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Bridget R Deemer, Ph.D.

Broadly, I am interested in how human activities are affecting the way that energy and nutrients cycle through ecosystems. My research aims to better characterize how reservoirs can affect the transport and transformation of carbon (C), nitrogen (N), and other biologically relevant elements.

My research also explores the potential role of management in affecting ecosystem function. Identifying  reservoir management win-wins as well as trade-offs is critical as the quantity and quality of water becomes increasingly variable under a changing climate.  Currently, I am working on a project to understand how conditions in Lake Powell (and the associated management of Glen Canyon Dam) are affecting ecosystem metabolism in the Colorado River.

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A boat on the Colorado River in front of a rock outcrop containing a concrete structure.

Uncovering the Base of the Food Web: Primary Production Dynamics in the Colorado River

Algae, phytoplankton, and rooted macrophytes represent the base of many aquatic food webs and are known as primary producers. Through photosynthesis, these organisms convert sunlight energy into chemical energy (i.e., carbon) that in turn fuels the growth of animals such as macroinvertebrates and fish. This project uses high frequency measurements of dissolved oxygen, which is a by-product of...
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Ecosystems, Energy & Wildlife, Fisheries Program, Southwest Biological Science Center
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Uncovering the Base of the Food Web: Primary Production Dynamics in the Colorado River

Algae, phytoplankton, and rooted macrophytes represent the base of many aquatic food webs and are known as primary producers. Through photosynthesis, these organisms convert sunlight energy into chemical energy (i.e., carbon) that in turn fuels the growth of animals such as macroinvertebrates and fish. This project uses high frequency measurements of dissolved oxygen, which is a by-product of...
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Modeled and measured greenhouse gas emissions from Lake Powell and bathymetric analysis of tributary littoral habitat at different water levels

This data release contains model inputs used to estimate surface water greenhouse gas fluxes from two large arid reservoirs, Lake Powell and Lake Mead. The release also contains empirical, spatially explicit water quality and greenhouse gas data from a single field survey conducted in Lake Powell in July of 2017. Finally, this release contains surface area estimates of shallow (< 15m) tributary re
By
Southwest Biological Science Center

Carbon, nitrogen, and phosphorus content of adult emergent Diptera before and after a fire-storm sequence in the Colorado River near Shinumo Creek, Grand Canyon, AZ

This dataset includes total phosphorus (TP), total nitrogen (TN), and total carbon (TC) concentrations as well as &amp;amp;delta;15N and &amp;amp;delta;13C composition, and overall C:N:P stoichiometry for adult emergent Diptera from the Colorado River, Grand Canyon, AZ. The samples were collected before and after a fire and subsequent storm occurred in the Shinumo Watershed, a tributary to the Col
By
Southwest Biological Science Center

Calcium, magnesium and total dissolved solids data as well as modeled salinity and mass balance estimates for Lake Powell, 1952-2017

These data were compiled to quantify the role of Lake Powell in modulating salinity and reducing overall salt flux from the Upper Colorado River Basin downstream. In addition, these data were used to infer summertime calcite precipitation in Lake Powell (the major proposed sink for salt within the system). The Lake Powell Calcium Magnesium data contains summertime surface water calcium and magnesi
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Southwest Biological Science Center

Spatiotemporal methane emission from global reservoirs

Inland aquatic systems, such as reservoirs, contribute substantially to global methane (CH4) emissions; yet are among the most uncertain components of the total CH4 budget. Reservoirs have received recent attention as they may generate high CH4 fluxes. Improved quantification of these CH4 fluxes, particularly their spatiotemporal distribution, is key to realistically incorporating them in CH4 mode
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Ecosystems, Southwest Biological Science Center

Half of global methane emissions come from highly variable aquatic ecosystem sources

Atmospheric methane is a potent greenhouse gas that plays a major role in controlling the Earth’s climate. The causes of the renewed increase of methane concentration since 2007 are uncertain given the multiple sources and complex biogeochemistry. Here, we present a metadata analysis of methane fluxes from all major natural, impacted and human-made aquatic ecosystems. Our revised bottom-up global
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Ecosystems, Southwest Biological Science Center

Drivers of methane flux differ between lakes and reservoirs, complicating global upscaling efforts

Methane is an important greenhouse gas with growing atmospheric concentrations. Freshwater lakes and reservoirs contribute substantially to atmospheric methane concentrations, but the magnitude of this contribution is poorly constrained. Uncertainty stems partially from whether the sites currently sampled represent the global population as well as incomplete knowledge of which environmental variab
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Ecosystems, Southwest Biological Science Center

Greenhouse gas emissions from an arid-zone reservoir and their environmental policy significance: Results from existing global models and an exploratory dataset

Reservoirs in arid regions often provide critical water storage but little is known about their greenhouse gas (GHG) footprint. While there is growing appreciation of the role reservoirs play as GHG sources, there is a lack of understanding of GHG emission dynamics from reservoirs in arid regions and implications for environmental policy. Here we present initial GHG emission measurements from Lake
By
Ecosystems, Southwest Biological Science Center

Changes in prey, turbidity, and competition reduce somatic growth and cause the collapse of a fish population

Somatic growth exerts strong control on patterns in the abundance of animal populations via effects on maturation, fecundity, and survival rates of juveniles and adults. In this paper, we quantify abiotic and biotic drivers of rainbow trout growth in the Colorado River, AZ, and the resulting impact on spatial and temporal variation in abundance. Inferences are based on approximately 10,000 observa
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Ecosystems, Southwest Biological Science Center

Calcite precipitation in Lake Powell reduces alkalinity and total salt loading to the Lower Colorado River Basin

Reservoirs can retain and transform carbon, nitrogen, phosphorus, and silica, but less is known about their effects on other biogeochemically relevant solutes. The salinization of freshwater ecosystems is a growing concern in many regions, and the role of reservoirs in salinity transport is an important research frontier. Here, we examine how a large desert southwest reservoir, Lake Powell, has al
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Ecosystems, Water Resources, Southwest Biological Science Center

Methane emissions from artificial waterbodies dominate the carbon footprint of irrigation: A study of transitions in the food-energy-water-climate nexus (Spain, 1900-2014)

Irrigation in the Mediterranean region has been used for millennia and has greatly expanded with industrialization. Irrigation is critical for climate change adaptation, but it is also an important source of greenhouse gas emissions. This study analyzes the carbon (C) footprint of irrigation in Spain, covering the complete historical process of mechanization. A 21-fold total, 6-fold area-based, an
By
Ecosystems, Southwest Biological Science Center

Pre-USGS Publications

Deemer, B.R., J.A. Harrison, 2019, Summer redox dynamics in a eutrophic reservoir and sensitivity to a summer’s end drawdown event: Ecosystems, v: 22, p. 1618-1632, https://doi.org/10.1007/s10021-019-00362-0.
Reed, D.C., B.R. Deemer, S. van Grinsven, and J.A. Harrison. 2017. Are elusive anaerobic pathways key methane sinks in eutrophic lakes and reservoirs? Biogeochemistry doi: 10.1007/s10533-017-0356-3
Hayes, N.M, B.R. Deemer, J.R. Corman, N.R. Razavi, and K.E. Strock. 2017. Key differences between lakes and reservoirs modify climate signals: A case for a new conceptual model. Limnology and Oceanography Letters doi: 10.1002/lol2.10036
Harrison, J.A., B.R. Deemer, M.K. Birchfield, and M.T. O’Malley. 2017. Reservoir water level drawdowns accelerate and amplify methane emission. Environmental Science & Technology doi: 10.1021/acs.est.6b03185
Deemer, B.R., J.A. Harrison, S. Li, J. Beaulieu, T. DelSontro, N. Barros, M.A. dos Santos, J.F.Bezerra-Neto, S.M. Powers, and J.A. Vonk. 2016. Greenhouse gas emissions from reservoir water surfaces: A new global synthesis. BioScience doi: 10.1093/biosci/biw117
Deemer, B.R., S.M. Henderson, and J.A. Harrison. 2015. Chemical mixing in the bottom boundary layer of a eutrophic reservoir: the effects of internal seiching on nitrogen dynamics. Limnology and Oceanography 60: 1642-1655.
Deemer, B.R., K.E. Goodwin, T.A. Lee, M.K. Birchfield, K. Dallavis, J. Emerson, D. Freeman, E. Henry, L. Wynn, and J.A. Harrison. 2012. Elevated nitrogen and phosphorus concentrations in urbanizing southwest Washington streams. Northwest Science 86: 237-247.
Henderson, S.M., and B.R. Deemer. 2012. Vertical propagation of lakewide internal waves. Geophysical Research Letters 39: doi:10.1029/2011GL050534.
Deemer, B.R., J.A. Harrison, and E.W. Whitling. 2011. Microbial dinitrogen and nitrous oxide production in a small eutrophic reservoir: an in situ approach to quantifying hypolimnetic process rates. Limnology and Oceanography 56: 1189-1199.

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