Effects of Dual Fronts on the Spatial Pattern of Chlorophyll-a Concentrations in and off the Changjiang River Estuary

Li, Weiqi; Ge, Jianzhong; Ding, Pingxing; Ma, Jianfei; Glibert, Patricia M.; Chen, Lingxin

doi:10.1007/s12237-020-00893-z

Cited by 35 publications

(44 citation statements)

References 48 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Previous studies suggested that algal blooms are prone to emerge in the front region (Franks, 1992;Tang et al, 2003). Phytoplankton blooms are often associated with fronts not only because of the optimal growth environment but also since hydrodynamics transport phytoplankton horizontally and aggregates phytoplankton in the front region (Tang et al, 2006;Wang et al, 2019b;Li et al, 2021). After the MEC, the plume structure was modulated, and the front region should also be dislocated.…”

Section: Effect Of the Mega Estuarine Constructions-induced Suspended Sediment Concentration Variationmentioning

confidence: 99%

Regulation of Algal Bloom Hotspots Under Mega Estuarine Constructions in the Changjiang River Estuary

Wang

2022

Front. Mar. Sci.

View full text Add to dashboard Cite

Massive large-scale engineering projects have been built in river estuaries around the world, but their effects on environments in the surrounding coastal waters were less emphasized compared to those due to the watershed projects. In this study, we used the Changjiang River Estuary as an example to show that a significant consequence can be resulted in such a situation. Through analyzing the harmful algal bloom events data and the chlorophyll satellite data, we investigate the spatiotemporal variations of algal blooms in the estuary and its adjacent water. The results indicate that the location of algal bloom hotspot changed over the period of the estuarine constructions. Furthermore, using a well-validated numerical model, we explored the mechanisms responsible for such an ecosystem regime shift. It was found that after the estuarine constructions were built, the surface chlorophyll maximum was attenuated and part of it migrated landward north of the river mouth but was strengthened south of the river mouth and extended seaward. Alternations of the nutrient concentration distribution and turbidity distribution induced by river plume deviation are responsible for the redistribution of the high chlorophyll concentration area. By contrast, the direct impact of the Three Gorges Dam through changing the runoff and sediments flux, which has been highlighted in numerous studies, was less important than expected. Given the fact that Three Gorges Dam and mega estuarine constructions were built in a similar period, any observed regime shift of hydrodynamic and ecological status outside the estuary should be interpreted with particular caution.

show abstract

Section: Effect Of the Mega Estuarine Constructions-induced Suspended Sediment Concentration Variationmentioning

confidence: 99%

Regulation of Algal Bloom Hotspots Under Mega Estuarine Constructions in the Changjiang River Estuary

Wang

2022

Front. Mar. Sci.

View full text Add to dashboard Cite

show abstract

“…This was due to the synergies of light, nutrient conditions, and temperature. Weak light penetration in the nearshore region and nutrient deficiency offshore both limit phytoplankton growth (W. Li et al, 2021;Z. Y. Zhu et al, 2009).…”

Section: Primary Production and Relations To Hypoxiamentioning

confidence: 99%

“…Y. Zhu et al, 2009). In contrast, the optimal balance between light and nutrients can be achieved near the CDW plume boundary (i.e., the transitional region; W. Li et al, 2021;Ning et al, 2004;Y. H. Wang et al, 2019;Z.…”

Section: Primary Production and Relations To Hypoxiamentioning

confidence: 99%

Coastal Upwelling Combined With the River Plume Regulates Hypoxia in the Changjiang Estuary and Adjacent Inner East China Sea Shelf

Yao

Zhao

et al. 2021

JGR Oceans

View full text Add to dashboard Cite

The Changjiang (Yangtze River) Estuary (CE) and adjacent inner East China Sea (ECS) shelf are among the most well‐known hypoxic aquatic environments. However, the coupled effects of coastal upwelling and the river plume on hypoxic dynamics in this region are rarely examined. Based on observations off the CE and Zhejiang coast in the summer of 2018, the dynamic mechanisms were revealed by highlighting the combined role of the river plume and upwelling in regulating hypoxia. The bottom hypoxic water formed in the steep slope on the inner ECS shelf expands upward and seaward. Coastal upwelling and the river plume combine to regulate the primary production regime and hypoxia. The frontal regions in the upper layers are prone to phytoplankton blooms, while the convergent slope generally acts as a hot spot of bottom hypoxic center along cross‐shelf sections. The regional selectivity of hypoxia is responsible for the decoupling between locations of bottom‐water hypoxia and upper‐water phytoplankton patches. The upwelling transports oxygen‐deficient water to the upper layers, resulting in shoreward shoaling of the oxycline. Meanwhile, mainly forced by the seaward expansion of low‐oxygen water protruding from the bottom hypoxia in the sloping region, a pronounced midlayer hypoxic plume forms. Together, upwelling and offshore spreading potentially expand the spatial volume of the hypoxic zone. Vertical secondary circulation and subsequent physical–biogeochemical processes leading to hypoxia are indicated off the CE and Zhejiang coast. Our results demonstrate that the combination of upwelling and the river plume plays an important role in regulating the spatial distribution of coastal and estuarine hypoxia.

show abstract

“…Hence, the total suspended matters (TSM) concentrations in the HZB are relatively high and can even reach 5000 mg•dm −3 [10,11]. In contrast, in its adjacent waters, such as the CJE and the Xiangshan Bay, the TSM concentrations are approximately 200 mg•dm −3 [12,13], two orders of magnitude lower than that in the HZB. These unique physical and chemical characteristics keep the chlorophyll a (Chl) and PP at a low level in the HZB.…”

Section: Introductionmentioning

confidence: 99%

Spatial and Temporal Variations of Chlorophyll a and Primary Productivity in the Hangzhou Bay

Wang

Chen

Zhou

et al. 2022

JMSE

View full text Add to dashboard Cite

The Hangzhou Bay (HZB) is an important part of the Zhoushan fishing ground, the most productive region in the Eastern China Seas. Although HZB remains eutrophication all year round, its chlorophyll a (Chl) and primary productivity (PP) are usually significantly lower than those in the adjacent waters. In the present study, we presented the Chl and PP distributions in the HZB and analyzed their correlations with environmental factors in four seasons. The field observation showed that Chl and PP had significant seasonal variations, and was highest in the summer (1.66 ± 0.61 mg·m−3 and 12.11 ± 12.25 mg C·m−3·h−1, respectively). Total suspended matters (TSM) concentration was the key environmental factor that constrains PP in the study area. High concentration of TSM reduced light exposure (LE, the annual mean value was 0.92 ± 0.81 Einstein·m−2·day−1) in the mixed layer of the HZB, which was much lower than the saturated light intensity of phytoplankton growth, and thus caused a strong light limitation in the HZB. However, the seasonal variations in the photosynthesis rates (PB) and Chl did not coincide. This fact suggested that the growth rate was not the only factor controlling seasonal variations of phytoplankton biomass. In winter, the very high TSM and strong mixing might reduce the zooplankton grazing rate, and lead to a relatively high concentration of Chl during the very low LE and PB period. These results implied that, in the HZB, the extremely turbid water could affect both phytoplankton growth and loss, which was probably the major mechanism responsible for the complex phytoplankton spatial and temporal variations.

show abstract

Effects of Dual Fronts on the Spatial Pattern of Chlorophyll-a Concentrations in and off the Changjiang River Estuary

Cited by 35 publications

References 48 publications

Regulation of Algal Bloom Hotspots Under Mega Estuarine Constructions in the Changjiang River Estuary

Regulation of Algal Bloom Hotspots Under Mega Estuarine Constructions in the Changjiang River Estuary

Coastal Upwelling Combined With the River Plume Regulates Hypoxia in the Changjiang Estuary and Adjacent Inner East China Sea Shelf

Spatial and Temporal Variations of Chlorophyll a and Primary Productivity in the Hangzhou Bay

Contact Info

Product

Resources

About