Effect of cage culture on sedimentary heavy metal and water nutrient pollution: Case study in Sansha Bay, China.

The aquaculture area in China's coastal waters has increased rapidly from 6000 km2 in 1990 to 22,000 km2 in 2020. Despite extensive research regarding the effect of coastal aquaculture on water and sediment pollution, evaluating the quantitative relationship between aquaculture and pollutants remains challenging. Sansha Bay, the world's largest cage aquaculture base for Pseudosciaena crocea, is a typical enclosed bay used for investigating aquaculture pollution. A cage culture database is established from 2000 to 2020 in Sansha Bay. Meanwhile, 236 sediment samples from 3 sediment cores and 67 water samples from 4 transects are obtained from the bay for experiments. The main indicators are five nutrients (NO3-, SiO32-, PO43-, NH4+, and NO2-) in the water samples, the grain size, the heavy metal (Zn, Cu, Pb, Cr, Cd, and As) content, and the 210Pb radioactivity in sediment samples. Based on data obtained and a new calculation method, the annual increment in Zn, Cu, As, Cd, Pb, and Cr contents in the cultured zone is shown to increase by 2137 %, 1881 %, 506 %, 300 %, 202 %, and 118 % in 2000-2018, respectively, as compared with the levels in a noncultured zone. The activities of the cage culture increased NO3- by 9 %, PO43- by 30 %, NH4+ by 115 %, and NO2- by 232 %, compared with natural conservative mixing processes, such as the mixing of SiO32-, in 2020. A novel quantitative approach with broad applicability is proposed to evaluate the magnitude of anthropogenically induced environmental contamination. The effectiveness of the proposed technique is demonstrated through a case study conducted in Sansha Bay, China.

Discovery of quinazolin-4-one-based non-covalent inhibitors targeting the severe acute respiratory syndrome coronavirus 2 main protease (SARS-CoV-2 Mpro).

The COVID-19 pandemic caused by SARS-CoV-2 continues to pose a great threat to public health while various vaccines are available worldwide. Main protease (Mpro) has been validated as an effective anti-COVID-19 drug target. Using medicinal chemistry and rational drug design strategies, we identified a quinazolin-4-one series of nonpeptidic, noncovalent SARS-CoV-2 Mpro inhibitors based on baicalein, 5,6,7-trihydroxy-2-phenyl-4H-chromen-4-one. In particular, compound C7 exhibits superior inhibitory activity against SARS-CoV-2 Mpro relative to baicalein (IC50 = 0.085 ± 0.006 and 0.966 ± 0.065 µM, respectively), as well as improved physicochemical and drug metabolism and pharmacokinetics (DMPK) properties. In addition, C7 inhibits viral replication in SARS-CoV-2-infected Vero E6 cells more effectively than baicalein (EC50 = 1.10 ± 0.12 and 5.15 ± 1.64 µM, respectively) with low cytotoxicity (CC50 ＞ 50 µM). An X-ray co-crystal structure reveals a non-covalent mechanism of action, and a noncanonical binding mode not observed by baicalein. These results suggest that C7 represents a promising lead for development of more effective SARS-CoV-2 Mpro inhibitors and anti-COVID-19 drugs.

Changes of Neolithic subsistence in south Hangzhou Bay coast, eastern China: An adaptive strategy to landscape processes.

The transition from hunting and gathering to agricultural subsistence is a striking feature of the Neolithic revolution worldwide. Known as the cradle of a series of representative Neolithic cultures, south Hangzhou Bay (SHB) witnessed substantial changes in both landscape and human subsistence during the Holocene, yet the relationship between them was not well established. Here, we combined archaeobotanical results from sediment cores with archaeological findings to illustrate the subsistence changes during the Neolithic regime in the context of the landscape process in SHB. Our result showed that SHB was inundated by marine transgression 8,200 years ago without significant human imprints. At 8,200-7,600 cal yr. BP, the initial coastal wetland formation at locations with the semi-enclosed landscape would have facilitated the activities of hunting-gathering, incipient rice cultivation, and collecting seafood if accessible. Pollen and phytoliths evidence from multiple sediment cores in the Yaojiang Valley (YJV) suggested a desalinization process of wetland in the following hundreds of years. This amelioration of the environment had favored the intermittent rice cultivation at various locations in the YJV, where archaeological evidence was absent. Since 7,000-6,600 cal yr. BP, as freshwater wetland expanded with coastal progradation, a wide variety of food resources became available. Meanwhile, rice domestication began to serve as a crucial food supplement as evidenced by both microfossil results and archaeological findings. With the expansion of the coastal plain after 5,500 cal yr. BP, rice farming became widespread and rice consumption was increasingly important in the diet, as supported by discoveries of upgraded farming tools, abundant rice remains, and ancient rice paddies. Above all, the change of subsistence from hunting-gathering to rice farming exhibited an adaptive strategy in response to landscape evolution from an initial marine-influenced setting to a later coastal plain.

Discovery of 4'-O-methylscutellarein as a potent SARS-CoV-2 main protease inhibitor.

The coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has resulted in millions of deaths and seriously threatened public health and safety. Despite COVID-19 vaccines being readily popularized worldwide, targeted therapeutic agents for the treatment of this disease remain very limited. Here, we studied the inhibitory activity of the scutellarein and its methylated derivatives against SARS-CoV-2 main protease (Mpro) by the fluorescence resonance energy transfer (FRET) assay. Among all the methylated derivatives we studied, 4'-O-methylscutellarein exhibited the most promising enzyme inhibitory activity in vitro, with the half-maximal inhibitory concentration value (IC50) of 0.40 ± 0.03 µM. Additionally, the mechanism of action of the hits was further characterized through enzyme kinetic studies and molecular docking. Overall, our results implied that 4'-O-methylscutellarein could be a primary lead compound with clinical potential for the development of inhibitors against the SARS-CoV-2 Mpro.

Marine aquaculture regulates dissimilatory nitrate reduction processes in a typical semi-enclosed bay of southeastern China.

Marine aquaculture in semi-enclosed bays can significantly influence nutrient cycling in coastal ecosystems. However, the impact of marine aquaculture on the dynamics of dissimilatory nitrate reduction processes (DNRPs) and the fate of reactive nitrogen remain poorly understood. In this study, the rates of DNRPs and the abundances of related functional genes were investigated in aquaculture and non-aquaculture areas. The results showed that marine aquaculture significantly increased the denitrification (DNF) and dissimilatory nitrate reduction to ammonium (DNRA) rates and decreased the rate of anaerobic ammonium oxidation (ANA), as compared with non-aquaculture sites. DNF was the dominant pathway contributing to the total nitrate reduction, and its contribution to the total nitrate reduction significantly increased from 66.72% at non-aquaculture sites to 78.50% at aquaculture sites. Marine aquaculture can significantly affect the physicochemical characteristics of sediment and the abundances of related functional genes, leading to variations in the nitrate reduction rates. Although nitrate removal rates increased in the marine aquaculture area, ammonification rates and the nitrogen retention index in the aquaculture areas were 2.19 and 1.24 times, respectively, higher than those at non-aquaculture sites. Net reactive nitrogen retention exceeded nitrogen removal in the aquaculture area, and the retained reactive nitrogen could diffuse with the tidal current to the entire bay, thereby aggravating N pollution in the entire study area. These results show that marine aquaculture is the dominant source of nitrogen pollution in semi-enclosed bays. This study can provide insights into nitrogen pollution control in semi-enclosed bays with well-developed marine aquaculture.

Overlooked contribution of water column to nitrogen removal in estuarine turbidity maximum zone (TMZ).

Estuarine systems are important sites of eliminating reactive nitrogen (N) delivered from land to sea. Numerous studies have focused on N cycling in estuarine sediment. However, the N elimination role of suspended sediments in estuarine turbid water column, which might provide anaerobic microenvironment for N loss, is rarely considered. This study examined the community dynamics and activities of denitrifying and anaerobic ammonium oxidation (anammox) bacteria in the water column of the turbidity maximum zone (TMZ) of the Yangtze Estuary, using molecular and 15N isotope-tracing techniques. Results showed that the anammox bacterial community was dominated by Candidatus Kuenenia and Candidatus Brocadia in the TMZ water column, while the main nirS-harboring denitrifiers were affiliated with Rhodobacterales. The denitrifying nirS gene was two orders of magnitude more abundant than anammox bacterial 16S rRNA gene, ranging from 1.77 × 105 to 1.42 × 108 copies l-1 and from 7.68 × 104 to 4.27 × 106 copies l-1, respectively. Compared with anammox, denitrification, with rates of 0.88 to 20.83 µmol N l-1 d-1, overwhelmingly dominated the N removal in the TMZ water column and was significantly correlated to suspended sediment concentrations (SSC). Based on the measured N removal rates, it was estimated that about 2.5 × 105 ton N was annually removed from the TMZ water column, accounting for approximately 18.5% of the total inorganic N (TIN) discharged from the Yangtze River. Overall, this study implies the importance of estuarine turbid water column in controlling N budget, and also improves the understanding of N loss mechanisms in estuarine TMZ systems.