scholarly journals Recycling and fluxes of carbon gases in a stratified boreal lake following experimental carbon addition

2014 ◽  
Vol 11 (11) ◽  
pp. 16447-16495 ◽  
Author(s):  
H. Nykänen ◽  
S. Peura ◽  
P. Kankaala ◽  
R. I. Jones
Keyword(s):  
Organic Carbon ◽  
Water Column ◽  
Dissolved Inorganic Carbon ◽  
Stable Carbon Isotope ◽  
Boreal Lakes ◽  
Co2 Production ◽  
Strength Increase ◽  
Humic Lakes ◽  
Ch4 Oxidation ◽  
Anoxic Layer

Abstract. Partly anoxic stratified humic lakes are important sources of methane (CH4) and carbon dioxide (CO2) to the atmosphere. We followed the fate of CH4 and CO2 in a small boreal stratified lake, Alinen Mustajärvi, during 2007–2009. In 2008 and 2009 the lake received additions of dissolved organic carbon (DOC) with stable carbon isotope ratio (δ13C) around 16‰ higher than that of local allochthonous DOC. Carbon transformations in the water column were studied by measurements of δ13C of CH4 and of the dissolved inorganic carbon (DIC). Furthermore, CH4 and CO2 production, consumption and emissions were estimated. Methane oxidation was estimated by a diffusion gradient method. The amount, location and δ13C of CH4-derived biomass and CO2 in the water column were estimated from the CH4 oxidation pattern and from measured δ13C of CH4. Release of CH4 and CO2 to the atmosphere increased during the study. Methane production and almost total consumption of CH4 mostly in the anoxic water layers, was equivalent to the input from primary production (PP). δ13C of CH4 and DIC showed that hydrogenotrophic methanogenesis was the main source of CH4 to the water column, and methanogenic processes in general were the reasons for the 13C-enriched DIC at the lake bottom. CH4 and DIC became further 13C-enriched in the anoxic layer of the water column during the years of DOC addition. Even gradient diffusion measurements showed active CH4 oxidation in the anoxic portion of the water column; there was no clear 13C-enrichment of CH4 as generally used to estimate CH4 oxidation strength. Increase in δ13C-CH4 was clear between the metalimnion and epilimnion where the concentration of dissolved CH4 and the oxidation of CH4 were small. Thus, 13C-enrichment of CH4 does not reveal the main location of methanotrophy in a lake having simultaneous anaerobic and aerobic oxidation of CH4. Overall the results show that organic carbon is processed efficiently to CH4 and CO2 and recycled in the anoxic layer of stratified boreal lakes by CH4 oxidation. In spite of this, increased DOC input led to increased greenhouse gas release, mainly as CO2 but also as CH4. Due to the predominantly anaerobic CH4 oxidation, a relatively small amount of CH4-derived biomass was produced, while a large amount of CH4-derived CO2 was produced in the anoxic bottom zone of the lake.

scholarly journals Importance of intertidal sediment processes and porewater exchange on the water column biogeochemistry in a pristine mangrove creek (Ras Dege, Tanzania)

2007 ◽  
Vol 4 (1) ◽  
pp. 317-348 ◽  
Author(s):  
S. Bouillon ◽  
J. J. Middelburg ◽  
F. Dehairs ◽  
A. V. Borges ◽  
G. Abril ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Water Column ◽  
Driving Forces ◽  
Dissolved Inorganic Carbon ◽  
High Tide ◽  
Particulate Material ◽  
Marine Phytoplankton ◽  
Intertidal Sediment ◽  
Freshwater Inputs ◽  
Tidal Variations

Abstract. We conducted diurnal sampling in a tidal creek (Ras Dege, Tanzania) to document the variations in a suite of creek water column characteristics and to determine the relative influence of tidal and biological driving forces. Since the creek has no upstream freshwater inputs, highest salinity was observed at low tide, due to evaporation effects and porewater seepage. Total suspended matter (TSM) and particulate organic carbon (POC) showed distinct maxima at periods of highest water flow, indicating that erosion of surface sediments and/or resuspension of bottom sediments were an important source of particulate material. Dissolved organic carbon (DOC), in contrast, followed the tidal variations and was highest at low tide. Stable isotope data of POC and DOC exhibit large variations in both pools, and followed tidal variations. Although the variation of δ13CDOC (−23.8 to −13.8‰) was higher than that of δ13CPOC (−26.2 to −20.5‰) due to the different end-member pool sizes, the δ13C signatures of both pools differed only slightly at low tide, but up to 9‰ at high tide. Thus, at low tide both DOC and POC originated from mangrove production. At high tide, on the other hand, the DOC pool had signatures consistent with a high contribution of seagrass-derived material, whereas the POC pool was dominated by marine phytoplankton. Daily variations in CH4, and partial pressure of CO2 (pCO2) were similarly governed by tidal influence and were up to 7- and 10-fold higher at low tide, which stresses the importance of exchange of porewater and diffusive fluxes to the water column. Furthermore, this illustrates that constraining an ecosystem-level budget of these greenhouse gases in tidal systems requires a careful appraisal of tidal variations. When assuming that the high dissolved inorganic carbon (DIC) levels in the upper parts of the creek (i.e. at low tide) are due to inputs from mineralization, δ13C data on DIC indicate that the source of the mineralized organic matter has a signature of −22.4‰, which shows that imported POC and DOC from the marine environment contributes strongly to overall mineralization within the mangrove system. Our data show a striking example of how biogeochemical processes in the intertidal zone appear to be prominent drivers of element concentrations and isotope signatures in the water column, and how pathways of dissolved and particulate matter exchange are fundamentally different. The estimated export of DIC through porewater exchange appears considerably larger than for DOC, suggesting that if this mechanism is indeed a major driver of solute exchange, benthic mineralization and subsequent export as DIC could represent a very significant and previously unaccounted fate of mangrove-derived C. Budgeting efforts should therefore pay attention to understanding the mechanisms and quantification of different pathways of exchange within and between both zones.

The Behavior of 14C and 13C in Estuarine Water: Effects of In Situ CO2 Production and Atmospheric Exchange

Radiocarbon ◽  
1980 ◽  
Vol 22 (3) ◽  
pp. 647-654 ◽  
Author(s):  
Elliott C Spiker
Keyword(s):  
Chesapeake Bay ◽  
Water Column ◽  
San Francisco ◽  
Dissolved Inorganic Carbon ◽  
San Francisco Bay ◽  
Co2 Production ◽  
Carbon Utilization ◽  
Model Calculations ◽  
Dominant Source ◽  
Atmospheric Exchange

The effects of nonconservative sources (inputs) and sinks (outputs) of carbon are indicated by the behavior of Δ14C and δ13C of the total dissolved inorganic carbon (ΣCO2) in San Francisco Bay and Chesapeake Bay. Isotopic distributions and model calculations indicate that in North San Francisco Bay the net CO2 flux to the atmosphere and carbon utilization in the water column are balanced by benthic production. Municipal waste appears to be a dominant source in South San Francisco Bav. In Chesapeake Bay, atmospheric exchange has increased the Δ14C and δ13C in the surface water. Decomposition of organic matter in the water column is indicated to be the dominant source of excess ΣCO2 in the deep water.

scholarly journals Methane oxidation in the waters of a humic-rich boreal lake stimulated by photosynthesis, nitrite, Fe(III) and humics

2021 ◽  
Vol 18 (10) ◽  
pp. 3087-3101
Author(s):  
Sigrid van Grinsven ◽  
Kirsten Oswald ◽  
Bernhard Wehrli ◽  
Corinne Jegge ◽  
Jakob Zopfi ◽  
...  
Keyword(s):  
Water Column ◽  
Methane Oxidation ◽  
Water Concentration ◽  
Eutrophic Lake ◽  
Boreal Lakes ◽  
Ch4 Oxidation ◽  
Anoxic Water ◽  
Ch4 Emissions ◽  
Oxidation Rates ◽  
Incubation Experiments

Abstract. Small boreal lakes are known to contribute significantly to global CH4 emissions. Lake Lovojärvi is a eutrophic lake in southern Finland with bottom water CH4 concentrations up to 2 mM. However, the surface water concentration, and thus the diffusive emission potential, was low (< 0.5 µM). We studied the biogeochemical processes involved in CH4 removal by chemical profiling and through incubation experiments. δ13C-CH4 profiling of the water column revealed a methane-oxidation hotspot just below the oxycline and zones of CH4 oxidation within the anoxic water column. In incubation experiments involving the addition of light and/or oxygen, CH4 oxidation rates in the anoxic hypolimnion were enhanced 3-fold, suggesting a major role for photosynthetically fueled aerobic CH4 oxidation. We observed a distinct peak in CH4 concentration at the chlorophyll-a maximum, caused by either in situ CH4 production or other CH4 inputs such as lateral transport from the littoral zone. In the dark anoxic water column at 7 m depth, nitrite seemed to be the key electron acceptor involved in CH4 oxidation, yet additions of Fe(III), anthraquinone-2,6-disulfonate and humic substances also stimulated anoxic CH4 oxidation. Surprisingly, nitrite seemed to inhibit CH4 oxidation at all other depths. Overall, this study shows that photosynthetically fueled CH4 oxidation can be a key process in CH4 removal in the water column of humic, turbid lakes, thereby limiting diffusive CH4 emissions from boreal lakes. Yet, it also highlights the potential importance of a whole suite of alternative electron acceptors, including humics, in these freshwater environments in the absence of light and oxygen.

scholarly journals Carbon Cycling and Organic Radiocarbon Reservoir Effect in a Meromictic Crater Lake (Lac Pavin, Puy-de-Dôme, France)

Radiocarbon ◽  
2013 ◽  
Vol 55 (2) ◽  
pp. 1029-1042 ◽  
Author(s):  
Patrick Albéric ◽  
Didier Jézéquel ◽  
Laurent Bergonzini ◽  
Emmanuel Chapron ◽  
Eric Viollier ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Water Column ◽  
Surface Waters ◽  
Crater Lake ◽  
Dissolved Inorganic Carbon ◽  
Organic Production ◽  
Data Set ◽  
Radiocarbon Dates ◽  
Reservoir Effect ◽  
Sediment Layers

Lac Pavin is a meromictic maar lake for which the interpretation of sediment radiocarbon dates is complicated by the existence of a largely undefined reservoir effect resulting from degradation of carbon stored in the bottom layer of the water column. A data set of the contemporary 14C distribution of dissolved and particulate organic pools in the water column is presented to address this issue. Dissolved inorganic carbon (DIC) and organic carbon (DOC), plankton, suspended particulate organic carbon (POCsusp), sinking POC (POCsink), and bottom sediment organic carbon (SOC) were analyzed. Present-day Δ14C values of DIC were measured ranging from −750′ in the monimolimnion to atmospheric values in lake surface waters and in spring inlet waters. A range of Δ14C values between −200 and −300′ was observed for superficial POCsusp, POCsink, SOC, and DOC. This relatively uniform 14C offset of the exported organic production from the surface waters to the bottom represents a contemporary reservoir effect of ∼2500 yr. Laminated buried sediment samples and terrestrial vegetal macro-remains were used to evaluate temporal reservoir effect variations since the formation of the crater lake (7 ka cal BP). Buried sediment layers presented a similar offset or showed larger differences between Δ14C values of bulk sediment and terrestrial plant remains (–400 to −500′). Furthermore, an almost 0-yr reservoir effect was inferred from the sediment layers deposited just above the volcanic bedrock at the early flooding of the crater, and increasing slightly within the first centuries of the lake's history. A second objective was to tentatively model a defined scenario of the cycling of carbon in the lake capable of predicting a modern reservoir effect. Alternative scenarios were then tested for which a larger contribution of deeper DIC would provide a model compatible with larger past reservoir effects. It is concluded that using Δ14C SOC variation in laminated lake sediments as a proxy of paleolimnological conditions may be valuable provided that more data on the dynamics of the 14C composition of plankton and more detailed sampling of laminated sediment layers are available.

Variability of ocean stratification, sea ice coverage and bioproduction off NE Greenland in the Late Glacial to Holocene reconstructed from planktic foraminifer morphotypes

2020 ◽  
Author(s):  
Robert F. Spielhagen ◽  
Andreas Mackensen
Keyword(s):  
Organic Carbon ◽  
Water Column ◽  
Dissolved Inorganic Carbon ◽  
Greenland Ice Sheet ◽  
Late Glacial ◽  
Laminated Sediments ◽  
The Arctic ◽  
Migration Activity ◽  
Near Surface ◽  
Ice Coverage

&lt;p&gt;We use stable isotope data from different morphotypes of the polar species Neogloboquadrina pachyderma in a sediment core from the NE Greenland continental margin (79&amp;#176;N) as proxies for the variability of salinity, ice coverage, and bioproductivity/carbon fluxes. Stable oxygen and carbon isotopes (d&lt;sup&gt;18&lt;/sup&gt;O, d&lt;sup&gt;13&lt;/sup&gt;C) were measured on both thin- and thick shelled specimens of planktic foraminifers N. pachyderma. Since this species is known to attain the thick carbonate crust of adult specimens in deeper water, the isotopic difference between thick-shelled (morphotypes 1 and 2, according to Eynaud, 2011) and thin-shelled specimens (morphotypes 4 and 5) is proposed to reflect the salinity difference between subsurface and near-surface waters. In Late Glacial sediments only minor d&lt;sup&gt;18&lt;/sup&gt;O differences between the morphotypes suggest an upper water mass structure with only minor salinity differences. The high d&lt;sup&gt;13&lt;/sup&gt;C difference of &gt;0.5&amp;#8240; is ascribed to strong quantitative differences in the decomposition of isotopically light organic carbon within the upper water column (likely from intense ice coverage and reduced bioproductivity) which precludes that the d&lt;sup&gt;18&lt;/sup&gt;O similarities merely result from a reduced vertical migration activity of the foraminifers. After 13 ka, a series of d&lt;sup&gt;18&lt;/sup&gt;O spikes (amplitudes &gt;1.5&amp;#8240; in morphotypes 4/5) preserved in laminated sediments reflects a strong freshwater event at the NE Greenland margin, likely related to the export of freshwater from the Arctic Ocean and/or the decay of the nearby outer Greenland Ice Sheet. Within these spikes, d&lt;sup&gt;18&lt;/sup&gt;O and d&lt;sup&gt;13&lt;/sup&gt;C differences of N. pachyderma morphotypes reach maximum values, pointing at extreme salinity differences in the upper few hundred meters of the water column and likely high portions of isotopically light dissolved inorganic carbon from terrestrial sources (meltwater). In the Holocene, d&lt;sup&gt;18&lt;/sup&gt;O differences are reduced to ca. 0.5&amp;#8240; and relatively low d&lt;sup&gt;13&lt;/sup&gt;C differences may indicate an activity of organic carbon decomposition reaching significantly deeper in the water column than in the glacial and deglacial, possibly related to a more open ice cover, enhanced bioproduction and higher C fluxes.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Reference&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;Eynaud, F., 2011. Planktonic foraminifera in the Arctic: potentials and issues regarding modern and quaternary populations. IOP Conf. Series, Earth and Environmental Science 14, 012005, doi:10.1088/1755-1315/14/1/012005&lt;/p&gt;

Sources of Dissolved Inorganic Carbon in Two Small Streams with Different Bedrock Geology: Insights from Carbon Isotopes

Radiocarbon ◽  
2015 ◽  
Vol 57 (3) ◽  
pp. 439-448 ◽  
Author(s):  
Naoto F Ishikawa ◽  
Ichiro Tayasu ◽  
Masako Yamane ◽  
Yusuke Yokoyama ◽  
Saburo Sakai ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Carbon Cycling ◽  
Carbonate Rock ◽  
Dissolved Inorganic Carbon ◽  
Stable Carbon Isotope ◽  
The Other ◽  
Biological Degradation ◽  
Small Streams ◽  
Limestone Bedrock

Radiocarbon natural abundances (Δ14C) are being increasingly used to trace carbon cycling in stream ecosystems. To understand the ultimate sources of carbon, we determined the stable carbon isotope ratios (δ13C) and Δ14C values of dissolved inorganic and organic carbon (DIC and DOC, respectively) and of particulate organic carbon (POC) in two small streams in central Japan, one of which flows over limestone bedrock (Seri) and the other does not (Fudoji). Investigations over four seasons revealed that the Δ14C values of the DIC (from −238‰ to −174‰ for Seri and −23‰ to +10‰ for Fudoji) were less variable than those of the other carbon fractions (DOC: from −400‰ to −138‰ for Seri and −2‰ to +103‰ for Fudoji; POC: from −164‰ to −60‰ for Seri and −55‰ to +37‰ for Fudoji). Based on mass balance calculations using the δ13C and Δ14C values, the proportions of carbon in the DIC originated from (1) atmospheric CO2 were 47% to 57% for Seri and 74% to 90% for Fudoji, (2) organic matter degradation were 29% to 35% for Seri and 4% to 21% for Fudoji, and (3) carbonate rock were 14% to 22% for Seri and 4% to 6% for Fudoji. We compared the results with previous studies that had been conducted in larger rivers and showed that in small streams, the dissolution of atmospheric CO2 and weathering of carbonate rock are more important factors in the carbon cycling than the biological degradation of organic matter.

scholarly journals Organic carbon production, mineralization and preservation on the Peruvian margin

2014 ◽  
Vol 11 (9) ◽  
pp. 13067-13126 ◽  
Author(s):  
A. W. Dale ◽  
S. Sommer ◽  
U. Lomnitz ◽  
I. Montes ◽  
T. Treude ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Water Column ◽  
Water Depth ◽  
Dissolved Inorganic Carbon ◽  
Sediment Accumulation ◽  
Inner Shelf ◽  
Global Database ◽  
Carbon Burial ◽  
Organic Carbon Burial

Abstract. Carbon cycling in Peruvian margin sediments (11° S and 12° S) was examined at 16 stations from 74 m on the inner shelf down to 1024 m water depth by means of in situ flux measurements, sedimentary geochemistry and modeling. Bottom water oxygen was below detection limit down to ca. 400 m and increased to 53 μM at the deepest station. Sediment accumulation rates and benthic dissolved inorganic carbon fluxes decreased rapidly with water depth. Particulate organic carbon (POC) content was lowest on the inner shelf and at the deep oxygenated stations (< 5%) and highest between 200 and 400 m in the oxygen minimum zone (OMZ, 15–20%). The organic carbon burial efficiency (CBE) was unexpectedly low on the inner shelf (< 20%) when compared to a global database, for reasons which may be linked to the frequent ventilation of the shelf by oceanographic anomalies. CBE at the deeper oxygenated sites was much higher than expected (max. 81%). Elsewhere, CBEs were mostly above the range expected for sediments underlying normal oxic bottom waters, with an average of 51 and 58% for the 11° S and 12° S transects, respectively. Organic carbon rain rates calculated from the benthic fluxes alluded to a very efficient mineralization of organic matter in the water column, with a Martin curve exponent typical of normal oxic waters (0.88 ± 0.09). Yet, mean POC burial rates were 2–5 times higher than the global average for continental margins. The observations at the Peruvian margin suggest that a lack of oxygen does not affect the degradation of organic matter in the water column but promotes the preservation of organic matter in marine sediments.

Seasonal variations of dominant phytoplankton in humic forest lakes

2007 ◽  
Vol 36 (2) ◽  
Author(s):  
Tomasz Joniak
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Water Column ◽  
Humic Substances ◽  
Community Composition ◽  
Seasonal Variations ◽  
Humic Lakes ◽  
Forest Lakes ◽  
Dissolved Humic Substances

Seasonal variations of dominant phytoplankton in humic forest lakesThis work presents the community composition, abundance and seasonal dominance of phytoplankton taxa in three hydrochemically different, mid-forest humic lakes. The largest number of taxa was observed in the oligohumic lake (76), with smaller numbers seen in the mesohumic (42) and polyhumic lakes (37), which were characterized by higher contents of dissolved humic substances carbon (DHSC). Along an increasing gradient of DHSC in a pool of dissolved organic carbon (DOC) the autotrophic algae were seen to disappear, being replaced by taxa with features of facultative heterotrophs and flagellated algae that are able to move in the water column.

scholarly journals Importance of intertidal sediment processes and porewater exchange on the water column biogeochemistry in a pristine mangrove creek (Ras Dege, Tanzania)

2007 ◽  
Vol 4 (3) ◽  
pp. 311-322 ◽  
Author(s):  
S. Bouillon ◽  
J. J. Middelburg ◽  
F. Dehairs ◽  
A. V. Borges ◽  
G. Abril ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Water Column ◽  
Driving Forces ◽  
Dissolved Inorganic Carbon ◽  
High Tide ◽  
Particulate Material ◽  
Marine Phytoplankton ◽  
Intertidal Sediment ◽  
Matter Transport ◽  
Water Height

Abstract. We sampled a tidal creek (Ras Dege, Tanzania) during a 24-h cycle to document the variations in a suite of creek water column characteristics and to determine the relative influence of tidal and biological driving forces. Since the creek has no upstream freshwater inputs, highest salinity was observed at low tide, due to evaporation effects and porewater seepage. Total suspended matter (TSM) and particulate organic carbon (POC) showed distinct maxima at periods of highest water flow, indicating that erosion of surface sediments and/or resuspension of bottom sediments were an important source of particulate material. Dissolved organic carbon (DOC), in contrast, varied in phase with water height and was highest at low tide. Stable isotope data of POC and DOC displayed large variations in both pools, and similarly followed the variations in water height. Although the variation of δ13CDOC (−23.8 to −13.8‰) was higher than that of δ13CPOC (−26.2 to −20.5‰), due to the different end-member pool sizes, the δ13C signatures of both pools differed only slightly at low tide, but up to 9‰ at high tide. Thus, at low tide both DOC and POC originated from mangrove production. At high tide, however, the DOC pool had signatures consistent with a high contribution of seagrass-derived material, whereas the POC pool was dominated by marine phytoplankton. Daily variations in CH4, and partial pressure of CO2 (pCO2) were similarly governed by tidal influence and were up to 7- and 10-fold higher at low tide, which stresses the importance of exchange of porewater and diffusive fluxes to the water column. When assuming that the high dissolved inorganic carbon (DIC) levels in the upper parts of the creek (i.e. at low tide) are due to inputs from mineralization, δ13C data on DIC indicate that the organic matter source for mineralization had a signature of −22.4‰. Hence, imported POC and DOC from the marine environment contributes strongly to overall mineralization within the mangrove system. Our data demonstrate how biogeochemical processes in the intertidal zone appear to be prominent drivers of element concentrations and isotope signatures in the water column, and how pathways of dissolved and particulate matter transport are fundamentally different.

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