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Abstract Satellite chlorophyll a (Chl) is an essential parameter for large-scale studies on changes in the marine ecosystem and biogeochemistry. However, in the eastern China seas (ECSs), the coexistence and interaction of turbid and clear water pose challenges to the application of standard satellite Chl products to studies on phytoplankton dynamics. Based on the empirical modification of the OC-CCI (Ocean Colour Climate Change Initiative) standard products, we herein provide a locally modified chlorophyll a (LMC) dataset and compare the large-scale Chl distributions with satellite and in-situ Chl datasets. Compared with standard Chl, LMC has a higher correlation with in-situ data (R2 = 0.58) and lower Bias (0.08) and is more consistent with the ship-measured Chl distributions. Using the LMC dataset, we analyzed the climatological Chl distributions in the ECSs and classified the Chl annual cycles into four types. Our results suggest that high Chl patterns not only rely on nutrient supply, but also relate to light conditions controlled by vertical mixing and suspended matter. The different Chl annual cycles are mainly caused by differences in the duration and range of nutrients and light limitation, and thus their distributions tend to vary with water depth. We believe that this work presents a more accurate dataset in the ECSs and can improve the understanding of local biogeochemical cycles. Highlights • We provided a new locally modified Chl dataset to reduce the overestimation of standard Chl products in ECSs. • Large-scale Chl distributions from satellite and ship-measured observations were compared in the study area. • Chl annual cycles in the ECSs were classified into 4 types and the environmental control mechanisms were revealed. [ABSTRACT FROM AUTHOR]

Most previous studies confirmed that marine phytoplankton biomass can increased dramatically and then formed blooms along the typhoon track after typhoon passage. However, many events of no significant responses to typhoons were neglected. In order to figure out the most important factor for bloom formation, a coupled physical-biogeochemical model was used to study the biogeochemical phytoplankton responses to all 79 typhoon events that affected the South China Sea (SCS) during 2000–2009. The major factors investigated included typhoon intensity and translation speed, Chlorophyll a concentration (Chl-a) and vertical nitrate transport in the euphotic zone before and after typhoon passage. The results revealed that phytoplankton blooms were triggered after 43 typhoon events, but no significant blooms were found after 36 other typhoons. Of the 43 typhoon events that triggered blooms, 24 were in the open ocean and 19 were on the coast. Subsurface blooms were detected after five typhoon events that did not trigger surface blooms. Over half of the typhoons that affect the oligotrophic SCS can trigger phytoplankton blooms, and contribute to the marine primary productivity. The mechanism of the above results were surveyed, we found that (1) an increased nitrate concentration is the basic and key precondition for phytoplankton blooming in the oligotrophic SCS; (2) typhoon intensity, and translation speed control the upward flux of nitrates together, and translation speed has more effect than intensity; (3) uplifted nitrates could trigger phytoplankton bloom, and Chl-a levels reached a peak 3 days later than nitrate levels; (4) mesoscale eddies and the nutricline depth before a typhoon’s arrival also affects bloom genesis; and (5) the composition of phytoplankton functional groups in the coast was adjusted by typhoon, which have more complex mechanism of bloom formation than that in the open ocean. In summary, the physical driving force that modulates blooms is vertical nutrient transportation in the SCS. [ABSTRACT FROM AUTHOR]

The workshop series on sediment dynamics of muddy coasts and estuaries focuses on international frontier issues and major social needs, such as land-sea interactions, estuarine and coastal monitoring, numerical simulation, sediment transport and its biogeochemical effects. The Third Workshop was held in Qingdao, China, in November 2018, hosted by the Institute of Estuarine and Coastal Studies, Ocean University of China. As a result of the Third Workshop, this special issue contains 18 papers with case studies of muddy coasts in the Bohai, Yellow and East China Seas in China and other regions worldwide. These papers represent the most recent advances in Chinese and international estuarine and coastal sediment research in the topics including 1) In-situ observations of sediment dynamics in muddy coasts and estuaries and satellite remote sensing; 2) Modelling of sediment transport and associated sedimentary processes; 3) Fluid mud transport and process in bottom boundary layer, and 4) Blue bay remediation action plan and coastal restoration. • The workshop series on sediment dynamics focuses on international frontier issues. • The Third Workshop was held in Qingdao, China, in November 2018. • This special issue contains 18 papers with case studies of muddy coasts/estuaries. • These papers represent the most recent advances in coastal sediment research. [ABSTRACT FROM AUTHOR]

Abstract: The Bohai Sea is a semi-enclosed inland sea with case-2 waters near the coast. A comprehensive set of optical data was collected during three cruises in June, August, and September 2005 in the Bohai Sea. The vertical profile measurements, such as chlorophyll concentration, water turbidity, downwelling irradiance, and diffuse attenuation coefficient, showed that the Bohai Sea was vertically stratified with a relative clear upper layer superimposed on a turbid lower layer. The upper layer was found to correspond to the euphotic zone and the deep chlorophyll maximum (DCM) occurs at the base of this layer. By tuning a semi-analytical model () for the Bohai Sea, we developed a method to derive water inherent optical properties and the depth of DCM from above-surface measurements. Assuming a ‘fake’ bottom in the stratified water, this new method retrieves the ‘fake’ bottom depth, which is highly correlated with the DCM depth. The average relative error between derived and measured values is 33.9% for phytoplankton absorption at 440nm, 25.6% for colored detrital matter (detritus plus gelbstoff) absorption at 440nm, and 24.2% for the DCM depth. This modified method can retrieve water inherent optical properties and monitor the depth of DCM in the Bohai Sea, and the method is also applicable to other stratified waters. [Copyright &y& Elsevier]

In March 2021, China experienced three dust events (Dust-1, 2, 3), especially the first of which was reported as the strongest one in recent ten years. Their environmental impacts have received great attention, demanding comprehensive study to assess such impacts quantitatively. Multiple advanced measurement methods, including satellite, ground-based lidar, online aerosol speciation instrument, and biogeochemical Argo float, were applied to examine and compare the transport paths, optical and chemical properties, and impacts of these three dust events on urban air quality and marine ecosystem. The results showed that Dust-1 exhibited the largest impacts on urban area, increasing PM 10 concentration in Beijing, Shuozhou, and Shijiazhuang up to 7525, 3819, and 2992 μg m -3 , respectively. However, due to fast movement of the Mongolian low-pressure cyclone, the duration of northwest wind over the land was quite short (e.g., only 10 h in Beijing), which prevented the transport of dust plume to the northwestern Pacific, resulting in limited impact on the ocean. Dust-2 and Dust-3, though weaker in intensity, were transported directly to the sea, and led to a substantial increase in chlorophyll-a concentration (up to near 3 times) in the northwestern Pacific, comparing to climatological value. This indicates that the impacts of dust events on ocean was not necessarily and positively correlated to their impacts on land. Based on the analyses of land-ocean-space integrated observational data and synoptic systems, this study examined how marine ecosystem responded to three significant Asian dust events in spring 2021 and quantitatively assessed the overall impacts of mega dust storms both on land and ocean, which could also provide an interdisciplinary research methodology for future research on strong aerosol emission events such as wildfire and volcanic eruption., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)