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As a key component of meridional overturning circulation, mid-deep circulation plays a crucial role in the vertical and meridional distribution of heat. However, due to a lack of observation data, current knowledge of the dynamics of mid-deep circulation currents moving through basin boundaries and complicated seabed topographies is severely limited. In this study, we combined oceanic observation data, bathymetric data, and numerical modeling of the northwest continental margin of the South China Sea to investigate (i) the main features of mid-deep circulation currents traveling through the central depression belt and (ii) how atmospheric-forcing (winds) mesoscale oceanic processes such as eddies and current–topography interactions modulate the mid-deep circulation patterns. Comprehensive results suggest that the convergence of different water masses and current–topography interactions take primary responsibility for the generation of instability and enhanced mixing within the central depression belt. By contrast, winds and mesoscale eddies have limited influence on the development of local circulation patterns at mid-deep depths (>400 m). This study emphasizes that the intensification and bifurcation of mid-deep circulation; specifically, those induced by a large depression belt morphology determine the local material cycle (temperature, salinity, etc.) and energy distribution. These findings provide insights for a better understanding of mid-deep circulation structures on the western boundary of ocean basins such as the South China Sea. [ABSTRACT FROM AUTHOR]

Sepsis-induced acute lung injury (ALI) is a life-threatening medical condition with high mortality and morbidity. Autophagy is involved in the pathophysiological process of sepsis-induced ALI, including inflammation, which indicates that regulating autophagy may be beneficial for this disease. Tomatidine, a natural compound abundant in unripe tomatoes, has been reported to have anti-inflammatory, anti-tumorigenic, and lipid-lowering effects. However, the biological functions and mechanisms of tomatidine in sepsis-induced ALI remain unknown. The principal objective of this study was to investigate the effect of tomatidine on sepsis-induced ALI. Cecal ligation and puncture (CLP) was used to induce septic lung injury in mice, and 10 mg/kg tomatidine was intraperitoneally injected into mice 2 h after the operation. The results of hematoxylin and eosin staining and assessment of lung edema and total protein levels in bronchoalveolar lavage fluid (BALF) demonstrated that tomatidine alleviated CLP-induced severe lung injuries such as hemorrhage, infiltration of inflammatory cells, and interstitial and alveolar edema in mice. Additionally, the levels of proinflammatory cytokines in BALF and lung tissues were measured by enzyme-linked immunosorbent assay (ELISA), and the results showed that tomatidine inhibited CLP-induced inflammatory damage to lungs. Moreover, the results of western blotting showed that tomatidine promoted autophagy during CLP-induced ALI. Mechanistically, immunofluorescence staining and western blotting were used to measure the protein levels of TLR4, phosphorylated NF-κB, phosphorylated IκBα, and phosphorylated MAPKs, showing that tomatidine inactivated NF-κB and MAPK signaling in lung tissues of CLP-induced ALI mice. In conclusion, tomatidine exerts protective effects against sepsis-induced severe damage to the lungs by inhibiting inflammation and activating autophagy in CLP-treated mice through inactivating the NF-κB and MAPK pathways, which may be an effective candidate for treating septic ALI. [ABSTRACT FROM AUTHOR]

Investigated is a transonic turbine blade tip with a squealer rim and a squealer recess, with a single dusting film cooling hole contained within the leading edge region of the squealer recess. Data are provided for transonic flow conditions for a range of film cooling blowing ratios for two tip gap values, using a linear cascade, with no relative motion between the blade and the casing. Surface heat transfer characteristics are measured using the transient impulse-response measurement approach, employed with infrared thermography. Line-averaged adiabatic film cooling effectiveness values, for the 1.4 mm tip gap, are generally very small along the pressure side rim, with only small, locally increased values along the suction side rim. For the 0.8 mm tip gap, line-averaged adiabatic film cooling effectiveness values are generally somewhat higher along the pressure side rim and along the suction side rim. In general, effectiveness values for both tip gap values, for these locations, and for the recess region, increase as the blowing ratio increases. As the tip gap decreases from 1.4 mm to 0.8 mm, line-averaged adiabatic film cooling effectiveness generally increases on the rims and downstream regions of the recess, with increased magnitudes which are spread over larger spatial surface areas. For tip gaps of 0.8 mm and 1.4 mm, for regions where the line-averaged heat transfer coefficient ratio deviates significantly from 1.00, values generally decrease as the blowing ratio increases. Across every region of the blade, line-averaged heat transfer coefficient ratios either decrease or remain approximately invariant, as the tip gap value decreases from 1.4 mm to 0.8 mm. [ABSTRACT FROM AUTHOR]

Assessing the trend of sea surface wind is important for understanding the response of the marine environment to climate change. Analysis of wind data reveals that the summer wind direction in the Pearl River Estuary (PRE) shifts anticlockwise at a rate of −0.36°yr−1 over the past 42 years (1979–2020). The mean wind direction in July shifts from 183.6° (in 1979) to 169.3° (in 2020) and is predicted as 142.1° by 2100. How this long-term wind direction change affects the PRE hydrodynamic circulation structure has not been examined yet. A fully calibrated high resolution 3D hydrodynamic model is used to evaluate the response of local hydrodynamics to wind direction shifting in this study. The model results indicate that both the cross-channel wind-driven transport and along-channel seaward flow are weakened as wind direction shifts. Consequently, the lateral circulation is slowed down significantly while the longitudinal exchange flow is weakened slightly. A remarkable increase in stratification occurs in the coastal sea adjacent to the Modaomen where hypoxia has been frequently reported. The residence time of Lingding Bay increases slightly. The Momentum budget indicates the wind direction shifting can cause major changes in the barotropic pressure term, which is mainly balanced by the baroclinic pressure term and diffusion term. [ABSTRACT FROM AUTHOR]

Nonlinear wave‐wave interaction (WWI) in the southern South China Sea (SCS) has rarely been investigated due to sparse field observation. By analyzing datasets recorded by two adjacent moorings, we find active nonlinear WWI among diurnal internal tides (D1 ITs), near‐inertial waves (NIWs), and D1‐f waves in this area. Although the blue shift of NIWs can provide part of the energy for D1‐f waves, the bulk of D1‐f energy was generated from the nonlinear WWI. Driven by the summer monsoon, a dipole of mesoscale eddies was formed off the central Vietnam coast and intruded into the study area. The anticyclonic eddy of the dipole reduced the local effective Coriolis frequency by providing negative vorticity and suppressed the nonlinear WWI locally. During the intrusion period, D1‐f waves almost vanished suggesting the important role of mesoscale eddy on adjusting the nonlinear WWI in the SCS. Plain Language Summary: Nonlinear wave‐wave interaction (WWI) n is a common phenomenon in the global ocean and it can transfer energy among wave motions with different spatial and temporal scales. Therefore, it plays important role in energy cascade and modulating global ocean circulation. In the high latitude of the northern South China Sea (SCS), nonlinear WWI has been studied extensively since the strongest internal wave over the world was triggered there. However, it was rarely concerned in the low latitude of the SCS. Based on direct field observation and data analysis, active WWI was found in the southern SCS. And the energy transfer mainly occurred among waves with the frequencies from near‐inertial to diurnal motions. Cyclonic/anticyclonic eddy can enhance/weaken nonlinear WWI largely through input of positive/negative vorticity. The anticyclonic eddy of the dipole off the central Vietnam coast almost determined the nonlinear WWI in the southern SCS during summer monsoon season. These spotlight the impact of background circulation on the WWI in the SCS. Key Points: Active nonlinear wave‐wave interaction among triad waves was observed in the southern South China SeaNonlinear wave‐wave interaction provided bulk energy for generating D1‐f wavesAnticyclonic eddy suppressed nonlinear wave‐wave interaction and reduced near‐inertial waves and D1‐f waves largely [ABSTRACT FROM AUTHOR]

Water‐mass transports in the vast and seemingly quiescent abyssal ocean, basically along topographically‐guided pathways, play a pivotal role in the Earth's climate. The pulse of abyssal circulations can be taken with observations at topographic choke points. The Yap‐Mariana Junction (YMJ) is the exclusive choke point through which the Lower Circumpolar Deep Water (LCDW) enters the Philippine Sea. Here, we quantify the LCDW transport and its variability based on mooring observations at the YMJ and the Mariana Trench (MT). The LCDW flows northward toward the Philippine Sea as an intensified current on the western side of the YMJ, with maximum mean velocity reaching 7.6 cm/s. The mean LCDW transports through the MT and the YMJ are 2.2 ± 1.0 Sv and 2.1 ± 0.4 Sv, respectively. Reversal flow at autumn in both the YMJ and MT is captured, indicating seasonal variability of the abyssal flow. Plain Language Summary: Water‐mass transports in the vast and seemingly quiescent abyssal ocean, basically along topographically‐guided pathways, play a pivotal role in the Earth's climate. In the North Pacific, the knowledge on the Yap‐Mariana Junction (YMJ), an exclusive choke point through which the Lower Circumpolar Deep Water (LCDW), the abyssal water from the Antarctic, enters the Philippine Sea, is sparse, leaving a gap in our understanding of the abyssal circulation in the Pacific and accordingly the global overturning circulation. To fill this gap, we quantify the LCDW transport and variability based on a densely distributed deep mooring array at the YMJ and the Mariana Trench. Based on this observational program, we reveal the velocity structure from ∼4,000 m down to the bottom across the YMJ, and estimate the LCDW transport. Besides, temporal variability of the abyssal flows through the YMJ and the Mariana Trench are investigated. This study illuminates the connectivity of abyssal flows between the YMJ and the Mariana Trench, and enhances our understanding of the abyssal circulation in the western North Pacific. Key Points: A densely distributed mooring array was deployed to observe the hitherto barely studied abyssal flow through the Yap‐Mariana JunctionVelocity section and volume transport (2.1±0.4 Sv) of the intense abyssal flow through the Yap‐Mariana Junction are acquiredPathway of the Lower Circumpolar Deep Water and its reversal in autumn are revealed [ABSTRACT FROM AUTHOR]

Ocean circulation in the Challenger Deep is rarely investigated due to sparse observations. Based on hydrographic data collected by two super‐deep Chinese "Sea‐Wing" gliders during September–October 2018, we analyzed water properties and ocean circulation structures in this trench. Results showed that the horizontal distribution of water properties is approximately a three layer structure, changing from a northeast‐southwest structure to a north‐south structure then to an east‐west structure as the depth increases from 3,000 to 7,000 m. This structure is a joint result of the water uplift, advection, and diffusion in the trench. The westward geostrophic flow, with 1.29 Sv (1 Sv = 106 m3 s−1) volume transport, dominates the deep layer of the Challenger Deep, gradually weakening with depth. The unexpectedly large volume transport, twice that of previous studies, might be due to temporal variations of LCDW (Lower Circumpolar Deep Water) intrusion from the Southern Ocean and different reference levels. Plain Language Summary: The Challenger Deep is the world deepest trench. It acts as a transition zone for deep ocean water transport from the Southern Ocean to the northwestern Pacific Ocean. The AABW (Antarctic bottom water) bring large volume of clod, salty, dense, high dissolved oxygen and low‐nutrient to this region and impact the local environment and biomass in this trench. Hence, it is a meaningful thing to explore the water characteristics, circulation and volume transport over this region. Limited by observation technology in the past, they are rarely studied by previous researchers. Present observations by new‐type super‐deep gliders give us a chance to achieve that goal. Results indicate that complex 3‐D structures of water properties and circulation show up in the Challenger Deep. And large water volume of LCDW (Lower Circumpolar Deep Water) is transported into this area. These results promote the knowledge of water mass properties and circulation in the Challenger Deep. Key Points: Water property in the Challenger Deep has a three‐layer structureWestward geostrophic flow dominated the Challenger Deep and its core is shallower in the westLarge volume transport of Lower Circumpolar Deep Water (LCDW) about 1.29 Sv passed through the trench area above 7,000 m [ABSTRACT FROM AUTHOR]

The excessive use of antibiotics speeds up the dissemination and aggregation of antibiotic resistance genes (ARGs) in the environment. The ARGs have been regarded as a contaminant of serious environmental threats on a global scale. The constant increase in aquaculture production has led to extensive use of antibiotics as a means to prevent and treat bacterial infections; there is a universal concern about the environmental risk of ARGs in the aquaculture environment. In this study, a survey was conducted to evaluate the abundance and distributions of 10 ARGs, bacterial community, and environmental factors in sediment samples from aquatic farms distributed in Anhui (AP1, AP2, and AP3), Fujian (FP1, FP2, and FP3), Guangxi (GP1, GP2, and GP3), Hainan (HP1, HP2, and HP3), and Shaanxi (SP1, SP2, and SP3) Province in China. The results showed that the relative abundance of total ARGs was higher in AP1, AP2, AP3, FP3, GP3, HP1, HP2, and HP3 than that in FP1, FP2, GP1, GP2, SP1, SP2, and SP3. The sul1 and tetW genes of all sediment samples had the highest abundance. The class 1 integron (intl1) was detected in all samples, and the result of Pearson correlation analysis showed that the intl1 has a positive correlation with the sul1 , sul2 , sul3 , bla OXA, qnrS , tetM , tetQ , and tetW genes. Correlation analysis of the bacterial community diversity and environmental factors showed that the Ca2+ concentration has a negative correlation with richness and diversity of the bacterial community in these samples. Of the identified bacterial community, Proteobacteria, Firmicutes, Chloroflexi, and Bacteroidota were the predominant phyla in these samples. Redundancy analysis showed that environmental factors (TN, TP, Cl–, and Ca2+) have a positive correlation with the bacterial community (AP1, GP1, GP2, GP3, SP1, SP2, and SP3), and the abundance of ARGs (sul1 , tetW , qnrS , and intl1) has a positive correlation with the bacterial community (AP2, AP3, HP1, HP2, and HP3). Based on the network analysis, the ARGs (sul1 , sul2 , bla CMY, bla OXA, qnrS , tetW , tetQ , tetM , and intl1) were found to co-occur with bacterial taxa from the phyla Chloroflexi, Euryarchaeota, Firmicutes, Halobacterota, and Proteobacteria. In conclusion, this study provides an important reference for understanding the environmental risk associated with aquaculture activities in China. [ABSTRACT FROM AUTHOR]

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Mucins are large glycoproteins that cover epithelial surfaces of the body and play important roles in prevention of inflammatory and various infectious diseases. In this study, five membrane‐bound and seven secreted mucin genes in the channel catfish were identified. All these identified mucin genes possess at least one PTS, von Willebrand D (VWD) or SEA domains. The expression of the 12 mucin genes in channel catfish was first studied with infection of Edwardsiella ictaluri and Flavobacterium columnare. Expression difference in MUC13a, MUC13, MUC2 and MUC5b was found in the intestine after E. ictaluri infection. Eight mucin gene expressions (except MUC3a, MUC2, MUC4 and MUC5f) were up‐regulated at 4 hr and down‐regulated after 24 hr in the gill with F. columnare infection. Expression level of MUC2 gene was up‐regulated in the intestine with E. ictaluri infection without no significant change in the gill under the F. columnare infection, which indicate that MUC2 is tissue‐specific gene expression and has different immune respond to two bacterial challenge. Taken together, the study showed mucin from the gill by F. columnare challenge induced an obvious response than mucin from the intestine with E. ictaluri infection. [ABSTRACT FROM AUTHOR]

Dissolved oxygen concentration is central in determining the water quality level for an aquatic ecosystem. In this article, we analyzed in situ dissolved oxygen and other related parameters from a dataset observed during 2004–2010 in Sanya Bay to find out its status in recent years and what controlled its seasonal variation. Different to worldwide coastal and estuarine ecosystems, dissolved oxygen concentrations in the Bay reached minimum values in autumn rather than summer during most of the seven years, while maximum values were seen in winter. Results showed that the seasonal trend of dissolved oxygen was mainly controlled by physical instead of biochemical processes. While many harmful factors normally act to lower dissolved oxygen concentration during summer, such as high surface water temperature, strong stratification, and large loads of nutrients from the river basin, upwelling driven by summer monsoons cooled down the bottom water. This increased dissolved oxygen saturation and hindered biochemical oxygen demand. On the contrary, the bottom water was warmed up abruptly during autumn, when upwelling was reduced due to the cessation of summer monsoon. This decreased bottom water dissolved oxygen saturation and enhanced some biochemical processes. Overall, dissolved oxygen values were greater than 6.0 mg l−1during most years, indicating a healthy water quality environment in the Bay. Nevertheless, low dissolved oxygen bottom water conditions (<6.0 mg l−1) still existed in the whole Bay during some seasons—like the summer of 2009—which indicates there is some concern for the current stage of water quality in the Bay. [ABSTRACT FROM PUBLISHER]

Being an estuary with the occasional appearance of hypoxia, the Pearl River estuary was selected to investigate its vertical exchange process by a validated 3-D numerical model. The concept of vertical exchange time was used to quantify the vertical exchange process and was calculated by adding a conservative tracer to the hydrodynamic model. The results revealed vertical exchange time has significant seasonal variation modulated by seasonally changed external forcing, and has similar structure with spatial variation in salinity. During the wet season, remarkably long vertical exchange times (>50 days) occurred at the lower estuary under 10 m depth, which was coincident with the frequently reported hypoxic zone. The entire Pearl River estuary was occupied by water mass with a vertical exchange time of <5 days during the dry season, which indicated the estuary's health condition during this period. Further analyses revealed the seasonal trend of vertical exchange time was closely related with salinity stratification and river runoff in which the lowest vertical exchange times can be estimated by linear regressions in certain stages. Tide modulated these exchange times in different time scales. Spring tide better mixed the water column and thus facilitated the vertical exchange process compared with neap tide. As a result, minimum vertical exchange time during spring tide was about 10 days shorter than that during neap tide. Flood-ebb tide also modulated vertical exchange time in the Pearl River estuary. Vertical exchange time varies with the tide and reached minimum and maximum values during valley and high tides, respectively. [ABSTRACT FROM PUBLISHER]

The Antarctic Bottom Water (AABW) current plays a crucial role in storing and transporting heat, water, and nutrients around the world. However, it is impossible to monitor AABW in the Plio-Pleistocene by direct measurement. Hence, abyssal erosion was usually chosen as an effective indicator of the presence of the AABW in the Indian and Eastern Pacific Oceans during that period. Here, we report a high-resolution magnetostratigraphy of a gravity core, the JL7KGC-01A from the south of the Mariana Trench, northwest Pacific Ocean. The main results are as follows: (1) polarity data suggest that the sequence recorded the late Gauss chron to the early Brunhes chron, including the Jaramillo, Cobb Mountain, and Olduvai normal subchrons; (2) the sedimentary processes in the study area since 2.9 Ma show three stages of sedimentation: 83 cm/Ma during 2.9–1.2 Ma, 183 cm/Ma during 1.2–0.7 Ma, and no sedimentation since ~0.7 Ma; (3) the area south of the Mariana Trench experienced a significant change in the deposition rate at 1.2 Ma, which could be correlated with the intensified desertification in inland Asia, and experienced a prominent depositional hiatus since the early middle Pleistocene, which likely resulted from the enhanced/expanded AABW. Based on these new polarity data and comparisons with previous studies around the Pacific Ocean, we therefore propose that the AABW experienced a notable change during the early–mid Pleistocene transition. [ABSTRACT FROM PUBLISHER]