Changes of the forest-savanna boundary in Brazilian Amazonia during the Holocene revealed by stable isotope ratios of soil organic carbon

Oecologia ◽  
1996 ◽  
Vol 108 (4) ◽  
pp. 749-756 ◽  
Author(s):  
T. Desjardins ◽  
A. C. Filho ◽  
A. Mariotti ◽  
C. Girardin ◽  
A. Chauvel
Keyword(s):  
Stable Isotope ◽  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Isotope Ratios ◽  
Stable Isotope Ratios ◽  
The Holocene ◽  
Brazilian Amazonia

Organic carbon stable isotope ratios of continental margin sediments

1977 ◽  
Vol 5 (3) ◽  
pp. 251-266 ◽  
Author(s):  
Patrick Gearing ◽  
Frank E. Plucker ◽  
P.L. Parker
Keyword(s):  
Stable Isotope ◽  
Organic Carbon ◽  
Continental Margin ◽  
Isotope Ratios ◽  
Stable Isotope Ratios ◽  
Carbon Stable Isotope

Novel insights into the origin of dissolved organic carbon in the Sunda Shelf Sea using stable isotope ratios of hydrogen (d2H) and carbon (d13C). 

2021 ◽  
Author(s):  
Nikita Kaushal ◽  
Cristian Gudasz ◽  
Yongli Zhou ◽  
Adriana Lopes dos Santos ◽  
Avneet Kaur ◽  
...  
Keyword(s):  
Organic Matter ◽  
Stable Isotope ◽  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Isotope Ratios ◽  
Southwest Monsoon ◽  
Coastal Ocean ◽  
Stable Isotope Ratios ◽  
Sunda Shelf ◽  
Shelf Sea

<p>Rivers deliver ~0.25 Pg C year<sup>-1</sup> of terrigenous dissolved organic carbon (tDOC) from land to shelf seas. As tDOC moves along the river, coastal ocean and deep ocean continuum, it undergoes complex biogeochemical processing that results in both chemical alteration and remineralisation. Remineralisation of tDOC to CO<sub>2 </sub>can contribute significantly to coastal ocean acidification and CO<sub>2</sub> emissions to the atmosphere. Our understanding of tDOC processing in coastal seas is still limited, in part because it is challenging to distinguish between marine and terrigenous DOC. The stable carbon isotope ratios (d<sup>13</sup>C) of the dissolved inorganic and organic carbon pools are commonly used to quantify tDOC, because terrestrial vegetation is typically more isotopically depleted (-32 to -25 ‰) compared to marine organic carbon (-24 to -20 ‰). However, this relatively small difference between the marine and terrigenous end-members can introduce large uncertainties in d<sup>13</sup>C-based estimates, particularly if tDOC originates from both C3 and C4 vegetation. End-member isotope ratio values with larger separation could potentially help to better quantify tDOC. Recent studies in freshwater ecosystems have shown that the stable isotope ratios (d<sup>2</sup>H) of the carbon bound non-exchangeable hydrogen fraction of dissolved organic matter (DOM) typically differs by more than 50 ‰ between terrestrially derived and aquatically derived dissolved organic matter. However, d<sup>2</sup>H has not yet been used as a tracer for tDOC in marine environments.</p><p>Here, we present results from a one year-long monthly time series of δ<sup>13</sup>C and δ<sup>2</sup>H at a coastal location in Southeast Asia’s Sunda Shelf Sea, where the southwest monsoon delivers a seasonal input of tDOC from tropical peatlands on Sumatra. We found that δ<sup>2</sup>H of solid-phase extracted DOM, as measured after dual water steam equilibration, ranged between -130 to ­­-150 ‰ during the southwest monsoon, but between -160 to -167 ‰ during other months. Fresh tDOC from peatland-draining rivers had values close to -100‰, and decreased somewhat upon partial photodegradation, while DOM produced in plankton enrichment cultures had values around -174‰. Values of d<sup>13</sup>C of DOC ranged from -25.5 to -23.0 ‰ during the southwest monsoon, and between -23.0 to -21.0 ‰ at other times. We will present preliminary mass balance calculations to estimate tDOC concentrations based on δ<sup>13</sup>C and δ<sup>2</sup>H. Our results suggest that δ<sup>2</sup>H can be a sensitive tracer of tDOC in the marine environment.</p>

Effects of oyster age on selective suspension-feeding and the chemical composition of biodeposits: insights from fatty acid analysis

2020 ◽  
Vol 644 ◽  
pp. 75-89
Author(s):  
T Sakamaki ◽  
K Hayashi ◽  
Y Zheng ◽  
M Fujibayashi ◽  
O Nishimura
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Stable Isotope ◽  
Organic Carbon ◽  
Isotope Ratios ◽  
The Body ◽  
Stable Isotope Ratios ◽  
Suspension Feeding ◽  
Carbon And Nitrogen ◽  
Body Tissues

The study objective was to clarify how the growth stages of the Pacific oyster Crassostrea gigas affect selective suspension-feeding of particulate organic matter (POM) and the composition of biodeposits. A day-long (22 h), continuous-flow mesocosm experiment was conducted with 3, 15, and 27 mo old oysters. The suspended particulate matter (PM), settled PM (mostly biodeposits in the oyster mesocosms), and oyster soft tissues were analysed to determine the content of fatty acids, organic carbon, and nitrogen, as well as the carbon and nitrogen stable isotope ratios to trace compositional changes in POM through oyster biodeposition. Regardless of oyster age, the stable isotope ratios of biodeposits were similar to those of the body tissues but not to those of the suspended PM, indicating that oysters selectively fed on assimilable fractions of POM. Compared with the suspended PM, a higher concentration of long-chain polyunsaturated fatty acids was found in the body tissues and, consequently, in the biodeposits; in contrast, the concentrations of shorter-chain fatty acids were generally lower in the biodeposits. Furthermore, the biodeposits produced by the older oysters had higher carbon, nitrogen, and fatty acid contents compared with the biodeposits produced by the 3 mo old oysters. The oxygen consumption rate of biodeposits was positively related to organic carbon content, but less so to fatty acid composition. Our findings demonstrate that older oysters not only produce larger amounts of biodeposits, but that these biodeposits have higher organic and fatty acid contents, potentially exhibiting greater effects on biogeochemical and ecological processes in nearby benthic habitats.

TRANSFER EFFICIENCY FROM PRIMARY PRODUCERS TO RUDITAPES PHILIPPINARUM ON AN INTERTIDAL FLAT IN HIROSHIMA BAY, JAPAN

2017 ◽  
Author(s):  
Sosuke Otani ◽  
Sosuke Otani ◽  
Akira Umehara ◽  
Akira Umehara ◽  
Haruka Miyagawa ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Secondary Production ◽  
Isotope Ratios ◽  
Ruditapes Philippinarum ◽  
Transfer Efficiency ◽  
Food Sources ◽  
Stable Isotope Ratios ◽  
Primary Producers ◽  
Nitrogen Stable Isotope ◽  
Carbon And Nitrogen

Fish yields of Ruditapes philippinarum have been decreased and the resources have not yet recovered. It needs to clarify food sources of R. philippinarum, and relationship between primary and secondary production of it. The purpose on this study is to reveal transfer efficiency from primary producers to R. philippinarum and food sources of R. philippinarum. The field investigation was carried out to quantify biomass of R. philippinarum and primary producers on intertidal sand flat at Zigozen beach in Hiroshima Bay, Japan. In particular, photosynthetic rates of primary producers such as Zostera marina, Ulva sp. and microphytobenthos were determined in laboratory experiments. The carbon and nitrogen stable isotope ratios for R. philippinarum and 8 potential food sources (microphytobenthos, MPOM etc) growing in the tidal flat were also measured. In summer 2015, the primary productions of Z. marina, Ulva sp. and microphytobenthos were estimated to be 70.4 kgC/day, 43.4 kgC/day and 2.2 kgC/day, respectively. Secondary production of R. philippinarum was 0.4 kgC/day. Contribution of microphytobenthos to R. philippinarum as food source was 56-76% on the basis of those carbon and nitrogen stable isotope ratios. Transfer efficiency from microphytobenthos to R. philippinarum was estimated to be 10-14%. It was suggested that microphytobenthos might sustain the high secondary production of R. philippinarum, though the primary production of microphytobenthos was about 1/10 compared to other algae.

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