drivers to constrain future ecosystem responses.
I studied geology at Stanford University (BS/MS) and received a PhD in Chemical Oceanography from the Massachusetts Institute of Technology and Woods Hole Oceanographic Institution Joint Program. There I studied groundwater discharge and associated chemical fluxes. Between going to school, I did a Fulbright Fellowship in Mauritius and worked at Woods Hole Oceanographic Institution. I came to the Woods Hole Coastal and Marine Science Center of the US Geological Survey in 2013 and have worked on coastal wetland and groundwater projects across the US.
Science and Products
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.
Collection, analysis, and age-dating of sediment cores from mangrove wetlands in San Juan Bay Estuary, Puerto Rico, 2016
We collected sediment cores to determine carbon burial rates and vertical sediment accretion from five sites in the San Juan Bay Estuary. Cores were radiometrically-dated using lead-210 and the Plum age model. Sites had soil C burial rates ranging from 50 grams per meter squared per year (g m-2 y-1) in the San José lagoon to 632 g m-2 y-1 in the Caño Martin Peña in recent decades.
Collection, analysis, and age-dating of sediment cores from Herring River wetlands and other nearby wetlands in Wellfleet, Massachusetts, 2015–17
U.S. Geological Survey collected fourteen sediment cores from different ecosystems within the tidally restricted Herring River estuary (four sites) and an estuary in Wellfleet Harbor near the Herring River dike (three sites) between 2015 and 2017. Collected cores were up to 70 cm in length with dry bulk density ranges from 0.03 to 2.39 grams per cubic centimeter and carbon content 0.23% to 46....
Collection, 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).
Nearshore groundwater seepage and geochemical data measured in 2015 at Guinea Creek, Rehoboth Bay, Delaware
The U.S. Geological Survey and the University of Delaware measured rates of SGD and concentrations of dissolved constituents, including nitrogen species, from recirculating ultrasonic and manual seepage meters, and in nearshore groundwater, on the southern shore of Guinea Creek, an estuarine tributary of Rehoboth Bay, in Millsboro, Delaware, in June, August, and October of 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
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 Pond in Mashpee, Massachusetts, within the Waquoit Bay National Estuarine Research Reserve, between 2012 and 2019.
Collection, analysis, and age-dating of sediment cores from a salt marsh platform and ponds, Rowley, Massachusetts, 2014-15
Sediment cores were collected from three sites within the Plum Island Ecosystems Long-Term Ecological Research (PIE-LTER) domain in Massachusetts to obtain estimates of long-term marsh decomposition and evaluate shifts in the composition and reactivity of sediment organic carbon in disturbed marsh environments.
Continuous Monitoring Data From Herring River Wetlands, Cape Cod, Massachusetts, 2015 to January 2020
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. The U.S. Geological Survey collected continuous monitoring data (including water level, soil temperature, air temperature, and meteorological parameters). These datasets can help evaluate key ecosystem drivers.
Continuous 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 cu
Collection, Analysis, and Age-Dating of Sediment Cores from Salt Marshes on the South Shore of Cape Cod, Massachusetts, From 2013 Through 2014
The accretion history of fringing microtidal salt marshes located on the south shore of Cape Cod, Massachusetts, was reconstructed from sediment cores collected in low and high marsh vegetation zones. The location of these marshes within protected embayments and the absence of large rivers on Cape Cod result in minimal sediment supply and a dominance of organic matter contribution to sediment...
Recent nitrogen storage and accumulation rates in mangrove soils exceed historic rates in the urbanized San Juan Bay Estuary (Puerto Rico, United States)
Tropical mangrove forests have been described as “coastal kidneys,” promoting sediment deposition and filtering contaminants, including excess nutrients. Coastal areas throughout the world are experiencing increased human activities, resulting in altered geomorphology, hydrology, and nutrient inputs. To effectively manage and sustain coastal...
Wigand, Cathleen; Oczkowski, Autumn; Branoff, Benjamin; Eagle, Meagan; Hanson, Alana; Martin, Rose M.; Balogh, Stephen; Miller, Kenneth; Huertas, Evelyn; Loffredo, Joseph; Watson, Elizabeth Recent carbon storage and burial exceed historic rates in the San Juan Bay estuary peri-urban mangrove forests (Puerto Rico, United States)
Mangroves sequester significant quantities of organic carbon (C) because of high rates of burial in the soil and storage in biomass. We estimated mangrove forest C storage and accumulation rates in aboveground and belowground components among five sites along an urbanization gradient in the San Juan Bay Estuary, Puerto Rico. Sites included the...
Wigand, Cathleen; Eagle, Meagan; Branoff, Benjamin; Balogh, Stephen; Miller, Kenneth; Martin, Rose M.; Hanson, Alana; Oczkowski, Autumn; Huertas, Evelyn; Loffredo, Joseph; Watson, Elizabeth Pore 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...
Tamborski, Joseph; Eagle, Meagan; Kurylyk, Barret L.; Kroeger, Kevin D.; Wang, Zhaoihui; Henderson, Paul; Charette, Matthew Groundwater discharge impacts marine isotope budgets of Li, Mg, Ca, Sr, and Ba
Groundwater-derived solute fluxes to the ocean have long been assumed static and subordinate to riverine fluxes, if not neglected entirely, in marine isotope budgets. Here we present concentration and isotope data for Li, Mg, Ca, Sr, and Ba in coastal groundwaters to constrain the importance of groundwater discharge in mediating the magnitude and...
Mayfield, Kimberly; Eisenhauer, Anton; Santiago Ramos, Danielle P.; Higgins, John A.; Horner, Tristan; Auro, Maureen; Magna, Tomas; Moosdorf, Nils; Charette, Matthew; Gonneea Eagle, Meagan; Brady, Carolyn; Komar, Nemanja; Peucker-Ehrenbrink, Bernard; Paytan, Adina Soil organic carbon development and turnover in natural and disturbed salt marsh environments
Salt marsh survival with sea‐level rise (SLR) increasingly relies on soil organic carbon (SOC) accumulation and preservation. Using a novel combination of geochemical approaches, we characterized fine SOC (≤1 mm) supporting marsh elevation maintenance. Overlaying thermal reactivity, source (δ13C), and age (F14C) information demonstrates several...
Luk, Sheron; Todd-Brown, Katherine; Eagle, Meagan; McNichol, Ann; Sanderman, Jonathan; Gosselin, Kelsey; Spivak, Amanda C. Modeling the spatial dynamics of marsh ponds in New England salt marshes
Ponds are common features on salt marshes, yet it is unclear how they affect large-scale marsh evolution. We developed a spatially explicit model that combines cellular automata for pond formation, expansion, and drainage, and partial differential equations for elevation dynamics. We use the mesotidal Barnstable marsh (MA, USA) as a case study,...
Mariotti, G.; Spivak, A.; Luk, S.Y.; Ceccherini, G.; Tyrrell, M.; Gonneea Eagle, Meagan Plant 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...
Wang, Fanning; Eagle, Meagan; Kroeger, Kevin D.; Spivak, Amanda C.; Tang, Jianwu 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
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...
Song, Shuzhen; Wang, Zhaohui Aleck; Gonneea Eagle, Meagan; Kroeger, Kevin D.; Chu, Sophie N.; Li, Daoji; Liang, Haorui Getting to the core of the matter
The topic of carbon sequestration in coastal salt marshes can serve as the basis of an investigation story line with plenty of authentic relevance and drama! Consider establishing the context with students as an introduction to this lesson. Many resources for teaching about carbon uptake and sequestration in coastal wetlands can be found at the...
Gonneea Eagle, Meagan Water 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...
Wang, Faming; Kroeger, Kevin D.; Gonneea Eagle, Meagan; Pohlman, John; Tang, Jianwu Salt 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...
Gonneea Eagle, Meagan; Maio, Christopher V.; Kroeger, Kevin D.; Hawkes, Andrea D.; Mora, Jordan; Sullivan, Richard; Madsen, Stephanie; Buzard, Richard M.; Cahill, Niamh; Donnelly, Jeffrey P. Uncertainty 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...
James Holmquist; Windham-Myers, Lisamarie; Blanca Bernal; Byrd, Kristin B.; Steve Crooks; Gonneea Eagle, Meagan; Nathan Herold; Sara Knox; Kroeger, Kevin D.; John McCombs; J. Patrick Megonigal; Lu Meng; James Morris; Ariana Sutton-Grier; Tiffany Troxler; Donald Weller
Groundwater discharge impacts marine isotope budgets.
Groundwater is an important pathway for materials to flow from land to sea. This is particularly true for materials that are concentrated in groundwater due to chemical interactions between water and aquifer rocks as groundwater flows to the coast.
Raising Awareness in the Classroom about Natural Hazards Facing U.S. Coastal Communities
USGS scientists present newly developed education outreach materials at the Smithsonian Science Education Academy for Teachers (SSEATs) held at the USGS National Headquarters in Reston, Virginia.