About

Brent A McKee is the Mary and Watts Hill Jr Distinguished Professor in the Department of Earth, Marine and Environmental Sciences at the University of North Carolina at Chapel Hill. His research focuses on land-ocean interactions and global change, with particular interest in the role of major rivers such as the Amazon, Changjiang, Huanghe, Orinoco, Danube, Columbia, and Mississippi in global biogeochemical cycles and global change. Rivers serve as the primary interface between continental and oceanic environments and are critical in global cycles such as carbon. McKee's work includes examining sediment and carbon dynamics in marsh and seagrass ecosystems, which are globally important natural sinks for organic carbon, as well as studying lakes and reservoirs to understand carbon burial and the input of emerging contaminants. His expertise in sediment geochemistry and river-ocean interactions contributes to understanding the processes that influence biogeochemical cycles and environmental change.

Research topics

• Environmental science
• Oceanography
• Geology
• Ecology
• Materials science
• Physics
• Geomorphology
• Biology

Selected publications

• Accretionary marsh levees act as emerging barriers to interior elevation gain

  Communications Earth & Environment · 2026-04-24

  articleOpen access

  Many small coastal plain watersheds have experienced extensive land clearing and increased sediment loading as coastal populations expand, yet microtidal marsh platforms are failing to keep pace with sea-level rise while adjacent subtidal areas are infilling. Here, we developed sub-decadal records of sedimentation from the shoreline into the salt marsh in watersheds with distinct land-use histories to determine how emerging microtopography may promote this disconnect. We find a divergence in marsh vertical evolution across short distances ( < 10 meters) and timescales ( < 20 years). Rapid accretion at the marsh edge ( > 10 millimeters per year), a product of sediment loading from deforestation and lateral shoreline erosion, is negatively correlated with contemporaneous interior marsh accretion, suggesting an increasingly prominent levee may reduce interior sedimentation by rerouting flow, trapping sediment, or inhibiting vegetation growth. These findings suggest pulses of suspended sediment can temporarily enhance levee prominence in ways that undermine marsh resilience to sea-level rise. Rapid marsh-edge accretion correlates negatively with contemporaneous interior accretion, suggesting that levee growth reduces interior sedimentation by rerouting flow, trapping sediment, or inhibiting vegetative growth, based on sub-decadal sedimentation records from distinct U.S. watersheds.

  PublisherDOI

• UTILIZING TEMPESTITE DEPOSITS AS REFERENCE HORIZONS IN  210Pb AGE MODELS FOR RECONSTRUCTING STORM HISTORY IN COASTAL DEPOSITIONAL ENVIRONMENTS

  SSRN Electronic Journal · 2025-01-01

  preprintOpen access
  PublisherDOI

• Impact of land-use change on salt marsh accretion

  Estuarine Coastal and Shelf Science · 2024-02-28 · 2 citations

  articleSenior author
  PublisherDOI

• Radionuclides in Estuarine and Coastal Systems

  Elsevier eBooks · 2024-01-01

  book-chapter
  PublisherDOI

• Anthropogenic impacts on tidal creek sedimentation since 1900

  PLoS ONE · 2023 · 7 citations

  • Environmental science
  • Oceanography
  • Geology

  Land cover and use around the margins of estuaries has shifted since 1950 at many sites in North America due to development pressures from higher population densities. Small coastal watersheds are ubiquitous along estuarine margins and most of this coastal land-cover change occurred in these tidal creek watersheds. A change in land cover could modify the contribution of sediments from tidal creek watersheds to downstream areas and affect estuarine habitats that rely on sediments to persist or are adversely impacted by sediment loading. The resilience of wetlands to accelerating relative sea-level rise depends, in part, on the supply of lithogenic sediment to support accretion and maintain elevation; however, subtidal habitats such as oyster reefs and seagrass beds are stressed under conditions of high turbidity and sedimentation. Here we compare sediment accumulation rates before and after 1950 using 210Pb in 12 tidal creeks across two distinct regions in North Carolina, one region of low relief tidal-creek watersheds where land cover change since 1959 was dominated by fluctuations in forest, silviculture, and agriculture, and another region of relatively high relief tidal-creek watersheds where land-use change was dominated by increasing suburban development. At eight of the creeks, mass accumulation rates (g cm-2 y-1) measured at the outlet of the creeks increased contemporaneously with the largest shift in land cover, within the resolution of the land-cover data set (~5-years). All but two creek sites experienced a doubling or more in sediment accumulation rates (cm yr-1) after 1950 and most sites experienced sediment accumulation rates that exceeded the rate of local relative sea-level rise, suggesting that there is an excess of sediment being delivered to these tidal creeks and that they may slowly be infilling. After 1950, land cover within one creek watershed changed little, as did mass accumulation rates at the coring location, and another creek coring site did not record an increase in mass accumulation rates at the creek outlet despite a massive increase in development in the watershed that included the construction of retention ponds. These abundant tidal-creek watersheds have little relief, area, and flow, but they are impacted by changes in land cover more, in terms of percent area, than their larger riverine counterparts, and down-stream areas are highly connected to their associated watersheds. This work expands the scientific understanding of connectivity between lower coastal plain watersheds and estuaries and provides important information for coastal zone managers seeking to balance development pressures and environmental protections.

  PublisherDOI

• Carbon accumulation rates are highest at young and expanding salt marsh edges

  Communications Earth & Environment · 2022 · 37 citations

  • Environmental science
  • Ecology
  • Geology

  Abstract An objective of salt marsh conservation, restoration, and creation is to reduce global carbon dioxide levels and offset emissions. This strategy hinges on measurements of salt marsh carbon accumulation rates, which vary widely creating uncertainty in monetizing carbon credits. Here, we show the 14–323 g C m −2 yr −1 range of carbon accumulation rates, derived from cores collected at seven sites in North Carolina U.S.A., results from the landward or basinward trajectory of salt marsh colonization and the intertidal space available for accretion. Rates increase with accelerating sea-level rise and are highest at young and expanding marsh edges. The highest carbon densities are near the upland, highlighting the importance of this area for building a rich stock of carbon that would be prevented by upland development. Explaining variability in carbon accumulation rates clarifies appraisal of salt marsh restoration projects and landscape conversion, in terms of mitigating green-house gas emissions.

  PublisherOA PDFDOI

• Salt Marsh Formation

  Cambridge University Press eBooks · 2021-04-22 · 3 citations

  book-chapterSenior author

  Historical records show a massive decline in salt marsh area (Pendleton et al. 2012), > 50% in many locations, such as sites in Australia (Saintilan and Williams, 2000; Rogers et al. 2006), the British Isles (Baily and Pearson, 2007), and New England, USA (Bertness et al. 2002). These losses are mainly fueled by an underappreciation of the large contributions of salt marsh to maintaining healthy and productive estuaries. Prior to the middle twentieth century, the value of salt marsh primarily depended on its potential for reclamation. Davis (1910) proclaimed that “…[salt marshes] are conspicuous, being generally unutilized for any purpose except for making a small amount of inferior hay, hence they are practically desert places, except where land values are sufficiently high to make it worth while to raise the surface above high tide level for building purposes, or to dike out the tides.” We now view salt marsh as a valuable estuarine habitat because it provides coastal protection from waves (Shepard et al. 2011), erosion control (Neumeier and Ciavola, 2004), water purification (Sousa et al. 2008), fish and bird habitat (Peterson and Turner, 1994; Van Eerden et al. 2005), carbon sequestration (Mcleod et al. 2011), and tourism/recreation (Barbier et al. 2011; Altieri et al. 2012). Salt marsh is also a coastal depositional environment that can accrete vertically over millennial time scales at rates equal to, or greater than, sea-level rise (Gehrels et al. 1996; Ouyang and Lee, 2014). The relatively high accretion rates and resistance of salt marshes to erosion (Mudd et al. 2010) make them valuable sites for preserving records of sea level (van de Plassche et al. 1998; Engelhart et al. 2011; Kemp et al. 2017), storms (Donnelly et al. 2001; Boldt et al. 2010; de Groot et al. 2011), and tsunamis (Morton et al. 2007; Komatsubara et al. 2008) in their sediments. Salt marsh loss and associated services have been pervasive globally, mainly due to the direct (grazing, ditching, pollution, etc.) and indirect (climate change) effects of human activities, resulting in the recent emphasis on restoration, conservation, and management (Lotze et al. 2006; Airoldi and Beck, 2007; Gedan et al. 2009). Although recent focus has been on better understanding of those mechanisms and processes that are related to salt marsh degradation, reviewing salt marsh formation and the different modes of salt marsh expansion will aid efforts aimed at preserving and increasing salt marsh habitat area and extracting climate and tectonic information from their sedimentary records.

  PublisherDOI

• Fjords

  Blackwell eBooks · 2020-02-03

  book-chapter

  This chapter reviews the present knowledge of the biogeochemistry of fjords, emphasizing sediment diagenesis and element cycling in oxic and anoxic fjords. The highly variable input of fresh water and sediment affects circulation and sedimentation patterns both within and between fjords. Fjords are diverse with respect to topography, hydrography, current regimes, tidal influence, chemistry, sediment input and transport, oxygen conditions, trophic status, productivity, human impact, andcommercial utilization. Fjords offer a great variety and spatial gradients of a number of interesting features, including water depth, sill depth, redox conditions, salinity, climate zones, level of anthropogenic influence, freshwater and sediment input, stratification, sediment types, sediment ecology, sediment biogeochemistry, and biological productivity. A better understanding of organic matter preservation in anoxic fjords could lead to a more effective use of these environments as records of historical changes in paleoproductivity or watershed land use.

  PublisherDOI

• Coastal sedimentation across North America doubled in the 20th century despite river dams

  Nature Communications · 2020 · 61 citations

  • Oceanography
  • Geology
  • Environmental science

  ) more than doubled after 1950 in coastal depocenters around North America. Sediment sources downstream of dams compensate for the river-sediment lost to impoundments. Sediment is accumulating in coastal depocenters at a rate that matches or exceeds relative sea-level rise, apart from rapidly subsiding Texas and Louisiana where water depths are increasing and intertidal areas are disappearing. Assuming no feedbacks, accelerating global sea-level rise will eventually surpass current sediment accumulation rates, underscoring the need for including coastal-sediment management in habitat-restoration projects.

  PublisherOA PDFDOI

• Continental Shelf Food Chains of the Northern Gulf of Mexico

  2019-05-20 · 1 citations

  book-chapter

  Biological productivity in the northern Gulf is significantly affected by the Mississippi River. The freshwater discharge (577 km3 yr-1, approx 10% of the volume of water on the shelf) contains high concentrations of dissolved nutrients (100-150 μmol N03 l-1). Flow is primarily constrained by prevailing winds to the continental shelf west of the Mississippi Delta. River plumes are regions of high phytoplankton stock (&gt;30 g Chi l-1) and production (5 g C m-2 d-1), high copepod stocks (nauplius concentrations &gt;1000 l-1) and high ichthyoplankton stocks (larval concentrations &gt;50 m-3). The high temperature of shelf waters assures high physiological rates, implying high rates of trophic transfer and high turnover rates. The primary fate of phytoplankton production is grazing by macrozooplankton and microzooplankton. However, sinking of phytoplankton and other organic material fuels the annual development of a band of hypoxic water along the Louisiana coast. Fisheries production is high; the northern Gulf supports the largest volume fishery in the United States, the Gulf menhaden, Brevoortia patronus. The Loop Current in its northernmost position affects shelf processes to the east of the Delta. Anticyclonic rings derived from the Loop Current occasionally impact on the Louisiana shelf west of the Delta but usually drift over to the western Gulf resulting in exchange of oceanic and shelf water off Texas.

  PublisherDOI

Frequent coauthors

• Antonio B. Rodriguez

  University of North Carolina at Chapel Hill

  24 shared

• Thomas S. Bianchi

  University of Florida

  18 shared

• Molly C. Bost

  NOAA National Centers for Coastal Ocean Science

  17 shared

• David J. DeMaster

  North Carolina State University

  16 shared

• Charles A. Nittrouer

  University of Washington

  13 shared

• Richard L. Miller

  13 shared

• Mead A. Allison

  9 shared

• Simone R. Alin

  NOAA Pacific Marine Environmental Laboratory

  8 shared