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Slowly sinking small particles in surface seawater are proven to be one of the major contributors to the mesopelagic carbon flux. Phytoplankton can respond rapidly to changes in the marine environment, so assessing the efficiency of their downward export can better constrain the relationship between carbon biomass and sinking fluxes. Here, we measured the sinking rates of individual phytoplankton (φindiv) after being subjected to Luzon cold eddy (LCE), warm eddy (WE) and spring warm pool (SWP), and explored the main influencing factors affecting cell sinking. The φindiv in the euphotic zone of the central South China Sea (ceSCS) was measured using the SETCOL method during the inter-monsoon period in April 2017. Diatoms (mainly rod-shaped) were sinking faster under the influence of SWP, with the highest carbon fluxes in the surface layer; WE leading to slow sinking of dinoflagellates, rapid sinking of cyanobacteria and a significant reduction in the number of phytoplankton species; diatoms sinking slowly due to the LCE. The φindiv of cylinder-shaped and rhombus-shaped cells in diatoms and fusiform-shaped and ellipsoid-shaped cells in dinoflagellates were significantly modulated by cell size. The setae structure of Chaetoceros can modulate the sinking behavior well in different environments. Our results indicate that in the open ocean, the shape and size of cells, the unique ecological niches of different species, and the original localization of cells are essential for the modulation of sinking. [ABSTRACT FROM AUTHOR]

Introduction: Tirzepatide is a novel hypoglycemic agent for type 2 diabetes mellitus (T2DM). However, the pathophysiology of T2DM in Asians is different from that in non-Asians, and there is no evidence to explain the differences in the efficacy and safety of tirzepatide between different races. Methods: A literature search was conducted in China National Knowledge Infrastructure (CNKI), PubMed, Cochrane Library, Clinical Trials.gov, and Embase databases for clinical studies of tirzepatide for T2DM. The data extraction process was done independently by two authors. All analyses were performed using STATA 14.0 software and Review Manager 5.3 software. Results: A total of 2118 patients with T2DM from 6 studies were involved, with doses of tirzepatide ranging from 5 to 15 mg administered subcutaneously once weekly. The results showed that compared with control/placebo, tirzepatide was more effective in decreasing fasting blood glucose (FBG) in non-Asians than in Asians, and 10 mg rather than 15 mg was the optimal dose to decrease FBG. Similarly, non-Asians were more effective than Asians in improving glycated hemoglobin (HbA1c). Asians were significantly more effective than non-Asians in reducing body weight and ≥ 5% weight loss. In terms of adverse events, the incidence of gastrointestinal adverse events was higher in Asians than in non-Asians at the same dose, while the incidence of metabolic and nutrition disorders was higher in non-Asians than in Asians. Conclusion: Tirzepatide is a novel agent for the treatment of diabetes and has different efficacy in Asians and non-Asians. Asians were more likely to experience weight loss and gastrointestinal adverse events, whereas non-Asians were more likely to have better glycemic control and more metabolic and nutritional disorders. Trial Registration: PROSPERO registration no. CRD42023489588. [ABSTRACT FROM AUTHOR]

Marine picophytoplankton (Pico) as a major contributor to primary productivity in oligotrophic waters, play a very important role in marine material cycle and energy conversion, and their key role in the carbon cycle and global climate change is increasingly emphasized. To study the factors affecting the dynamic distribution of Synechococcus, Prochlorococcus, and picoeukaryotes in the East China Sea (ECS), a marginal sea of the Northwest Pacific, we investigated 27 stations in May 2017, and collected 148 samples of Pico and nutrients from the surface to the bottom. By means of flow cytometry, the abundance of Pico was measured, and then we estimated the carbon biomass and analyzed the distribution of Pico. Finally, combined with the ECS unique geographical situation and hydrological regime, we evaluated various factors affecting the Pico in the ECS. In Pico community, the picoeukaryotes cell abundance was between 0.49×102−1.44×104 cells/mL. Prochlorococcus ranged from 1.36×103−3.47×104 cells/mL and Synechococcus ranged from 0.69×103−1.15×105 cells/mL. Synechococcus was the most, both in abundance and in carbon biomass. Picoeukaryotes were the least in abundance, but has larger contribution to carbon biomass than Prochlorococcus. Water temperature, salinity, and stability of water column influenced Pico distribution. Picoeukaryotes were abundant in the shelf sea, whereas Synechococcus and Prochlorococcus were detected in the northeast of Taiwan, China. This study provided basic information for the study of Pico communities in the ECS and its adjacent marine ecosystem. [ABSTRACT FROM AUTHOR]

The diazotrophic communities play an important role in sustaining primary productivity through adding new nitrogen to oligotrophic marine ecosystems. Yet, their composition in the oligotrophic Indian Ocean is poorly understood. Here, we report the first observation of phylogenetic diversity and distribution of diazotrophs in the Eastern Indian Ocean (EIO) surface water (to 200 m) during the pre-southwest monsoon period. Through high throughput sequencing of nifH genes, we identified diverse groups of diazotrophs in the EIO including both non-cyanobacterial and cyanobacterial phylotypes. Proteobacteria (mainly Alpha-, Beta-, and Gamma-proteobacteria) were the most diverse and abundant groups within all the diazotrophs, which accounted for more than 86.9% of the total sequences. Cyanobacteria were also retrieved, and they were dominated by the filamentous non-heterocystous cyanobacteria Trichodesmium spp. Other cyanobacteria such as unicellular diazotrophic cyanobacteria were detected sporadically. Interestingly, our qPCR analysis demonstrated that the depth-integrated gene abundances of the diazotrophic communities exhibited spatial heterogeneity with Trichodesmium spp. appeared to be more abundant in the Bay of Bengal (p < 0.05), while Sagittula castanea (Alphaproteobacteria) was found to be more dominating in the equatorial region and offshores (p < 0.05). Non-metric multidimensional scaling analysis (NMDS) further confirmed distinct vertical and horizontal spatial variations in the EIO. Canonical correspondence analysis (CCA) indicated that temperature, salinity, and phosphate were the major environmental factors driving the distribution of the diazotroph communities. Overall, our study provides the first insight into the diversity and distribution of the diazotrophic communities in EIO. The findings from this study highlight distinct contributions of both non-cyanobacteria and cyanobacteria to N2 fixation. Moreover, our study reveals information that is critical for understanding spatial heterogeneity and distribution of diazotrophs, and their vital roles in nitrogen and carbon cycling. [ABSTRACT FROM AUTHOR]