Human land uses enhance sediment denitrification and N2O production in Yangtze lakes primarily by influencing lake water quality
Biogeosciences Discuss., 12, 7815-7844, doi:10.5194/bgd-12-7815-2015, 2015
Tree water relations trigger monoterpene emissions from Scots pine stem during spring recovery
Summary: Especially boreal coniferous trees emit plenty of volatile monoterpenes into the atmosphere. At our measurement site in Finland, we found a spring-time relation between the high monoterpene emission from Scots pine stem and tree water relations. Hence, we suggest that the transient monoterpene burst was a consequence of the spring recovery of the stem and that the dominant processes and environmental drivers triggering the monoterpene emissions are different between pine stems and foliage.
Biogeosciences Discuss., 12, 7783-7814, doi:10.5194/bgd-12-7783-2015, 2015
Wind-driven interannual variability of sea ice algal production over the western Arctic Chukchi Borderland
Summary: We have summarized our findings on seasonal and interannual variability of sea ice algal production and biomass over the western Arctic Chukchi Boderland using a pan-Arctic sea ice-ocean modeling approach. In particular, we focused on the relationship with wind pattern. Coupling physical and biogeochemical analyses would provide originality of our study.
Biogeosciences Discuss., 12, 7739-7781, doi:10.5194/bgd-12-7739-2015, 2015
Iron encrustations on filamentous algae colonized by Gallionella-related bacteria in a metal-polluted freshwater stream
Summary: We studied filamentous macroscopic algae growing in metal-rich stream water that leaked out in a former uranium-mining district. These algae were encrusted with Fe-deposits that were associated with microbes, mainly Gallionella-related Fe-oxidizing bacteria, and extracellular polymeric substances. Algae with lower number of chloroplasts often exhibited discontinuous series of precipitates likely due to the intercalary growth of algal filaments which allowed them to avoid fatal encrustation.
Biogeosciences Discuss., 12, 7705-7737, doi:10.5194/bgd-12-7705-2015, 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
Seasonal hydrology drives rapid shifts in the flux and composition of dissolved and particulate organic carbon and mercury in the Fraser River, Canada
Summary: This study presents seasonal cycles of organic carbon and mercury concentrations and organic matter composition in the Fraser River. Dissolved organic matter patterns are linked to flushing of shallow soil layers during spring snowmelt and fall rain events. Hg export does not indicate contamination from pollution or legacy gold mining. Organic carbon export--as both area-normalized yield and the proportion of basin primary productivity--in the Fraser is typical of large rivers globally.
Biogeosciences Discuss., 12, 7613-7669, doi:10.5194/bgd-12-7613-2015, 2015
Radiocarbon isotopic evidence for assimilation of atmospheric CO2 by the seagrass Zostera marina
Summary: Our empirical study first shows the quantitative evidence of assimilating atmospheric modern CO2 by the seagrass Zostera marina, by analyzing the radiocarbon isotope concentrations (Δ14C) of both the seagrass and two carbon sources in a brackish lagoon. CO2 exchange between the air and water would occur at the very thin film of water over the air-exposed seagrass leaves. Our finding offers better understanding of the role of seagrass meadows in global coastal carbon dynamics.
Biogeosciences Discuss., 12, 7599-7611, doi:10.5194/bgd-12-7599-2015, 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
Parameterization of biogeochemical sediment–water fluxes using in-situ measurements and a steady-state diagenetic model
Summary: In low oxygen environments, the lack of oxygen influences sediment biogeochemistry and in turn sediment-water fluxes. These non-linear interactions are often missing from biogeochemical circulation models because sediment models are computationally expensive. A method for parameterizing realistic sediment-water fluxes is presented and applied to the Mississippi River Dead Zone where high primary production, stimulated by excess nutrient loads, promotes low bottom water conditions in summer.
Biogeosciences Discuss., 12, 7537-7575, doi:10.5194/bgd-12-7537-2015, 2015
Derivation of greenhouse gas emission factors for peatlands managed for extraction in the Republic of Ireland and the UK
Summary: We quantified carbon dioxide emissions from drained peat extraction sites in the Republic of Ireland and the United Kingdom, and also measured a range of greenhouse gases that are released to the atmosphere with the burning of peat. Our derived carbon dioxide emission factors were considerably lower than those derived by the IPCC, which has major implications for National Inventory reporting under the United Nations Framework Convention on Climate Change (UNFCCC) and the Kyoto Protocol.
Biogeosciences Discuss., 12, 7491-7535, doi:10.5194/bgd-12-7491-2015, 2015
Detecting methane ebullition on thermokarst lake ice using high resolution optical aerial imagery
Summary: We used multi-temporal high-resolution aerial images of an Alaskan thermokarst lake acquired following freeze-up to map and characterize methane ebullition bubbles trapped in lake ice. We assessed their spatial pattern and also analyzed the spatio-temporal variability of seep occurrences. Our study helped to reveal the location and relative sizes of high- and low-flux seepage zones within the lake. A large number of seeps demonstrated spatio-temporal stability over our two-year study period.
Biogeosciences Discuss., 12, 7449-7490, doi:10.5194/bgd-12-7449-2015, 2015
Salinization alters fluxes of bioreactive elements from streams and soils across land use
Biogeosciences Discuss., 12, 7411-7448, doi:10.5194/bgd-12-7411-2015, 2015
Air–sea CO2 fluxes and the controls on ocean surface pCO2 variability in coastal and open-ocean southwestern Atlantic Ocean: a modeling study
Summary: We investigate surface ocean pCO2 and air-sea CO2 fluxes climatological variability through biogeochemical modeling in the southwestern Atlantic Ocean. Surface ocean pCO2 spatio-temporal variability was found to be controlled mainly by temperature and Dissolved Inorganic Carbon (DIC). Biological production, physical transport and solubility are the main controlling processes. With different behaviors on subtropical and subantarctic open ocean, and on inner/outer continental shelves.
Biogeosciences Discuss., 12, 7369-7409, doi:10.5194/bgd-12-7369-2015, 2015
A comparison of benthic foraminiferal Mn/Ca and sedimentary Mn/Al as proxies of relative bottom water oxygenation in the low latitude NE Atlantic upwelling system
Summary: We highlight the proxy potential of foraminiferal Mn/Ca determined by Secondary Ion Mass Spectrometry and Flow-Through Inductively Coupled Plasma Optical Emission Spectroscopy for recording changes in bottom water oxygen conditions. Comparisons with Mn sediment bulk measurements from the same sediment core largely agree with the results. High foraminiferal Mn/Ca occurs in samples from times of high productivity export and corresponds with the benthic foraminiferal faunal composition.
Biogeosciences Discuss., 12, 7335-7367, doi:10.5194/bgd-12-7335-2015, 2015
Colored dissolved organic matter in shallow estuaries: the effect of source on quantification
Summary: Colored dissolved organic matter (CDOM) is a factor in determining penetration of light in estuaries. Important plant species growing in the beds of estuaries depend on such light penetration for survival. Previous studies have used CDOM fluorescence to approximate light absorption by CDOM but have found variable relationships between fluorescence and absorbance. This paper describes this variability in three east coast estuaries, and shows that this conversion is dependent on CDOM source.
Biogeosciences Discuss., 12, 7301-7333, doi:10.5194/bgd-12-7301-2015, 2015
Nitrogen cycling in shallow low oxygen coastal waters off Peru from nitrite and nitrate nitrogen and oxygen isotopes
Biogeosciences Discuss., 12, 7257-7299, doi:10.5194/bgd-12-7257-2015, 2015
Effects of nitrate and phosphate supply on chromophoric and fluorescent dissolved organic matter in the Eastern Tropical North Atlantic: a mesocosm study
Biogeosciences Discuss., 12, 7209-7255, doi:10.5194/bgd-12-7209-2015, 2015
Characterization of active and total fungal communities in the atmosphere over the Amazon rainforest
Biogeosciences Discuss., 12, 7177-7207, doi:10.5194/bgd-12-7177-2015, 2015
Including high frequency variability in coastal ocean acidification projections
Summary: In this manuscript, habitat-specific acidification projections are presented for four near-shore habitats in the Southern California Bight using high-temporal resolution pH sensor data: surf zone, kelp forest, canyon edge, and the shelf break. All habitats were within 5 km of one another, and exhibited unique, habitat-specific CO2 variability signatures and acidification trajectories, demonstrating the importance of making projections in the context of habitat-specific CO2 signatures.
Biogeosciences Discuss., 12, 7125-7176, doi:10.5194/bgd-12-7125-2015, 2015
Responses of leaf traits to climatic gradients: adaptive variation vs. compositional shifts
Summary: By analysing the quantitative leaf-traits along extensive temperature and moisture gradients with generalized linear models, we found that metabolism-related traits are universally acclimated to environmental conditions, rather than being fixed within plant functional types. The results strongly support a move towards Dynamic Global Vegetation Models in which continuous, adaptive trait variation provides the fundamental mechanism for changes in ecosystem properties along environmental gradients.
Biogeosciences Discuss., 12, 7093-7124, doi:10.5194/bgd-12-7093-2015, 2015
Impacts of climate and reclamation on temporal variations in CH4 emissions from different wetlands in China: from 1950 to 2010
Summary: Natural wetlands in China have experienced extensive conversion and climate warming, which makes the estimation of methane emission from wetlands highly uncertain. In this paper, we simulated an increase of 25.5% in national CH4 fluxes from 1950 to 2010, which was mainly induced by climate warming. Although climate warming has accelerated CH4 fluxes, the total amount of national CH4 emissions decreased by approximately 2.35 Tg (1.91－2.81 Tg), due to a large wetland loss of 17.0 million ha.
Biogeosciences Discuss., 12, 7055-7091, doi:10.5194/bgd-12-7055-2015, 2015
Methane distribution, flux, and budget in the East China Sea and Yellow Sea
Summary: Obvious seasonal variations of the distribution and emission of methane in the ECS and YS were reported based on data collected during five cruises in 2011. A box model was used to calculate the methane budget in the ECS, identify the main sources and sinks of dissolved methane in this area, and estimate the contribution of different sources to total methane quantitatively. It indicated that the most important source of methane in the ECS was in situ production in the water column.
Biogeosciences Discuss., 12, 7017-7053, doi:10.5194/bgd-12-7017-2015, 2015
Evaluating the Community Land Model in a pine stand with 13CO2 labeling and shading manipulations
Biogeosciences Discuss., 12, 6971-7015, doi:10.5194/bgd-12-6971-2015, 2015
Two decades of inorganic carbon dynamics along the Western Antarctic Peninsula
Summary: Evaluation of a unique 20 year long timeseries of inorganic carbon and nutrient observations from the Western Antarctic Peninsula region shows that summertime biological productivity and meltwater input drive a large range of surface aragonite saturation states from values < 1 (undersaturated) up to 3.9. pCO2 measurements from fall and spring indicate a statistically significant increasing trend of up to 23 μatm decade-1, pointing towards first signs of ocean acidification.
Biogeosciences Discuss., 12, 6929-6969, doi:10.5194/bgd-12-6929-2015, 2015
Effect of elevated CO2 on organic matter pools and fluxes in a summer, post spring-bloom Baltic Sea plankton community
Biogeosciences Discuss., 12, 6863-6927, doi:10.5194/bgd-12-6863-2015, 2015
Influence of tree size, taxonomy, and edaphic conditions on heart rot in mixed-dipterocarp Bornean rainforests: implications for aboveground biomass estimates
Summary: Heart rot is a frequently acknowledged, yet poorly constrained, source of error in forest biomass estimates. We quantified the frequency and severity of heart rot in stems felled in a Bornean rainforest and evaluated its association with tree size, taxonomy, and edaphic conditions. Heart rot infection rates varied among tree taxa, and heart rot frequency increased with tree size. Heart rot encompassed 9% of stem volume, and percent forest biomass lost to rot was greater on low fertility soils.
Biogeosciences Discuss., 12, 6821-6861, doi:10.5194/bgd-12-6821-2015, 2015
Energy balance closure on a winter wheat stand: comparing the eddy covariance technique with the soil water balance method
Biogeosciences Discuss., 12, 6783-6820, doi:10.5194/bgd-12-6783-2015, 2015
Enhanced pH up-regulation enables the cold-water coral Lophelia pertusa to sustain growth in aragonite undersaturated conditions
Summary: We investigated the ability of cold-water corals to deal with changes in ocean pH. We uniquely combined morphological assessment with boron isotope analysis to determine if changes in growth are related to changes in control of calcification pH. We found that the cold-water coral Lophelia pertusa can maintain the skeletal morphology, growth patterns as well as internal calcification pH. This has important implications for their future occurrence and explains their cosmopolitan distribution.
Biogeosciences Discuss., 12, 6757-6781, doi:10.5194/bgd-12-6757-2015, 2015
Phytoplankton dynamics driven by vertical nutrient fluxes during the spring inter-monsoon period in the northeastern South China Sea
Summary: Phytoplankton patchiness in the northeastern SCS during May 2014 could be largely controlled by vertical nutrient fluxes including turbulent diffusion and curl-driven upwelling. There was an increasing turbulent diffusion but decreasing curl-driven upwelling from the coastal upwelling zones to the offshore pelagic zones. Elevated fluxes near Dongsha led to net growth of a diatom-rich community, whereas low fluxes near southwest Taiwan resulted in a decline of a picoplankton bloom.
Biogeosciences Discuss., 12, 6723-6755, doi:10.5194/bgd-12-6723-2015, 2015
Reconsidering the role of carbonate ion concentration in calcification by marine organisms
Summary: Calcification by marine organisms reacts to changing seawater carbonate chemistry but it is unclear which components of the carbonate system drive the observed response. This study uncovers proportionalities between different carbonate chemistry parameters. 1) These enable us to understand why calcification often correlates well with carbonate ion concentration. 2) They imply that net CaCO3 formation in high latitudes is not more vulnerable to ocean acidification than formation in low latitudes.
Biogeosciences Discuss., 12, 6689-6722, doi:10.5194/bgd-12-6689-2015, 2015
Physical processes of thermokarst lakes in the continuous permafrost zone of northern Siberia – observations and modeling (Lena River Delta, Siberia)
Summary: We show that lakes in northern Siberia are very efficient with respect to energy absorption and mixing using measurements as well as numerical modeling. We show that i) the lakes receive substantial energy for warming from net shortwave radiation; ii) convective mixing occurs beneath the ice cover, follow beneath the ice cover, following ice break-up, summer, and fall iii) modeling suggests that the annual mean net heat flux across the bottom sediment boundary is approximately zero.
Biogeosciences Discuss., 12, 6637-6688, doi:10.5194/bgd-12-6637-2015, 2015
Effects of varied nitrate and phosphate supply on polysaccharidic and proteinaceous gel particles production during tropical phytoplankton bloom experiments
Biogeosciences Discuss., 12, 6589-6635, doi:10.5194/bgd-12-6589-2015, 2015
Oxygen minimum zones in the tropical Pacific across CMIP5 models: mean state differences and climate change trends
Summary: We analyze simulations of the Pacific Ocean oxygen minimum zones (OMZs) from 11 Earth System model contributions to the Coupled Model Intercomparison Project Phase 5, focusing on the mean state, climate change projections, and interannual variability. We analyze biases with respect to observations and consistency of results across simulations.
Biogeosciences Discuss., 12, 6525-6587, doi:10.5194/bgd-12-6525-2015, 2015
Soil microbial nutrient constraints along a tropical forest elevation gradient: a belowground test of a biogeochemical paradigm
Summary: We measured indices of soil microbial nutrient status in lowland, sub-montane and montane tropical forests along a natural gradient spanning 3400 m in elevation in the Peruvian Andes. We show that soil microorganisms shift investment in nutrient acquisition from P to N between lowland and montane tropical forests, suggesting that different nutrients regulate soil microbial metabolism and the soil carbon balance in these ecosystems.
Biogeosciences Discuss., 12, 6489-6523, doi:10.5194/bgd-12-6489-2015, 2015
Effects of fluctuating hypoxia on benthic oxygen consumption in the Black Sea (Crimean Shelf)
Biogeosciences Discuss., 12, 6445-6488, doi:10.5194/bgd-12-6445-2015, 2015
Coupling the chemical dynamics of carbonate and dissolved inorganic nitrogen systems in the eutrophic and turbid inner Changjiang (Yangtze River) Estuary
Biogeosciences Discuss., 12, 6405-6443, doi:10.5194/bgd-12-6405-2015, 2015
Environmental forcing does not induce diel or synoptic variation in carbon isotope content of forest soil respiration
Summary: Soil respiration and its stable isotopes were studied in a subalpine forest. There was strong diel variability in soil efflux, but not in the isotope content of soil efflux or CO2 from biological activity in the soil. Following rain, soil efflux increased, but the isotope content of these fluxes did not change. Temporal variation in the isotope content of soil efflux was unrelated to environmental variables. Results confirmed established theory regarding diffusive soil gas transport.
Biogeosciences Discuss., 12, 6361-6404, doi:10.5194/bgd-12-6361-2015, 2015
Earthworm impact on the global warming potential of a no-tillage arable soil
Summary: The impacts of earthworms on the greenhouse gas emissions has received much attention recently. We studied the importance of the earthworm Lumbricus terrestris on the emissions in no-till arable soil, both in the field and in laboratory. The results suggest that L. terrestris can markedly regulate the effects of cultivation practises on the global warming potential of arable soil and that high N2O emissions observed in no-till soils can partly be explained by its abundance.
Biogeosciences Discuss., 12, 6325-6359, doi:10.5194/bgd-12-6325-2015, 2015
Seasonal and size-dependent variations in the phytoplankton growth and microzooplankton grazing in the southern South China Sea under the influence of the East Asian monsoon
Biogeosciences Discuss., 12, 6285-6324, doi:10.5194/bgd-12-6285-2015, 2015
Co-variation of metabolic rates and cell-size in coccolithophores
Summary: Metabolic rates and cell-size in coccolithophore algae co-vary consistently in a large number of separate culture experiments as temperature, irradiance, nutrient and pCO2 conditions change. These changes are comparable to the changes in cell size observed in the natural environment, both in the modern ocean and in marine sediments. Changes in coccolithophore cell size in the field will help understand how this key phytoplancton species reacts to climate change.
Biogeosciences Discuss., 12, 6215-6284, doi:10.5194/bgd-12-6215-2015, 2015
New insights into the organic carbon export in the Mediterranean Sea from 3-D modeling
Summary: The dissolved fraction of organic carbon has already been identified as a major source of carbon at depth in the Mediterranean Sea, however export estimation from observations are scarce. We developped a coupling between an hydrodynamical simulation (NEMO-MED12) and a biogeochemical model (Eco3M-MED) to provide at Basin scale an evaluation of organic carbon export, its variability and its form. Dissolved organic carbon appears to be dominant in most regions, especially in the Eastern Basin.
Biogeosciences Discuss., 12, 6147-6213, doi:10.5194/bgd-12-6147-2015, 2015
The Measuring Ammonia in Nature (MAN) network in the Netherlands
Biogeosciences Discuss., 12, 6115-6146, doi:10.5194/bgd-12-6115-2015, 2015
Dam tailwaters compound the effects of reservoirs on the longitudinal transport of organic carbon in an arid river
Summary: Dams impact river reaches. Upstream of dams, reservoirs transform terrestrial organic carbon and produce authochthonous – derived organic carbon. In addition, tailwater reaches below dams may produce and export similar amounts of organic carbon as stored behind dams. Our work demonstrates that not only do reservoirs need to be considered for their capacity to store and transform organic carbon, but also the combined impact of their tailwater ecosystems should to be considered as well.
Biogeosciences Discuss., 12, 6081-6114, doi:10.5194/bgd-12-6081-2015, 2015
Probing the past 30 year phenology trend of US deciduous forests
Summary: We performed model inter-comparison and selected best model capturing the spatial and temporal variations of observations to predict trend of forest phenology over the past 3 decades. Our results show that phenological trends, which are dominantly driven by temperature changes, are not uniform over the contiguous U.S., with a significant spring advance in the East, an autumn delay in the Northeast and West, but no evidence of change elsewhere.
Biogeosciences Discuss., 12, 6037-6080, doi:10.5194/bgd-12-6037-2015, 2015
Inter-decadal changes in the intensity of the Oxygen Minimum Zone off Concepción, Chile (~ 36° S) over the last century
Biogeosciences Discuss., 12, 6003-6035, doi:10.5194/bgd-12-6003-2015, 2015
Comment on "Solute specific scaling of inorganic nitrogen and phosphorus uptake in streams" by Hall et al. (2013)
Biogeosciences Discuss., 12, 5991-6001, doi:10.5194/bgd-12-5991-2015, 2015
Model estimates of climate controls on pan-Arctic wetland methane emissions
Summary: We used a process-based model to investigate the sensitivities of pan-Arctic wetland methane emissions to climate factors, as a function of climate. Over the period 1960-2006, temperature was the dominant driver of trends in emissions. Wetlands north of 60N were temperature-limited, and wetlands south of 60N latitude were water-limited. Projected future warming will cause water-limited wetlands to expand northward over the next century, lessening the role of temperature in the future.
Biogeosciences Discuss., 12, 5941-5989, doi:10.5194/bgd-12-5941-2015, 2015
Quantifying the influence of CO2 seasonality on future ocean acidification
Summary: Our results show that accounting for oceanic CO2 seasonality is crucial to projecting the future onset of critical ocean acidification levels (i.e. aragonite under-saturation). In particular, seasonality will bring forward the initial onset of month-long under-saturation by a global average of 17 years. Importantly, wide-spread under-saturation is projected to occur once atmospheric CO2 reaches 486ppm in the North Pacific and 511ppm in the Southern Ocean, independent of emissions scenario.
Biogeosciences Discuss., 12, 5907-5940, doi:10.5194/bgd-12-5907-2015, 2015
Influence of wood density in tree-ring based annual productivity assessments and its errors in Norway spruce
Summary: Annual variations in wood density partially compensated ring width variations in Picea abies. If neglected, annual biomass increment was underestimated by up to 15%. The relative prediction interval of plot-level annual biomass increment ranged from 20 to 40%. The uncertainty related to the allometric models parameters were about 10% only. The errors related to variations in wood density were much larger, the biggest component being the variability between trees.
Biogeosciences Discuss., 12, 5871-5905, doi:10.5194/bgd-12-5871-2015, 2015
Optimising methodology for determining the effect of ocean acidification on bacterial extracellular enzymes
Summary: pH has a significant effect on the artificial fluorophore for glucosidase and protease activity, while artificial aminopeptidase substrate alters the pH of seawater. Reduction of coastal seawater pH to 7.8 was shown to increase β-glucosidase activity rapidly (0.5h), while no significant response was detected for leucine aminopeptidase. Seawater acidified by bubbling CO2 gas resulted in elevated β-glucosidase activity and bacterial cell numbers, although seasonal effects were observed.
Biogeosciences Discuss., 12, 5841-5870, doi:10.5194/bgd-12-5841-2015, 2015
Environmental drivers of drought deciduous phenology in the Community Land Model
Summary: We compared monthly leaf area index (LAI) estimates from the Community Land Model (CLM) in stress/drought deciduous regions of the world to a satellite derived estimate of LAI. This comparison revealed an issue in the CLM in which leaves begin to grow during the dry season due to unrealistic soil water movement. We introduced a rainfall trigger to the stress deciduous algorithm to address this issue, then showed the impacts of this change on the fire cycle and stored carbon.
Biogeosciences Discuss., 12, 5803-5839, doi:10.5194/bgd-12-5803-2015, 2015
Controls on terrestrial carbon feedbacks by productivity vs. turnover in the CMIP5 Earth System Models
Summary: Terrestrial carbon feedbacks are a large uncertainty in climate change. We separate modeled feedback responses into those governed by changed carbon inputs (productivity) and changed outputs (turnover). The disaggregated responses show that both are important in controlling inter-model uncertainty. Interactions between productivity and turnover are also important, and research must focus on these interactions for more accurate projections of carbon cycle feedbacks.
Biogeosciences Discuss., 12, 5757-5801, doi:10.5194/bgd-12-5757-2015, 2015
Seasonal characterization of CDOM for lakes in semi-arid regions of Northeast China using excitation-emission matrices fluorescence and parallel factor analysis (EEM-PARAFAC)
Summary: Our results of this study show that 1) Two humic-like peaks C and two protein-like B and T peaks were identified using PARAFAC in CDOM for lakes in Northeast China; 2)The average fluorescence intensity of the four components differed with seasonal variation; 3) Components 1 and 2 exhibited strong linear correlation (R2=0.633); 4)There were significantly positive linear relationships between CDOM absorption coefficients and Fmax; 5)A significant relationship (R2=0.931) was found between salinity
Biogeosciences Discuss., 12, 5725-5756, doi:10.5194/bgd-12-5725-2015, 2015
Linking dissolved organic matter composition to metal bioavailability in agricultural soils: effect of anionic surfactants
Summary: Irrigation with greywater can increase the risk of metal toxicity to plants and soil organisms due to the presence of anionic surfactants derived from household products. Three agricultural soils were treated with anionic surfactants and the total concentration of soluble metal increased. However, that was accompanied by the solubilisation of soil organic compounds that bind metals and yield complexes of low bioavailability, which substantially reduces the potential risk of metal toxicity.
Biogeosciences Discuss., 12, 5697-5723, doi:10.5194/bgd-12-5697-2015, 2015
Dynamics of air–sea CO2 fluxes in the North-West European Shelf based on Voluntary Observing Ship (VOS) and satellite observations
Biogeosciences Discuss., 12, 5641-5695, doi:10.5194/bgd-12-5641-2015, 2015
Effects of flooding on organic carbon consumption in the East China Sea
Biogeosciences Discuss., 12, 5609-5639, doi:10.5194/bgd-12-5609-2015, 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
Estimation of nutrient contributions from the ocean across a river basin using stable isotope analysis
Summary: Recycling of total nitrogen (TN) from the ocean to river basin ecosystems has been actively investigated. Previous studies demonstrated that marine-derived nutrients (MDN) play a large role in river ecosystems. However, little research has been devoted to understanding the contribution of runs of salmon to MDN across the entire river basin. Therefore we conducted field experiments to understand the recycling of TN from the ocean across an entire river basin using stable isotope analysis.
Biogeosciences Discuss., 12, 5535-5557, doi:10.5194/bgd-12-5535-2015, 2015
Seasonal variation in vegetation water content estimated from proximal sensing and MODIS time series in a Mediterranean Fluxnet site
Biogeosciences Discuss., 12, 5503-5533, doi:10.5194/bgd-12-5503-2015, 2015
Is average chain length of plant lipids a potential proxy for vegetation, environment and climate changes?
Biogeosciences Discuss., 12, 5477-5501, doi:10.5194/bgd-12-5477-2015, 2015
Mitigation of agriculture emissions in the tropics: comparing forest land-sparing options at the national level
Summary: Emission from agriculture-driven deforestation can be mitigated by reducing the expansion of agriculture into forests through intensification and utilizing non-forested land for agriculture. Climate smart agriculture can reduce emissions from existing agricultural land. Tropical countries which are priorities for action, can be identified by assessing the mitigation potential of these interventions, by assessing capacity for implementation and the risks associated with these approaches.
Biogeosciences Discuss., 12, 5435-5475, doi:10.5194/bgd-12-5435-2015, 2015
Reconstructing European forest management from 1600 to 2010
Summary: Studying century-scale ecological processes and their legacy effects requires accounting for forest management. In this study we produce spatially and temporally explicit maps of European forest management from 1600 to 2010. The most important changes between 1600 and 2010 are: an increase of 593 000km2 in conifers at the expense of deciduous forest, a 612 000km2 decrease in unmanaged forest, a 152 000km2 decrease in coppice management, and a 818 000km increase in high stand management.
Biogeosciences Discuss., 12, 5365-5433, doi:10.5194/bgd-12-5365-2015, 2015
Responses of N2O flux to water level fluctuation and other environmental factors at littoral zone of Miyun Reservoir: a comparison with CH4 fluxes
Biogeosciences Discuss., 12, 5333-5363, doi:10.5194/bgd-12-5333-2015, 2015
Evidence for biological shaping of hair ice
Summary: We investigated an unusual ice type, called hair ice. It grows on the surface of dead wood of broad-leaf trees at temperatures slightly below 0°C.We describe this phenomenon and present our biological, physical and chemical investigations to gain insight in the properties and processes related to hair ice: we found, that a winter-acive fungus in the wood is required. Ice segregation is the common mechanism. Chemical analyses show a complex mixture of several thousand lignin/ tannin compounds.
Biogeosciences Discuss., 12, 5293-5332, doi:10.5194/bgd-12-5293-2015, 2015
Detection and attribution of global change effects on river nutrient dynamics in a large Mediterranean basin
Summary: Nitrate and dissolved phosphate concentration time-series (1980-2011) from 50 sampling stations across a large Mediterranean river basin were analyzed using Dynamic Factor Analysis and complementary methods in order to disentangle the role of hydrology, land-use practices, and global climatic phenomena on nutrient patterns, with the overall aim of understanding how the different aspects of global change affected nutrient dynamics in the basin.
Biogeosciences Discuss., 12, 5259-5291, doi:10.5194/bgd-12-5259-2015, 2015
The greenhouse gas balance of a drained fen peatland is mainly controlled by land-use rather than soil organic carbon content
Biogeosciences Discuss., 12, 5201-5258, doi:10.5194/bgd-12-5201-2015, 2015
Links between surface productivity and deep ocean particle flux at the Porcupine Abyssal Plain (PAP) sustained observatory
Summary: This study uses observations from both a mooring at the surface and a sediment trap at around 3000m in the northeast Atlantic. Observations of nitrogen and carbon are used to calculate the seasonal net community production (NCP) and new production, and we find that there is a larger uptake of carbon than would traditionally be expected. Only a small fraction of the surface production reaches the sediment trap, and using a particle-tracking approach we find that the source regions vary widely.
Biogeosciences Discuss., 12, 5169-5199, doi:10.5194/bgd-12-5169-2015, 2015
Air–sea CO2 fluxes in the East China Sea based on multiple-year underway observations
Biogeosciences Discuss., 12, 5123-5167, doi:10.5194/bgd-12-5123-2015, 2015
Predicting landscape-scale CO2 flux at a pasture and rice paddy with long-term hyperspectral canopy reflectance measurements
Summary: This research used a long-term dataset of near-surface canopy hyperspectral reflectance collected over five years to test the ability of these measurements to predict ecosystem carbon flux at a pasture and rice paddy in the California Delta, USA. We determined that each reflectance sampling event best captured the integrated prior week of carbon dioxide uptake, providing an important benchmark for understanding the lagged correlation between ecosystem carbon uptake and biochemical reflectance.
Biogeosciences Discuss., 12, 5079-5122, doi:10.5194/bgd-12-5079-2015, 2015
The oxygen isotope composition of phosphate released from phytic acid by the activity of wheat and Aspergillus niger phytase
Biogeosciences Discuss., 12, 5055-5077, doi:10.5194/bgd-12-5055-2015, 2015
Hydrologic controls on DOC, As and Pb export from a polluted peatland – the importance of heavy rain events, antecedent moisture conditions and hydrological connectivity
Biogeosciences Discuss., 12, 5015-5053, doi:10.5194/bgd-12-5015-2015, 2015
Optical sampling of the flux tower footprint
Summary: Optical sampling expands our understanding of the "breathing" of terrestrial ecosystems beyond what is possible by eddy covariance alone. The light-use efficiency (LUE) model provides a useful conceptual framework for integrating optical and CO2 flux measurements. Contrasting optical and flux behaviour can reveal distinct optical types that provide key information on flux controls. Practical applications include assessment of ecosystem health, productivity and biospheric carbon sequestration.
Biogeosciences Discuss., 12, 4973-5014, doi:10.5194/bgd-12-4973-2015, 2015
Response of key stress-related genes of the seagrass Posidonia oceanica in the vicinity of submarine volcanic vents
Summary: The effects of two marine volcanic vents, utilized as proxy of ocean acidification and global changes, are studied at molecular level in P. oceanica (seagrass). Stress-related genes (antioxidants and HSP) were differently activated in the two sites, at comparable CO2 levels. Metal detoxification genes were mostly down-regulated. This suggest that plants face different types of stressors and that factors other than CO2 and acidification, can cause stress to marine organisms near volcanic vents.
Biogeosciences Discuss., 12, 4947-4971, doi:10.5194/bgd-12-4947-2015, 2015
Macroalgae contribute to nested mosaics of pH variability in a sub-Arctic fjord
Summary: The Arctic Ocean is considered the most vulnerable ecosystem to ocean acidification (OA) but very little information is available on natural variability of pH in the Arctic coastal zone. We report pH-variability at various scales in a Greenland fjord. Variability ranged up to 0.2-0.3 pH units horizontally and vertically in the fjord, between seasons and on diel basis in kelp forests and was extreme in tidal pools. Overall, primary producers played a fundamental role in producing mosaics of pH.
Biogeosciences Discuss., 12, 4907-4945, doi:10.5194/bgd-12-4907-2015, 2015
Thermokarst-lake methanogenesis along a complete talik profile
Summary: The relative magnitude of thermokarst-lake CH4 production in surface sediments vs. deeper thawed permafrost is not well understood. We assessed CH4 production potentials from a lake sediment core and adjacent permafrost tunnel in interior Alaska. CH4 production was highest in the organic-rich surface lake sediments and recently-thawed permafrost at the bottom of the talik, implying CH4 production is highly variable and that both modern and ancient OM are important to lake CH4 production.
Biogeosciences Discuss., 12, 4865-4905, doi:10.5194/bgd-12-4865-2015, 2015
A model analysis of climate and CO2 controls on tree growth in a semi-arid woodland
Biogeosciences Discuss., 12, 4769-4800, doi:10.5194/bgd-12-4769-2015, 2015
Multi-molecular tracers of terrestrial carbon transfer across the pan-Arctic – Part 1: Comparison of hydrolysable components with plant wax lipids and lignin phenols
Summary: Currently very few studies have examined the distribution and fate of hydrolysable organic carbon (OC) in the arctic sediments, whose fate remains unclear in the context of climate change. Our study focuses on the source, distribution and fate of hydrolysable OC as compared with plant wax lipids and lignin phenols in the sediments of nine arctic and sub-arctic rivers. This multi-molecular approach allows a comprehensive investigation of terrestrial OC transfer via arctic rivers.
Biogeosciences Discuss., 12, 4721-4767, doi:10.5194/bgd-12-4721-2015, 2015
A large CO2 sink enhanced by eutrophication in a tropical coastal embayment (Guanabara Bay, Rio de Janeiro, Brazil)
Summary: Air-water fluxes of CO2 were monitored in Guanabara Bay (SE-Brazil), a tropical eutrophic coastal embayment. In contrast with other estuaries worldwilde, Guanabara Bay behaves as an annual sink of CO2 (-19.6 molC m2 yr), a property due to the concomitant effects of strong radiation intensity, thermal stratification, and high availability of nutrients which promotes massive phytoplankton development. The calculated annual CO2 sink matched the organic carbon burial reported in the literature.
Biogeosciences Discuss., 12, 4671-4720, doi:10.5194/bgd-12-4671-2015, 2015
Stable isotopes in barnacles as a tool to understand green sea turtle (Chelonia mydas) regional movement patterns
Summary: We report on the oxygen isotope signatures in green sea turtle (Chelonia mydas) barnacles (Platylepas sp.) to suggest likely regional movement patterns by mapping these onto a predictive oxygen isotope map of the Pacific. Discussing barnacle proxies potential relevance as an alternative tool with which to study green sea turtle migration, we find that these could complement traditional methods of studying connectivity between turtle populations and help inform more effective conservation policy.
Biogeosciences Discuss., 12, 4655-4669, doi:10.5194/bgd-12-4655-2015, 2015
Resilience to temperature and pH changes in a future climate change scenario in six strains of the polar diatom Fragilariopsis cylindrus
Summary: Climate change may not affect phytoplankton species as such, but may lead to changes in population structure of a species, with strains exhibiting high phenotypic plasticity dominating the population. Simulated climate scenarios showed that combined effects of increased temperature and acidification counterbalanced each other in the ecologically important model organism Fragilariopsis cylindrus. The variation among strains was larger than the variation observed due to the changes in parameters.
Biogeosciences Discuss., 12, 4627-4654, doi:10.5194/bgd-12-4627-2015, 2015
Water column biogeochemistry of oxygen minimum zones in the eastern tropical North Atlantic and eastern tropical South Pacific Oceans
Biogeosciences Discuss., 12, 4495-4556, doi:10.5194/bgd-12-4495-2015, 2015
Simultaneous high C fixation and high C emissions in Sphagnum mires
Summary: While pristine, growing peatlands are often considered to be net sinks of carbon dioxide (CO2), fluxes vary considerably and these systems can be net sinks or sources of CO2. To explain part of this huge variation, we here present a phenomenon of peat moss (Sphagnum) driven CO2 production. Due to the acid excreted by Sphagnum, bicarbonate in the surface water is transformed into CO2. Thus, while these systems have high CO2 fixation rates due to growing Sphagnum, they show a net emission of CO2.
Biogeosciences Discuss., 12, 4465-4494, doi:10.5194/bgd-12-4465-2015, 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
Chemical footprints of anthropogenic nitrogen deposition on recent soil C : N ratios in Europe
Summary: Spatial clustering of anthropogenic nitrogen deposition reveals that European C:N ratio varies more across soils of natural ecosystems with low pollution. It turns out that surprisingly only such soils are the most affected by nitrogen accumulation and therefore most responsive to short-term N supply. While an inverse correlation between atmospheric nitrogen and soil C:N seems intuitive, we provide novel insights into the real magnitude and spatial distribution of this relationship since 1880.
Biogeosciences Discuss., 12, 4315-4330, doi:10.5194/bgd-12-4315-2015, 2015
Seagrass meadows as a globally significant carbonate reservoir
Summary: There has been a growing interest in quantifying the capacity of seagrass ecosystems to act as carbon sinks as a natural way of offsetting anthropogenic carbon emissions to the atmosphere. However, most of the efforts have focused on the organic fraction and ignored the inorganic carbon pool. This study offers the first global assessment of the PIC stocks and accumulation rates in seagrass sediments, identifying these ecosystems as important contributors to carbonate dynamics in coastal areas.
Biogeosciences Discuss., 12, 4107-4138, doi:10.5194/bgd-12-4107-2015, 2015
Multiple soil nutrient competition between plants, microbes, and mineral surfaces: model development, parameterization, and example applications in several tropical forests
Biogeosciences Discuss., 12, 4057-4106, doi:10.5194/bgd-12-4057-2015, 2015
A new parameterization for surface ocean light attenuation in Earth System Models: assessing the impact of light absorption by colored detrital material
Summary: Light absorption by colored detrital material (CDM) was included in a fully coupled Earth System Model. Greater light limitation associated with CDM caused biological productivity to move higher up the water column, which increased surface chlorophyll and biomass. Concurrently, total biomass decreased leaving more nutrients in the water. Regional changes were analyzed by comparing the competing factors of diminished light availability and increased nutrient availability on phytoplankton growth.
Biogeosciences Discuss., 12, 3905-3942, doi:10.5194/bgd-12-3905-2015, 2015
Drivers and uncertainties of future global marine primary production in marine ecosystem models
Summary: We analyze changes of marine net primary production (NPP) and its drivers for the 21st century in 9 marine ecosystem models under the RCP8.5 scenario. NPP decreases in 5 models, increases in 1 model and 3 models show no significant trend. The main drivers include stronger nutrient limitation, but in many models warming-induced increases in phytoplankton growth outbalance the nutrient effect. Temperature-driven increases in grazing and other loss processes cause a net decrease in biomass and NPP.
Biogeosciences Discuss., 12, 3731-3824, doi:10.5194/bgd-12-3731-2015, 2015
Anthropogenic point and non-point nitrogen inputs into Huai River Basin and their impacts on riverine ammonia-nitrogen flux
Biogeosciences Discuss., 12, 3577-3615, doi:10.5194/bgd-12-3577-2015, 2015
Spatiotemporal patterns of tundra fires: late-Quaternary charcoal records from Alaska
Summary: Tundra fires may have increased as a result of anthropogenic climate change. To evaluate this hypothesis in the context of natural variability, we reconstructed fire history of the late Quaternary in the Alaskan tundra. Fire-return intervals are spatially variable, ranging from 1648 to 6045 years at our sites. The rarity of historical fires implies that increased fire frequency may greatly alter the structure and function of tundra ecosystems.
Biogeosciences Discuss., 12, 3177-3209, doi:10.5194/bgd-12-3177-2015, 2015
Fundamental molecules of life are pigments which arose and evolved to dissipate the solar spectrum
Summary: We show that the fundamental molecules of life (those common to all three domains of life; archea, bacteria, and eukaryote) including nucleotides, amino acids, enzyme cofactors, and porphyrin agglomerates, absorb light strongly from 230 to 280nm (in the UV-C) and have chemical affinity to RNA and DNA. This supports the "thermodynamic dissipation theory for the origin of life" which suggests that life and evolution got its start by dissipating the prevailing Archean UV-C sunlight into heat.
Biogeosciences Discuss., 12, 2101-2160, doi:10.5194/bgd-12-2101-2015, 2015
Phosphorus release capacity of soluble P fertilizers and insoluble rock phosphate in response to phosphate solubilizing bacteria and poultry manure and their effect on plant growth promotion and P utilization efficiency of chilli (Capsicum annuum L.)
Summary: P release capacity of soil amended with RP varied between 6.0–11.5mg kg-1 while the soluble P fertilizers i.e. SSP and DAP displayed a maximum of 73 and 68mg P kg-1 at the start of the experiment (day 0). However, the P released tendency from SSP and DAP declined during incubation and at the end 82 and 79% of P initially present had been lost from the mineral pool. Integrated use of PSB and PM with RP in ½RP+½PM+PSB treatment stimulated P mineralization by releasing a maximum of 25mg P kg-1.
Biogeosciences Discuss., 12, 1839-1873, doi:10.5194/bgd-12-1839-2015, 2015
Constraints on the applicability of the organic temperature proxies UK'37, TEX86 and LDI in the subpolar region around Iceland
Summary: This research reports a test the applicability of three organic-derived temperature proxies (UK'37, TEX86 and LDI) at high latitudes around Iceland. A range of samples including suspended particular material (SPM), trapped descending particles and surface sediments were collected for testing the different proxies in the water column and the sediment.The combination of three independent SST organic proxies provided important information about seasonality or differences in habitat depth.
Biogeosciences Discuss., 12, 1113-1153, doi:10.5194/bgd-12-1113-2015, 2015
Modeling the global emission, transport and deposition of trace elements associated with mineral dust
Summary: A new technique to determine a size-fractionated global soil elemental emission inventory based on a global soil and a mineralogical datasets is introduced. Spatial variability of mineral dust elemental fractions (8 elements such as Ca,Fe,Al ) is identified on a global scale, particularly for Ca. The ratio of Ca/Al, ranged between 0.1-5.0, and is confirmed as an indicator of dust source regions by global dust model. Total and soluble dust element fluxes into different ocean basins are estimated.
Biogeosciences Discuss., 11, 17491-17541, doi:10.5194/bgd-11-17491-2014, 2014
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
Environmental factors controlling lake diatom communities: a meta-analysis of published data
Summary: I re-analyze information published during the last decades concerning the effect of different environmental predictors on the structure of benthic diatom communities in world lakes, providing a scientific basis for the implementation of new paleoenvironmental inference models. I consider highly relevant the publication of this article in a widely known journal, provided the noticeable demand on paleolimnological meta-studies supporting the use of such biological proxies at a pancontinental scale
Biogeosciences Discuss., 11, 15889-15909, doi:10.5194/bgd-11-15889-2014, 2014