Climatology and trends of Dissolved Organic Carbon in coastal waters off Sarawak, Borneo

2020 ◽  
Author(s):  
Nivedita Sanwlani ◽  
Patrick Martin ◽  
Nagur Cherukuru ◽  
Moritz Muller ◽  
Christopher Evans
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Coastal Waters ◽  
Distribution Patterns ◽  
Northeast Monsoon ◽  
Study Region ◽  
South West Monsoon ◽  
Ocean Carbon ◽  
Carbon Store

<p>South-East Asian peatlands are a globally significant carbon store. Rivers draining these peatlands have some of the highest dissolved organic carbon (DOC) concentrations in the world and account for up to 10% of the global land-to-ocean carbon flux, thus representing an important input to the marine carbon cycle. The release of DOC from peatlands is a natural process, yet the rapid and extensive transformation of these peatlands for agriculture over the past two decades is thought to have increased fluvial carbon losses significantly. However, not only do we lack a firm understanding of the fate of this terrigenous DOC in tropical seas, the distribution and long-term variability in DOC have never been studied at large scales in SE Asia. We will present the seasonal climatology (2002-2018) of spatial distribution patterns of DOC concentrations and optical properties (absorption coefficients, spectral slope) of colored dissolved organic matter (CDOM) for coastal waters of Sarawak, Malaysian Borneo derived using a regionally tailored semi-analytical inversion model from MODIS Aqua. Our results reveal substantial inputs of DOC from Sarawak rivers DOC close to shore exceeds 125 µM, and CDOM across the study region shows predominantly terrigenous spectral signatures. DOC concentrations were higher during the rainier northeast monsoon than during the drier south-west monsoon. Our data suggest that long-term increases in DOC concentration have occurred across parts of our study region from 2002–2018, which has implications for the aquatic light regime and coastal biogeochemistry[PM5]. These results will be discussed in the context of past anthropogenic disturbance to coastal peatlands.</p>

scholarly journals Effect of Acidified Versus Frozen Storage on Marine Dissolved Organic Carbon Concentration and Isotopic Composition

Radiocarbon ◽  
2016 ◽  
Vol 59 (3) ◽  
pp. 843-857 ◽  
Author(s):  
Brett D Walker ◽  
Sheila Griffin ◽  
Ellen R M Druffel
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Standard Procedure ◽  
Frozen Storage ◽  
Open Ocean ◽  
Field Collection ◽  
Organic Carbon Concentration ◽  
Large Numbers ◽  
Logistical Problem

AbstractThe standard procedure for storing/preserving seawater dissolved organic carbon (DOC) samples after field collection is by freezing (–20°C) until future analysis can be made. However, shipping and receiving large numbers of these samples without thawing presents a significant logistical problem and large monetary expense. Access to freezers can also be limited in remote field locations. We therefore test an alternative method of preserving and storing samples for the measurement of DOC concentrations ([DOC]), stable carbon (δ13C), and radiocarbon (as ∆14C) isotopic values via UV photooxidation (UVox). We report a total analytical reproducibility of frozen DOC samples to be [DOC]±1.3 µM, ∆14C±9.4‰, and δ13C±0.1‰, comparable to previously reported results (Druffel et al. 2013). Open Ocean DOC frozen versus acidified duplicates were on average offset by ∆DOC±1.1 µM, ∆∆14C± –1.3‰, and ∆δ13C± –0.1‰. Coastal Ocean frozen vs. acidified sample replicates, collected as part of a long-term (380-day) storage experiment, had larger, albeit consistent offsets of ∆DOC±2.2 µM, ∆∆14C±1.5‰, and ∆δ13C± –0.2‰. A simple isotopic mass balance of changes in [DOC], ∆14C, and δ13C values reveals loss of semi-labile DOC (2.2±0.6 µM, ∆14C=–94±105‰, δ13C=–27±10‰; n=4) and semi-recalcitrant DOC (2.4±0.7 µM, ∆14C=–478±116‰, δ13C=–23.4±3.0‰; n=3) in Coastal and Open Ocean acidified samples, respectively.

scholarly journals Potential for long‐term transfer of dissolved organic carbon from riparian zones to streams in boreal catchments

2015 ◽  
Vol 21 (8) ◽  
pp. 2963-2979 ◽  
Author(s):  
José L. J. Ledesma ◽  
Thomas Grabs ◽  
Kevin H. Bishop ◽  
Sherry L. Schiff ◽  
Stephan J. Köhler
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Riparian Zones

scholarly journals Dissolved organic carbon and dissolved nitrogen in soil under different fertilization treatments

2011 ◽  
Vol 52 (No. 2) ◽  
pp. 55-63 ◽  
Author(s):  
S.S. Gonet ◽  
B. Debska
Keyword(s):  
Surface Layer ◽  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Cattle Slurry ◽  
Soil Horizons ◽  
Mineral Fertilization ◽  
Labile Organic Matter ◽  
Dissolved Nitrogen ◽  
After Effect

The objective of the study was to evaluate the effects of long-term fertilization of a sandy soil with differentiated doses of cattle slurry as well as its after-effect action on the possibilities of migration of dissolved organic carbon (DOC) and dissolved nitrogen (DNt) down to deeper layers of the soil profile. DOC and DNt were extracted with borate buffer and 0.004M CaCl<sub>2</sub> solution. Evaluation of effects of cattle slurry on the content of DOC and DNt was done in comparison with mineral fertilization. It was shown that the use of cattle slurry in the doses of 100 and 200&nbsp;m<sup>3</sup>/ha caused a significant increase of labile organic matter in the 0&ndash;25 and 25&ndash;50 cm layers of soil. As compared with mineral fertilization the application of slurry increased also the amounts of extracted DNt, but only in the surface layer. The DNt content in the deeper soil horizons did not depend on the kind of fertilization. Concentrations of DOC and DNt in the extracts depended not only on their content in soil but it was also modified substantially by the extractant used.

Long-term patterns of dissolved organic carbon in lakes across eastern Canada: Evidence of a pronounced climate effect

2009 ◽  
Vol 55 (1) ◽  
pp. 30-42 ◽  
Author(s):  
Jan Zhang ◽  
Jeff Hudson ◽  
Richard Neal ◽  
Jeff Sereda ◽  
Thomas Clair ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Eastern Canada ◽  
Climate Effect

scholarly journals Hydrological processes and permafrost regulate magnitude, source and chemical characteristics of dissolved organic carbon export in a peatland catchment of northeastern China

2017 ◽  
Author(s):  
Yuedong Guo ◽  
Changchun Song ◽  
Wenwen Tan ◽  
Xianwei Wang ◽  
Yongzheng Lu
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Climate Warming ◽  
Northeastern China ◽  
Organic Layer ◽  
Chemical Characteristics ◽  
Carbon Export ◽  
Study Region ◽  
Growing Seasons ◽  
Doc Export

Abstract. Permafrost thawing in peatland has the potential to alter the catchment export of dissolved organic carbon (DOC), thus influencing carbon cycling in linked aquatic and ocean ecosystems. However, peatland along the southern margins of Eurasian permafrost are seldom examined in spite of the presence of considerable risks associated with degradation due to climate warming. This study examines dynamics of DOC export from a permafrost peatland catchment located in northeastern China during the growing seasons of 2012 to 2014. Our findings show that runoff processes affect observed DOC concentrations, magnitudes, sources, and chemical characteristics of stream discharge. The entire catchment exhibits strong potential for annual DOC exporting (4.87 g C m−2), and DOC from the peatland landscape alone is estimated to amount to 12.89 g C m−2. Annual DOC export processes are closely related to total discharge levels, and floods contribute to approximately 85 % of DOC export levels. Flood volumes derived mainly from peat pore water stored in the upper organic layer of the soil profile prior to rainfall events, creating a strong linkage between discharge and DOC concentrations. DOC source and chemical characteristics, as indicated by three fluorescence indexes, have changed regularly according to source shifts occurring as a result of flood and baseflow processes. A deepening of the active layer due to climate warming should elevate proportions of microbial-originated DOC in the baseflow. Given expected future increases in precipitation, our results show that the magnitude of DOC exports from the study region will increase.

scholarly journals Dissolved organic carbon dynamics in a UK podzolic moorland catchment: linking storm hydrochemistry, flow path analysis and sorption experiments

2012 ◽  
Vol 9 (1) ◽  
pp. 209-251 ◽  
Author(s):  
M. I. Stutter ◽  
S. M. Dunn ◽  
D. G. Lumsdon
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Soil Conditions ◽  
Dry Period ◽  
Flow Paths ◽  
Selective Filtration ◽  
Antecedent Conditions ◽  
Doc Concentration ◽  
Mineral Soils

Abstract. Better knowledge of spatial and temporal delivery of dissolved organic Carbon (DOC) in small catchments is required to understand the mechanisms behind reported long-term changes in C fluxes from some peatlands. We monitored two storms with contrasting seasons and antecedent conditions in a small upland UK moorland catchment. We examined DOC concentrations and specific UV absorbance (SUVA at 285 nm), together with solute concentrations required to undertake end member mixing analyses to define dominant flow paths contributing to streamflow. This was combined with laboratory soil-solution equilibrations. We aimed to resolve how seasonal biogeochemical processing of DOC and flowpath changes in organo-mineral soils combine to affect DOC exported via the stream. An August storm following a dry period gave maximum DOC concentration of 10 mg l−1. Small DOC:DON ratios (16–28) and SUVA (2.7–3.6 l mg−1 m−1) was attributed to filtration of aromatic compounds associated with up to 53% B horizon flow contributions. This selective filtration of high SUVA DOC was reproduced in the experimental batch equilibration system. For a November storm, wetter antecedent soil conditions led to enhanced soil connectivity with the stream and seven times greater DOC stream-load (maximum concentration 16 mg l−1). This storm had a 63% O horizon flow contribution at its peak, limited B horizon buffering and consequently more aromatic DOC (SUVA 3.9–4.5 l mg−1 m−1 and DOC:DON ratio 35–43). We suggest that simple mixing of waters from different flow paths cannot alone explain the differences in DOC compositions between August and November and biogeochemical processing of DOC is required to fully explain the observed stream DOC dynamics. This is in contrast to other studies proposing hydrological controls and provides evidence that DOC biogeochemistry must be incorporated in modelling to predict the impacts of changes in DOC delivery to aquatic systems.

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