Fluxes of nutrients from the tropical River Hooghly at the land ocean boundary of Sundarbans, NE Coast of Bay of Bengal, India
TL;DR: In this article, a biogeochemical model of the Hooghly estuary was used to estimate the annual fluxes of inorganic nutrients in the Sundarbans mangrove forest.
About: This article is published in Journal of Marine Systems.The article was published on 2006-08-01. It has received 225 citations till now. The article focuses on the topics: Southeast asian & Estuary.
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TL;DR: The results showed downward trends concentrations and loads of dissolved silicate (DSi) over the past 50 years due to dam constructions in the Changjiang River, but dissolved nitrogen (DIN) and dissolved inorganic phosphate (DIP) exhibited remarkable upward trends.
Abstract: With intense anthropogenic perturbations in the Changjiang (Yangtze) River basin, the riverine loads and compositions of materials into the Changjiang Estuary have greatly changed, resulting in dramatic deterioration in the Changjiang Estuary and adjacent sea environments. Based on a long-term data set of the material loads into the Changjiang Estuary, changing trends and associated impacted factors were presented. The results showed downward trends concentrations and loads of dissolved silicate (DSi) over the past 50 years due to dam constructions in the Changjiang River. However, dissolved nitrogen (DIN) and dissolved inorganic phosphate (DIP) exhibited remarkable upward trends due to the increase of the population and the use of large-scale chemical fertilizer in the Changjiang River basin. The sharp decrease in the ratio of DSi/DIN and the increase in the ratio of DIN/DIP could cause increased Red tide bloom and decreased dissolved oxygen in the Changjiang Estuary. In addition, even though water discharge has remained almost constant, the suspended sediment discharge was shown to be sharply decreased due to the construction of dams.
251 citations
TL;DR: In this article, the authors show that carbon stock is lower in the tropical mangrove forest than in the terrestrial tropical forest and their annual increase exhibits faster turn over than the tropical forest.
170 citations
TL;DR: Lupker et al. as discussed by the authors used a Rouse-based method to integrate the chemical composition of river sediments to derive the annual flux and grain size distributions of the sediments.
Abstract: [1] The Ganga River is one of the main conveyors of sediments produced by Himalayan erosion Determining the flux of elements transported through the system is essential to understand the dynamics of the basin This is hampered by the chemical heterogeneity of sediments observed both in the water column and under variable hydrodynamic conditions Using Acoustic Doppler Current Profiler (ADCP) acquisitions with sediment depth profile sampling of the Ganga in Bangladesh we build a simple model to derive the annual flux and grain size distributions of the sediments The model shows that ca 390 (±30) Mt of sediments are transported on average each year through the Ganga at Haring Bridge (Bangladesh) Modeled average sediment grain size parameters D 50 and D 84 are 27 (±4) and 123 (±9) mm, respectively Grain size parameters are used to infer average chemical compositions of the sediments owing to a strong grain size chemical composition relation The integrated sediment flux is characterized by low Al/Si and Fe/Si ratios that are close to those inferred for the Himalayan crust This implies that only limited sequestration occurs in the Gangetic floodplain The stored sediment flux is estimated to ca 10% of the initial Himalayan sediment flux by geochemical mass balance The associated, globally averaged sedimentation rates in the floodplain are found to be ca 008 mm/yr and yield average Himalayan erosion rate of ca 09 mm/yr This study stresses the need to carefully address the average composition of river sediments before solving large‐scale geochemical budgets Citation: Lupker, M, C France‐Lanord, J Lave, J Bouchez, V Galy, F Metivier, J Gaillardet, B Lartiges, and J-L Mugnier (2011), A Rouse‐based method to integrate the chemical composition of river sediments: Application to the Ganga basin,
168 citations
Journal Article•
TL;DR: Evidence that the Indian Sundarbans is experiencing the effects of climate change over the last three decades is presented, showing significant long-term variation in surface water temperature, salinity, pH, dissolved oxygen, and transparency.
Abstract: We present evidence that the Indian Sundarbans is experiencing the effects of climate change over the last three decades. Observations of selected variables, such as the surface water temperature, salinity, pH, dissolved oxygen, and transparency show significant long-term variation over a period of 27 years (1980-2007). Specifically, the temperature in these waters has risen at the rate of 0.5°C per decade, much higher than that observed globally or for the Indian Ocean. Increasing melting of Himalayan ice might have decreased the salinity at the mouth of the Ganges River, at the western end of this deltaic complex. At the same time, salinity has increased on the eastern sector, where the connections to the meltwater sources have become extinct due to heavy siltation of the Bidyadhari Channel. The long-term changes in dissolved oxygen, pH level, transparency and water quality are also examined. The ecological impact of such changes warrants future study.
139 citations
TL;DR: This study suggests that the variation in trace metals content with depth or between mangrove and estuarine system results largely from metal input due to anthropogenic activities rather than diagenetic processes.
Abstract: Four sediment cores were collected from selected locations of Sundarbans mangroves and Hooghly estuary, northeast coast of India to establish 210Pb geochronology and trace metal distribution in sediments. Core sites were chosen to reflect a matrix of variable anthropogenic input and hydrological conditions. The vertical distribution of 210Pbxs (210Pbtotal–226Ra) provided reliable geochronological age to calculate the mass accumulation rates and historic trace element inputs and their variations. The mass accumulation rates ranged from 0.41 g cm−2 year−1 (estuarine region) to 0.66 g cm−2 year−1 (mangrove region). Both in mangroves and estuarine systems, Fe–Mn oxy-hydroxides are observed to be a major controlling factor for trace metal accumulation when compared to organic carbon. Core collected from Hooghly estuary shows less contamination when compared to the mangrove region due to high energy and mostly coarse grained. Fe-normalized enrichment factors (EFs) of trace metals were calculated based on crustal trace element abundances. The EFs are typically >1 for Cd, Pb, Co, and Cu indicating that these metals are highly enriched while other metals such as Zn, Ni, Cr, and Mn show no enrichment or depletion. Both Sundarbans mangroves and Hooghly estuary have been receiving considerable pollution loads from anthropogenic sources such as industrial, domestic, and shipping activities in recent times, indicating high concentration of metals in the top few layers. This study suggests that the variation in trace metals content with depth or between mangrove and estuarine system results largely from metal input due to anthropogenic activities rather than diagenetic processes.
131 citations
Cites background from "Fluxes of nutrients from the tropic..."
...The depth of the water column varies from 10 to 15 m (Mukhopadhyay et al. 2006)....
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Proceedings Article•
01 Jan 1963
4,497 citations
"Fluxes of nutrients from the tropic..." refers background in this paper
...0psu) relative to the requirement for the growth of plankton of composition C/N/P=106:16:1 (Redfield et al., 1963) The high C/N and C/P ratios in the Hooghly estuary might result from the excess supply of inorganic carbon or carbohydrate from tree leaves and other terrestrial organic matter compared to N and P (Boyle et al....
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TL;DR: The authors showed that rivers with large sediment loads (annual discharges greater than about $15 \times 10^{6}$ tons) contribute about $7 −times 10 −9$ tons of suspended sediment to the ocean yearly.
Abstract: New data and new estimates from old data show that rivers with large sediment loads (annual discharges greater than about $15 \times 10^{6}$ tons) contribute about $7 \times 10^{9}$ tons of suspended sediment to the ocean yearly. Extrapolating available data for all drainage basins, the total suspended sediment delivered by all rivers to the oceans is about $13.5 \times 10^{9}$ tons annually; bedload and flood discharges may account for an additional $1-2 \times 10^{9}$ tons. About 70% of this total is derived from southern Asia and the larger islands in the Pacific and Indian Oceans, where sediment yields are much greater than for other drainage basins.
3,409 citations
"Fluxes of nutrients from the tropic..." refers background in this paper
...Roughly 85% of it is minerals and the remainder is organic matter from which nutrients are released during estuarine transport (Milliman and Meade, 1983; Milliman and Syvitski, 1992)....
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TL;DR: In this paper, data from 280 rivers discharging to the ocean indicates that sediment loads/yields are a log-linear function of basin area and maximum elevation of the river basin.
Abstract: Analysis of data from 280 rivers discharging to the ocean indicates that sediment loads/yields are a log-linear function of basin area and maximum elevation of the river basin. Other factors controlling sediment discharge (e.g., climate, runoff) appear to have secondary importance. A notable exception is the influence of human activity, climate, and geology on the rivers draining southern Asia and Oceania. Sediment fluxes from small mountainous rivers, many of which discharge directly onto active margins (e.g., western South and North America and most high-standing oceanic islands), have been greatly underestimated in previous global sediment budgets, perhaps by as much as a factor of three. In contrast, sediment fluxes to the ocean from large rivers (nearly all of which discharge onto passive margins or marginal seas) have been overestimated, as some of the sediment load is subaerially sequestered in subsiding deltas. Before the proliferation of dam construction in the latter half of this century, rivers...
3,227 citations
2,078 citations