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At least 37 records · Page 2Linked to original sources
USGS2007

Manganese biogeochemistry in a central Czech Republic catchment

Mn biogeochemistry was studied from 1994 to 2003 in a small forested catchment in the central Czech Republic using the watershed mass balance approach together with measurements of internal stores and fluxes. Mn inputs in bulk deposition were relatively constant during a period of sharply decreasing acidic deposition, suggesting that the Mn source was terrestrial, and not from fossil fuel combustion. Mn inputs in bulk deposition and Mn supplied by weathering each averaged 13 mg m-2 year-1 (26 mg m -2 year-1 total input), whereas Mn export in streamwater and groundwater averaged 43 mg m-2 year-1. Thus an additional Mn source is needed to account for 17 mg m-2 year -1. Internal fluxes and pools of Mn were significantly greater than annual inputs and outputs. Throughfall Mn flux was 70 mg m-2 year-1, litterfall Mn flux was 103 mg m-2 year -1, and Mn net uptake by vegetation was 62 mg m-2 year-1. Large pools of labile or potentially labile Mn were present in biomass and surficial soil horizons. Small leakages from these large pools likely supply the additional Mn needed to close the watershed mass balance. This leakage may reflect an adjustment of the ecosystem to recent changes in atmospheric acidity. ?? 2007 Springer Science+Business Media B.V.

Water, Air, & Soil Pollution↗
USGS2009

The stable carbon isotope biogeochemistry of acetate and other dissolved carbon species in deep subseafloor sediments at the northern Cascadia Margin

Ocean drilling has revealed the existence of vast microbial populations in the deep subseafloor, but to date little is known about their metabolic activities. To better understand the biogeochemical processes in the deep biosphere, we investigate the stable carbon isotope chemistry of acetate and other carbon-bearing metabolites in sediment pore-waters. Acetate is a key metabolite in the cycling of carbon in anoxic sediments. Its stable carbon isotopic composition provides information on the metabolic processes dominating acetate turnover in situ. This study reports our findings for a methane-rich site at the northern Cascadia Margin (NE Pacific) where Expedition 311 of the Integrated Ocean Drilling Program (IODP) sampled the upper 190 m of sediment. At Site U1329, δ 13 C values of acetate span a wide range from −46.0‰ to −11.0‰ vs. VPDB and change systematically with sediment depth. In contrast, δ 13 C values of both the bulk dissolved organic carbon (DOC) (−21.6 ± 1.3‰ vs. VPDB) and the low-molecular-weight compound lactate (−20.9 ± 1.8‰ vs. VPDB) show little variability. These species are interpreted to represent the carbon isotopic composition of fermentation products. Relative to DOC, acetate is up to 23.1‰ depleted and up to 9.1‰ enriched in 13 C. Broadly, 13 C-depletions of acetate relative to DOC indicate flux of carbon from acetogenesis into the acetate pool while 13 C-enrichments of pore-water acetate relative to DOC suggest consumption of acetate by acetoclastic methanogenesis. Isotopic relationships between acetate and lactate or DOC provide new information on the carbon flow and the presence and activity of specific functional microbial communities in distinct biogeochemical horizons of the sediment. In particular, they suggest that acetogenic CO 2 -reduction can coexist with methanogenic CO 2 -reduction, a notion contrary to the hypothesis that hydrogen levels are controlled by the thermodynamically most favorable electron-accepting process. Further, the isotopic relationship suggests a relative increase in acetate flow to acetoclastic methanogenesis with depth although its contribution to total methanogenesis is probably small. Our study demonstrates how the stable carbon isotope biogeochemistry of acetate can be used to identify pathways of microbial carbon turnover in subsurface environments. Our observations also raise new questions regarding the factors controlling acetate turnover in marine sediments.

Geochimica et Cosmochimica Acta↗
USGS2014

Comparative biogeochemistry-ecosystem-human interactions on dynamic continental margins

The ocean’s continental margins face strong and rapid change, forced by a combination of direct human activity, anthropogenic CO 2 -induced climate change, and natural variability. Stimulated by discussions in Goa, India at the IMBER IMBIZO III, we (1) provide an overview of the drivers of biogeochemical variation and change on margins, (2) compare temporal trends in hydrographic and biogeochemical data across different margins (3) review ecosystem responses to these changes, (4) highlight the importance of margin time series for detecting and attributing change and (5) examine societal responses to changing margin biogeochemistry and ecosystems. We synthesize information over a wide range of margin settings in order to identify the commonalities and distinctions among continental margin ecosystems. Key drivers of biogeochemical variation include long-term climate cycles, CO 2 -induced warming, acidification, and deoxygenation, as well as sea level rise, eutrophication, hydrologic and water cycle alteration, changing land use, fishing, and species invasion. Ecosystem responses are complex and impact major margin services including primary production, fisheries production, nutrient cycling, shoreline protection, chemical buffering, and biodiversity. Despite regional differences, the societal consequences of these changes are unarguably large and mandate coherent actions to reduce, mitigate and adapt to multiple stressors on continental margins.

Journal of Marine Systems↗
USGS2013

Effects of canopy tree species on belowground biogeochemistry in a lowland wet tropical forest

Tropical rain forests are known for their high biological diversity, but the effects of plant diversity on important ecosystem processes in this biome remain unclear. Interspecies differences in both the demand for nutrients and in foliar and litter nutrient concentrations could drive variations in both the pool sizes and fluxes of important belowground resources, yet our understanding of the effects and importance of aboveground heterogeneity on belowground biogeochemistry is poor, especially in the species-rich forests of the wet tropics. To investigate the effects of individual tree species on belowground biogeochemical processes, we used both field and laboratory studies to examine how carbon (C), nitrogen (N), and phosphorus (P) cycles vary under nine different canopy tree species – including three legume and six non-legume species – that vary in foliar nutrient concentrations in a wet tropical forest in southwestern Costa Rica. We found significant differences in belowground C, N and P cycling under different canopy tree species: total C, N and P pools in standing litter varied by species, as did total soil and microbial C and N pools. Rates of soil extracellular acid phosphatase activity also varied significantly among species and functional groups, with higher rates of phosphatase activity under legumes. In addition, across all tree species, phosphatase activity was significantly positively correlated with litter N/P ratios, suggesting a tight coupling between relative N and P inputs and resource allocation to P acquisition. Overall, our results suggest the importance of aboveground plant community composition in promoting belowground biogeochemical heterogeneity at relatively small spatial scales.

Soil Biology and Biochemistry↗
USGS2006

A molecular dawn for biogeochemistry

Biogeochemistry is at the dawn of an era in which molecular advances enable the discovery of novel microorganisms having unforeseen metabolic capabilities, revealing new insight into the underlying processes regulating elemental cycles at local to global scales. Traditionally, biogeochemical inquiry began by studying a process of interest, and then focusing downward to uncover the microorganisms and metabolic pathways mediating that process. With the ability to sequence functional genes from the environment, molecular approaches now enable the flow of inquiry in the opposite direction. Here, we argue that a focus on functional genes, the microorganisms in which they reside, and the interaction of those organisms with the broader microbial community could transform our understanding of many globally important biogeochemical processes. ?? 2006 Elsevier Ltd. All rights reserved.

Trends in Ecology and Evolution↗
USGS2021

Incorporating biogeochemistry into dryland restoration

Dryland degradation is a persistent and accelerating global problem. Although the mechanisms initiating and maintaining dryland degradation are largely understood, returning productivity and function through ecological restoration remains difficult. Water limitation commonly drives slow recovery rates within drylands; however, the altered biogeochemical cycles that accompany degradation also play key roles in limiting restoration outcomes. Addressing biogeochemical changes and resource limitations may help improve restoration efforts within this difficult-to-restore biome. In the present article, we present a synthesis of restoration literature that identifies multiple ways biogeochemical understandings might augment dryland restoration outcomes, including timing restoration around resource cycling and uptake, connecting heterogeneous landscapes, manipulating resource pools, and using organismal functional traits to a restoration advantage. We conclude by suggesting ways to incorporate biogeochemistry into existing restoration frameworks and discuss research directions that may help improve restoration outcomes in the world's highly altered dryland landscapes.

BioScience↗
USGS2016

Optimizing available network resources to address questions in environmental biogeochemistry

An increasing number of network observatories have been established globally to collect long-term biogeochemical data at multiple spatial and temporal scales. Although many outstanding questions in biogeochemistry would benefit from network science, the ability of the earth- and environmental-sciences community to conduct synthesis studies within and across networks is limited and seldom done satisfactorily. We identify the ideal characteristics of networks, common problems with using data, and key improvements to strengthen intra- and internetwork compatibility. We suggest that targeted improvements to existing networks should include promoting standardization in data collection, developing incentives to promote rapid data release to the public, and increasing the ability of investigators to conduct their own studies across sites. Internetwork efforts should include identifying a standard measurement suite—we propose profiles of plant canopy and soil properties—and an online, searchable data portal that connects network, investigator-led, and citizen-science projects.

BioScience↗
USGS2016

Microbial antimony biogeochemistry: Enzymes, regulation, and related metabolic pathways

Antimony (Sb) is a toxic metalloid that occurs widely at trace concentrations in soil, aquatic systems, and the atmosphere. Nowadays, with the development of its new industrial applications and the corresponding expansion of antimony mining activities, the phenomenon of antimony pollution has become an increasingly serious concern. In recent years, research interest in Sb has been growing and reflects a fundamental scientific concern regarding Sb in the environment. In this review, we summarize the recent research on bacterial antimony transformations, especially those regarding antimony uptake, efflux, antimonite oxidation, and antimonate reduction. We conclude that our current understanding of antimony biochemistry and biogeochemistry is roughly equivalent to where that of arsenic was some 20 years ago. This portends the possibility of future discoveries with regard to the ability of microorganisms to conserve energy for their growth from antimony redox reactions and the isolation of new species of “antimonotrophs.”

Applied and Environmental Microbiology↗
USGS2014

Nitrogen transport within an agricultural landscape: insights on how hydrology, biogeochemistry, and the landscape intersect to control the fate and transport of nitrogen in the Mississippi Delta

Nitrogen (N) is a ubiquitous contaminant throughout agricultural landscapes due to both the application of inorganic and organic fertilizers to agricultural fields and the general persistence of nitrate (NO 3 ) in oxygenated aqueous environments (Denver et al. 2010; Domagalski et al. 2008; Green et al. 2008; Coupe 2001; Nolan and Stoner 2000). In order to understand why excess N occurs various hydrologic systems (environments), it is important to consider potential sources, the locations of these sources in the watershed, and the timing of the application of sources with respect to the movement of water. To learn how to manage N in a watershed, it is necessary to identify and quantify flow paths and biogeochemical conditions, which ultimately combine to determine transport and fate. If sources, transport mechanisms, and biogeochemical controls were uniformly distributed, it would be possible to manage N uniformly throughout a watershed. However, uniform conditions are rare to nonexistent in the natural world and in the landscape altered for agricultural production. In order to adjust management activities on the landscape to have the greatest effect, it is important to understand the fate and transport N within the intersection of hydrology and biogeochemistry, that is, to understand the extent and duration of the hydrologic and biogeochemical controls as N is routed through and among each hydrologic compartment.

Mississippi Delta↗
USGS2007

The biogeochemistry and occurrence of unusual plant species inhabiting acidic, metal-rich water, Red Mountain, Bonnifield district, Alaska Range: Chapter J in Recent U.S. Geological Survey studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada--results of a 5-year project

This report presents results on the occurrence and biogeochemistry of unusual plant species, and of their supporting sediment, in an undisturbed volcanogenic massive sulfide deposit in the Tintina Gold Province (see fig. 1 of Editors’ Preface and Overview). The extraordinary plant assemblage found growing in the acidic metal-rich waters that drain the area is composed predominantly of bryophytes (liverworts and mosses). Ferricrete-cemented silty alluvial sediments within seeps and streams are covered with the liverwort Gymnocolea inflata, whereas the mosses Polytrichum commune and P. juniperinum inhabit the area adjacent to the water and within the splash zone. Both the liverwort-encrusted sediment and Polytrichum thalli have high concentrations of major- and trace-metal cations (for example, Al, As, Cu, Fe, Hg, La, Mn, Pb, and Zn). Soils in the area do not reflect the geochemical signature of the mineral deposit, and we suspect that they are most influenced by the chemistry of airborne dust (aeolian material) derived from outside the area.

Alaska;Yukon↗
USGS2021

Evaluating a laboratory flume microbiome as a window into natural riverbed biogeochemistry

Riverbeds are hotspots for microbially-mediated reactions that exhibit pronounced variability in space and time. It is challenging to resolve biogeochemical mechanisms in natural riverbeds, as uncontrolled settings complicate data collection and interpretation. To overcome these challenges, laboratory flumes are often used as proxies for natural riverbed systems. Flumes capture spatiotemporal variability and thus allow for controlled investigations of riverbed biogeochemistry. These investigations implicitly rely on the assumption that the flume microbiome is similar to the microbiome of natural riverbeds. However, this assumption has not been tested and it is unknown how the microbiome of a flume compares to natural aquatic settings, including riverbeds. To evaluate the fundamental assumption that a flume hosts a microbiome similar to natural riverbed systems, we used 16s rRNA gene sequencing and publicly available data to compare the sediment microbiome of a single large laboratory flume to a wide variety of natural ecosystems including lake and marine sediments, river, lake, hyporheic, soil, and marine water, and bank and wetland soils. Richness and Shannon diversity metrics, analyses of variance, Bray-Curtis dissimilarity, and analysis of the common microbiomes between flume and river sediment all indicated that the flume microbiome more closely resembled natural riverbed sediments than other ecosystems, supporting the use of flume experiments for investigating natural microbially-mediated biogeochemical processes in riverbeds.

Frontiers in Water↗
USGS2008

Nitrogen biogeochemistry of submarine groundwater discharge

To investigate the role of the seepage zone in transport, chemical speciation, and attenuation of nitrogen loads carried by submarine groundwater discharge, we collected nearshore groundwater samples (n = 328) and examined the distribution and isotopic signature (δ 15 N) of nitrate and ammonium. In addition, we estimated nutrient fluxes from terrestrial and marine groundwater sources. We discuss our results in the context of three aquifer zones: a fresh groundwater zone, a shallow salinity transition zone (STZ), and a deep STZ. Groundwater plumes containing nitrate and ammonium occurred in the freshwater zone, whereas the deep STZ carried almost exclusively ammonium. The distributions of redox-cycled elements were consistent with theoretical thermodynamic stability of chemical species, with sharp interfaces between water masses of distinct oxidation : reduction potential, suggesting that microbial transformations of nitrogen were rapid relative to dispersive mixing. In limited locations in which overlap occurs between distribution of nitrate with that of ammonium and dissolved Fe 2+ , changes in concentration and in δ 15 N suggest loss of all species. Concurrent removal of NO 3 − and NH 4 + , both in freshwater and the deep STZ, might occur through a range of mechanisms, including heterotrophic or autotrophic denitrification, coupled nitrfication : denitrification, anammox, or Mn oxidation of NH 4 + . Loss of nitrogen was not apparent in the shallow STZ, perhaps because of short water residence time. Despite organic Cpoor conditions, the nearshore aquifer and subterranean estuary are biogeochemically active zones, where attenuation of N loads can occur. Extent of attenuation is controlled by the degree of mixing of biogeochemically dissimilar water masses, highlighting the critical role of hydrogeology in N biogeochemistry. Mixing is related in part to thinning of the freshwater lens before discharge and to dispersion at the fresh : saline groundwater interface, features common to all submarine groundwater discharge zones.

Limnology and Oceanography↗
USGS2008

Investigating gas hydrate as a factor in accretionary margin frontal ridge slope failures and cold seep biogeochemistry

During August 2008, a research expedition (2008-007-PGC) was carried out offshore Vancouver Island on the northern Cascadia Margin (Figure 1) to study the role of gas hydrate in slope stability and cold seep biogeochemistry. The cruise was organized by the Geological Survey of Canada (GSC) as part of the Earth Science Sector, Natural Gas Hydrate Program, Natural Resources Canada (NRCan). This international collaboration included McGill University, University of Victoria, the U.S. Geological Survey, Florida State University, and the U.S. Department of Energy.

Fire in the Ice: NETL Methane Hydrate Newsletter↗
USGS2008

Porewater biogeochemistry and soil metabolism in dwarf red mangrove habitats (Twin Cays, Belize)

Seasonal variability in biogeochemical signatures was used to elucidate the dominant pathways of soil microbial metabolism and elemental cycling in an oligotrophic mangrove system. Three interior dwarf mangrove habitats (Twin Cays, Belize) where surface soils were overlain by microbial mats were sampled during wet and dry periods of the year. Porewater equilibration meters and standard biogeochemical methods provided steady-state porewater profiles of pH, chloride, sulfate, sulfide, ammonium, nitrate/nitrite, phosphate, dissolved organic carbon, nitrogen, and phosphorus, reduced iron and manganese, dissolved inorganic carbon, methane and nitrous oxide. During the wet season, the salinity of overlying pond water and shallow porewaters decreased. Increased rainwater infiltration through soils combined with higher tidal heights appeared to result in increased organic carbon inventories and more reducing soil porewaters. During the dry season, evaporation increased both surface water and porewater salinities, while lower tidal heights resulted in less reduced soil porewaters. Rainfall strongly influenced inventories of dissolved organic carbon and nitrogen, possibly due to more rapid decay of mangrove litter during the wet season. During both times of year, high concentrations of reduced metabolites accumulated at depth, indicating substantial rates of organic matter mineralization coupled primarily to sulfate reduction. Nitrous oxide and methane concentrations were supersaturated indicating considerable rates of nitrification and/or incomplete denitrification and methanogenesis, respectively. More reducing soil conditions during the wet season promoted the production of reduced manganese. Contemporaneous activity of sulfate reduction and methanogenesis was likely fueled by the presence of noncompetitive substrates. The findings indicate that these interior dwarf areas are unique sites of nutrient and energy regeneration and may be critical to the overall persistence and productivity of mangrove-dominated islands in oligotrophic settings. ?? 2008 Springer Science+Business Media B.V.

Biogeochemistry↗
USGS2025

Seasonal synchronicity and multi-decadal stability of headwater biogeochemistry in the northern temperate zone

Temporal patterns in chemistry of headwater streams reflect responses of water and elemental cycles to perturbations occurring at local to global scales. We evaluated multi-scale temporal patterns in up to 32 y of monthly observations of stream chemistry (ammonium, calcium, dissolved organic carbon, nitrate, total dissolved phosphorus, and sulfate) in 22 reference catchments within the northern temperate zone of North America. Multivariate autoregressive state-space (MARSS) models were applied to quantify patterns at multi-decadal, seasonal, and shorter intervals during a period that encompassed warming climate, seasonal changes in precipitation, and regional declines in atmospheric deposition. Significant long-term trends in solute concentrations within a subset of the catchments were consistent with recovery from atmospheric deposition (e.g., calcium, nitrate, sulfate) and increased precipitation (e.g., dissolved organic carbon). Lack of evidence for multi-decadal trends in most catchments suggests resilience of northern temperate ecosystems or that subtle net effects of simultaneous changes in climate and disturbance regimes do not result in directional trends. Synchronous seasonal oscillations of solute concentrations occurred across many catchments, reflecting shared climate and biotic drivers of seasonality within the northern temperate zone. Despite shared patterns among catchments at a seasonal scale, multi-scale temporal patterns were statistically distinct among even adjacent headwater catchments, implying that local attributes of headwater catchments modify the signals imparted by atmospheric phenomena and regional disturbances. To effectively characterize hydrologic and biogeochemical responses to changing climate and disturbance regimes, catchment monitoring programs could include multiple streams with contributing areas that encompass regional heterogeneity in vegetation, topography, and elevation. Overall, detection of long-term patterns and trends requires monitoring multiple catchments at a frequency that captures periodic variation (e.g., seasonality) and a duration encompassing the perturbations of interest.

Biogeochemistry↗
USGS2015

Ocean circulation and biogeochemistry moderate interannual and decadal surface water pH changes in the Sargasso Sea

The oceans absorb anthropogenic CO 2 from the atmosphere, lowering surface ocean pH, a concern for calcifying marine organisms. The impact of ocean acidification is challenging to predict as each species appears to respond differently and because our knowledge of natural changes to ocean pH is limited in both time and space. Here we reconstruct 222 years of biennial seawater pH variability in the Sargasso Sea from a brain coral, Diploria labyrinthiformis . Using hydrographic data from the Bermuda Atlantic Time-series Study and the coral-derived pH record, we are able to differentiate pH changes due to surface temperature versus those from ocean circulation and biogeochemical changes. We find that ocean pH does not simply reflect atmospheric CO 2 trends but rather that circulation/biogeochemical changes account for >90% of pH variability in the Sargasso Sea and more variability in the last century than would be predicted from anthropogenic uptake of CO 2 alone.

Geophysical Research Letters↗
USGS2022

Hydrology and biogeochemistry datasets from Sleepers River Research Watershed, Danville, Vermont, USA

The Sleepers River Research Watershed (SRRW) in Danville, Vermont, USA, was established in 1957 by the U.S Department of Agriculture, Agricultural Research Service (ARS). The 111-km 2 area was selected as a representative mixed-land-use upland landscape in the northeastern USA, with the objective to study fundamental hydrological processes. The U.S. Geological Survey (USGS) currently operates SRRW and is the fourth federal agency to lead it. SRRW has hosted historic research on snowmelt modelling and streamflow generation processes, and USGS has augmented this hydrological foundation with biogeochemical cycling research. This data note describes five freely available data releases in stable repositories, extending to the late 2010s, from the indicated start date: aqueous chemistry and isotopes (1991); precipitation, water temperature, and streamflow (1991); groundwater levels (1991); ground frost depth (1983); and snow depth and water equivalent (1960). USGS research at SRRW is expected to continue, and we plan to update these releases every 1–3 years.

Vermont↗
USGS2000

Mercury biogeochemistry in the Idrija River, Slovenia, from above the mine into the Gulf of Trieste

The Idrija Mine is the second largest Hg mine in the world which operated for 500 years. Mercury (Hg)-laden tailings still line the banks, and the system is a threat to the Idrija River and water bodies downstream including the Soca/Isonzo River and the Gulf of Trieste in the northern Adriatic Sea. A multidisciplinary study was conducted in June 1998 on water samples collected throughout the Idrija and Soca River systems and waters and sediments in the Gulf. Total Hg in the Idrija River increased >20-fold downstream of the mine from <3 to >60 ng liter-1 with methyl mercury (MeHg) accounting for ~0.5%. Concentrations increased again downstream and into the estuary with MeHg accounting for nearly 1.5% of the total. While bacteria upstream of the mine did not contain mercury detoxification genes (mer), such genes were detected in bacteria collected downstream. Benthic macroinvertebrate diversity decreased downstream of the mine. Gulf waters near the river mouth contained up to 65 ng liter-1 total Hg with ~0.05 ng liter-1 MeHg. Gulf sediments near the river mouth contained 40 ??g g-1 total Hg with MeHg concentrations of about 3 ng g-1. Hg in sediment pore waters varied between 1 and 8 ng liter-1, with MeHg accounting for up to 85%. Hg methylation and MeHg demethylation were active in Gulf sediments with highest activities near the surface. MeHg was degraded by an oxidative pathway with >97% C released from MeHg as CO2. Hg methylation depth profiles resembled profiles of dissolved MeHg. Hg-laden waters still strongly impact the riverine, estuarine, and marine systems. Macroinvertebrates and bacteria in the Idrija River responded to Hg stress, and high Hg levels persist into the Gulf. Increases in total Hg and MeHg in the estuary demonstrate the remobilization of Hg, presumably as HgS dissolution and recycling. Gulf sediments actively produce MeHg, which enters bottom waters and presumably the marine food chain. (C) 2000 Academic Press.

Conference Paper↗