Spatiotemporal variations of organic matter sources in two mangrove-fringed estuaries in Hainan, China

2020 ◽  
Author(s):  
Mengfan Chu ◽  
Julian P. Sachs ◽  
Hailong Zhang ◽  
Yang Ding ◽  
Gui’e Jin ◽  
...  
Keyword(s):  
Organic Matter ◽  
Stable Carbon Isotopes ◽  
Hainan Island ◽  
Temporal Variations ◽  
Transport Processes ◽  
Coastal Sediments ◽  
Terrestrial Plants ◽  
Mangrove Plant ◽  
Carbon Burial ◽  
Aquatic Productivity

<p>Mangrove systems represent important long-term sinks for carbon since they have much higher carbon burial rates than terrestrial forests or typical coastal ecosystem. However, quantifying the sources of organic matter (OM) in estuarine and coastal sediments, where mangroves occur but are not the only source of OM, is challenging due to the variety of OM sources and diverse transport processes in these dynamic environments. The sources of OM in surface sediments of two mangrove-fringed estuaries in Hainan Province, China, were investigated using the mangrove specific biomarker taraxerol and other lipid biomarkers, as well as stable carbon isotopes. Mixing models based on the concentration of taraxerol, plant wax <em>n</em>-alkanes and δ<sup>13</sup> C<sub>OM</sub> indicate that terrestrial non-mangrove plant OM accounted for 52-72% of the OM in the two estuaries, aquatic OM from phytoplankton and/or seagrass accounted for 8-29%, and OM from mangroves comprised 16-26% of the total. Terrestrial plants contributed 16-20% more of the OM to sediments of Bamen Bay, which is on the wetter, eastern side of Hainan Island, than to Danzhou Bay, but aquatic OM (algae plus seagrass) fraction was 17% lower than that in Danzhou Bay sediments. In both estuaries, mangrove and aquatic OM fractions increased seaward while the terrestrial OM fraction decreased. Terrestrial fraction in BMB sediments is 12% higher in summer compared to autumn, which is offset by a comparable reduction in the mangrove OM fraction, as well as higher aquatic OM fractions in both estuaries. This may be caused by enhanced river discharge, more efficient mangrove leaf litter transport offshore, and/or higher aquatic productivity. The biomarker and carbon isotope approach used here can be applied to semi-quantitatively estimate spatial and temporal variations of the sources of organic carbon in tropical estuarine and coastal sediments, a major sink for carbon in the ocean.</p>

The dynamics of organic matter in soil size and density fractions traced by stable carbon isotopes

2003 ◽  
Vol 22 (2) ◽  
pp. 179-184 ◽  
Author(s):  
Liu Qiming ◽  
Wang Shijie ◽  
Piao Hechun ◽  
Ouyang Ziyuan
Keyword(s):  
Organic Matter ◽  
Carbon Isotopes ◽  
Stable Carbon Isotopes ◽  
Stable Carbon ◽  
Density Fractions

Spatio-temporal Variations of Dissolved Organic Matter in a German Forested Mountainous Headwater Catchment

2015 ◽  
Vol 14 (4) ◽  
pp. vzj2015.01.0005 ◽  
Author(s):  
Roland Bol ◽  
Andreas Lücke ◽  
Wolfgang Tappe ◽  
Sirgit Kummer ◽  
Martina Krause ◽  
...  
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Temporal Variations ◽  
Spatio Temporal ◽  
Headwater Catchment

scholarly journals Coastal hypoxia and sediment biogeochemistry

2009 ◽  
Vol 6 (7) ◽  
pp. 1273-1293 ◽  
Author(s):  
J. J. Middelburg ◽  
L. A. Levin
Keyword(s):  
Organic Matter ◽  
Bottom Water ◽  
Water Exchange ◽  
Transport Processes ◽  
Ecosystem Dynamics ◽  
Ecosystem Functions ◽  
Oxygen Levels ◽  
Concise Review ◽  
Water Oxygen ◽  
Sediment Biogeochemistry

Abstract. The intensity, duration and frequency of coastal hypoxia (oxygen concentration <63 μM) are increasing due to human alteration of coastal ecosystems and changes in oceanographic conditions due to global warming. Here we provide a concise review of the consequences of coastal hypoxia for sediment biogeochemistry. Changes in bottom-water oxygen levels have consequences for early diagenetic pathways (more anaerobic at expense of aerobic pathways), the efficiency of re-oxidation of reduced metabolites and the nature, direction and magnitude of sediment-water exchange fluxes. Hypoxia may also lead to more organic matter accumulation and burial and the organic matter eventually buried is also of higher quality, i.e. less degraded. Bottom-water oxygen levels also affect the organisms involved in organic matter processing with the contribution of metazoans decreasing as oxygen levels drop. Hypoxia has a significant effect on benthic animals with the consequences that ecosystem functions related to macrofauna such as bio-irrigation and bioturbation are significantly affected by hypoxia as well. Since many microbes and microbial-mediated biogeochemical processes depend on animal-induced transport processes (e.g. re-oxidation of particulate reduced sulphur and denitrification), there are indirect hypoxia effects on biogeochemistry via the benthos. Severe long-lasting hypoxia and anoxia may result in the accumulation of reduced compounds in sediments and elimination of macrobenthic communities with the consequences that biogeochemical properties during trajectories of decreasing and increasing oxygen may be different (hysteresis) with consequences for coastal ecosystem dynamics.

scholarly journals Effects of temperature and organic pollution on nutrient cycling in marine sediments

2015 ◽  
Vol 12 (15) ◽  
pp. 4565-4575 ◽  
Author(s):  
C. Sanz-Lázaro ◽  
T. Valdemarsen ◽  
M. Holmer
Keyword(s):  
Climate Change ◽  
Organic Matter ◽  
Nutrient Cycling ◽  
Water Column ◽  
Temperature Rise ◽  
Nutrient Release ◽  
Organic Pollution ◽  
Coastal Sediments ◽  
Effect Of Temperature ◽  
Climate Change Scenarios

Abstract. Increasing ocean temperature due to climate change is an important anthropogenic driver of ecological change in coastal systems. In these systems sediments play a major role in nutrient cycling. Our ability to predict ecological consequences of climate change is enhanced by simulating real scenarios. Based on predicted climate change scenarios, we tested the effect of temperature and organic pollution on nutrient release from coastal sediments to the water column in a mesocosm experiment. PO43− release rates from sediments followed the same trends as organic matter mineralization rates, increased linearly with temperature and were significantly higher under organic pollution than under nonpolluted conditions. NH4+ release only increased significantly when the temperature rise was above 6 °C, and it was significantly higher in organic polluted compared to nonpolluted sediments. Nutrient release to the water column was only a fraction from the mineralized organic matter, suggesting PO43− retention and NH4+ oxidation in the sediment. Bioturbation and bioirrigation appeared to be key processes responsible for this behavior. Considering that the primary production of most marine basins is N-limited, the excess release of NH4+ at a temperature rise > 6 °C could enhance water column primary productivity, which may lead to the deterioration of the environmental quality. Climate change effects are expected to be accelerated in areas affected by organic pollution.

scholarly journals Granulated Coal Ash – used Method for Remediation of Organic Matter Enriched Coastal Sediments

2015 ◽  
Vol 116 ◽  
pp. 326-333 ◽  
Author(s):  
Kenji Nakamoto ◽  
Tadashi Hibino ◽  
Kazutoshi Hino ◽  
Narong Touch
Keyword(s):  
Organic Matter ◽  
Coal Ash ◽  
Coastal Sediments

Small-Scale Distribution of Bacteria, Enzymatic Activities, and Organic Matter in Coastal Sediments

2001 ◽  
Vol 42 (2) ◽  
pp. 177-185 ◽  
Author(s):  
R. Danovaro ◽  
M. Armeni ◽  
A. Dell'Anno ◽  
M. Fabiano ◽  
E. Manini ◽  
...  
Keyword(s):  
Organic Matter ◽  
Enzymatic Activities ◽  
Coastal Sediments ◽  
Small Scale
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