A5043435909- Climate change and permafrost
- Cryospheric studies and observations
- Geology and Paleoclimatology Research
- Coral and Marine Ecosystems Studies
- Methane Hydrates and Related Phenomena
- Isotope Analysis in Ecology
- Marine and fisheries research
- Groundwater and Isotope Geochemistry
- Geological Studies and Exploration
- Indigenous Studies and Ecology
- Peatlands and Wetlands Ecology
- Atmospheric and Environmental Gas Dynamics
- Marine animal studies overview
- Marine Bivalve and Aquaculture Studies
- Radioactive element chemistry and processing
- Marine Biology and Ecology Research
- Tree-ring climate responses
- Geochemistry and Geologic Mapping
- Groundwater flow and contamination studies
- Pleistocene-Era Hominins and Archaeology
- Landslides and related hazards
- Plant Water Relations and Carbon Dynamics
- Geochemistry and Elemental Analysis
- Paleontology and Stratigraphy of Fossils
- Arctic and Antarctic ice dynamics
Los Alamos National Laboratory
2014-2024
Texas Tech University
2009
Oak Ridge National Laboratory
2009
United States Geological Survey
2009
University of Illinois Chicago
2009
McMaster University
1996-2000
Los Alamos National Security (United States)
2000
Summary The high incidence of coral disease in shallow coastal marine environments suggests seawater depth and pollution have an impact on the microbial communities inhabiting healthy tissues. A study was undertaken to determine how bacterial tissues Montastraea annularis change at 5 m, 10 m 20 water varying proximity urban centre seaport Willemstad, Curaçao, Netherlands Antilles. Analyses terminal restriction fragment length polymorphisms (TRFLP) 16S rRNA gene sequences show significant...
Not as hot we thought Earth's early oceans appear not to have been some suggested. The oxygen isotope composition of marine carbonates has changed markedly over the past 3.5 billion years. However, it difficult determine whether that is because a cooling seawater (from temperatures high 70°C) or an actual change in water. Galili et al. calibrated temperature-dependent fractionation between iron oxides and aqueous solutions constructed record covering 2 Their findings suggest water, rather...
Abstract Climate change and thawing permafrost in the Arctic will significantly alter landscape hydro‐geomorphology distribution of soil moisture, which have cascading effects on climate feedbacks (CO 2 CH 4 ) plant microbial communities. Fundamental processes critical to predicting active layer hydrology are not well understood. This study applied water stable isotope techniques ( δ H 18 O) infer sources mixing waters a polygonal tundra Barrow, Alaska (USA), August September 2012. Results...
Abstract Polygonal ground is a signature characteristic of Arctic lowlands, and carbon release from permafrost thaw can alter feedbacks to ecosystems climate. This study describes the first comprehensive spatial examination active layer biogeochemistry that extends across high‐ low‐centered, ice wedge polygons, their features, with depth. Water chemistry measurements 54 analytes were made on surface pore waters collected near Barrow, Alaska, USA. Significant differences observed between...
MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout JournalEditorsTheme Sections 301:135-148 (2005) - doi:10.3354/meps301135 Stable isotopic composition of deep-sea gorgonian corals Primnoa spp.: a new archive surface processes Owen A. Sherwood1,*, Jeffrey M. Heikoop2, David B. Scott1, Michael J. Risk3, Thomas P. Guilderson4,5, Richard McKinney6 1Centre for Environmental and Geology,...
Mixing models are powerful tools for identifying biogeochemical sources and determining mixing fractions in a sample. However, identification of actual source contributors is often not simple, compositions typically vary or even overlap, significantly increasing model uncertainty calculated fractions. This study compares three probabilistic methods, Stable Isotope Analysis R (SIAR), pure Monte Carlo technique (PMC), Reference Source (SIRS) model, new that estimates systems with more than...
Abstract Arctic soils contain a large pool of terrestrial C and are interest due to their potential for releasing significant carbon dioxide (CO 2 ) methane (CH 4 the atmosphere. Due substantial landscape heterogeneity, predicting ecosystem‐scale CH CO production is challenging. This study assessed dissolved inorganic (DIC = Σ (total) in watershed drainages Barrow, Alaska as critical convergent zones regional geochemistry, substrates, nutrients. In July September 2013, surface waters...
In situ recovery (ISR) uranium (U) mining mobilizes U in its oxidized hexavalent form (U(VI)) by oxidative dissolution of from the roll-front deposits. Postmining natural attenuation residual U(VI) at ISR mines is a potential remediation strategy. Detection and monitoring naturally occurring reducing subsurface environments are important for successful implementation this scheme. We used isotopic tracers (238)U/(235)U (δ(238)U), (234)U/(238)U activity ratio, (34)S/(32)S (δ(34)S), geochemical...
Perchlorate (ClO4−) is ubiquitous in the environment. It produced naturally by atmospheric photochemical reactions, and also synthesized large quantities for military, aerospace, industrial applications. Nitrate-enriched salt deposits of Atacama Desert (Chile) contain high concentrations natural ClO4−, have been exported worldwide since mid-1800s use agriculture. The widespread introduction synthetic agricultural ClO4− into environment has contaminated numerous municipal water supplies....
We use uranium (U) isotope ratios to detect and quantify the extent of natural U reduction in groundwater across a roll front redox gradient. Our study was conducted at Smith Ranch-Highland situ recovery (ISR) mine eastern Wyoming, USA, where economic deposits occur Paleocene Fort Union formation. To evaluate fate aqueous adjacent ore body, we investigated chemical composition samples from roll-front type body surrounding monitoring wells previously mined area. The 238U/235U varies by...
MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout JournalEditorsTheme Sections 180:131-138 (1999) - doi:10.3354/meps180131 Cross-continental shelf trends in coral δ15N on Great Barrier Reef: further consideration of reef nutrient paradox P. W. Sammarco1,*, M. J. Risk2, H. Schwarcz2, Heikoop2,** 1Louisiana Universities Consortium (LUMCON), 8124 Hwy. 56, Chauvin, Louisiana 70344, USA...
Nitrogen isotope values from coral tissue collected over depth–light gradients are reported Jamaica and Zanzibar. The suite consists of multiple specimens three species (Montastrea annularis, Porites astreoides, Agaricia agaricites) sampled at increasing depths. For each species, combined tissue/zooxanthellae δ15N decreases significantly with decreasing availability photosynthetically active radiation. Zanzibar sample was colonies (all lobata). Multiple samples, occupying different depths...
Research Article| August 01, 1996 Modern iron ooids from a shallow-marine volcanic setting: Mahengetang, Indonesia Jeffrey M. Heikoop; Heikoop 1Department of Geology, McMaster University, 1280 Main Street West, Hamilton, Ontario L8S 4M1, Canada Search for other works by this author on: GSW Google Scholar Cameron J. Tsujita; Tsujita Michael Risk; Risk Tomas Tomascik; Tomascik 2The Ecology Indonesian Seas, EMDI Project, School Resource and Environmental Studies, Dalhousie 1312 Robie Street,...
Abstract The nitrate (NO 3 − ) dual isotope approach was applied to snowmelt, tundra active layer pore waters, and underlying permafrost in Barrow, Alaska, USA, distinguish between NO derived from atmospheric deposition versus that microbial nitrification. Snowmelt had an signal with δ 15 N averaging −4.8 ± 1.0‰ (standard error of the mean) 18 O 70.2 1.7‰. In primarily occurred at concentrations suitable for isotopic analysis relatively dry oxic centers high‐centered polygons. average...
Abstract Background and Aims Beneficial plant–microbe interactions can improve plant performance under drought; however, we know less about how drought-induced shifts in microbial communities affect traits. Methods We cultivated Zea mays fritted clay with soil microbiomes originating from contrasting environments (agriculture or forest) two irrigation treatments (well-watered water limited). Using this design, investigated whether conditioning was carried forward through the microbiome to a...
Chihuahueños Bog (2925 m) in the Jemez Mountains of northern New Mexico contains one few records late-glacial and postglacial development mixed conifer forest southwestern North America. The record extends to over 15,000 cal yr BP. An Artemisia steppe, then an open Picea woodland grew around a small pond until ca. 11,700 BP when Pinus ponderosa became established. C/N ratios, δ 13 C 15 N values indicate both terrestrial aquatic organic matter was incorporated into sediment. Higher...