The long‐term freshening and nutrient increases in summer surface water in the northern East China Sea in relation to Changjiang discharge variation

Siswanto, Eko; Nakata, Hideaki; Matsuoka, Yoshikazu; Tanaka, Katsuhisa; Kiyomoto, Yoko; Okamura, Kazumaro; Zhu, Jianrong; Ishizaka, Joji

doi:10.1029/2008jc004812

Cited by 49 publications

(37 citation statements)

References 26 publications

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“…Nitrate is the predominant DIN (dissolved inorganic nitrogen) species in the ECS, and new nitrogen is supplied by many rivers (Wong et al, 1998;Wang, 2006;Siswanto et al, 2008a;Liu et al, 2010b), intrusions from surrounding oceans (see below), bottom water (Hung and Gong, 2011;Shiozaki et al, 2011) and occasional deposition from the atmosphere (Nakamura et al, 2005(Nakamura et al, , 2006Kodama et al, 2011). The water on the continental shelf in the northern ECS is a mixture of Changjiang Diluted Water (CDW), Kuroshio Surface Water (KSW), Kuroshio Subsurface Water (KSSW), Yellow Sea Cold Water Mass (YSCWM), and Taiwan Warm Current Water (TWCW) (e.g., Ichikawa and Beardsley, 2002;Liu et al, 2010b).…”

Section: Y Umezawa Et Al: Seasonal Shift Of the Nitrate Sources In mentioning

confidence: 99%

Seasonal shifts in the contributions of the Changjiang River and the Kuroshio Current to nitrate dynamics in the continental shelf of the northern East China Sea based on a nitrate dual isotopic composition approach

et al. 2014

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Abstract. The northern East China Sea (ECS) serves as a spawning and nursery ground for many species of fish and squid. To clarify the basis of the food web in the northern ECS, we examined the nitrate (NO 3 ) dynamics along four latitudinal transects based on stable nitrogen and oxygen isotopes of NO 3 (δ 15 N NO 3 and δ 18 O NO 3 ) and temperaturesalinity dynamics in both winter (February 2009) and summer (July 2009 and July 2011). The δ 15 N NO 3 and δ 18 O NO 3 , which were distinctly different among the potential NO 3 sources, were useful for clarifying NO 3 sources and its actual usage by phytoplankton. In winter, Kuroshio Subsurface Water (KSSW) and the Yellow Sea Mixed Water (YSMW) predominantly contributed to NO 3 distributed in the shelf water. In the surface water of the Okinawa Trough, NO 3 from the KSSW, along with a temperature increase caused by an intrusion of Kuroshio Surface Water (KSW), seemed to stimulate phytoplankton growth. In summer, Changjiang Diluted Water (CDW), Yellow Sea Cold Water Mass (YSCWM), and KSSW affected the distribution and abundance of NO 3 in the northern ECS, depending on precipitation in the Changjiang drainage basin and the development of the YSCWM in the shelf bottom water. Although isotopic fractionation during NO 3 uptake by phytoplankton seemed to drastically increase δ 15 N NO 3 and δ 18 O NO 3 in summer, relatively light nitrate with δ 15 N NO 3 lower than expected from this fractionation effect might be explained by contribution of atmospheric nitrogen and/or nitrification to NO 3 dynamics in the surface and subsurface layers. If the latter were a dominant process, this would imply a tightly coupled nitrogen cycle in the shelf water of the northern ECS.

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Section: Y Umezawa Et Al: Seasonal Shift Of the Nitrate Sources In mentioning

confidence: 99%

Seasonal shifts in the contributions of the Changjiang River and the Kuroshio Current to nitrate dynamics in the continental shelf of the northern East China Sea based on a nitrate dual isotopic composition approach

et al. 2014

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“…The ECS is significantly influenced by river discharge from the Changjiang (Gong et al, 1996). In summer, it receives enormous amounts of freshwater containing very high concentrations of nitrogen (Gong et al, 1996;Siswanto et al, 2008). The nutrient-rich freshwater mixes with the surrounding high-salinity waters, forming the Changjiang diluted water (CDW) with a thickness of about 10-20 m in the mid-shelf area, which extends offshore and moves northeastward near Jeju Island to the Tsushima Strait (TS) (Yamaguchi et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

Influence of the Changjiang River on the light absorption properties of phytoplankton from the East China Sea

et al. 2014

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Abstract. Phytoplankton light absorption properties were investigated at the surface and subsurface chlorophyll a maximum (SCM) layer in the East China Sea (ECS), a marginal sea which is strongly influenced by the Changjiang discharge in summer. Results from ECS were compared with those from the Tsushima Strait (TS) where the influence of Changjiang discharge is less. The probable controlling factors, packaging effect (cell size) and pigment composition of total chlorophyll a (Tchl a)-specific absorption coefficient (a * ph (λ)) were examined by the corresponding measurements of pigments identified by high-performance liquid chromatography. We observed distinct phytoplankton size structure and thereby absorption properties between ECS and TS. At the surface, mixed populations of micro-, nanoand pico-phytoplankton were recorded in ECS while picophytoplankton dominated in TS, generating a lower average a * ph (λ) in ECS than in TS. Within SCM, average a * ph (λ) was higher in ECS than in TS because of the dominance of nano-and micro-phytoplankton in ECS and TS, respectively. By pooling surface and SCM samples, we found regular trends in phytoplankton size-fraction versus Tchl a; and correlations between a * ph (λ) and Tchl a consistent with previous observations for the global ocean in TS but not in ECS. In ECS phytoplankton size-fraction was not correlated with Tchl a, which consequently caused poor relationships between a * ph (λ) and Tchl a. The abnormal values mainly originated from the surface low-salinity waters and SCM waters beneath them. At high Tchl a, a * ph (λ) of these samples was substantially higher compared to the values in TS and from the global regressions, which was attributable to the lower micro-phytoplankton fraction, and higher nano-and/or pico-phytoplankton fractions in ECS. These observations indicated that the distinct light absorption properties of phytoplankton in ECS were possibly influenced by the Changjiang discharge. Our findings imply that general bio-optical algorithms proposed based on the correlations between a * ph (λ) and Tchl a or the patterns in size-fraction versus Tchl a are not applicable in ECS, and need to be carefully considered when using these general algorithms in river-influenced regions.

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“…This may be related to the enhanced nutrient concentrations by river and estuarine discharge. Due to anthropogenic activities such as various agricultural and industry 20 activities, nutrient-rich water discharges into the East China Sea, especially in the summer (Siswanto et al, 2008;Zhang et al, 2017). This is especially evident in the higher Chla concertation (> 6 mg m -3 ) observed in the MCJR (Fig.…”

Section: Seasonal Variations Of the Psc In The Ecsmentioning

confidence: 98%

Phytoplankton size class in the East China Sea derived from MODIS satellite data

Zhang¹,

Wang²,

Qiu³

et al. 2018

Preprint

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Abstract. The distribution of the phytoplankton size class (PSC) and the variations in the size classes are key to understanding 10 ocean biogeochemical processes and ecosystem. Remote sensing of the PSC in the East China Sea (ECS) remains a challenge, although many PSC algorithms have been developed. Here based on a local dataset from the ECS, a regional model was tuned to infer the PSC from the spectral features of normalized phytoplankton absorption (aph) using a principal component analysis approach. Before applying the refined model to the real MODIS (Moderate Resolution Imaging Spectroradiometer) data, reconstructing satellite Rrs at 412 and 443 nm becomes critical through modeling them from Rrs between 469 and 555 nm using 15 multiple regression analyses. Satellite-derived PSC values compare well with those derived from pigment composition, which demonstrates the potential of satellite ocean color data to estimate PSC distributions in the ECS from space. The refined model was applied to aph derived from Rrs observations collected by MODIS over the ECS from 2003 to 2016. Seasonal images show that the PSC distribution was heterogeneous in both temporal and spatial scales. Seasonal variations of the PSC in the ECS were probably affected by a combination of the water column stability, upwelling, sea surface temperature, and the Kuroshio 20Current. Additionally, human activity and riverine discharge may also influence the PSC distributions in the ECS, especially in coastal regions.Biogeosciences Discuss., https://doi

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The long‐term freshening and nutrient increases in summer surface water in the northern East China Sea in relation to Changjiang discharge variation

Cited by 49 publications

References 26 publications

Seasonal shifts in the contributions of the Changjiang River and the Kuroshio Current to nitrate dynamics in the continental shelf of the northern East China Sea based on a nitrate dual isotopic composition approach

Seasonal shifts in the contributions of the Changjiang River and the Kuroshio Current to nitrate dynamics in the continental shelf of the northern East China Sea based on a nitrate dual isotopic composition approach

Influence of the Changjiang River on the light absorption properties of phytoplankton from the East China Sea

Phytoplankton size class in the East China Sea derived from MODIS satellite data

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