scholarly journals Dissolved organic matter from tropical peatlands reduces shelf sea light availability in the Singapore Strait, Southeast Asia

2021 ◽  
Author(s):  
P Martin ◽  
N Sanwlani ◽  
TWQ Lee ◽  
JMC Wong ◽  
K Chang ◽  
...  
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Southeast Asia ◽  
Light Availability ◽  
Tropical Peatlands ◽  
Shelf Sea ◽  
Singapore Strait

scholarly journals Dissolved organic matter from tropical peatlands impacts shelf sea light availability on coral reefs in the Singapore Strait, Southeast Asia

2021 ◽  
Author(s):  
Patrick Martin ◽  
Nivedita Sanwlani ◽  
Tiffany Wan Qi Lee ◽  
Joel Meng Cheng Wong ◽  
Kristy Chang ◽  
...  
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Southeast Asia ◽  
Light Absorption ◽  
Time Series Data ◽  
Light Availability ◽  
Series Data ◽  
Underwater Light ◽  
Tropical Peatlands ◽  
Shelf Seas

AbstractShelf seas provide valuable ecosystem services, but their productivity and ecological functioning depend critically on sunlight transmitted through the water column. Anthropogenic reductions in underwater light availability are thus recognized as a serious threat to coastal habitats. The flux of strongly light-absorbing coloured dissolved organic matter (CDOM) from land to sea may have increased world-wide, but how this has altered the availability and spectral quality of light in shelf seas remains poorly known. Here, we present time-series data from the Sunda Shelf in Southeast Asia, where the monsoon-driven reversal in ocean currents supplies water enriched in CDOM from tropical peatlands for part of the year, resulting in 5–10-fold seasonal variation in light absorption by CDOM. We show that this terrigenous CDOM can dominate underwater light absorption at wavelengths up to 500 nm, and shift in the underwater irradiance spectrum towards longer wavelengths. The seasonal presence of terrigenous CDOM also causes the depth of 10% light penetration to shoal by 1–5 m, or 10–45%. We further estimate that on average 0.6 m, or 25%, of this terrigenous CDOM-mediated shoaling might be attributable to the enhanced loss of dissolved organic matter caused by peatland disturbance. We show that the seasonal change in the light environment is correlated with photo-acclimation by phytoplankton, and infer that terrigenous CDOM likely contributes to limiting the depth distribution of photosynthetic corals. Our results thus reveal an ecologically important but largely overlooked impact of human modifications to carbon fluxes that is likely becoming increasingly important in coastal seas.

scholarly journals Composition and cycling of dissolved organic matter from tropical peatlands of coastal Sarawak, Borneo, revealed by fluorescence spectroscopy and PARAFAC analysis

2018 ◽  
Author(s):  
Yongli Zhou ◽  
Patrick Martin ◽  
Moritz Müller
Keyword(s):  
Organic Matter ◽  
Fluorescence Spectroscopy ◽  
Dissolved Organic Matter ◽  
Coastal Waters ◽  
Southeast Asian ◽  
Low Concentrations ◽  
Tropical Peatlands ◽  
Shelf Seas ◽  
High Concentrations ◽  
High Degree

Abstract. Southeast Asian peatlands supply ~ 10 % of the global flux of dissolved organic carbon (DOC) from land to the ocean, but the biogeochemical cycling of this peat-derived DOC in coastal environments is still poorly understood. Here, we use fluorescence spectroscopy and parallel factor (PARAFAC) analysis to distinguish different fractions of dissolved organic matter (DOM) in peat-draining rivers, estuaries, and coastal waters of Sarawak, Borneo. The terrigenous fractions showed high concentrations at freshwater stations within the rivers, and conservative mixing with seawater across the estuaries. The autochthonous DOM fraction, in contrast, showed low concentrations throughout our study area at all salinities. The DOM pool was also characterized by a high degree of humification in all rivers and estuaries up to salinity 25. These results indicate a predominantly terrestrial origin of the riverine DOM pool. Only at salinities > 25 did we observe an increase in the proportion of autochthonous relative to terrestrial DOM. Natural sunlight exposure experiments with river water and seawater showed high photolability of the terrigenous DOM fractions, suggesting that photodegradation may account for the observed changes in DOM composition in coastal waters. Nevertheless, we estimate based on our fluorescence data that at least 20 %–25 % of the DOC at even our most marine stations (salinity > 31) was terrestrial in origin, indicating that peatlands likely play an important role in the carbon biogeochemistry of Southeast Asian shelf seas.

Origin, composition, and transformation of dissolved organic matter in tropical peatlands

2014 ◽  
Vol 137 ◽  
pp. 35-47 ◽  
Author(s):  
L. Gandois ◽  
R. Teisserenc ◽  
A.R. Cobb ◽  
H.I. Chieng ◽  
L.B.L. Lim ◽  
...  
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Tropical Peatlands

scholarly journals From canals to the coast: dissolved organic matter and trace metal composition in rivers draining degraded tropical peatlands in Indonesia

2020 ◽  
Vol 17 (7) ◽  
pp. 1897-1909 ◽  
Author(s):  
Laure Gandois ◽  
Alison M. Hoyt ◽  
Stéphane Mounier ◽  
Gaël Le Roux ◽  
Charles F. Harvey ◽  
...  
Keyword(s):  
Organic Matter ◽  
Trace Metals ◽  
Organic Carbon ◽  
Dissolved Organic Matter ◽  
Dissolved Organic Carbon ◽  
Trace Metal ◽  
Strong Association ◽  
Secondary Source ◽  
Tropical Peatlands ◽  
Blackwater Rivers

Abstract. Worldwide, peatlands are important sources of dissolved organic matter (DOM) and trace metals (TMs) to surface waters, and these fluxes may increase with peatland degradation. In Southeast Asia, tropical peatlands are being rapidly deforested and drained. The blackwater rivers draining these peatland areas have high concentrations of DOM and the potential to be hotspots for CO2 release. However, the fate of this fluvial carbon export is uncertain, and its role as a trace metal carrier has never been investigated. This work aims to address these gaps in our understanding of tropical peatland DOM and associated elements in the context of degraded tropical peatlands in Indonesian Borneo. We quantified dissolved organic carbon and trace metal concentrations in the dissolved and fine colloidal (<0.22 µm) and coarse colloidal (0.22–2.7 µm) fractions and determined the characteristics (δ13C, absorbance, fluorescence: excitation-emission matrix and parallel factor – PARAFAC – analysis) of the peatland-derived DOM as it drains from peatland canals, flows along the Ambawang River (blackwater river) and eventually mixes with the Kapuas Kecil River (whitewater river) before meeting the ocean near the city of Pontianak in West Kalimantan, Indonesia. We observe downstream shifts in indicators of in-stream processing. An increase in the δ13C of dissolved organic carbon (DOC), along with an increase in the C1∕C2 ratio of PARAFAC fluorophores, and a decrease in SUVA (specific UV absorbance) along the continuum suggest the predominance of photo-oxidation. However, very low dissolved oxygen concentrations also suggest that oxygen is quickly consumed by microbial degradation of DOM in the shallow layers of water. Blackwater rivers draining degraded peatlands show significantly higher concentrations of Al, Fe, Pb, As, Ni and Cd compared to the whitewater river. A strong association is observed between DOM, Fe, As, Cd and Zn in the dissolved and fine colloid fraction, while Al is associated with Pb and Ni and present in a higher proportion in the coarse colloidal fraction. We additionally measured the isotopic composition of lead released from degraded tropical peatlands for the first time and show that Pb originates from anthropogenic atmospheric deposition. Degraded tropical peatlands are important sources of DOM and trace metals to rivers and a secondary source of atmospherically deposited contaminants.

scholarly journals From Canals to the Coast: Dissolved Organic Matter and Trace Metal Composition in Rivers Draining Degraded Tropical Peatlands in Indonesia

2019 ◽  
Author(s):  
Laure Gandois ◽  
Alison May Hoyt ◽  
Stéphane Mounier ◽  
Gaël Le Roux ◽  
Charles Franklin Harvey ◽  
...  
Keyword(s):  
Organic Matter ◽  
Trace Metals ◽  
Dissolved Organic Matter ◽  
Trace Metal ◽  
Carbon Export ◽  
Tropical Peatlands ◽  
Metal Composition ◽  
High Concentrations ◽  
Peatland Degradation ◽  
Co2 Release

Abstract. Worldwide, peatlands are important sources of dissolved organic matter (DOM) and trace metals (TM) to surface waters and these fluxes may increase with peatland degradation. In Southeast Asia, tropical peatlands are being rapidly deforested and drained. The black rivers draining these peatland areas have high concentrations of DOM, and the potential to be hotspots for CO2 release. However, the fate of this fluvial carbon export is uncertain, and its role as a trace metal carrier has never been investigated. This work aims to address these gaps in our understanding of tropical peatland DOM and associated elements in the context of degraded tropical peatlands of Indonesian Borneo. We quantified dissolved organic carbon and trace metals concentrations in the dissolved and fine colloidal (

scholarly journals Distribution and C / N stoichiometry of dissolved organic matter in the North Sea in summer 2011–12

2017 ◽  
Author(s):  
Saisiri Chaichana ◽  
Tim Jickells ◽  
Martin Johnson
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
North Sea ◽  
General Pattern ◽  
Bottom Layer ◽  
The North ◽  
Carbon Pump ◽  
Shelf Sea ◽  
The North Sea ◽  
Strong Control

Abstract. We present the distribution and C : N stoichiometry of dissolved organic matter (DOM) in the North Sea in 2 summers (August 2011 and August 2012), with supporting data from the intervening winter (January 2012). This data demonstrates local variability superimposed on a general pattern of decreasing DOM with increasing salinity, suggesting strong control over broad scale concentrations by mixing between riverine sources and the open North Atlantic. We observe differences in DOC and DON concentrations and gradients between the two summers, leading to an estimated 10–20 Tg difference in the DOM carbon inventory between the 2 years, which is of the same order as the annual uptake of atmospheric CO2 by the North Sea system, and thus significant for the carbon budget of the North Sea. Differences were particularly pronounced in the bottom layer of the seasonally stratifying Northern North Sea, with higher DOC and lower DON in 2011 and lower C : N ratio and more moderate concentrations of DOC and DON in 2012. Using other data we consider the extent to which these differences in the concentrations and C : N ratio of DOM could be due to differences in the biogeochemistry or physical circulation in the 2 years, or a combination of both. We discuss the implications of these observations for the shelf sea carbon pump and the export of carbon rich organic matter off the shelf.

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