Assessment and analysis of the chlorophyll-a concentration variability over the Vietnamese coastal waters from the MERIS ocean color sensor (2002–2012)

Loisel, Hubert; Vantrepotte, Vincent; Ouillon, Sylvain; Ngoc, Dat Dinh; Herrmann, Marine; Tran, Viet; Mériaux, Xavier; Dessailly, David; Jamet, Cédric; Duhaut, Thomas; Nguyen, Huan Huu; Nguyen, Thao Van

doi:10.1016/j.rse.2016.12.016

Cited by 70 publications

(63 citation statements)

References 58 publications

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“…This would have important consequences on the sediment deposition in the delta that seems to have already shifted from a net depositional (accretion) regime into a net erosion regime (Anthony et al, 2015;Liu et al, 2017). The nutrient inputs to the continental shelf from the Mekong delta sustain high phytoplankton growth in the Mekong River plume (Grosse et al, 2010), which is one the most productive areas of the South China Sea (Liu et al, 2002;Qiu et al, 2011;Gao et al, 2013;Loisel et al, 2017).…”

Section: Description Of the Mekong River And Deltamentioning

confidence: 99%

Carbon dynamics and CO2 and CH4 outgassing in the Mekong delta

2018

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Abstract. We report a data set of biogeochemical variables related to carbon cycling obtained in the three branches (M y Tho, Hàm Luông, Có Chiên) of the Mekong delta (Bén Tre province, Vietnam) in December 2003, April 2004, and October 2004. Both the inner estuary (upstream of the mouth) and the outer estuary (river plume) were sampled, as well as side channels. The values of the partial pressure of CO 2 (pCO 2 ) ranged between 232 and 4085 ppm, O 2 saturation level (%O 2 ) between 63 and 114 %, and CH 4 between 2 and 2217 nmol L −1 , within the ranges of values previously reported in temperate and tropical meso-and macro-tidal estuaries. Strong seasonal variations were observed. In the upper oligohaline estuary, low pCO 2 (479-753 ppm) and high %O 2 (98-106 %) values were observed in April 2004 most probably related to freshwater phytoplankton growth owing to low freshwater discharge (1400 m 3 s −1 ) and increase in water residence time; during the two other sampling periods with a higher freshwater discharge (9300-17 900 m 3 s −1 ), higher pCO 2 (1895-2664 ppm) and lower %O 2 (69-84 %) values were observed in the oligohaline part of the estuary. In October 2004, important phytoplankton growth occurred in the offshore part of the river plume as attested by changes in the contribution of particulate organic carbon (POC) to total suspended matter (TSM) (%POC) and the stable isotope composition of POC (δ 13 C-POC), possibly related to low TSM values (improvement of light conditions for phytoplankton development), leading to low pCO 2 (232 ppm) and high %O 2 (114 %) values. Water in the side channels in the Mekong delta was strongly impacted by inputs from the extensive shrimp farming ponds. The values of pCO 2 , CH 4 , %O 2 , and the stable isotope composition of dissolved inorganic carbon (δ 13 C-DIC) indicated intense organic matter degradation that was partly mediated by sulfate reduction in sediments, as revealed by the slope of total alkalinity (TA) and DIC covariations. The δ 13 C-POC variations also indicated intense phytoplankton growth in the side channels, presumably due to nutrient enrichment related to the shrimp farming ponds. A data set in the mangrove creeks of the Ca Mau province (part of the Mekong delta) was also acquired in April and October 2004. These data extended the range of variability in pCO 2 and %O 2 with more extreme values than in the Mekong delta (Bén Tre), with maxima and minima of 6912 ppm and 37 %, respectively. Similarly, the maximum CH 4 concentration (686 nmol L −1 ) was higher in the Ca Mau province mangrove creeks than in the Mekong delta (Bén Tre, maximum 222 nmol L −1 ) during the October 2004 cruise (rainy season and high freshwater discharge period). In April 2004 (dry season and low freshwater discharge period), the CH 4 values were much lower than in October 2004 (average 19 ± 13 and 210 ± 158 nmol L −1 , respectively) in the Ca Mau province mangrove creeks, owing to the higher salinity (average 33.2 ± 0.6 and 14.1 ± 1.2, respectively) that probably led to higher sedim...

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Section: Description Of the Mekong River And Deltamentioning

confidence: 99%

Carbon dynamics and CO2 and CH4 outgassing in the Mekong delta

2018

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“…As far as Sentinel2 is concerned, the lack of a spectral band at around 412 nm will certainly limit the performance of chl a inversion methods, as it has been long demonstrated that such a spectral band improves the deconvolution of chl a, PIM, and CDOM absorption (Carder et al, 1999). For sensors equipped with a spectral band at 412 nm such as MERIS, the ocean color 5 (OC5) algorithm (Gohin et al, 2002) has been recently recommended in recent intercomparison studies of the North West European (Tilstone et al, 2017) and Vietnamese (Loisel et al, 2017) coastal waters. As already indicated by Vanhellemont and Ruddick (2016), several other limitations specific to Sentinel2 can also arise, due to its relatively wide bands, low signal-to-noise ratio, and lack of vicarious calibration.…”

Section: Advantages and Limitations Of Sentinel2 For Aquaculture Applmentioning

confidence: 99%

Shellfish Aquaculture from Space: Potential of Sentinel2 to Monitor Tide-Driven Changes in Turbidity, Chlorophyll Concentration and Oyster Physiological Response at the Scale of an Oyster Farm

2017

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The algorithms of Novoa et al. (2017) and Gons et al. (2005) were recalibrated and applied to Sentinel2 data to retrieve suspended particulate matter (SPM) and chlorophyll a (chl a) concentration in the environmentally and economically important intertidal zones. Sentinel2-derived chl a and SPM concentration distributions were analyzed at the scale of an oyster farm over a variety of tidal conditions. Sentinel2 imagery was then coupled with ecophysiological modeling to analyze the influence of tide-driven chl a and SPM dynamics on oyster clearance and chl consumption rates. Within the studied oyster farming site (Bourgneuf Bay along the French Atlantic coast), chl consumption rate mirrored the changes in chl a concentration during neap tides, whereas oyster clearance and chl consumption rates were both negatively impacted by high SPM concentration during spring tides.

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“…This may in part be attributed to overestimation of retrieved NPP near the coast (e.g. Loisel et al, 2017). Off the coast, the model simulates well the crossshore gradient of productivity.…”

Section: Model Validationmentioning

confidence: 94%

“…The 60 offshore jet also appears to advect water with high chlorophyll (CHL) to the interior of the central SCS (Chen et al, 2014;Loisel et al, 2017;Tang et al, 2004). While the importance of circulation to the VBUS biogeochemical system has been noted in some previous studies (Dippner et al, 2006;Liu et al, 2012;Xie et al, 2003), the detailed processes are unclear.…”

Section: Introduction 25mentioning

confidence: 97%

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Physical Modulation to the Biological Productivity in the Summer Vietnam Upwelling System

Lu¹,

Liao²,

Yan³

et al. 2018

Preprint

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Abstract. Biological productivity in the summer Vietnam boundary upwelling system in the western SouthChina Sea, as in many coastal upwelling systems, is strongly modulated by wind. However, the role of ocean 15 circulation and mesoscale eddies has not been elucidated. Here we show a close spatio-temporal covariability between primary production and kinetic energy. High productivity is associated with high kinetic energy, which accounts for ~15% of the production variability. Results from a physical-biological coupled model reveal that the elevated kinetic energy and intensified circulation can be explained by the separation of the upwelling current system. The separated current forms an eastward jet into the interior South China Sea, 20 and the associated southern gyre traps nutrient and favors productivity. When separation is absent, the model shows weakened circulation and eddy activity, with ~21% less nitrate inventory and ~16% weaker primary productivity.

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Assessment and analysis of the chlorophyll-a concentration variability over the Vietnamese coastal waters from the MERIS ocean color sensor (2002–2012)

Cited by 70 publications

References 58 publications

Carbon dynamics and CO<sub>2</sub> and CH<sub>4</sub> outgassing in the Mekong delta

Carbon dynamics and CO<sub>2</sub> and CH<sub>4</sub> outgassing in the Mekong delta

Shellfish Aquaculture from Space: Potential of Sentinel2 to Monitor Tide-Driven Changes in Turbidity, Chlorophyll Concentration and Oyster Physiological Response at the Scale of an Oyster Farm

Physical Modulation to the Biological Productivity in the Summer Vietnam Upwelling System

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Assessment and analysis of the chlorophyll-a concentration variability over the Vietnamese coastal waters from the MERIS ocean color sensor (2002–2012)

Cited by 70 publications

References 58 publications

Carbon dynamics and CO&lt;sub&gt;2&lt;/sub&gt; and CH&lt;sub&gt;4&lt;/sub&gt; outgassing in the Mekong delta

Carbon dynamics and CO&lt;sub&gt;2&lt;/sub&gt; and CH&lt;sub&gt;4&lt;/sub&gt; outgassing in the Mekong delta

Shellfish Aquaculture from Space: Potential of Sentinel2 to Monitor Tide-Driven Changes in Turbidity, Chlorophyll Concentration and Oyster Physiological Response at the Scale of an Oyster Farm

Physical Modulation to the Biological Productivity in the Summer Vietnam Upwelling System

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Carbon dynamics and CO<sub>2</sub> and CH<sub>4</sub> outgassing in the Mekong delta

Carbon dynamics and CO<sub>2</sub> and CH<sub>4</sub> outgassing in the Mekong delta