Scott H Ensign

Scott H Ensign
Stroud Water Research Center · Administration and Research

PhD, Ecology, UNC Chapel Hill

About

49
Publications
11,176
Reads
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2,181
Citations
Introduction
I'm an ecosystem ecologist working to discover how plants, animals, and microbes interact within rivers and how the results of those processes influence how people and society interact with rivers. In collaboration with my colleagues, I make biogeochemical measurements, perform experiments, and interpret results using statistical models and analysis. I'm particularly interested in developing new measurement technologies for aquatic environments, exploring how sea level rise affects rivers, and implementing conservation techniques that improve both ecological conditions and the utility people derive from freshwater ecosystems.
Additional affiliations
December 2013 - present
North Carolina State University
Position
  • Professor (Associate)
November 2013 - February 2018
Planktos Instruments, LLC
Position
  • Owner
February 2011 - November 2012
United States Geological Survey
Position
  • Research Ecologist
Education
August 2005 - December 2010
August 2002 - May 2004
August 1992 - May 1996
University of North Carolina at Wilmington
Field of study
  • Environemental Studies

Publications

Publications (49)
Article
Full-text available
Riverine algal groups with distinct life histories can generate unique patterns of structural and functional behavior. As such, novel methods to discriminate between these groups can improve the understanding of river ecosystem processes. We examined benthic vs. planktonic contributions to suspended algal biomass by monitoring suspended chlorophyll...
Article
The Defense Coastal/Estuarine Research Program (DCERP) was a 10-year multi-investigator project funded by the Department of Defense to improve understanding of ecosystem processes and their interactions with natural and anthropogenic stressors at the Marine Corps Base Camp Lejeune (MCBCL) located in coastal North Carolina. The project was aimed at...
Article
Sunlight is a critical resource in aquatic systems driving photosynthesis, photodegradation of organic matter and contaminants, animal behavior, and the activity of human pathogens. In rivers, solutes, materials, and organisms are turbulently mixed across the water column during downstream transport and exposed to highly variable sunlight. However,...
Article
Low-cost, open-source data collectors and a suite of collaborative online tools are making big leaps in the field of watershed monitoring.
Article
Carbon (C) standing stocks, C mass balance, and soil C burial in tidal freshwater forested wetlands (TFFW) and TFFW transitioning to low-salinity marshes along the upper estuary are not typically included in "blue carbon" accounting, but may represent a significant C sink. Results from two salinity transects along the tidal Waccamaw and Savannah ri...
Article
Sea-level rise is pushing freshwater tides upstream into formerly non-tidal rivers. This tidal extension may increase the area of tidal freshwater ecosystems and offset loss of ecosystem functions due to salinization downstream. Without considering how gains in ecosystem functions could offset losses, landscape-scale assessments of ecosystem functi...
Article
Full-text available
A comprehensive carbon budget was constructed to quantify carbon flows through the freshwater-marine continuum of a temperate, microtidal estuary. We performed coordinated measurements of dissolved inorganic carbon and total organic carbon fluxes to resolve spatial variability between and along the channel and shoals and diel variability across the...
Article
A central goal in limnology is measurement of physical, biogeochemical, and biological process rates. We can measure process rates from the temporal and spatial patterns they create in a measured variable, and we use 3 approaches for making those measurements: the fixed-site approach for detecting temporal pattern at a location, the snapshot approa...
Chapter
Stream channels are scaled to the amount of water and sediment they convey. The amount and size of bed sediment, composition of bank material, type of channel vegetation (both riparian and in-stream), and valley morphology (slope and width) influence channel size and shape. Interactions and feedbacks among these six bio-hydro-geomorphic controls di...
Article
Measurements and modeling of salt marsh morphodynamics typically focus on the sediment fraction suspended in water, but another fraction moves at the air- water interface on water surface tension. We compared the geomorphic significance of this surface microlayer sedi- ment fraction to the suspended fraction in a mesohaline, microtidal salt marsh i...
Article
Improving mechanistic prediction of shoreline response to sea level rise is currently limited by 1) morphologic complexity of tidal creek shorelines that confounds application of mechanistic models, and 2) availability of suspended sediment measurements to parameterize mechanistic models. To address these challenges we developed a metric to disting...
Article
We examined seasonal and spatial patterns in dissolved organic carbon (DOC) and chromophoric dissolved organic matter (CDOM) in the Chowan River watershed, North Carolina, a blackwater river which discharges into the second largest estuary in the United States, the Albemarle–Pamlico Estuarine System. From April 2008 to May 2010, DOC concentration d...
Article
We measured rates of sediment, C, N, and P accumulation at four floodplain sites spanning the nontidal through oligohaline Choptank and Pocomoke Rivers, Maryland, USA. Ceramic tiles were used to collect sediment for a year and sediment cores were collected to derive decadal sedimentation rates using 137Cs. The results showed highest rates of short-...
Article
Denitrification in tidal freshwater river channels and their adjoining freshwater wetlands greatly affects nitrogen export from river networks, yet the relative importance of these two habitats to nitrogen export has not been examined. Knowledge of how these habitats contribute to denitrification of the river nitrogen load is critical for improving...
Article
Full-text available
zooplankton on an estuary's phytoplankton: Inferences from a synthesis of 30 years of data. Ecosphere 5(7): Abstract. Phytoplankton biomass is commonly used as a water quality metric in the management of anthropogenic nitrogen and phosphorus loading, yet interpretation of the long-term response of phytoplankton biomass to nutrient regulation may be...
Article
[1] The hydrologic processes by which tide affects river channel and riparian morphology within the tidal freshwater zone are poorly understood, yet are fundamental to predicting the fate of coastal rivers and wetlands as sea level rises. We investigated patterns of sediment accretion in riparian wetlands along the non-tidal through oligohaline por...
Article
Full-text available
Sediment accretion was measured at four sites in varying stages of forest-to-marsh succession along a fresh-tooligohaline gradient on the Waccamaw River and its tributary Turkey Creek (Coastal Plain watersheds, South Carolina) and the Savannah River (Piedmont watershed, South Carolina and Georgia). Sites included tidal freshwater forests, moderatel...
Article
Full-text available
ACKNOWLEDGMENTS We thank the Water Resources,Research,Institute of The University of North Carolina (Project #70156) for financial support. Additional funding was,provided,by the Cape Fear River Program,and the Z. Smith Reynolds Foundation. We thank Matthew
Article
Tidal freshwater wetlands (TFW) alter nitrogen concentrations in river water, but the role of these processes on a river’s downstream nitrogen delivery is poorly understood. We examined spatial and temporal patterns in denitrification in TFW of four rivers in North Carolina, USA and evaluated the relative importance of denitrification rate and inun...
Article
How does river hydrology and morphology change due to tidal influence? We contend that this is a question of particular consequence to many earth surface disciplines, but one that has not been adequately addressed. Previous studies have relied on gradients in channel morphology and stratigraphy to infer energy regime of channels. However, in tidal...
Article
Full-text available
At the interface of estuarine tides and freshwater rivers lie wetland and aquatic ecosystems, which experience dramatic effects of sea level rise. There, nontidal channels and riparian floodplains are transforming into tidal ecosystems, and tidal freshwater ecosystems are receiving increasing salinity. These river-floodplain systems have both fluvi...
Article
1. Coastal rivers can have long tidally influenced reaches that are affected by tides but do not contain saline water. These tidal freshwater reaches have steep geomorphic gradients where the river transitions from narrow, heavily shaded streams to wide, unshaded channels. The influence of these gradients on river ecosystem production is poorly und...
Article
While much research exists for rivers and creeks that are entirely within the tidal zone, little geomorphic research exists for the region where rivers encounter tides. TFZs have distinct ecosystem processes shaped by upstream watershed fluxes and tidal forcing from downstream. Population growth worldwide is increasing rapidly in coastal areas; und...
Article
Full-text available
Water quality data at 12 sites within an urban, a suburban, and a rural stream were collected contemporaneously during four wet and eight dry periods. The urban stream yielded the highest biochemical oxygen demand (BOD), orthophosphate, total suspended sediment (TSS), and surfactant concentrations, while the most rural stream yielded the highest to...
Conference Paper
Background/Question/Methods The Chowan River in North Carolina is subject to two environmental management efforts: nutrient reduction intended to curtail the occurrence and severity of phytoplankton blooms and a moratorium on river herring harvest intended to allow these highly depleted species to recover. It is unknown to what extent zooplanktivo...
Article
Understanding environmental processes begins with mental conceptualizations of system components and interactions. Conceptualizing rivers begins with adopting one of two reference frames for observing movement: Eulerian, wherein the flux of objects is observed in a spatially bounded area, or Lagrangian, wherein specific objects are tracked through...
Article
Full-text available
Tidal freshwater zones (TFZ) of coastal rivers link terrestrial watersheds to the ocean and are characterized by large, regularly inundated riparian zones. We investigated the effect of riparian denitrification on nitrogen flux in the TFZ Newport River, North Carolina (U.S.A.) by developing an empirical model of denitrification and parameterizing i...
Article
Full-text available
1] Over the past 3 decades, nutrient spiraling has become a unifying paradigm for stream biogeochemical research. This paper presents (1) a quantitative synthesis of the nutrient spiraling literature and (2) application of these data to elucidate trends in nutrient spiraling within stream networks. Results are based on 404 individual experiments on...
Article
Water quality monitoring of estuarine ecosystems relies on measurement of biogeochemically important ele- ments, including nitrogen (N), phosphorus (P), carbon (C), and silicon (Si) at a time-step relevant to the environ- mental conditions affecting the estuary. To improve the temporal resolution of sample collection from the Neuse River estuary, N...
Article
Streams alter the concentration of nutrients they transport and thereby influence nutrient loading to estuaries downstream; however, the relationship between in-stream uptake, discharge variability, and subsequent nutrient export is poorly understood. In this study, in-stream N and P uptake were examined in the stream network draining a row-crop ag...
Conference Paper
As of the date this proceedings was sent to the printer it appeared that the Author/Presenter would not be attending our conference. According to ASABE policy, if a paper is not presented it can not be included in the conference proceedings. The paper was removed after the page numbers for the book were applied so the remaining page numbers represe...
Article
We investigated physical, chemical, and biological variables contributing to biochemical oxygen demand (BOD) in 17 North Carolina lotic and lentic water bodies affected by mild to severe hypoxia. Phytoplankton production created the dominant reservoir of labile carbon driving BOD, and subsequent hypoxia, in a Piedmont river subject to algal blooms,...
Article
We examined the effect of in-channel flow obstructions such as vegetation and coarse woody debris (CWD) on transient storage and nutrient uptake by using experimental channel manipulations. Transient storage and nutrient uptake were measured under existing conditions in a vegetated agricultural stream and a shaded blackwater stream, and measurement...
Article
Agricultural runoff from coastal plain watersheds contributes nitrogen to downstream estuarine and coastal waters. Nitrogen fuels eutrophication, which has resulted in increased algal biomass, hypoxia, and fish kills in the Neuse River Estuary, North Carolina. Denitrification is the sole mechanism of permanent nitrogen removal along the riverine to...
Article
Full-text available
The objectives of this study were: (1) define the best method of using digital bathymetric data to compute estuarine flushing time using the fraction of freshwater method and (2) use this method to compare flushing times of two neighboring estuaries of different trophic state. We examined the sensitivity of the fraction of freshwater method to vari...
Article
Full-text available
Numerous studies have shown that accumulation of excessive soil phosphorus raises the potential for phosphorus export and eutrophication of adjacent surface waters. Soil phosphorus data from the North Carolina Agronomy Division's database were analyzed for two-year periods spanning the decades of the 1980s and 1990s for 39 eastern North Carolina co...
Article
Blackwater stream systems are the most abundant type of freshwater lotic system on the Coastal Plain of the eastern United States. Many of these ecosystems drain watersheds that receive large anthropogenic nutrient inputs, whereas some blackwater systems remain relatively pristine. A series of nutrient addition experiments was carried out over a fo...
Article
The objectives of this study were: (1) define the best method of using digital bathymetric data to compute estuarine flushing time using the fraction of freshwater method and (2) use this method to compare flushing times of two neighboring estuaries of different trophic state. We examined the sensitivity of the fraction of freshwater method to vari...
Article
Monthly inflow and outflow data were collected from three wet detention ponds in Wilmington, North Carolina, for a 29-mo period. Two ponds drained urban areas consisting primarily of residential, mixed services, and retail usage, while the third mainly drained residential and golf course areas. One of the urban ponds achieved significant reductions...
Article
The Goshen Swamp, a fourth order blackwater creek in southeastern North Carolina, was clearcut of 130 acres of riparian and seasonally flooded forest in late May through September 1998. Downstream water quality had been monitored monthly for 2 1/2 years before the clearcut, during the clearcut, and for two years following the clearcut. The objectiv...
Article
Full-text available
Coastal areas in the United States and many other countries are considered to be desirable regions to live and recreate. However, as human use of coastal land and water increases, so does the incidence of aquatic-borne disease from contact with contaminated water and eating contaminated shellfish. Movement of humans into coastal areas both greatly...
Article
Full-text available
We used nutrient addition bioassays to examine the effects of organic and inorganic nutrient loading on stream planktonic chlorophyll and ATP in the Black River and Northeast Cape Fear River of North Carolina. Additions of ammonium, inorganic N+P, and urea produced significant algal increases during bioassays in spring and summer. Urea stimulated c...
Article
In the summer of 1996, southeastern North Carolina, United States, was struck by two hurricanes, with the second (Hurricane Fran) doing considerably more damage than the first (Hurricane Bertha). The Cape Fear watershed, largest in North Carolina, suffered from severe water quality problems for weeks following Fran, including a massive fish kill in...
Article
Full-text available
ACKNOWLEDGMENTS We thank the Water Resources Research Institute of The University of North Carolina (Projects #7O 17 1 and #7O 177) for financial support. Additional financial support was provided by the Lower Cape Fear River Program. We thank Jesse Cook, Heather CoVan, Virginia Johnson, Douglas Parsons, ChristiG. Chris Shank and Ashley Skeen for f...

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Projects

Projects (3)
Project
We are calculating shoreline and watershed characteristics for all 12-digit Marine HUCs in the United States. Research Questions: What percentage of the USA coastline is drained by large versus small watersheds? What is the drainage length and area for every stream and river outlet in the USA?