Geology, Geophysics, and Geochemistry Stable Isotope Laboratory (GSIL)
The GSIL is a state-of-the-art facility located on the Denver Federal Center that specializes in the measurement of light stable isotope — Hydrogen (H), Carbon (C), Nitrogen (N), Oxygen (O), and Sulfur (S) — compositions and other chemical and biomarker analytes in matrices relevant to the Earth sciences. Chemical and isotopic tracers offer novel insights into ecosystem biogeochemistry, food webs, animal nutrition and physiology. Moreover, these tracers provide environmental proxy information for processes critical to the evolution of ecosystems, distributions of wildlife species and populations, and at a range of spatial and temporal scales. Inference from chemical and isotopic tracers therefore offers essential information that can support wildlife and habitat management, conservation actions, and assessment of environmental change.
Wildlife nutrition
...is a key aspect of animal fitness. Isotopic data are a primary tool for diet estimation, assessment of macronutrient assimilation, and the allocation of resources to short-term energy production, storage, and lean body mass. Metrics include trophic enrichment factors, tissue turnover rates, routing dynamics, assimilated dietary proportions, and resource use.
Biogeography
...refers to the spatial domain of animal distributions and isotopic data are especially useful in resolving broadscale movements by migratory species. This work leverages isoscape models to relate animal tissues with spatially explicit environmental isotopic compositions for assessing migratory connectivity, population identification and mixing, and habitat relations.
Biogeochemistry
...is an essential underlying control on ecosystem health, function, and structure. Chemical, biomarker, and isotopic data are key tools for resolving details of elemental cycles, interactions among elemental cycles, and relationships among the geosphere, hydrosphere, and biosphere. Tracer data are commonly used to inform on sources, rates, and fates of elements.
Ecosystem stressors
...include abiotic factors such as temperature, water quality, and disturbances, as well as biotic factors such as non-native species invasions. Chemical and isotopic data are routinely used for inference to identify resource use, impairment, and food web perturbations.
Lab Capabilities
The GSIL maintains three isotope ratio mass spectrometers for both dual inlet and continuous flow applications, a single quadrupole GC-MSD system, as well as vacuum extraction lines and other sample preparatory capabilities to analyze the chemical and isotopic compositions in virtually any inorganic/organic matrix.
The laboratory dates to the 1960’s and currently staffs three research grade scientists – two geologists (Alison Piasecki, Julia McIntosh) and one ecologist (Craig Stricker). Research interests are diverse, aligned with Mission Area science priorities, and supports collaborations with other Federal, State, and academic institutions.






Food Webs and Wildlife Nutrition
Ecosystem Biogeochemistry
Wildlife Biogeography
Environmental Stressors
Isotope and Chemical Methods for Mineral and Geoenvironmental Assessments and Support of USGS Science Strategy
The GSIL is a state-of-the-art facility located on the Denver Federal Center that specializes in the measurement of light stable isotope — Hydrogen (H), Carbon (C), Nitrogen (N), Oxygen (O), and Sulfur (S) — compositions and other chemical and biomarker analytes in matrices relevant to the Earth sciences. Chemical and isotopic tracers offer novel insights into ecosystem biogeochemistry, food webs, animal nutrition and physiology. Moreover, these tracers provide environmental proxy information for processes critical to the evolution of ecosystems, distributions of wildlife species and populations, and at a range of spatial and temporal scales. Inference from chemical and isotopic tracers therefore offers essential information that can support wildlife and habitat management, conservation actions, and assessment of environmental change.
Wildlife nutrition
...is a key aspect of animal fitness. Isotopic data are a primary tool for diet estimation, assessment of macronutrient assimilation, and the allocation of resources to short-term energy production, storage, and lean body mass. Metrics include trophic enrichment factors, tissue turnover rates, routing dynamics, assimilated dietary proportions, and resource use.
Biogeography
...refers to the spatial domain of animal distributions and isotopic data are especially useful in resolving broadscale movements by migratory species. This work leverages isoscape models to relate animal tissues with spatially explicit environmental isotopic compositions for assessing migratory connectivity, population identification and mixing, and habitat relations.
Biogeochemistry
...is an essential underlying control on ecosystem health, function, and structure. Chemical, biomarker, and isotopic data are key tools for resolving details of elemental cycles, interactions among elemental cycles, and relationships among the geosphere, hydrosphere, and biosphere. Tracer data are commonly used to inform on sources, rates, and fates of elements.
Ecosystem stressors
...include abiotic factors such as temperature, water quality, and disturbances, as well as biotic factors such as non-native species invasions. Chemical and isotopic data are routinely used for inference to identify resource use, impairment, and food web perturbations.
Lab Capabilities
The GSIL maintains three isotope ratio mass spectrometers for both dual inlet and continuous flow applications, a single quadrupole GC-MSD system, as well as vacuum extraction lines and other sample preparatory capabilities to analyze the chemical and isotopic compositions in virtually any inorganic/organic matrix.
The laboratory dates to the 1960’s and currently staffs three research grade scientists – two geologists (Alison Piasecki, Julia McIntosh) and one ecologist (Craig Stricker). Research interests are diverse, aligned with Mission Area science priorities, and supports collaborations with other Federal, State, and academic institutions.





