A numerical study of the seasonal variations of nutrients in the Changjiang River estuary and its adjacent sea area

Fan, Wei; Song, Jinbao

doi:10.1016/j.ecolmodel.2014.07.026

Cited by 35 publications

(14 citation statements)

References 21 publications

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“…Similarly, the Mississippi River in concert with the local wind field seems to be the main control on year-to-year variability in hypoxic area in the NGoM. There, episodic upwelling-favorable winds can result in an offshore transport of Mississippi FW and nutrients, leading to a reduction in stratification and O 2 consumption and thus hypoxia (Feng et al, 2014).…”

Section: Comparison With the Northern Gulf Of Mexicomentioning

confidence: 98%

Quantifying the contributions of riverine vs. oceanic nitrogen to hypoxia in the East China Sea

et al. 2020

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Abstract. In the East China Sea, hypoxia (oxygen ≤ 62.5 mmol m−3) is frequently observed off the Changjiang (or Yangtze River) estuary covering up to about 15 000 km2. The Changjiang is a major contributor to hypoxia formation because it discharges large amounts of freshwater and nutrients into the region. However, modeling and observational studies have suggested that intrusions of nutrient-rich oceanic water from the Kuroshio Current also contribute to hypoxia formation. The relative contributions of riverine vs. oceanic nutrient sources to hypoxia have not been estimated before. Here, we combine a three-dimensional physical-biogeochemical model with an element-tracing method to quantify the relative contributions of nitrogen from different riverine and oceanic sources to hypoxia formation during 2008–2013. Our results suggest that the hypoxic region north of 30∘ N is dominated by Changjiang inputs, with its nitrogen loads supporting 74 % of oxygen consumption. South of 30∘ N, oceanic nitrogen sources become more important, supporting 39 % of oxygen consumption during the hypoxic season, but the Changjiang remains the main control on hypoxia formation also in this region. Model scenarios with reduced Changjiang nitrogen loads and reduced open-ocean oxygen levels suggest that nitrogen load reductions can significantly reduce hypoxia in the East China Sea and counteract a potential future decline in oxygen supply from the open ocean into the region.

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Section: Comparison With the Northern Gulf Of Mexicomentioning

confidence: 98%

Quantifying the contributions of riverine vs. oceanic nitrogen to hypoxia in the East China Sea

et al. 2020

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“…The study area has a complex hydrographic structure in summer, reflecting the interacting effects of Changjiang River discharge, the Taiwan Warm Current (TWC), and the Kuroshio Current (Isobe, 2008). Some observations and numerical experiments have indicated that the TWC could supply additional nutrients to the ECS, and support phytoplankton blooms there (Chung et al, 2001;Fan & Song, 2014;Jiang et al, 2015). However, other in situ surveys suggest that the warm waters in the northern Taiwan Strait are relative oligotrophic due to nutrient consumption in the Taiwan Strait itself (Liu et al, 2000;Liu, Chao, et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

Riverine and Oceanic Nutrients Govern Different Algal Bloom Domain Near the Changjiang Estuary in Summer

Yang

Greenwood

et al. 2020

JGR Biogeosciences

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The Changjiang Estuary and adjacent sea area in the East China Sea suffer from frequent harmful algal blooms. However, the relative importance of riverine nutrient input from the Changjiang River and oceanic nutrient input from the Taiwan Warm Current and Kuroshio Current to the development and distribution of summer phytoplankton blooms in this area remains unclear. To address this problem, we deployed a coupled physical-biological model. The coupled model successfully reproduces the main hydrographic and biogeochemical features in this domain. Both satellite observations and model results show two regions of elevated chlorophyll concentrated in this site. Simulated results show that harmful algal blooms in the region north of the Zhoushan Islands are mainly driven by riverine nutrients from the Changjiang River, while algal blooms in the region south of the Zhoushan Islands are mainly controlled by nutrients from the open ocean. Nutrient input, particularly phosphate, from the Kuroshio subsurface water contributes most to the accumulation of dinoflagellate biomass and chlorophyll in the southern region, while the Taiwan Warm Current has less influence. This has implications for nutrient control and land management practices: Although reducing riverine nutrient loads may significantly reduce phytoplankton growth north of the Zhoushan Islands, it will have little effect in the area to the south. Plain Language Summary Blooms of microscopic algae that can be harmful to marine ecosystems and commercial fisheries are increasingly common during the summer months in the Changjiang Estuary and adjacent sea area in the East China Sea. The Changjiang River is traditionally considered as the dominant source of nutrients driving these harmful algal blooms. In this study, we show that although this appears to be true for algal blooms occurring to the north and northeast of the river estuary, algal blooms that occur along the coast to the south of the river estuary are mainly regulated by nutrient input from the open ocean. Intrusion of the Kuroshio subsurface water to the south of the Changjiang Estuary is shown to be particularly important in supplying the dissolved phosphate necessary for the algae in the southern region to bloom in large quantities.

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“…intrusion determines the bottom nutrient conditions in the shelf (Fan & Song, 2014), which supplies nutrients for phytoplankton blooming through diapycnal mixing or upwelling (Tseng et al, 2014;Yang et al, 2013). On the other hand, strong tidal-induced mixing suspends the bottom sediments and forms a turbidity maximum zone (TMZ) in the inner estuarine area (Figure 1; Li & Zhang, 1998;Wu et al, 2012), while strong stratification restricts sediment resuspension into the upper layers in the plume area .…”

Section: Introductionmentioning

confidence: 99%

“…In the spring (April to May), Prorocentrum donghaiense Lu is dominant, whereas in the summer (June) the Skeletonema costatum dominates (Ou et al, ). In addition to species succession, dynamic processes and environmental factors that control the phytoplankton distribution have been investigated based on observational data (eg., Gong et al, ; Wang et al, ; Zhou et al, ; Zhu et al, ) and numerical models (eg., Fan & Song, ; Li et al, ; Liu et al, ; Sun et al, ; Wang et al, ; Yang et al, ). Previous observational studies suggested that light conditions (i.e., turbidity) in nearshore waters (Jiang et al, ; Zhu et al, ) and phosphate concentrations in offshore waters (Huang et al, ; Wang et al, ) limit phytoplankton blooms in the Changjiang River Estuary.…”

Section: Introductionmentioning

confidence: 99%

Phytoplankton Blooms off a High Turbidity Estuary: A Case Study in the Changjiang River Estuary

Wang

Lin

et al. 2019

JGR Oceans

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The occurrence of phytoplankton blooms in estuarine and coastal waters is codetermined by the export of fluvial nutrients and other water properties such as turbidity. In this study, the Changjiang River Estuary was used as an example to investigate the intrinsic link between river plume dynamics, riverine nutrient loading, suspended sediment concentration, and phytoplankton blooms with a coupled hydrodynamic-sediment-ecosystem numerical model. Suspended sediment concentration from the sediment module was used to parameterize light attenuation in waters, which, in association with river plume dynamics, was found to impact phytoplankton distribution. Data that was collected in situ, in addition to satellite data for chlorophyll, nutrients, and suspended sediments, were used to validate the model, which performed well. The surface high chlorophyll centers exhibited a patch-like pattern from the northeast to the south off the Changjiang River mouth. The high chlorophyll concentration within the river plume was mainly determined by riverine nutrient exports, and potential phosphate limitation occurred away from the river mouth. The chlorophyll concentration decreased dramatically shoreward of the sediment front, which was controlled by the bottom river plume front. The bottom plume front was an intrinsic feature of the Changjiang River plume and similar river plume systems, which set a boundary separating the well-mixed (turbid) nearshore waters and stratified (clear) offshore waters. Without considering the sediment shading effect, the model yielded an unrealistic chlorophyll distribution with artificially high values in the turbid area. This indicated that light attenuation was a key factor limiting phytoplankton blooms in turbid river estuaries.Plain Language Summary In estuaries and coastal waters, the aquatic environment is affected by both riverine nutrient input and water properties such as turbidity. The associated river plume may play an essential role in controlling water properties, thus influencing the aquatic environment such as the algal blooms. In the current study, a well-validated hydrodynamic-sediment-ecosystem model was used to simulate phytoplankton blooms and the dynamic link with the Changjiang River plume. The results showed that the surface suspended sediment front was of vital importance in determining the shoreward boundary of the phytoplankton bloom area. Light attenuation due to high turbidity became a major factor limiting phytoplankton blooms in turbid nearshore waters. In environments with a strong tidal influence, the surface suspended sediment front was closely related to the bottom river plume front, which gave rise to differences in water stabilization and thus resulted in turbid conditions on either side. The results of this study provided a good reference for understanding the phytoplankton distribution characteristics in estuaries with high turbidity.

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A numerical study of the seasonal variations of nutrients in the Changjiang River estuary and its adjacent sea area

Cited by 35 publications

References 21 publications

Quantifying the contributions of riverine vs. oceanic nitrogen to hypoxia in the East China Sea

Quantifying the contributions of riverine vs. oceanic nitrogen to hypoxia in the East China Sea

Riverine and Oceanic Nutrients Govern Different Algal Bloom Domain Near the Changjiang Estuary in Summer

Phytoplankton Blooms off a High Turbidity Estuary: A Case Study in the Changjiang River Estuary

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