Effects of dissolved oxygen and nutrients from the Kuroshio on hypoxia off the Changjiang River estuary

Tian, Di; Zhou, Feng; Zhang, Wenyan; Zhang, Han; Ma, Xiao; Guo, Xinyu

doi:10.1007/s00343-021-0440-3

Cited by 13 publications

(8 citation statements)

References 62 publications

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“…Excess nutrient input aggravates the degree of eutrophication in estuaries and offshore waters, coupled with global warming, and leads to an increase in the occurrence and intensity of hypoxic conditions (Breitburg et al, 2018). Since 1950, more than 500 coastal systems of hypoxia have been identified, with a total area of more than 245,000 km 2 (Diaz and Rosenberg, 2008;Breitburg et al, 2018), including the Gulf of Mexico (Del Giudice et al, 2019), Chesapeake Bay (Da et al, 2018), Lower St. Lawrence Estuary (Lefort et al, 2012), and the Yangtze River Estuary (Tian et al, 2021). The lack of oxygen in the sea area has gradually developed into a major global ecological and environmental problem.…”

Section: Habitat Decline and Regional Variationsmentioning

confidence: 99%

Habitat decline of the largest known Indo-Pacific humpback dolphin (Sousa chinensis) population in poorly protected areas associated with the hypoxic zone

Guo

Luo²,

Yu³

et al. 2022

Front. Mar. Sci.

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Reserve planning based on the investigation of the core habitat distribution of wild cetaceans is a powerful conservation strategy for protecting target species. However, studies on core habitats and their variations at the large-scale distribution of cetaceans are limited. In this study, we conducted a seven years (2015-2021) boat-based field observation surveys with highly applicable and generalized methods to analyze the habitat changes and how these changes influenced the largest known Indo-Pacific humpback dolphin (Sousa chinensis) population in the Pearl River Estuary (PRE), China. Our findings revealed that there is 3204 km2 of dolphin habitat in the PRE, and dolphin distribution preferences are related to nutrients and biological resources. The decreasing trend of dolphin sighting rates in most areas (73.2%) indicated that the dolphin habitat had declined, and the annual habitat decline rate (2.83%; 95% confidence interval: 0.58%-5.08%) was consistent with the population decline rate. The annual habitat decline rate in the hypoxic zone revealed that low dolphin sighting rates from March to October in the hypoxic zone was 0.43% faster than that in the non-hypoxic zone, indicating long-term sustained effects of summer hypoxia on the dolphin population. Existing reserves have partially prevented habitat decline. However, more than 82.3% of the habitat has not been effectively protected and encounters the threats of pollution and hypoxic stress. This study offers new scientific evidence for developing effective monitoring strategies for humpback dolphin populations in the PRE, and also help establish spatial planning and management measures for reserve habitats.

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Section: Habitat Decline and Regional Variationsmentioning

confidence: 99%

Habitat decline of the largest known Indo-Pacific humpback dolphin (Sousa chinensis) population in poorly protected areas associated with the hypoxic zone

Guo

Luo²,

Yu³

et al. 2022

Front. Mar. Sci.

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“…The biogeochemical module was based on the carbon, silicate, and nitrogen ecosystem (CoSiNE) model (Chai et al, 2002;Xiu and Chai, 2014). The coupled ROMS-CoSiNE model (hereafter BYESbio24) was capable of simulating the seasonal, and synoptic, variation of the hypoxic zone in the ECS (Zhou et al, 2017;Zhou et al, 2020;Tian et al, 2022).…”

Section: Model Descriptionmentioning

confidence: 99%

Response Process of Coastal Hypoxia to a Passing Typhoon in the East China Sea

Meng

Zhou

et al. 2022

Front. Mar. Sci.

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Details of the development of coastal hypoxia in response to the passage of Typhoon Bavi (2020) in the East China Sea were reconstructed by numerical modeling using a three-dimensional coupled physical–biogeochemical model. The model was validated via repeated surveys along a transect across a submerged river valley off the Changjiang Estuary before and after the passage of Typhoon Bavi. Before Bavi’s arrival, survey data indicated that the coastal hypoxia had formed off the Changjiang Estuary. However, the hypoxia was not eliminated but instead migrated and aggravated along the observed transect after the typhoon passage. This phenomenon cannot be attributed to the typhoon-induced mixing. Simulation results reveal that the observed development and spatial migration of hypoxia was mainly controlled by typhoon-induced oceanic advection. Results show that Bavi stimulated a regional quasi-barotropic cyclonic loop circulation and coastal downwelling reversing general summer circulation patterns. The onshore transport of the warmer shelf water and subsequent downwelling resulted in a warming of coastal water. The southward coastal current and downwelling induced by the typhoon also led to a migration of the hypoxic zone. Meanwhile, a massive transport of resuspended planktonic detritus from the steep inner shelf and the shallow Changjiang bank toward the submerged river valley occurred. This study reveals that the typhoon-driven currents can play an important role in the development of hypoxia and redistribution of deposited organic matter in coastal shelf seas, which may have both short- and long-term effects on the regional marine biogeochemical environment.

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“…Tian et al. (2021) reported that dissolved oxygen and phosphate are the most influential factors for Kuroshio to influence the environment around the Changjiang River Estuary. Chen et al.…”

Section: Introductionmentioning

confidence: 99%

“…Through a series of numerical experiments, Xu et al (2020) discovered that the input of nutrients, particularly phosphate, from the KSSW regulates the accumulation of dinoflagellate biomass and chlorophyll-a in the region south of the Zhoushan Islands. Tian et al (2021) reported that dissolved oxygen and phosphate are the most influential factors for Kuroshio to influence the environment around the Changjiang River Estuary. Chen et al (2021) confirmed the upwelling impact of high nutrient and low dissolved oxygen KSSW on phytoplankton bloom through in situ observations.…”

mentioning

confidence: 99%

Three Types of Typhoon‐Induced Upwellings Enhance Coastal Algal Blooms: A Case Study

Yang

et al. 2022

JGR Oceans

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Satellite data show that typhoon Chan‐hom did trigger an algal bloom several days after passing by the East China Sea. To investigate dynamic connections between this enhanced chlorophyll‐a and phosphate‐rich Kuroshio subsurface water (KSSW), we set up a fine‐resolution coupled physical‐biological model, which effectively reproduced the oceanic conditions during this typhoon. Furthermore, we released a passive tracer along a zonal transect northeast of Taiwan. The modeled surface tracer variations along the coast of Zhejiang agreed very well with satellite data and chlorophyll‐a changes in the biological model. The lowest structural similarity index between chlorophyll‐a and KSSW was 0.77. Model results along a coastal section imply that typhoon Chan‐hom induced additional upwellings and enhanced vertical mixing, leading to more KSSW outcropping. Through horizontal dynamic diagnostic and vertical velocity decomposition, we distinguished three types of dynamical mechanisms for the upward motions. At first, the linear wind Ekman effect existed around the coastal areas and led to intense Ekman pumping. Second, a pronounced nonlinear effect led to upwellings, and spectrum analysis revealed that this nonlinearity consisted of high‐frequency near‐inertial waves and low‐frequency coastal shelf waves. At last, an eddy field remained after the typhoon, continuously supplying nutrients upward to the surface layer by eddy‐induced Ekman pumping. This study reveals that these mechanisms may be general on the continental shelf, where typhoons can pump phosphate‐rich bottom water into the upper layer and enhance primary productivity there. The results also prove typhoon‐induced nonlinear wave motions on the continental shelf contribute to the outcrop of nutrients.

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Effects of dissolved oxygen and nutrients from the Kuroshio on hypoxia off the Changjiang River estuary

Cited by 13 publications

References 62 publications

Habitat decline of the largest known Indo-Pacific humpback dolphin (Sousa chinensis) population in poorly protected areas associated with the hypoxic zone

Habitat decline of the largest known Indo-Pacific humpback dolphin (Sousa chinensis) population in poorly protected areas associated with the hypoxic zone

Response Process of Coastal Hypoxia to a Passing Typhoon in the East China Sea

Three Types of Typhoon‐Induced Upwellings Enhance Coastal Algal Blooms: A Case Study

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