Hidden biosphere in an oxygen-deficient Atlantic open ocean eddy: future implications of ocean deoxygenation on primary production in the eastern tropical North Atlantic
Summary: The waters of the tropical Atlantic Open Ocean usually contain compareably high concentrations oxygen. Now, it became clear that there are watermasses related to eddies that are nearly anoxic. We surveyed one of those eddies and found a biosphere that largely differed from the usual biosphere present in this area with a specific community responsible for primary production and for degradation processes. Further, we found the very first indication for active nitrogen loss in the open Atlantic.
Biogeosciences Discuss., 12, 14175-14213, doi:10.5194/bgd-12-14175-2015, 2015
Identification and analysis of low molecular weight dissolved organic carbon in subglacial basal ice ecosystems by ion chromatography
Summary: We use a novel ion chromatographic analysis that provides the first identification and quantification of major low molecular weight dissolved organic carbon (LMW-DOC) compounds in basal ice. LMW-DOC concentrations were dependent on the bioavailability of the overridden organic carbon, which in turn, was influenced by the type of overridden material. The overridden material may thus act as a direct (abiotic leaching) and indirect (microbial cycling) source of DOC to the subglacial environment.
Biogeosciences Discuss., 12, 14139-14174, doi:10.5194/bgd-12-14139-2015, 2015
Contributions of dynamic environmental signals during life-cycle transitions to early life-history traits in lodgepole pine (Pinus contorta Dougl.)
Summary: We explored the causes and consequences for the evolution of life-history traits (seed dormancy & size) in lodgepole pine in British Columbia, Canada and found that dynamic climate rather than constant geography are the environmental driving forces in seed dormancy and size variations. Evapotranspiration and precipitation are the most critical climate variables and we predicted that levels of seed dormancy in lodgepole pine would increase across large geographical tracts in 2050s.
Biogeosciences Discuss., 12, 14105-14138, doi:10.5194/bgd-12-14105-2015, 2015
Data-based estimates of the ocean carbon sink variability – first results of the Surface Ocean pCO2 Mapping intercomparison (SOCOM)
Summary: This study investigates variations in the CO2 uptake of the ocean from year to year. These variations have been calculated from measurements of the surface-ocean carbon content by various different interpolation methods. The equatorial Pacific is estimated to be the region with the strongest year-to-year variations, tied to the El Nino phase. The global ocean CO2 uptake gradually increased since about year 2000. The comparison of the interpolation methods identifies these findings as robust.
Biogeosciences Discuss., 12, 14049-14104, doi:10.5194/bgd-12-14049-2015, 2015
Marine regime shifts in ocean biogeochemical models: a case study in the Gulf of Alaska
Summary: Regime shifts have been suggested in the late 1970s and late 1980s in the Gulf of Alaska with important consequences for fisheries. Here we investigate the ability of a suite of ocean biogeochemical models of varying complexity to simulate these regime shifts. Our results demonstrate that ocean models can successfully simulate regime shifts in the Gulf of Alaska region, thereby improving our understanding of how changes in physical conditions are propagated from lower to upper trophic levels.
Biogeosciences Discuss., 12, 14003-14048, doi:10.5194/bgd-12-14003-2015, 2015
Uncertainty analysis of gross primary production partitioned from net ecosystem exchange measurements
Summary: We present a Bayesian estimation of uncertainty in half-hourly GPP partitioned from flux tower measurements of NEE. The results show that it is possible to do this at any desirable time step. This, in turn, can be used to quantify the propagated uncertainty when validating process-based simulators. We further show the importance of using non-informative priors compared to informative priors of the parameters of flux partitioning model as they speed up calculation without loss of precision.
Biogeosciences Discuss., 12, 13967-14002, doi:10.5194/bgd-12-13967-2015, 2015
Methane dynamics in warming tundra of Northeast European Russia
Summary: Arctic region is experiencing an unprecedented rise in permafrost temperatures leading to permafrsot thawing with dire implications for ecosystem structure and functioning. Therefore, it imperative to understand the behaviour of arictic ecosystems under present climatic conditions so that we are equipped with the information to predict their future behaviour. This study presents field data on methane exchange from Seida, located in NW Siberia, Russia measured using various biogeochemical tools.
Biogeosciences Discuss., 12, 13931-13965, doi:10.5194/bgd-12-13931-2015, 2015
Evaluating sensitivity of silicate mineral dissolution rates to physical weathering using a soil evolution model (SoilGen2.25)
Summary: This study evaluated the sensitivity of silicate mineral dissolution rates to intrinsic and extrinsic factors using a soil evolution model, SoilGen2.25. Modelling results showed a dominant role of pH and a direct effect of soil texture on dissolution rates. Clay migration and plant nutrient recycling influenced the pH and thus the dissolution rates. These results demonstrate the need to couple different soil processes in order to explain differences between lab and field dissolution rates
Biogeosciences Discuss., 12, 13887-13929, doi:10.5194/bgd-12-13887-2015, 2015
Testing the D/H ratio of alkenones and palmitic acid as salinity proxies in the Amazon Plume
Biogeosciences Discuss., 12, 13859-13885, doi:10.5194/bgd-12-13859-2015, 2015
Estimation of microbial metabolism and co-occurrence patterns in fracture groundwaters of deep crystalline bedrock at Olkiluoto, Finland
Summary: Over 95% of the microbial communities in isolated groundwater in Olkiluoto bedrock, Finland, is composed of only a few common species. The remaining rare microbiome contains over 3- and 6-fold more microbial diversity. The rare microbiome is an unlimited source of genomic functionality in the ecosystem. These microorganisms can respond to change caused by physical or biological factors that may lead to alterations in the diversity and function of the microbial communities in crystalline bedrock.
Biogeosciences Discuss., 12, 13819-13857, doi:10.5194/bgd-12-13819-2015, 2015
Spatial distribution and sources of organic carbon in the surface sediment of the Bosten Lake, China
Biogeosciences Discuss., 12, 13793-13817, doi:10.5194/bgd-12-13793-2015, 2015
Climate-driven shifts in continental net primary production implicated as a driver of a recent abrupt increase in the land carbon sink
Summary: Recent analyses of the global carbon budget found a substantial increase in the land sink in the late 1980s whose origin remains unknown. Consistent with this shift, we find that plant growth has increased in the late 1980s especially in Eurasia and northern Africa. There climatic constraints on plant growth have eased possibly due to linked climate modes in the North Atlantic. Better understanding of North Atlantic climate may be essential for more credible projections of the land carbon sink.
Biogeosciences Discuss., 12, 13767-13791, doi:10.5194/bgd-12-13767-2015, 2015
Molecular characterization of dissolved organic matter from subtropical wetlands: a comparative study through the analysis of optical properties, NMR and FTICR/MS
Summary: Wetlands commonly feature high levels of natural dissolved organic matter (DOM), a critical component in their biogeochemical functions. Here we describe the first detailed, comparative, molecular characterization of DOM in three sub-tropical, pulsed, wetlands, using optical properties, high field nuclear magnetic resonance and ultrahigh resolution mass spectrometry, and compare compositional features to variations in organic matter sources and flooding characteristics.
Biogeosciences Discuss., 12, 13711-13765, doi:10.5194/bgd-12-13711-2015, 2015
Characterizing Leaf Area Index (LAI) and Vertical Foliage Profile (VFP) over the United States
Summary: This paper provides a unique insight into vertical distribution of leaf area index across North American ecosystems using spaceborne lidar data. This data set of leaf area index and vertical foliage profile can help set up a baseline of canopy structure needed for evaluating climate and land use induced forest changes at continental scale in the future.
Biogeosciences Discuss., 12, 13675-13710, doi:10.5194/bgd-12-13675-2015, 2015
Spring bloom onset in the Nordic Seas
Summary: We investigated the bloom onset in the Nordic Seas using 5 bio-optical floats. We found that the float data are consistent with two possible scenarios for the onset of blooms in the Nordic Seas. The Nordic Seas blooms could have started either when the light became sufficiently abundant that the division rates exceeded the loss rates, or when the photoperiod, the number of daily light hours experienced by phytoplankton, exceeded a critical value.
Biogeosciences Discuss., 12, 13631-13673, doi:10.5194/bgd-12-13631-2015, 2015
Unusual biogenic calcite structures in two shallow lakes, James Ross Island, Antarctica
Biogeosciences Discuss., 12, 13593-13629, doi:10.5194/bgd-12-13593-2015, 2015
Nitrogen cycling in the subsurface biosphere: nitrate isotopes in porewaters underlying the oligotrophic North Atlantic
Summary: In the sediments underlying the global oligotrophic ocean, low levels of microbial activity persist, despite low input of organic matter from surface ocean productivity. Using measured nitrogen and oxygen isotopes of porewater nitrate we estimate the magnitude and extent of microbial nitrogen cycling. We find evidence for the overlap of both denitrification as well as autotrophic pathways such as nitrification and nitrogen fixation - pointing to a relatively large role for subsurface autotrophy.
Biogeosciences Discuss., 12, 13545-13591, doi:10.5194/bgd-12-13545-2015, 2015
The potential effects of fresh water content on the primary production in the Chukchi Sea
Biogeosciences Discuss., 12, 13511-13544, doi:10.5194/bgd-12-13511-2015, 2015
Protist communities in a marine oxygen minimum zone off Costa Rica by 454 pyrosequencing
Summary: Photosynthetic Dinoflagellates predominated in the surface, while potential parasitic Dinoflagellates and Ciliates dominated in the OMZ and deeper water in Costa Rica Dome. Total and active protists in the anoxic core were distinct from those in others depths. Reduced community diversity and presence of parasitic/symbiotic trophic lifestyles in the suboxic/anoxic OMZ suggests that oxygen deficiency could cause a change of protist community and the associated microbial food web as well.
Biogeosciences Discuss., 12, 13483-13509, doi:10.5194/bgd-12-13483-2015, 2015
Mediterranean climate since the Middle Pleistocene: a 640 ka stable isotope record from Lake Ohrid (Albania/Macedonia)
Biogeosciences Discuss., 12, 13427-13481, doi:10.5194/bgd-12-13427-2015, 2015
Technical Note: A generic law-of-the-minimum flux limiter for simulating substrate limitation in biogeochemical models
Biogeosciences Discuss., 12, 13399-13425, doi:10.5194/bgd-12-13399-2015, 2015
Hydroxy fatty acids in fresh snow samples from northern Japan: long-range atmospheric transport of Gram-negative bacteria by Asian winter monsoon
Summary: Our manuscript represents the first field-based data set on the abundances of hydroxy fatty acids (FAs) in fresh snow and its filtering capacity to reduce hydroxy FAs burden from the atmosphere.
• Hydroxy fatty acids (FAs) in snow indicate contribution from soil microbes and higher plants.
• Air mass back-trajectories reveal their transport from Russia, Siberia and China.
Biogeosciences Discuss., 12, 13375-13397, doi:10.5194/bgd-12-13375-2015, 2015
Using satellite data to improve the leaf phenology of a global Terrestrial Biosphere Model
Summary: Previous model evaluation studies have shown that Terrestrial Biosphere Models (TBMs) need a better representation of model phenology, but the model deficiency could be related to incorrect model parameters or inaccurate model structure. This paper presenting a framework for optimising the parameters of phenology models that are commonly used in TBMs. It further demonstrates that the optimisation can result in changes to trends in vegetation productivity and an improvement in gross C fluxes.
Biogeosciences Discuss., 12, 13311-13373, doi:10.5194/bgd-12-13311-2015, 2015
Seasonal, sub-seasonal and spatial fluctuations in oxygen-depleted bottom waters in an embayment of an eastern boundary upwelling system: St Helena Bay
Summary: Seasonal, sub-seasonal and spatial fluctuations in bottom dissolved oxygen (DO) are examined in St Helena Bay, the largest and most productive bay of the southern Benguela upwelling system. Superimposed on the seasonal decline of DO concentrations in bottom waters were sub-seasonal events of hypoxia and anoxia linked to episodic deposition of organic matter as dictated by cell death processes of exceptional dinoflagellate blooms as indicated by increases in bottom Chl a concentrations.
Biogeosciences Discuss., 12, 13283-13309, doi:10.5194/bgd-12-13283-2015, 2015
Ash leachates from some recent eruptions of Mount Etna (Italy) and Popocatépetl (Mexico) volcanoes and their impact on amphibian living freshwater organisms
Biogeosciences Discuss., 12, 13241-13282, doi:10.5194/bgd-12-13241-2015, 2015
Contrasting pH buffering patterns in neutral-alkaline soils along a 3600 km transect in northern China
Biogeosciences Discuss., 12, 13215-13240, doi:10.5194/bgd-12-13215-2015, 2015
Southwestern Tropical Atlantic coral growth response to atmospheric circulation changes induced by ozone depletion in Antarctica
Biogeosciences Discuss., 12, 13193-13213, doi:10.5194/bgd-12-13193-2015, 2015
Spatial and temporal trends in summertime climate and water quality indicators in the coastal embayments of Buzzards Bay, Massachusetts
Biogeosciences Discuss., 12, 13159-13192, doi:10.5194/bgd-12-13159-2015, 2015
Natural variability in the surface ocean carbonate ion concentration
Summary: We investigate variability in surface ocean carbonate chemistry using output from a 1000-year control simulation of an Earth System Model. We find that the detection timescale for trends is strongly influenced by the variability. As the scientific community seeks to detect the anthropogenic influence on ocean carbonate chemistry, these results will aid the interpretation of trends calculated from spatially- and temporally-sparse observations.
Biogeosciences Discuss., 12, 13123-13157, doi:10.5194/bgd-12-13123-2015, 2015
EUROSPEC: at the interface between remote sensing and ecosystem CO2 flux measurements in Europe
Biogeosciences Discuss., 12, 13069-13121, doi:10.5194/bgd-12-13069-2015, 2015
The root economics spectrum: divergence of absorptive root strategies with root diameter
Biogeosciences Discuss., 12, 13041-13067, doi:10.5194/bgd-12-13041-2015, 2015
Improved end-member characterization of modern organic matter pools in the Ohrid Basin (Albania, Macedonia) and evaluation of new palaeoenvironmental proxies
Summary: Lake Ohrid is situated in the southern Balkans between Albania and Macedonia. It is a unique ecosystem with remarkable biodiversity and a sediment record of past climate that goes back more than a million years. Detailed reconstructions of past climate development and human alteration of the environment require underpinned and so in this study we go the present day lake vegetation and catchment soils and test new proxies over one of the known recent cooling events of the region 8200 years ago.
Biogeosciences Discuss., 12, 12975-13039, doi:10.5194/bgd-12-12975-2015, 2015
Millennial changes in North Atlantic oxygen concentrations
Summary: Models predict a decrease in future ocean O2, driven by surface water freshening in the polar regions and associated reduction in ocean circulation. Here we assess this effect in the past, focussing on the response of deep and intermediate waters from the North Atlantic Ocean during large-scale ice rafting and millennial scale cooling events of the last glacial. Our assessment agrees with the models, but also highlights the importance of biological processes driving ocean O2 changes.
Biogeosciences Discuss., 12, 12947-12973, doi:10.5194/bgd-12-12947-2015, 2015
Technical Note: A simple calculation algorithm to separate high-resolution CH4 flux measurements into ebullition and diffusion-derived components
Summary: Processes driving the production, transformation and transport of CH4 in wetlands are highly complex. Thus, serious challenges are constitutes in terms of process understanding, potential drivers and the calculation of reliable CH4 emission estimates. We present a simple calculation algorithm to separate CH4 fluxes measured with closed chambers into diffusion- and ebullition-derived components, which helps facilitating the identification of underlying dynamics and potential drivers.
Biogeosciences Discuss., 12, 12923-12945, doi:10.5194/bgd-12-12923-2015, 2015
Stable isotope study of a new chondrichthyan fauna (Kimmeridgian, Porrentruy, Swiss Jura): an unusual freshwater-influenced isotopic composition for the hybodont shark Asteracanthus
Summary: The oxygen isotopic composition of chondrichthyan teeth from the Late Jurassic of the Swiss Jura was measured to get ecological information. The main finding is a freshwater-influenced isotopic signature for the shark Asteracanthus (Hybodontiformes), classically considered as marine. Since those teeth were found in marine deposits and do not show any sign of transportation, we propose, in addition to a mainly marine ecology, excursions into areas of lower salinity, possibly for reproduction.
Biogeosciences Discuss., 12, 12899-12921, doi:10.5194/bgd-12-12899-2015, 2015
Climate change impacts on net primary production (NPP) and export production (EP) regulated by increasing stratification and phytoplankton community structure in CMIP5 models
Summary: Global NPP and EP are reduced considerably for RCP8.5; negative response of NPP and EP to stratification increases reflects a bottom-up control; Models with dynamic phytoplankton community structure show larger declines in EP than in NPP driven by phytoplankton community composition shifts; projections of the NPP response to climate change depend on the phytoplankton community structure, the efficiency of the biological pump, and the levels of regenerated production.
Biogeosciences Discuss., 12, 12851-12897, doi:10.5194/bgd-12-12851-2015, 2015
Optimizing the impact of temperature on bio-hydrogen production from food waste and its derivatives under no pH control using statistical modelling
Biogeosciences Discuss., 12, 12823-12850, doi:10.5194/bgd-12-12823-2015, 2015
Soil N2O and NO emissions from land use and land-use change in the tropics and subtropics: a meta-analysis
Summary: Land use change in the tropics may substantially alter soil N2O and NO emissions. We summarised available data and developed a set of statistical models that allows tropical countries to estimate, for example, agricultural N2O emissions from fertilisation rate and water filled pore space. Further, intermediate land use stages and time since conversion are often crucially lacking, whereas they could represent significant sources. Other gaps were peat forests and oil palm and soy plantations.
Biogeosciences Discuss., 12, 12783-12821, doi:10.5194/bgd-12-12783-2015, 2015
Dissolved organic carbon lability and stable isotope shifts during microbial decomposition in a tropical river system
Summary: Rivers transport a large amount of carbon as dissolved organic carbon (DOC). Our incubation experiments on water of the Tana River, Kenya, showed that microbial decomposition of 10-60% of the initial DOC occurred within the first 24-48h. Simultaneously, there was a decrease in isotopic composition, indicating that DOC derived from C4 vegetation is preferentially decomposed. This has implications for the assessment of vegetation in a catchment based on isotope signatures of riverine carbon.
Biogeosciences Discuss., 12, 12761-12782, doi:10.5194/bgd-12-12761-2015, 2015
Ocean dynamic processes causing spatially heterogeneous distribution of sedimentary caesium-137 massively released from the Fukushima Dai-ichi Nuclear Power Plant
Biogeosciences Discuss., 12, 12713-12759, doi:10.5194/bgd-12-12713-2015, 2015
Phytoplankton calcification as an effective mechanism to prevent cellular calcium poisoning
Summary: The white cliffs of Dover date back to the Cretaceous and are made up by microscopic chalky shells which were produced mainly by marine phytoplankton (coccolithophores). This is iconic proof for their success at times of relatively high seawater calcium concentrations and, as shown here, to be linked to their ability to precipitate calcium as chalk. The invention of calcification can thus be considered an evolutionary milestone allowing coccolithophores to thrive at times when others struggled.
Biogeosciences Discuss., 12, 12691-12712, doi:10.5194/bgd-12-12691-2015, 2015
Application of the 15N-Gas Flux method for measuring in situ N2 and N2O fluxes due to denitrification in natural and semi-natural terrestrial ecosystems and comparison with the acetylene inhibition technique
Biogeosciences Discuss., 12, 12653-12689, doi:10.5194/bgd-12-12653-2015, 2015
Influence of timing of sea ice retreat on phytoplankton size during marginal ice zone bloom period in the Chukchi and Bering shelves
Summary: This study provides the general relationship between the timing of sea ice retreat and phytoplankton size structure during marginal ice zone bloom period in the Chukchi and Bering shelves using satellite remote sensing approach. We also found not only the length of ice-free season but also annual phytoplankton size positively correlated with annual net primary production.
Biogeosciences Discuss., 12, 12611-12651, doi:10.5194/bgd-12-12611-2015, 2015
Looking beyond stratification: a model-based analysis of the biological drivers of oxygen depletion in the North Sea
Summary: We used the ECOHAM5 model to provide a consistent picture of the physical and biological drivers of hypoxia in the North Sea under stratified conditions. Regions susceptible to hypoxia are characterised by low tidal mixing and moderate water depth (~45 m). Variations in upper layer productivity drive the inter-annual variability of bottom O2 conditions. The model-based analysis revealed that benthic and pelagic remineralisation account for 90% of bottom O2 consumption observed at North Dogger.
Biogeosciences Discuss., 12, 12543-12610, doi:10.5194/bgd-12-12543-2015, 2015
The carbon cycle in Mexico: past, present and future of C stocks and fluxes
Summary: We modelled the carbon (C) cycle in Mexico for three different time periods: past (20th century), present (2000-2005) and future (2006-2100). We used different available products to estimate C stocks and fluxes in the country. Contrary to other current estimates, our results showed that Mexico was a C sink and this is likely to continue in the next century (unless the most extreme climate-change scenarios are reached).
Biogeosciences Discuss., 12, 12501-12541, doi:10.5194/bgd-12-12501-2015, 2015
Skeletal mineralogy of coral recruits under high temperature and pCO2
Summary: In recent years much research has focussed on whether corals will be able to build their skeletons under predicted ocean acidification. One strategy corals may employ is changing the mineralogy of their skeletons from aragonite to the less soluble polymorph of calcium carbonate; calcite. Here we show that newly settled coral recruits are unable to produce calcite in their skeletons under near-future elevations in pCO2, which may leave them more vulnerable to ocean acidification.
Biogeosciences Discuss., 12, 12485-12500, doi:10.5194/bgd-12-12485-2015, 2015
Contribution of Marine Group II Euryarchaeota to cyclopentyl tetraethers in the Pearl River estuary and coastal South China Sea: impact on the TEX86 paleothermometer
Biogeosciences Discuss., 12, 12455-12484, doi:10.5194/bgd-12-12455-2015, 2015
The impact of sedimentary alkalinity release on the water column CO2 system in the North Sea
Summary: Alkalinity released from sediments of the souther North Sea can play an important role in the carbon cycle of the North Sea by lowering the pCO2 of the seawater and thus increasing the CO2 flux between the atmosphere and the water. However, not ever single mole alkalinity generated in sediments leads to an additional CO2 uptake, as certain reactions in the water column can negate the respective alkalinity release.
Biogeosciences Discuss., 12, 12395-12453, doi:10.5194/bgd-12-12395-2015, 2015
Do land surface models need to include differential plant species responses to drought? Examining model predictions across a latitudinal gradient in Europe
Summary: Future climate change has the potential to increase drought in many regions of the globe, making it essential that land surface models (LSMs) used in coupled climate models, realistically capture the drought responses of vegetation. We tested whether variable drought sensitivities are needed in a LSM, to explain the observed large-scale patterns of drought, across a latitudinal gradient in Europe during the 2003 heatwave. Our results indicate that LSMs will over-estimate drought impacts in drier
Biogeosciences Discuss., 12, 12349-12393, doi:10.5194/bgd-12-12349-2015, 2015
Optical properties and bioavailability of dissolved organic matter along a flow-path continuum from soil pore waters to the Kolyma River, Siberia
Summary: In this study, we provide new findings with regards to the spatial distribution of dissolved organic matter (DOM) concentration, bioavailability, and optical properties during mid-summer hydrologic conditions throughout the Kolyma River basin in Northeast Siberia. This is particularly critical for this region, where the future fate of organic carbon currently frozen in permafrost soils (and whether it ultimately is released as CO2 and CH4) is tightly linked to the lability of this material.
Biogeosciences Discuss., 12, 12321-12347, doi:10.5194/bgd-12-12321-2015, 2015
Effects of dust additions on phytoplankton growth and DMS production in high CO2 northeast Pacific HNLC waters
Biogeosciences Discuss., 12, 12281-12319, doi:10.5194/bgd-12-12281-2015, 2015
Projected climate change impacts on North Sea and Baltic Sea: CMIP3 and CMIP5 model based scenarios
Summary: We investigated the potential future climate change impacts to the North Sea and the Baltic Sea ecosystem using a coherent regional downscaling strategy. Multi-model ensembles using CMIP3 and CMIP5 scenarios are examined and comparing projected changes with the present day reference condition, we predicted an increase in Sea Surface Temperature in both the seas, decrease in primary production in the North Sea and an increase in primary production in the Baltic Sea.
Biogeosciences Discuss., 12, 12229-12279, doi:10.5194/bgd-12-12229-2015, 2015
Thermo-erosion gullies boost the transition from wet to mesic vegetation
Biogeosciences Discuss., 12, 12191-12228, doi:10.5194/bgd-12-12191-2015, 2015
Spatial variability of diploptene δ13C values in thermokarst lakes: the potential to analyse the complexity of lacustrine methane cycling
Biogeosciences Discuss., 12, 12157-12189, doi:10.5194/bgd-12-12157-2015, 2015
Phototrophic pigment diversity and picophytoplankton abundance in permafrost thaw lakes
Summary: Permafrost thaw lakes are a subject of increasing research interest given their abundance across the northern landscape. Our aim in the present study was to characterize the photosynthetic communities in a range of subarctic thaw lakes using a combination of HPLC analysis of algal and bacterial pigments, flow cytometry and molecular analysis. Our results showed that the thaw lakes contain diverse phototrophic communities and are a previously unrecognized habitat for abundant picophotoautotrophs.
Biogeosciences Discuss., 12, 12121-12156, doi:10.5194/bgd-12-12121-2015, 2015
Metagenomic analyses of the late Pleistocene permafrost – additional tools for reconstruction of environmental conditions
Summary: A comparative analysis of the metagenomes from two 30,000 year-old permafrost samples, one of lake-alluvial origin and the other from late Pleistocene Ice Complex sediments, revealed significant differences within microbial communities. The late Pleistocene Ice Complex sediments (which have been characterized by the absence of methane with lower values of redox-potential and Fe2+ content) showed both a low abundance of methanogenic archaea and enzymes from the carbon, nitrogen and sulfur cycles.
Biogeosciences Discuss., 12, 12091-12119, doi:10.5194/bgd-12-12091-2015, 2015
Nitrogen export from a boreal stream network following forest harvesting: seasonal nitrate removal and conservative export of organic forms
Summary: The key findings of this study are the following: The mobilization of inorganic forms of nitrogen from the terrestrial environment to streams was increased by ~15 fold following forest harvesting. These concentrations combined with the higher discharge from harvested streams enhanced the loads into the stream network. A major fraction, ~70%, of the nitrate load was removed within the network before reaching the outlet; removal was seasonal. Organic N forms were exported close-to conservative.
Biogeosciences Discuss., 12, 12061-12089, doi:10.5194/bgd-12-12061-2015, 2015
A parameterization of respiration in frozen soils based on substrate availability
Summary: Respiration in frozen soils is limited to within the thin water films surrounding soil particles. We parameterize volumetric water content (VWC) in frozen soil to represent the fraction of thawed carbon to simulate substrate availability. Simulated VWC and respiration match in situ and soil incubation data. The parameterization is most applicable when simulating carbon dynamics in permafrost for time scales of 100 years or greater.
Biogeosciences Discuss., 12, 12027-12059, doi:10.5194/bgd-12-12027-2015, 2015
Model aided quantification of dissolved carbon and nitrogen release after windthrow disturbance in an Austrian karst system
Summary: We consider the time period before and after a wind disturbance in an Austrian karst system. Using a process-based flow and solute transport simulation model we estimate impacts on DIN and DOC. We show that DIN increases for several years while DOC remains within its pre-disturbance variability. Simulated transit times indicate that impact passes through the hydrological system within some months but with a small fraction exceeding transit times of even a year.
Biogeosciences Discuss., 12, 11987-12026, doi:10.5194/bgd-12-11987-2015, 2015
Role of zooplankton dynamics for Southern Ocean phytoplankton biomass and global biogeochemical cycles
Summary: We present a global biogeochemical model which incorporates ecosystem dynamics based on the representation of ten plankton functional types, and use the model to quantitatively assess the relative roles of iron versus grazing in determining phytoplankton biomass in the Southern Ocean. Our results suggest that the observed low phytoplankton biomass in the Southern Ocean during summer is primarily explained by the dynamics of the Southern Ocean zooplankton community rather than iron limitation.
Biogeosciences Discuss., 12, 11935-11985, doi:10.5194/bgd-12-11935-2015, 2015
Sun-induced Chlorophyll fluorescence and PRI improve remote sensing GPP estimates under varying nutrient availability in a typical Mediterranean savanna ecosystem
Summary: Sun-induced Chlorophyll fluorescence and Photochemical reflectance index revealed controls of climate and nutrient availability on photosynthesis (GPP). Meteo-driven models (MM) were unable to describe nutrient-induced effects on GPP. Important implication can be derived from these results and uncertainties in the prediction of global GPP still remain when MM do not account for plant nutrient availability.
Biogeosciences Discuss., 12, 11891-11934, doi:10.5194/bgd-12-11891-2015, 2015
Microbial nutrient limitation in arctic lakes in a permafrost landscape of southwest Greenland
Summary: This study investigates microbial nutrient limitation patterns across a region of southwest Greenland in relation to environmental factors. Using microbial enzyme activities to infer nutrient limitation patterns, we determined most lakes are P limited. Further, P limitation was tightly controlled by lake dissolved organic carbon (DOC) concentration.
Biogeosciences Discuss., 12, 11863-11890, doi:10.5194/bgd-12-11863-2015, 2015
Modelling anomalies in the spring and autumn land surface phenology of the European forest
Biogeosciences Discuss., 12, 11833-11861, doi:10.5194/bgd-12-11833-2015, 2015
Nonlinear thermal and moisture dynamics of high Arctic wetland polygons following permafrost disturbance
Summary: Bowl shaped ice-wedge polygons in permafrost regions can retain snowmelt water and moisture in their centre. At Bylot Isl. (NU, CA), those undisturbed polygons were homogeneous in their centre (ground temperature and moisture, plant cover and species). A rapidly developing thermal erosion gully breached polygons ridges, disturbing and changing the aforementioned elements in the ground. Eroded polygons had a varying response following the breach, heterogeneity being their new equilibrium state.
Biogeosciences Discuss., 12, 11797-11831, doi:10.5194/bgd-12-11797-2015, 2015
Controls on microalgal community structures in cryoconite holes upon high Arctic glaciers, Svalbard
Summary: The diversity of microalgae and cyanobacteria in cryoconites on three high Arctic glaciers was investigated. Possible bottom-up controls via nutrient limitation, wind dispersal, and hydrological stability were measured. Grazer populations were quantified to estimate the effect of top-down controls. Nutrient limitation appeared to be the most important control on the diversity and competition outcomes of microalgae and cyanobacteria.
Biogeosciences Discuss., 12, 11751-11795, doi:10.5194/bgd-12-11751-2015, 2015
Carbon dynamics in highly heterotrophic subarctic thaw ponds
Biogeosciences Discuss., 12, 11707-11749, doi:10.5194/bgd-12-11707-2015, 2015
Modern to millennium-old greenhouse gases emitted from freshwater ecosystems of the eastern Canadian Arctic
Summary: We report on greenhouse gas (GHG) emissions in permafrost aquatic systems of the Eastern Canadian Arctic. We found strikingly different ages, sources and emission rates depending on aquatic system types. Small and shallow ponds generally emitted young (modern to a few centuries old) GHG, whereas larger and deeper lakes released much older GHG, in particular millennium-old CH4 from lake central areas. To our knowledge, this work is the first to report on GHG age from Canadian Arctic lakes.
Biogeosciences Discuss., 12, 11661-11705, doi:10.5194/bgd-12-11661-2015, 2015
Organically fertilized tea plantation stimulates N2O emissions and lowers NO fluxes in subtropical China
Biogeosciences Discuss., 12, 11625-11659, doi:10.5194/bgd-12-11625-2015, 2015
Technical Note: An improved guideline for rapid and precise sample preparation of tree-ring stable isotope analysis
Biogeosciences Discuss., 12, 11587-11623, doi:10.5194/bgd-12-11587-2015, 2015
Structural and functional study of the nematode community from the Indian western continental margin with reference to habitat heterogeneity and oxygen minimum zone
Biogeosciences Discuss., 12, 11537-11585, doi:10.5194/bgd-12-11537-2015, 2015
Annual South American forest loss estimates based on passive microwave remote sensing (1990–2010)
Biogeosciences Discuss., 12, 11499-11535, doi:10.5194/bgd-12-11499-2015, 2015
Mercury in coniferous and deciduous upland forests in Northern New England, USA: implications from climate change
Summary: Our study investigated the effect of coniferous and deciduous vegetation on Hg cycling in forest soil. We quantified Hg in aboveground vegetation and soil horizons at eight paired forest sites. Organic horizons at coniferous stands had greater Hg concentrations and pools than at deciduous stands. Mineral soil Hg pools did not vary with vegetation type but varied with soil chemical properties. Our simple box model estimates Hg retention is significantly longer in soils at coniferous stands.
Biogeosciences Discuss., 12, 11463-11498, doi:10.5194/bgd-12-11463-2015, 2015
Seagrass beds as ocean acidification refuges for mussels? High resolution measurements of pCO2 and O2 in a Zostera marina and Mytilus edulis mosaic habitat
Biogeosciences Discuss., 12, 11423-11461, doi:10.5194/bgd-12-11423-2015, 2015
Trend and climatic sensitivity of vegetation phenology in semiarid and arid ecosystems in the US Great Basin during 1982–2011
Summary: We found that changes in wintertime and springtime precipitation played a more important role in the interannual variability of mean vegetation greenness while climate warming was mainly responsible for the 30-year positive trend in the magnitudes of mean vegetation greenness in the dryland ecosystems in the U.S. Great Basin during 1982-2011.
Biogeosciences Discuss., 12, 11387-11422, doi:10.5194/bgd-12-11387-2015, 2015
Effect of sporadic destratification, seasonal overturn and artificial mixing on CH4 emissions at the surface of a subtropical hydroelectric reservoir (Nam Theun 2 Reservoir, Lao PDR)
Biogeosciences Discuss., 12, 11349-11385, doi:10.5194/bgd-12-11349-2015, 2015
Low methane (CH4) emissions downstream of a monomictic subtropical hydroelectric reservoir (Nam Theun 2, Lao PDR)
Biogeosciences Discuss., 12, 11313-11347, doi:10.5194/bgd-12-11313-2015, 2015
Carbon dynamics in boreal peat-lands of the Yenisey region, Western Siberia
Biogeosciences Discuss., 12, 11279-11311, doi:10.5194/bgd-12-11279-2015, 2015
Concentration maxima of volatile organic iodine compounds in the bottom layer water and the cold, dense water over the Chukchi Sea in the western Arctic Ocean: a possibility of production related to degradation of organic matter
Biogeosciences Discuss., 12, 11245-11278, doi:10.5194/bgd-12-11245-2015, 2015
The abiotic contribution to total CO2 flux for soils in arid zone
Biogeosciences Discuss., 12, 11217-11244, doi:10.5194/bgd-12-11217-2015, 2015
Soil resources and climate jointly drive variations in microbial biomass carbon and nitrogen in China's forest ecosystems
Summary: Soil microbial biomass carbon (Cmic) and nitrogen (Nmic) and microbial quotient varied substantially across China’s forest ecosystems (CV 61–96%). Soil resources and climate together explained 24–41% of the variations. Cmic:Nmic ratio declined slightly with soil C:N ratio and changed with latitude and climate, suggesting a plastic homeostasis of microbial C-N stoichiometry. Divergent responses of microbial quotient of C and N to environment imply different mechanisms regulating Cmic and Nmic.
Biogeosciences Discuss., 12, 11191-11216, doi:10.5194/bgd-12-11191-2015, 2015
Quantifying importance and scaling effects of atmospheric deposition of inorganic fixed nitrogen for the eutrophic Black Sea
Biogeosciences Discuss., 12, 11159-11190, doi:10.5194/bgd-12-11159-2015, 2015
The role of snow cover and soil freeze/thaw cycles affecting boreal-arctic soil carbon dynamics
Summary: We found that regional warming promotes widespread deepening of soil thaw in the pan-Arctic area and continued warming will most likely promote permafrost degradation in the warm permafrost areas. We also found that deeper snow pack enhances soil respiration from deeper soil carbon pool more than temperature does, particularly in the cold permafrost areas, where a large amount of soil carbon is stored in deep perennial frozen soils but potentially vulnerable to mobilization from climate change.
Biogeosciences Discuss., 12, 11113-11157, doi:10.5194/bgd-12-11113-2015, 2015
Chlorophyll a specific Δ14C, δ13C and δ15N values in stream periphyton: implications for aquatic food web studies
Summary: We determined the isotopic composition of chlorophyll a in periphytic algae attached to a streambed substrate (periphyton). Although the bulk isotopic composition of periphyton is recognized as a surrogate for the photosynthetic algal community, our results indicate that the bulk periphyton matrix at the study site consists of 89%–95% algal carbon and 5%–11% terrestrial organic carbon. We also discuss how the compound-specific isotope analysis can contribute to the development of stream ecology.
Biogeosciences Discuss., 12, 11089-11111, doi:10.5194/bgd-12-11089-2015, 2015
Trichodesmium and nitrogen fixation in the Kuroshio
Summary: The high abundance of Trichodesmium and active nitrogen fixation in the Kuroshio were not explained by the nutrient distributions (nitrate, phosphate, and iron). We observed a Trichodesmium bloom and high nitrogen fixation near islands situated along the Kuroshio. Numetical experiments demonstrated that Trichodesmium around the islands could be generally delivered to the Kuroshio. These results suggest that the island mass effect is likely important for determining diazotrophy in the Kuroshio.
Biogeosciences Discuss., 12, 11061-11087, doi:10.5194/bgd-12-11061-2015, 2015
Coastal upwelling off Peru and Mauritania inferred from helium isotope disequilibrium
Biogeosciences Discuss., 12, 11019-11059, doi:10.5194/bgd-12-11019-2015, 2015
Landscape-scale changes in forest canopy structure across a partially logged tropical peat swamp
Biogeosciences Discuss., 12, 10985-11018, doi:10.5194/bgd-12-10985-2015, 2015
Reviews and Syntheses: Ocean acidification and its potential impacts on marine ecosystems
Biogeosciences Discuss., 12, 10939-10983, doi:10.5194/bgd-12-10939-2015, 2015
Air–water fluxes and sources of carbon dioxide in the Delaware Estuary: spatial and seasonal variability
Summary: Due to its extensive geographic size, one may conceptually model the Delaware Estuary as being a funnel-shaped estuarine systems. In this case, air-water CO2 fluxes in the heterotrophic upper estuary are significantly influenced by intense river-borne CO2 degassing akin to river-dominated estuarine systems. On the other hand, the more dominant autotrophic lower estuary is governed by water column biological processes and seasonal temperature cycles akin to marine-dominated estuarine systems.
Biogeosciences Discuss., 12, 10899-10938, doi:10.5194/bgd-12-10899-2015, 2015
Comparing models of microbial-substrate interactions and their response to warming
Summary: Simple microbial decomposition models show distinct responses to warming under different assumptions of how complex organic matter is broken down. If there are limitations other than microbial enzyme availability, the short term respiration response is dampened, and the decomposition dynamics resembles traditional first order decay used in most biogeochemistry models. Further, microbial adjustment to respiratory cost for enzyme production reduces overall sensitivity to temperature.
Biogeosciences Discuss., 12, 10857-10897, doi:10.5194/bgd-12-10857-2015, 2015
Quantifying regional, time-varying effects of cropland and pasture on vegetation fire
Summary: People worldwide use fire to manage agriculture, but often also suppress fire in the landscape surrounding their fields. Here, we estimate the net result of these effects of cropland and pasture on fire at a regional, monthly level. Pasture is shown, for the first time, to contribute strongly to global patterns of burning. Our results could be used to improve representations of burning in global vegetation and climate models, improving our understanding of how people affect the Earth system.
Biogeosciences Discuss., 12, 10817-10855, doi:10.5194/bgd-12-10817-2015, 2015
Reviews and Syntheses: Effects of permafrost thaw on arctic aquatic ecosystems
Summary: In this review we give an overview of the current state of knowledge regarding how permafrost thaw affects aquatic systems. We describe the general impacts of thaw on aquatic ecosystems, pathways of organic matter and contaminant release and degradation, resulting emissions and burial, and effects on ecosystem structure and functioning. We conclude with an overview of potential climate feedbacks and recommendations for future research.
Biogeosciences Discuss., 12, 10719-10815, doi:10.5194/bgd-12-10719-2015, 2015
Sharp ecotones spark sharp ideas: comment on "Structural, physiognomic and above-ground biomass variation in savanna-forest transition zones on three continents – how different are co-occurring savanna and forest formations?" by Veenendaal et al. (2015)
Summary: Remote sensing studies indicate that tropical forest and savanna can be alternative stable states maintained by a feedback between tree cover and fire. Veenendaal et al. (2015) attempted to refute this hypothesis with an extensive field study of the vegetation structure and soil conditions at forest-savanna transition zones. With a re-analysis of their data and a conceptual model we show that in fact the results agree with the idea of forest-savanna bistability.
Biogeosciences Discuss., 12, 10707-10717, doi:10.5194/bgd-12-10707-2015, 2015
Impacts of prescribed burning on soil greenhouse gas fluxes in a suburban native forest of south-eastern Queensland, Australia
Biogeosciences Discuss., 12, 10679-10706, doi:10.5194/bgd-12-10679-2015, 2015
Permafrost coverage, watershed area and season control of dissolved carbon and major elements in western Siberian rivers
Summary: The governing parameter of DOC and major element concentrations and fluxes in western Siberia is latitude. High fluxes in the continuous permafrost zone of frozen peat bogs stem from the fact that the underlining mineral layer is not reactive, protected by the permafrost so that the major part of the active layer is located within the organic (peat) matrix and not the mineral matrix. Possible changes in export fluxes of DOC and major river water components under permafrost thaw are quantified.
Biogeosciences Discuss., 12, 10621-10677, doi:10.5194/bgd-12-10621-2015, 2015
The organic sea surface microlayer in the upwelling region off Peru and implications for air–sea exchange processes
Biogeosciences Discuss., 12, 10579-10619, doi:10.5194/bgd-12-10579-2015, 2015
Seasonal dynamics of carbon and nutrients from two contrasting tropical floodplain systems in the Zambezi River Basin
Summary: Two large floodplains retain the peak flows in the Zambezi River System – the dam-impacted Kafue Flats and the rather pristine Barotse Plains. Here we show that the inputs of organic matter and nutrients from such floodplains to the river are strongly affected by the presence of hydropower dams. Environmental assessments of dam impacts should therefore consider changes in water quality.
Biogeosciences Discuss., 12, 10545-10578, doi:10.5194/bgd-12-10545-2015, 2015
Application of clustering techniques to study environmental characteristics of microbialite-bearing aquatic systems
Summary: Microbialites (rocks formed by the activity of microbes) are important geobiologic structures with a ~3.5 billion year record. Despite this, the formation of microbialites is still poorly understood. This study provides a statistical treatment of the geochemistry of several microbialite-forming environments, as well as ‘control’ environments that do not form microbialtes. It is the aim of this manuscript to discern what characteristics are integral to the formation of microbialites.
Biogeosciences Discuss., 12, 10511-10544, doi:10.5194/bgd-12-10511-2015, 2015
Water use strategies of a young Eucalyptus urophylla forest in response to seasonal change of climatic factors in South China
Summary: a) More dramatically decreased hydralic conductivity when stomatal conductance was decreasing may shed some light on the mechanism of the high WUE of Eucalyptus when exposed to drought conditions. b) As tree grows, ks is more sensitive to water loss. c) The decrease in stomatal sensitivity of GSref to D along the radiation gradient accounted for an important aspect of “plastic characteristics” for E. urophylla.
Biogeosciences Discuss., 12, 10469-10510, doi:10.5194/bgd-12-10469-2015, 2015
Effects of a windthrow disturbance on the carbon balance of a broadleaf deciduous forest in Hokkaido, Japan
Summary: Using the eddy covariance and biometrical methods, the carbon budget was measured in a deciduous broadleaf forest in Japan, where accidental damage by a strong typhoon damaged 40% of trees. Before the disturbance, the forest was an evident carbon sink, and it subsequently transformed to net a carbon source. GPP only decreased by 6% just after the disturbance. On the other hand, Re increased by 39%. Undergrowth dwarf bamboo has an important role in the carbon budget.
Biogeosciences Discuss., 12, 10425-10468, doi:10.5194/bgd-12-10425-2015, 2015
Lateral carbon fluxes and CO2 outgassing from a tropical peat-draining river
Summary: Tropical peatlands are an important source of organic carbon to rivers. However, due to the remoteness of these ecosystems, data are scarce. We present the first combined assessment of both lateral organic carbon fluxes and CO2 emissions from an undisturbed tropical peat-draining river. Compared to the organic carbon concentrations, CO2 fluxes to the atmosphere were actually relatively moderate, which we attributed to the short water residence time.
Biogeosciences Discuss., 12, 10389-10424, doi:10.5194/bgd-12-10389-2015, 2015
Responses of soil microbial communities and enzyme activities to nitrogen and phosphorus additions in Chinese fir plantations of subtropical China
Summary: We examined how N and P addition influenced soil microbial community composition and enzyme activities in subtropical China. The results showed that C and N cycling enzymes were more sensitive to nutrient additions than P cycling enzymes and Gram positive bacteria were most closely related to soil nutrient cycling enzymes. Combined additions of N and P fertilizer were recomoned to promote soil fertility and microbial activity in this kind of plantation.
Biogeosciences Discuss., 12, 10359-10387, doi:10.5194/bgd-12-10359-2015, 2015
Two-dimensional distribution of living benthic foraminifera in anoxic sediment layers of an estuarine mudflat (Loire Estuary, France)
Summary: We present a new rapid and accurate protocol to simultaneously sample benthic living foraminifera in two dimensions in a centimeter scale vertical grid and dissolved iron in high resolution (200µm). The main characteristics of A. tepida distribution are interpreted as a combination of passive downward transport by biomixing into deeper suboxic sediment layers and a subsequent mobility driven by a sensitivity to geochemical gradients.
Biogeosciences Discuss., 12, 10311-10358, doi:10.5194/bgd-12-10311-2015, 2015
Net ecosystem production in a Little Ice Age moraine: the role of plant functional traits
Summary: Vegetation growth after glaciers retreat can be an important feedback to increasing atmospheric CO2. We monitored, with transparent and opaque chambers, the carbon fluxes of two vegetation communities on an alpine glacier forefield over two growing seasons. We showed that different plant physiology determines the sign of the net carbon exchange. A C3 grassland, having higher assimilation rates, was a net CO2 sink, while CAM rosettes were a net source.
Biogeosciences Discuss., 12, 10271-10310, doi:10.5194/bgd-12-10271-2015, 2015
Co-occurrence patterns in aquatic bacterial communities across changing permafrost landscapes
Summary: Bacterial co-occurrence patterns were non-random, with evidence of habitat preferences. Co-occurrence networks revealed complex interdependencies within the bacterioplankton communities and showed contrasting linkages to environmental conditions among the main bacterial phyla. The thaw ponds and lakes networks were composed of a limited number of highly connected taxa, which render these communities more resilient to environmental change, but sensitive to the loss of these keystone species.
Biogeosciences Discuss., 12, 10233-10269, doi:10.5194/bgd-12-10233-2015, 2015
Modeling micro-topographic controls on boreal peatland hydrology and methane fluxes
Biogeosciences Discuss., 12, 10195-10232, doi:10.5194/bgd-12-10195-2015, 2015
Differences between coastal and open ocean distributions of N2O in the oxygen minimum zone off Peru
Biogeosciences Discuss., 12, 10167-10193, doi:10.5194/bgd-12-10167-2015, 2015
An inversion approach for determining production depth and temperature sensitivity of soil respiration
Summary: This study examines an inversion approach for estimating Q10 and depth of production using a physically based soil model, constrained by observed high-frequency surface fluxes and/or 5 concentrations. Inversions using exclusively surface flux measurements were successful, but using multiple shallow subsurface CO2 measurements yielded the best results. This work is a first step toward building a reliable computing framework for removing physical artifacts from high frequency soil CO2 data.
Biogeosciences Discuss., 12, 10137-10166, doi:10.5194/bgd-12-10137-2015, 2015
Soil carbon sequestration by three perennial legume pastures is greater in deeper soil layers than in the surface soil
Biogeosciences Discuss., 12, 10115-10135, doi:10.5194/bgd-12-10115-2015, 2015
A process-based model for ammonia emission from urine patches, GAG (Generation of Ammonia from Grazing): description, validation and sensitivity analysis
Summary: We have been developed a process-based, weather-driven model for ammonia emission from a urine patch and assessed its sensitivity to various factors. The model can simulate the ammoniacal nitrogen content, pH and the water content of the soil under a urine patch. The validation showed that the simulated parameters are well captured by the model. The sensitivity analysis highlighted the vital role of temperature in ammonia exchange. The model is potentially suitable for larger scale application.
Biogeosciences Discuss., 12, 10059-10113, doi:10.5194/bgd-12-10059-2015, 2015
Annual litterfall dynamics and nutrient deposition depending on elevation and land use at Mt. Kilimanjaro
Biogeosciences Discuss., 12, 10031-10057, doi:10.5194/bgd-12-10031-2015, 2015
Changing nutrient stoichiometry affects phytoplankton production, DOP build up and dinitrogen fixation – a mesocosm experiment in the eastern tropical North Atlantic
Biogeosciences Discuss., 12, 9991-10029, doi:10.5194/bgd-12-9991-2015, 2015
Composition and sources of sedimentary organic matter in the deep Eastern Mediterranean Sea
Biogeosciences Discuss., 12, 9935-9989, doi:10.5194/bgd-12-9935-2015, 2015
Thermocline mixing and vertical oxygen fluxes in the stratified central North Sea
Biogeosciences Discuss., 12, 9905-9934, doi:10.5194/bgd-12-9905-2015, 2015
Speciation and distribution of P associated with Fe and Al oxides in aggregate-sized fraction of an arable soil
Biogeosciences Discuss., 12, 9879-9903, doi:10.5194/bgd-12-9879-2015, 2015
Earth system responses to cumulative carbon emissions
Biogeosciences Discuss., 12, 9839-9877, doi:10.5194/bgd-12-9839-2015, 2015
Controls on dissolved organic matter (DOM) degradation in a headwater stream: the influence of photochemical and hydrological conditions in determining light-limitation or substrate-limitation of photo-degradation
Summary: This study investigates how sunlight, dissolved organic matter (DOM) concentration and composition, and hydrology interact to control DOM degradation in headwater streams. In Imnavait Creek, a shallow, low-relief stream in the Arctic, DOM degradation by sunlight was limited by light under all conditions. Study results were used to synthesize controls on DOM degradation by sunlight for a river reach, expressed as a function of light attenuation and water residence times.
Biogeosciences Discuss., 12, 9793-9838, doi:10.5194/bgd-12-9793-2015, 2015
Water quality, isoscapes and stoichioscapes of seagrasses indicate general P limitation and unique N cycling in shallow water benthos of Bermuda
Summary: The landscape-scale spatial pattern in the elemental and isotopic composition of organisms offers valuable information about the ecological processes operating across the landscape. When used in parallel, spatial patterns in stable isotopic composition (called isoscapes) and elemental stoichiometry (we propose the term "stoichioscapes") of seagrasses in Bermuda indicate nutrient sources and unique nitrogen cycling on this isolated oceanic platform.
Biogeosciences Discuss., 12, 9751-9791, doi:10.5194/bgd-12-9751-2015, 2015
Challenges in modelling spatiotemporally varying phytoplankton blooms in the Northwestern Arabian Sea and Gulf of Oman
Summary: Interannual variability of phytoplankton blooms in northwestern Arabian Sea and Gulf of Oman is examined. Interannual variability of the wintertime bloom is dominated by cyclonic eddies which vary in location from one year to another. We suggest that for the model to simulate the observed wintertime blooms within cyclones, it will be necessary to represent this relatively unusual nutrient structure as well as the cyclonic eddies.
Biogeosciences Discuss., 12, 9651-9693, doi:10.5194/bgd-12-9651-2015, 2015
Precipitation legacy effects on dryland ecosystem carbon fluxes: direction, magnitude and biogeochemical carryovers
Summary: This simulation study found that dry legacy imposed positive impacts on net ecosystem production (NEP) whereas wet legacy had negative impacts on NEP, indicating that dry legacy can fostering more C sequestration and wet legacy more C release. The carryover of soil nitrogen was mainly responsible for the gross ecosystem production (GEP) responses while the carryovers of plant biomass, litter and soil organic matter were mainly responsible for the ecosystem respiration (Re) responses.
Biogeosciences Discuss., 12, 9613-9650, doi:10.5194/bgd-12-9613-2015, 2015
Micro-topographic variation in soil respiration and its controlling factors vary with plant phenophases in a desert-shrub ecosystem
Biogeosciences Discuss., 12, 9465-9495, doi:10.5194/bgd-12-9465-2015, 2015
An objective prior error quantification for regional atmospheric inverse applications
Biogeosciences Discuss., 12, 9393-9441, doi:10.5194/bgd-12-9393-2015, 2015
Impact of forest harvesting on water quality and fluorescence characteristics of dissolved organic matter in Eastern Canadian Boreal Shield lakes
Summary: In this study, we showed that logging activities have a short-term impact (one year after the perturbation) on water quality in boreal Eastern Canadian Shield lakes. However, this effect seems to mitigate two years after the perturbation. Further, the analysis of the absorbance and fluorescence data showed that while DOC concentrations did significantly increase in perturbed lakes, the DOM quality did not measurably change.
Biogeosciences Discuss., 12, 9307-9339, doi:10.5194/bgd-12-9307-2015, 2015
C : N : P stoichiometry at the Bermuda Atlantic Time-series Study station in the North Atlantic Ocean
Biogeosciences Discuss., 12, 9275-9305, doi:10.5194/bgd-12-9275-2015, 2015
Influence of mesoscale eddies on the distribution of nitrous oxide in the eastern tropical South Pacific
Summary: We present the first measurements of N2O across three mesoscale eddies in the eastern tropical South Pacific. Eddie's vertical structure, offshore transport, properties at the time of formation and increased primary production at the near-surface, determined the N2O distribution. Substantial depletion of N2O within the core of anticyclonic eddies suggests that although these are transient features, eddy-driven increase in N-loss processes in the Peruvian oxygen minimum zone can be significant.
Biogeosciences Discuss., 12, 9243-9273, doi:10.5194/bgd-12-9243-2015, 2015
Global assessment of Vegetation Index and Phenology Lab (VIP) and Global Inventory Modeling and Mapping Studies (GIMMS) version 3 products
Summary: We compared two new Earth observation based long-term global vegetation index products used in global change research (Global Inventory Modeling and Mapping Studies and Vegetation Index & Phenology Lab- VIP version 3). The two products showed a high level of consistency throughout the primary growing season and were less consistent during green-up and brown-down, which impacted trends in phenology. VIP was generally higher and more variable, which led to poorer correlations with in situ data.
Biogeosciences Discuss., 12, 9081-9120, doi:10.5194/bgd-12-9081-2015, 2015
Map-based prediction of organic carbon in headwaters streams improved by downstream observations from the river outlet
Summary: In this study we test whether river outlet chemistry can be used as an additional source of information to improve the prediction of the total organic carbon (TOC) of headwaters, relative to models based on map information alone. Including river outlet TOC as a predictor in the models gave 5-15% lower prediction errors than using map information alone. Thus, data on water chemistry measured at river outlets offers information which can complement GIS-based modelling of headwaters chemistry.
Biogeosciences Discuss., 12, 9005-9041, doi:10.5194/bgd-12-9005-2015, 2015
Reviews and synthesis: Carbon capture and storage monitoring – an integrated biological, biophysical and chemical approach
Summary: Here we review current knowledge about the impact of CO2 leaks from marine carbon capture storage sites, and use a recent case study to assess current monitoring techniques. We integrate aspects of microbiology, geophysics, chemistry and bioinformatics to suggest a future integrative monitoring technique, using metagenomics, to prevent large-scale leakages and associated consequences. This novel approach is generic and can be adapted to other systems of interest for environmental monitoring.
Biogeosciences Discuss., 12, 8909-8937, doi:10.5194/bgd-12-8909-2015, 2015
The first records of deep-sea fauna – a correction and discussion
Summary: The recovery of a basket star in 1818 from deep waters of Baffin Bay is often cited as the first organism that was brought up from the deep sea. Yet recoveries of stalked crinoids from the Caribbean and catches of several bathyal fishes occurred decades earlier. Yet these accidental catches remained largely neglected during the 19th and 20th century because the bathyal nature of these animals was not recognized.
Biogeosciences Discuss., 12, 8883-8907, doi:10.5194/bgd-12-8883-2015, 2015
Fossil invertebrates records in cave sediments and paleoenvironmental assessments: a study of four cave sites from Romanian Carpathians
Biogeosciences Discuss., 12, 8849-8881, doi:10.5194/bgd-12-8849-2015, 2015
Short-term changes in a microplankton community in the Chukchi Sea during autumn: consequences of a strong wind event
Summary: We studied short-term changes in microplankton community in the western Arctic Ocean with regards to responses to the strong wind event （SWE）during autumn (September 2013). SWE supplied sufficient nutrients to the surface layer that then enhance the small pennate diatom bloom under the weak stratification water column. SWE during autumn may have function to accelerate the seasonal succession of the microplankton community from summer to winter.
Biogeosciences Discuss., 12, 8789-8817, doi:10.5194/bgd-12-8789-2015, 2015
Spatial and seasonal contrasts of sedimentary organic matter in floodplain lakes of the central Amazon basin
Biogeosciences Discuss., 12, 8747-8787, doi:10.5194/bgd-12-8747-2015, 2015
Integrated radar and lidar analysis reveals extensive loss of remaining intact forest on Sumatra 2007–2010
Summary: We integrated satellite Synthetic Aperture Radar (SAR), lidar and forest plot data to calculate the amount and loss of above ground biomass in remaining tall natural forests in a section of Sumatra, with quantified uncertainties. We estimate very high deforestation rates of 3.8% yr-1, and the loss of 11.3% remaining forest biomass in only three years. L-band SAR is valuable for penetrating cloud for deforestation analyses, and for reliably estimating the carbon emissions from land use change.
Biogeosciences Discuss., 12, 8573-8614, doi:10.5194/bgd-12-8573-2015, 2015
Carbonate saturation state of surface waters in the Ross Sea and Southern Ocean: controls and implications for the onset of aragonite undersaturation
Summary: We calculate the carbonate saturation state of surface water from the Ross Sea and along a transect between the Ross Sea and southern Chile using ~ 1700 total alkalinity measurements. Our results suggest that variability in surface carbonate saturation state is driven by biological productivity. We argue that in the Ross Sea the aragonite saturation state of surface water during the early spring never falls below 1.2.
Biogeosciences Discuss., 12, 8429-8465, doi:10.5194/bgd-12-8429-2015, 2015
Biodegradability of dissolved organic carbon in permafrost soils and waterways: a meta-analysis
Summary: We found that dissolved organic carbon (DOC) in arctic soils and aquatic systems is increasingly degradable with increasing permafrost extent. Also, DOC seems less degradable when moving down the fluvial network in continuous permafrost regions, i.e. from streams to large rivers, suggesting that highly bioavailable DOC is lost in headwater streams. We also recommend a standardized DOC incubation protocol to facilitate future comparison on processing and transport of DOC in a changing Arctic.
Biogeosciences Discuss., 12, 8353-8393, doi:10.5194/bgd-12-8353-2015, 2015
Greenhouse gas balance of cropland conversion to bioenergy poplar short rotation coppice
Summary: The suitability of a land conversion from cropland to short rotation coppice (SRC) of poplar in Central Italy was investigated comparing the respective GHG budgets, including biogenic and anthropogenic CO2, CH4 and N2O fluxes, change in soil C stocks and effects of biomass use. Land conversion was suitable from a GHG perspective, saving 2358 ± 835 gCO2eq m-2, as C exports in the cropland compensated all the C taken up by plants, while in the SRC only in part. Soil non-CO2 fluxes were negligible
Biogeosciences Discuss., 12, 8035-8084, doi:10.5194/bgd-12-8035-2015, 2015
Age depth-model for the past 630 ka in Lake Ohrid (Macedonia/Albania) based on cyclostratigraphic analysis of downhole gamma ray data
Biogeosciences Discuss., 12, 7671-7703, doi:10.5194/bgd-12-7671-2015, 2015
Isotopically enriched ammonium shows high nitrogen turnover in the pile top zone of dairy manure compost
Summary: δ15N-NH4+-N of dairy manure compost piles was studied. Piles with bulking agent showed significantly higher value 17.7±1.3‰ than that of the piles without bulking agent (11.8±0.9‰) at the end of the process, reflecting significant higher nitrogen conversion and NH3 loss occurred in the pile with bulking agent. The pile top samples which showed very high NH4+-N concentrations with significantly enriched δ15N values (12.7-29.8‰) indicate extremely high nitrogen conversion occurred in this zone.
Biogeosciences Discuss., 12, 7577-7598, doi:10.5194/bgd-12-7577-2015, 2015
Halocarbon emissions and sources in the equatorial Atlantic Cold Tongue
Summary: This manuscript covers the first measurements of CHBr3, CH2Br2 and CH3I from the equatorial Atlantic during the Cold Tongue season, identifying this region and season as a source for these compounds. For the first time, we calculated diapycnal fluxes, and showed that the fluxes from below the mixed layer to the surface are not sufficient to balance the mixed layer budget. Hence, we conclude that mixed layer production has to take place despite a pronounced sub-mixed-layer-maximum.
Biogeosciences Discuss., 12, 5559-5608, doi:10.5194/bgd-12-5559-2015, 2015
Interdependencies between temperature and moisture sensitivities of CO2 emissions in European land ecosystems
Summary: Our experiments showed that in cold areas (e.g. northern latitudes or mountain areas) warming as well as rain events will have a larger impact on CO2 emissions. Increased moisture in dry areas or drying of wet areas will largely promote CO2 emissions. Irrigation of arable lands might have a higher impact on CO2 emissions in warmer regions in the South of Europe than in the North.
Biogeosciences Discuss., 12, 4433-4464, doi:10.5194/bgd-12-4433-2015, 2015
Stable isotope paleoclimatology of the earliest Eocene using kimberlite-hosted mummified wood from the Canadian Subarctic
Summary: The recent discovery of mummified wood (non-petrified) within kimberlite diamond mines in Northwest Territories, Canada, has prompted a paleoclimatic investigation of the time in which the trees grew - the earliest Eocene (ca. 53.3 Ma). Multiple proxy records derived from these samples suggest that during greenhouse climates of the Eocene, subarctic Canada was characterized by high temperatures (+16 C above modern), and multidecadal variability in cloudiness and temperature on 20-30 year cycles.
Biogeosciences Discuss., 11, 16269-16308, doi:10.5194/bgd-11-16269-2014, 2014