Biological carbon pump responses to multiscale physical processes: a review of sediment trap studies in the South China Sea

Accurately assessing the capacity of the modern ocean to photosynthetically fix and sequester atmospheric CO2, termed the biological carbon pump (BCP), is a key component in studies on the marine carbon cycle and the global climate system. Particulate organic carbon (POC) flux into the ocean interior is an important indicator of the BCP strength, and it can be directly measured by sediment traps on time scales from days to years. This study has been conducted in the South China Sea (SCS) for over three decades. The SCS is one of the largest tropical marginal seas, located in the Asian monsoon region with frequent occurrence of dynamic physical processes and anthropogenic perturbations. It hosts an ideal natural laboratory to investigate the response of the BCP to multiscale physical processes. In this mini review, we briefly introduce the study history of mooring sediment traps in the SCS, synthesize the processes that regulate the temporal variability in mesopelagic POC flux, and how it is sensitive to climate changes. The time-series characteristics of the POC flux are clearly linked to primary production, as well as the key physical processes in the upper layer. The seasonal East Asian monsoon, intraseasonal eddies, aerosol deposition and interannual El Niño Southern Oscillation (ENSO) events are the main controlling factors over weekly to yearly timescales. Together, they suggest that the multiscale physical forcing in the upper layer regulates the mesopelagic POC export flux by controlling nutrient supplementation and subsequent POC production

Distribution and Risk Assessment of Heavy Metals in Sediment from Bohai Bay, China

Sediment core and porewater samples from the Western coastal tidal flat in Bohai Bay, China, were collected for meals and physical-chemical properties analysis. The vertical distribution characteristics of eight metals along the core was investigated based on 137Cs and 210Pb radionuclide dating. The chemical fractions of six metals (Cu, Pb, Zn, Ni, Mn and Cd) were also measured based on the modified European Community Bureau of Reference (BCR) sequential extraction procedures to better understand the mobility and bioavailability of these metals in the sediment. In addition, geoaccumulation index (Igeo) and risk assessment code (RAC) are used to assess risk status of these metals in the environment. 210Pb measurement indicates a sedimentation rate of about −1.87 cm∙year−1. The metals Cu, Zn, Pb and Ni show similar vertical distributions throughout the core, while Mn and Cd show different distribution patterns. Ni, Cu, Pb and Zn are strongly associated with the residual fraction while Mn and Cd are dominant in the acid-soluble fraction. According to the estimated diffusive fluxes, the Zn ions were the most mobilized, followed by Cu, Ni, Pb, and to a lesser extent Cd. The result of Igeo shows that Ni in sediments does not reflect any pollution, and Cu, Pb and Zn are in a level from unpolluted to modest polluted throughout the core. Mn and Cd have obvious anthropogenic sources. Based on the RAC, Cd and Mn pose a high to very high risk to the local environment, respectively, due to the significant percentage of exchangeable fraction. Clay content is significantly positively correlated with Ni, Cu, Al and Fe, and Cu, Pb, Zn and Ni might originate from the same sources or be influenced by similar geochemical processes. River runoff and atmospheric deposition are important sources for heavy metals, and since 1998, domestic sewage discharge might have had an important influence on the source of heavy metals (except for Cd and Mn)

Table_1_Identifying the wetlands of international importance in Beibu Gulf along the East Asian – Australasian Flyway, based on multiple citizen science datasets.xlsx

The Beibu Gulf (Gulf of Tonkin, Vinh Bac Bo in Vietnamese), located midway along the East Asian-Australasian Flyway (EAAF), is a critical stopover and wintering region for migratory waterbirds. This transboundary coastal region, spanning between China and Vietnam, harbors diverse wetland habitats that provide refuge to waterbird species, including highly threatened species such as the spoon-billed sandpiper (CR) and the black-faced spoonbill (EN). However, the scarcity of comprehensive assessments regarding waterbird abundances, distribution, key wetland habitats, and regional threats hinders our understanding of its conservation significance at the flyway level. Further research is needed to address these knowledge gaps and facilitate effective conservation efforts in the Beibu Gulf. By synthesizing accessible citizen science datasets and published records from wetland sites in south China and northeast Vietnam, we concluded that at least 97 waterbird species used the Gulf’s wetlands during their annual cycle. Among surveys conducted from 2014 to 2022, 6 and 13 waterbird species were considered as first and second class protected species under the National Key Protected Wild Animal List in China; 2 species were listed as Critically Endangered on the IUCN Red List, 5 as Endangered and 2 as Vulnerable, underlying the critical importance of the Beibu Gulf for the survival of these species. Our study identified 25 sites in the Beibu Gulf that met the criteria for designation as internationally important wetlands. Alarmingly, less than a quarter (n = 6, or 24%) of these sites benefit from national or international protection. Localized threats, including aquatic resource harvesting, hunting, and aquaculture/fisheries, were widespread in the region. This study provides a crucial scientific baseline for continued waterbird monitoring, site prioritization, and the development of effective habitat management plans to conserve vital coastal wetland habitats in the Beibu Gulf in China and Vietnam.</p

Table_3_Identifying the wetlands of international importance in Beibu Gulf along the East Asian – Australasian Flyway, based on multiple citizen science datasets.xlsx

The Beibu Gulf (Gulf of Tonkin, Vinh Bac Bo in Vietnamese), located midway along the East Asian-Australasian Flyway (EAAF), is a critical stopover and wintering region for migratory waterbirds. This transboundary coastal region, spanning between China and Vietnam, harbors diverse wetland habitats that provide refuge to waterbird species, including highly threatened species such as the spoon-billed sandpiper (CR) and the black-faced spoonbill (EN). However, the scarcity of comprehensive assessments regarding waterbird abundances, distribution, key wetland habitats, and regional threats hinders our understanding of its conservation significance at the flyway level. Further research is needed to address these knowledge gaps and facilitate effective conservation efforts in the Beibu Gulf. By synthesizing accessible citizen science datasets and published records from wetland sites in south China and northeast Vietnam, we concluded that at least 97 waterbird species used the Gulf’s wetlands during their annual cycle. Among surveys conducted from 2014 to 2022, 6 and 13 waterbird species were considered as first and second class protected species under the National Key Protected Wild Animal List in China; 2 species were listed as Critically Endangered on the IUCN Red List, 5 as Endangered and 2 as Vulnerable, underlying the critical importance of the Beibu Gulf for the survival of these species. Our study identified 25 sites in the Beibu Gulf that met the criteria for designation as internationally important wetlands. Alarmingly, less than a quarter (n = 6, or 24%) of these sites benefit from national or international protection. Localized threats, including aquatic resource harvesting, hunting, and aquaculture/fisheries, were widespread in the region. This study provides a crucial scientific baseline for continued waterbird monitoring, site prioritization, and the development of effective habitat management plans to conserve vital coastal wetland habitats in the Beibu Gulf in China and Vietnam.</p

Alkaloids from Gelsemium elegans

Three new alkaloids, gelsebanine (1), 14α-hydroxyelegansamine (2), and 14α-hydroxygelsamydine (3), and a new extraction artifact , gelsebamine (4), together with 12 known alkaloids, were isolated from the stems and leaves of Gelsemium elegans. The structures of 1−4 were determined by spectroscopic methods, especially 2D NMR techniques. Compounds 1−4 were evaluated for cytotoxic activity against four tumor cell lines, and gelsebamine (4) selectively inhibited the A-549 human lung adenocarcinoma cell line