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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2020

Tracking Improvement in Simulated Marine Biogeochemistry Between CMIP5 and CMIP6

Purpose of Review The changes or updates in ocean biogeochemistry component have been mapped between CMIP5 and CMIP6 model versions, and an assessment made of how far these have led to improvements in the simulated mean state of marine biogeochemical models within the current generation of Earth system models (ESMs). Recent Findings The representation of marine biogeochemistry has progressed within the current generation of Earth system models. However, it remains difficult to identify which model updates are responsible for a given improvement. In addition, the full potential of marine biogeochemistry in terms of Earth system interactions and climate feedback remains poorly examined in the current generation of Earth system models. Summary Increasing availability of ocean biogeochemical data, as well as an improved understanding of the underlying processes, allows advances in the marine biogeochemical components of the current generation of ESMs. The present study scrutinizes the extent to which marine biogeochemistry components of ESMs have progressed between the 5th and the 6th phases of the Coupled Model Intercomparison Project (CMIP).

Marine Biogeochemistry↗
NASA NTRS2010

The Sensitivity of Simulated Ocean Biogeochemistry to Forcing Fields Derived from NCEP and MERRA Reanalysis Products

Ocean biogeochemistry models are typically forced by atmospheric and oceanic data derived from reanalysis products. For the NASA Ocean Biogeochemistry Model (NOBM) such reanalysis forcing fields include: surface wind stress, sea surface temperature, ice distributions, shortwave radiation, surface wind speeds and surface atmospheric pressure. Additionally, proper computation of ocean irradiance requires reanalysis products of relative humidity and precipitable water (in addition to aerosol and cloud information which is derived from satellite data). The question posed here is, does the choice of reanalysis products make a difference in the representation of ocean biology and biogeochemistry? NOBM was forced by NCEP and MERRA reanalysis products for the period 2002-2009. We find that in 2009 global distributions and abundances of biological variables (total chlorophyll and nutrients) and carbon (dissolved inorganic and organic carbon and surface pCO2) were similar between the two different forcing fields. Global statistical comparisons with satellite and in situ data also showed negligible differences.

Gregg, Watson↗
NASA NTRS1985

Planetary ecology; Proceedings of the Sixth International Symposium on Environmental Biogeochemistry, Santa Fe, NM, October 10-14, 1983

Topics presented include biological evolution and planetary chemistry; C-1 compounds; transport, deposition, and weathering; sulfur transformations; ground water; transformation processes for nitrogen oxides; and soils. Papers are presented on immunological studies on the organic matrix of recent and fossil invertebrate shells; biogenic gases in sediments deposited since Miocene times on the Walvis Ridge, South Atlantic Ocean; aspects of the biogeochemistry of Big Soda Lake, NV; mesophilic manganese-oxidizing bacteria from hydrothermal discharge areas at 21 deg North on the East Pacific Rise; and autotrophic growth and iron oxidation and inhibition kinetics of Leptospirillum ferrooxidans. Consideration is also given to thermophilic archaebacteria occurring in submarine hydrothermal areas; fate of sulfate in a soft-water, acidic lake; geochemical conditions in the ground water environment; microbial transformations as sources and sinks for nitrogen oxides; and the biogeochemistry of soil phosphorus.

Caldwell, D. E.↗
NASA NTRS1990

The biogeochemistry of metal cycling

The results of the Planetary Biology and Microbial Ecology's summer 1987 program are summarized. The purpose of the interdisciplinary PBME program is to integrate, via lectures and laboratory work, the contributions of university and NASA scientists and student interns. The 1987 program examined various aspects of the biogeochemistry of metal cycling, and included such areas as limnology, metal chemistry, metal geochemistry, microbial ecology, and interactions with metals. A particular area of focus was the use of remote sensing in the study of biogeochemistry. Abstracts and bibliographies of the lectures and reports of the laboratory projects are presented.

Nealson, Kenneth H.↗
NASA NTRS1999

Spectrometry of Pasture Condition and Biogeochemistry in the Central Amazon

Regional analyses of Amazon cattle pasture biogeochemistry are difficult due to the complexity of human, edaphic, biotic and climatic factors and persistent cloud cover in satellite observations. We developed a method to estimate key biophysical properties of Amazon pastures using hyperspectral reflectance data and photon transport inverse modeling. Remote estimates of live and senescent biomass were strongly correlated with plant-available forms of soil phosphorus and calcium. These results provide a basis for monitoring pasture condition and biogeochemistry in the Amazon Basin using spaceborne hyperspectral sensors.

Asner, Gregory P.↗
NASA NTRS2019

The Terrestrial Organism and Biogeochemistry Spatial Sampling Design for the National Ecological Observatory Network

The National Ecological Observatory Network (NEON) seeks to facilitate ecological prediction at a continental scale by measuring processes that drive change and responses at sites across the United States for thirty years. The spatial distribution of observations of terrestrial organisms and soil within NEON sites is determined according to a “design‐based” sample design that relies on the randomization of sampling locations. Development of the sample design was guided by high‐level NEON objectives and the multitude of data products that will be subjected to numerous analytical approaches to address the causes and consequences of ecological change. A requirement framework permeates the NEON design, ensuring traceability from each facet of the design to the high‐level requirements that make the NEON mission statement actionable. Requirements were developed for the terrestrial sample design to guide the key components of the design: Randomizing the sample locations ensures the unbiased collection of data, is appropriate for organisms and soil, and provides data suitable for a variety of analyses. Stratification increases efficiency and allows sampling to focus on those parts of the landscape measured by other NEON observation platforms. Attention to the sample size and spatial plot allocation ensures that data products will be sufficient to inform questions asked of the data and the NEON objectives. Establishing a framework with the capacity for re‐evaluate and design iteration allows for adaption to unexpected challenges and optimization of the sample design based on early data returns. The utility of the NEON sampling design is highlighted by its application across terrestrial systems. The data generated from this unique design will be used to quantify patterns in: the abundance and diversity of small mammals, breeding birds, insects, and soil microbes; vegetation structure, biomass, productivity, and diversity; and soil biogeochemistry.

National Ecological Observatory Network↗
NASA NTRS2020

Uncertainty Quantification of Global Net Methane Emissions From Terrestrial Ecosystems Using a Mechanistically Based Biogeochemistry Model

Quantification of methane (CH4) emissions from wetlands and its sinks from uplands is still fraught with large uncertainties. Here, a methane biogeochemistry model was revised, parameterized, and verified for various wetland ecosystems across the globe. The model was then extrapolated to the global scale to quantify the uncertainty induced from four different types of uncertainty sources including parameterization, wetland type distribution, wetland area distribution, and meteorological input. We found that global wetland emissions are 212 ± 62 and 212 ± 32 Tg CH4 year−1 (1Tg = 1012 g) due to uncertain parameters and wetland type distribution, respectively, during 2000–2012. Using two wetland distribution data sets and three sets of climate data, the model simulations indicated that the global wetland emissions range from 186 to 212 CH4 year−1 for the same period. The parameters were the most significant uncertainty source. After combining the global methane consumption in the range of −34 to −46 Tg CH4 year−1, we estimated that the global net land methane emissions are 149–176 Tg CH4 year−1 due to uncertain wetland distribution and meteorological input. Spatially, the northeast United States and Amazon were two hotspots of methane emission, while consumption hotspots were in the Eastern United States and eastern China. During 1950–2016, both wetland emissions and upland consumption increased during El Niño events and decreased during La Niña events. This study highlights the need for more in situ methane flux data, more accurate wetland type, and area distribution information to better constrain the model uncertainty.

wetland methane emission↗
NASA NTRS2000

Hydrogen Biogeochemistry in Anaerobic and Photosynthetic Ecosystems

The simple biochemistry of molecular hydrogen is central to a large number of microbial processes, affecting the interaction of organisms with each other and with the environment. In anoxic sediments, a great majority of microbial redox processes involve hydrogen as a reactant, product or potential by-product. Accordingly, the energetics (thermodynamics) of each of these processes is affected by variations in local H2 concentrations. It has long been established that this effect is important in governing microbe-microbe interactions and there are multiple demonstrations that "interspecies hydrogen transfer" can alter the products of, inhibit/stimulate, or even reverse microbial metabolic reactions. In anoxic sediments, H2 concentrations themselves are thought to be controlled by the thermodynamics of the predominant H2-consuming microbial process. In sediments from Cape Lookout Bight, this relationship quantitatively describes the co-variation of H2 concentrations with temperature (for methanogens and sulfate reducers) and with sulfate concentration (for sulfate reducers). The quantitative aspect is import= for two reasons: 1) it permits the modeling of H2-sensitive biogeochemistry, such as anaerobic methane oxidation or pathways of organic matter remineralization, as a function of environmental controls; 2) for such a relationship to be observed requires that intracellular biochemistry and bioenergetics are being directly expressed in a component of the extracellular medium. H2 could therefore be utilized a non-invasive probe of cellular energetic function in intact microbial ecosystems. Based on the latter principle we have measured down-core profiles of H2 and other relevant physico-chemical parameters in order to calculate the metabolic energy yields (DG) that support microbial metabolism in Cape Lookout Bight sediments. Methanogens in this system apparently function with energy yields significantly smaller than the minimum requirements suggested by pure culture studies. Our recent work has extended the study of hydrogen to cyanobacterial mat communities. The large amounts of reducing power generated during photosynthetic activity carry the potential to contribute a swamping term to the H2 economy of the anaerobic microbial populations within the mat - and thereby to alter the population structure and biogeochemical function of the mat as a whole. In hypersaline microbial mats, we observe a distinct diel cycle in H2 production and a substantial corresponding flux. On an early Earth dominated by microbial mats, this transmission of photosynthetic reducing power may have carried important implications for both biospheric and atmospheric evolution.

Hoehler, Tori M.↗
NASA NTRS2020

Impacts of Water Clarity Variability on Temperature and Biogeochemistry in the Chesapeake Bay

Estuarine water clarity depends on the concentrations of aquatic constituents, such as colored dissolved organic matter, phytoplankton, inorganic suspended solids, and detritus, which are influenced by variations in riverine inputs. These constituents directly affect temperature because when water is opaque, sunlight heats a shallower layer of the water compared to when it is clear. Despite the importance of accurately predicting temperature variability, many numerical modeling studies do not adequately account for this key process. In this study, we quantify the effect of water clarity on heating by comparing two simulations of a hydrodynamic-biogeochemical model of the Chesapeake Bay for the years 2001–2005, in which (1) water clarity is constant in space and time for the computation of solar heating, compared to (2) a simulation where water clarity varies with modeled concentrations of light-attenuating materials. In the variable water clarity simulation, the water is more opaque, particularly in the northern region of the Bay. This decrease in water clarity reduces the total heat, phytoplankton, and nitrate throughout the Bay. During the spring and summer months, surface temperatures in the northern Bay are warmer by 0.1 °C and bottom temperatures are colder by 0.2 °C in the variable light attenuation simulation. Warmer surface temperatures encourage phytoplankton growth and nutrient uptake near the head of the Bay, and fewer nutrients are transported downstream. These impacts are greater during higher river flow years, when differences in temperature, nutrients, phytoplankton, and zooplankton extend further seaward compared to other years. This study demonstrates the consequences of utilizing different light calculations for estuarine heating and biogeochemistry.

water clarity↗
NASA NTRS1973

Biogeochemistry and biogeology research projects

Summaries of work initiated or completed during the year in the areas of biochemistry and biology are reported. Topics include: studying humic substances through geologic time; analyzing the benzene and hexane soluble portions of the benzene-methanol extracts from the same standard suite for hydrocarbons; finding a pyrolytic technique and applying it to single taxa of fossil microorganisms and individual microorganisms; and discovering to what extent humic substances become converted to kerogen and retained in sediments. A list of publications is included.

Cloud, P.↗
NASA NTRS1972

Biogeochemistry of aragonite mud and oolites.

Amino acids were determined on an analyzer similar to that described by Hare (1969) in carbonate mud samples from locations in the Bahamas, Bermuda, Persian Gulf, and Florida Bay, and in oolites from the Gulf of Suez, the Abu Dhabi coast, the Bahamas, and Baffin Bay, Texas. A histogram, tables, and chromatograms of the results are given.

Mitterer, R. M.↗
NASA NTRS1980

The carbon isotope biogeochemistry of the individual hydrocarbons in bat guano and the ecology of insectivorous bats in the region of Carlsbad, New Mexico

The structures and C-13 contents of individual alkanes extracted from bat guano found in the Carlsbad region of New Mexico can be related to both the photosynthetic pathways of the local plants and the feeding habits of the insects that support the bats. Carbon isotopic analyses of the 62 most important plant species in the Pecos River Valley, the most significant feeding area for the Carlsbad bats, reveal the presence of 29 species with C3 photosynthesis and 33 species, mostly grasses, with C4 photosynthesis. Although the abundances of nonagricultural C3 and C4 plants are similar, alfalfa and cotton, both C3 plants, constitute over 95 per cent of the crop biomass. The molecular composition of the bat guano hydrocarbons is fully consistent with an insect origin. Two isotopically distinct groups of insect branched alkanes were discerned. These two groups of alkanes derived from two chemotaxonomically distinct populations of insects possessing distinctly different feeding habits. It is likely that one population grazes predominantly on crops whereas the other population prefers native vegetation. This and other isotopic evidence supports the notion that crop pests constitute a major percentage of the bats' diet.

Desmarais, D. J.↗
NASA NTRS1980

The carbon isotope biogeochemistry of the individual hydrocarbons in bat guano and the ecology of the insectivorous bats in the region of Carlsbad, New Mexico

The structures and C-13 contents of individual hydrocarbons extracted from bat guano found in the Carlsbad region of New Mexico are analyzed in order to elucidate details of the carbon flow in the plant-insect-bat ecosystem. Carbon isotopic analyses indicate that equivalent numbers of plants with C3 and C4 photosynthetic pathways occupy the feeding area of the bats, which supports alfalfa and cotton as well as native plants. The molecular composition of the guano is consistent with an origin in two distinct populations of insects with different feeding habits, one of which may graze predominantly on crops. It is also pointed out that isotopic analyses of more ancient guano deposits may be useful in characterizing prevalent vegetation and climate of earlier periods.

Des Marais, D. J.↗
NASA NTRS1984

Global Biogeochemistry: an Overview

The dynamic biogeochemical equilibria among the major pools of carbon, nitrogen, sulfur, and phosphorus represented by terrestrial biomes, the world's oceans, and the troposphere are disturbed. Since even the most rapid processes of adjustments among the reservoirs take decades, new equilibria are far from established. These human-induced perturbations and the system's subsequent responses constitute an on-going biogeochemical experiment at the global level. Current and new information must be combined in a way that allows testing of various hypotheses about the workings of global biogeochemical systems. This enables assessment of current knowledge and evaluation of the gaps.

Moore, B., III↗