Controls on in situ oxygen and dissolved inorganic carbon dynamics in peats of a temperate fen

Abstract. The short-term fate of phytodetritus was investigated across the Pakistan margin of the Arabian Sea at water depths ranging from 140 to 1850 m, encompassing the oxygen minimum zone (~100–1100 m). Phytodetritus sedimentation events were simulated by adding ~44 mmol 13C-labelled algal material per m2 to surface sediments in retrieved cores. Cores were incubated in the dark, at in situ temperature and oxygen concentrations. Overlying waters were sampled periodically, and cores were recovered and sampled (for organisms and sediments) after durations of two and five days. The labelled carbon was subsequently traced into bacterial lipids, foraminiferan and macrofaunal biomass, and dissolved organic and inorganic pools. The majority of the label (20 to 100%) was in most cases left unprocessed in the sediment at the surface. The largest pool of processed carbon was found to be respiration (0 to 25% of added carbon), recovered as dissolved inorganic carbon. Both temperature and oxygen were found to influence the rate of respiration. Macrofaunal influence was most pronounced at the lower part of the oxygen minimum zone where it contributed 11% to the processing of phytodetritus.

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SPATIAL DISTRIBUTION OF DISSOLVED INORGANIC CARBON IN YAMATO RIVER AND ITS EFFECT ON CARBON DYNAMICS IN THE COASTAL ESTUARINE WATERS

Journal of Japan Society of Civil Engineers Ser B2 (Coastal Engineering) ◽

10.2208/kaigan.76.2_i_931 ◽

2020 ◽

Vol 76 (2) ◽

pp. I_931-I_936

Author(s):

Noriko HARADA ◽

Toru ENDO ◽

Tomoki SAIKI ◽

Tetsuji OKUDA ◽

Satoshi ASAOKA ◽

...

Keyword(s):

Spatial Distribution ◽

Inorganic Carbon ◽

Dissolved Inorganic Carbon ◽

Carbon Dynamics ◽

Estuarine Waters

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The responses of phytoplankton communities to elevated CO2 show seasonal variations in the highly eutrophic Lake Taihu

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/cjfas-2015-0151 ◽

2016 ◽

Vol 73 (5) ◽

pp. 727-736 ◽

Cited By ~ 8

Author(s):

Xiaoli Shi ◽

Xuhui Zhao ◽

Min Zhang ◽

Zhou Yang ◽

Ping Xu ◽

...

Keyword(s):

Inorganic Carbon ◽

Dissolved Inorganic Carbon ◽

Net Primary Production ◽

Lake Taihu ◽

High Growth ◽

Eutrophic Lake ◽

High Growth Rate ◽

Four Seasons ◽

Phytoplankton Communities

From April 2012 to January 2013 (over four seasons), in situ microcosm experiments were conducted in Lake Taihu, perturbed over a range of pCO2 scenarios (270, 380, and 750 μatm; 1 atm = 101.325 kPa). The influence of CO2 level on microcosms was greatest during the spring because of the high growth rate of phytoplankton. In this season, rising CO2 levels caused a pH reduction, and the maximum reduction was 0.6 units when CO2 level was enhanced from the present level to 750 μatm. The doubling of CO2 level could increase the net primary production (NPP) by 65% during spring when the concentrations of other nutrients were maintained. The rise of NPP could cause a decline of dissolved inorganic carbon (DIC) concentration, and CO2 enrichment might mitigate the extent of this decline. Meanwhile, higher CO2 may slow or prevent a loss of diversity of phytoplankton in microcosms in this season. During the other three seasons, Microcystis predominated, and the percentage of cyanobacteria did not alter with the change of CO2. We did not observe a significant increase in the abundance of any taxa with the rise of CO2 during the in situ microcosm experiments.

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Estimates of ikaite export from sea ice to the underlying seawater in a sea ice–seawater mesocosm

The Cryosphere ◽

10.5194/tc-10-2173-2016 ◽

2016 ◽

Vol 10 (5) ◽

pp. 2173-2189 ◽

Cited By ~ 10

Author(s):

Nicolas-Xavier Geilfus ◽

Ryan J. Galley ◽

Brent G. T. Else ◽

Karley Campbell ◽

Tim Papakyriakou ◽

...

Keyword(s):

Sea Ice ◽

Water Column ◽

Inorganic Carbon ◽

Dissolved Inorganic Carbon ◽

Carbon Dynamics ◽

Total Alkalinity ◽

Main Process ◽

Saturation State ◽

Ice Growth ◽

Ice Melt

Abstract. The precipitation of ikaite and its fate within sea ice is still poorly understood. We quantify temporal inorganic carbon dynamics in sea ice from initial formation to its melt in a sea ice–seawater mesocosm pool from 11 to 29 January 2013. Based on measurements of total alkalinity (TA) and total dissolved inorganic carbon (TCO2), the main processes affecting inorganic carbon dynamics within sea ice were ikaite precipitation and CO2 exchange with the atmosphere. In the underlying seawater, the dissolution of ikaite was the main process affecting inorganic carbon dynamics. Sea ice acted as an active layer, releasing CO2 to the atmosphere during the growth phase, taking up CO2 as it melted and exporting both ikaite and TCO2 into the underlying seawater during the whole experiment. Ikaite precipitation of up to 167 µmolkg−1 within sea ice was estimated, while its export and dissolution into the underlying seawater was responsible for a TA increase of 64–66 µmolkg−1 in the water column. The export of TCO2 from sea ice to the water column increased the underlying seawater TCO2 by 43.5 µmolkg−1, suggesting that almost all of the TCO2 that left the sea ice was exported to the underlying seawater. The export of ikaite from the ice to the underlying seawater was associated with brine rejection during sea ice growth, increased vertical connectivity in sea ice due to the upward percolation of seawater and meltwater flushing during sea ice melt. Based on the change in TA in the water column around the onset of sea ice melt, more than half of the total ikaite precipitated in the ice during sea ice growth was still contained in the ice when the sea ice began to melt. Ikaite crystal dissolution in the water column kept the seawater pCO2 undersaturated with respect to the atmosphere in spite of increased salinity, TA and TCO2 associated with sea ice growth. Results indicate that ikaite export from sea ice and its dissolution in the underlying seawater can potentially hamper the effect of oceanic acidification on the aragonite saturation state (Ωaragonite) in fall and in winter in ice-covered areas, at the time when Ωaragonite is smallest.

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