Underway mapping of coastal seawater pH using an automated shipboard analyzer with spectrophotometric detection.

The development of field-deployable methods and instruments for the measurement of pH and other carbonate parameters is important for the assessment of the marine carbon cycle, ocean acidification and marine carbon dioxide removal techniques. In this study, a high-precision fully automated integrated syringe-pump-based environmental-water analyzer for pH (iSEA-pH) was developed. The pH is determined spectrophotometrically using purified indicator dye with a high precision (better than ±0.001) and high frequency (3.5 min/sample). For the short-term analysis, the measurement frequency was 18 h-1, which revealed pH = 7.8148 ± 0.0005 (n = 104) for aged surface seawater (S = 35) from the western Pacific. For long-term analysis, the measurement frequency was 2 h-1 for 4 days, and the results showed that pH = 7.8148 ± 0.0010 (n = 200). Three commonly used pH indicators (meta-cresol purple, thymol blue and phenol red) were purified with improved flash chromatography procedures. The autonomous iSEA-pH can automatically correct for the influence of temperature, salinity and other factors on pH measurements to achieve rapid and accurate on-site measurements, which meet the "climate" goal of the Global Ocean Acidification Observing Network (uncertainty is ±0.003). Three identical iSEA-pH systems were developed and successfully applied in mesocosm experiments and several coastal and open ocean cruises with excellent in field performance.

The interactions between olivine dissolution and phytoplankton in seawater: Potential implications for ocean alkalinization.

Ocean alkalinity enhancement, one of the ocean-based CO2 removal techniques, has the potential to assist us in achieving the goal of carbon neutrality. Olivine is considered the most promising mineral for ocean alkalinization enhancement due to its theoretically high CO2 sequestration efficiency. Olivine dissolution has been predicted to alter marine phytoplankton communities, however, there is still a lack of experimental evidence. The olivine dissolution process in seawater can be influenced by a range of factors, including biotic factors, which have yet to be explored. In this study, we cultivated two diatoms and one coccolithophore with and without olivine particles to investigate their interactions with olivine dissolution. Our findings demonstrate that olivine dissolution promoted the growth of all phytoplankton species, with the highly silicified diatom Thalassiosira pseudonana benefiting the most. This was probably due to the highly silicified diatom having a higher silicate requirement and, therefore, growing more quickly when silicate was released during olivine dissolution. Based on the structural characteristics and chemical compositions on the exterior surface of olivine particles, T. pseudonana was found to promote olivine dissolution by inhibiting the formation of the amorphous SiO2 layer on the surface of olivine and therefore enhancing the stoichiometric dissolution of olivine. However, the positive effects of T. pseudonana on olivine dissolution were not observed in the coccolithophore Gephyrocapsa oceanica or the non-silicate obligate diatom Phaeodactylum tricornutum. This study provides the first experimental evidence of the interaction between phytoplankton and olivine dissolution, which has important implications for ocean alkalinization research.

Satellite-estimated air-sea CO2 fluxes in the Bohai Sea, Yellow Sea, and East China Sea: Patterns and variations during 2003-2019.

The Bohai Sea (BS), Yellow Sea (YS), and East China Sea (ECS) together form one of the largest marginal sea systems in the world, including enclosed and semi-enclosed ocean margins and a wide continental shelf influenced by the Changjiang River and the strong western boundary current (Kuroshio). Based on in situ seawater pCO2 data collected on 51 cruises/legs over the past two decades, a satellite retrieval algorithm for seawater pCO2 was developed by combining the semi-mechanistic algorithm and machine learning method (MeSAA-ML-ECS). MeSAA-ML-ECS introduced semi-analytical parameters, including the temperature-dependent seawater pCO2 (pCO2,therm) and upwelling index (UISST), to characterise the combined effect of atmospheric CO2 forcing, thermodynamic effects, and multiple mixing processes on seawater pCO2. The best-selected machine learning algorithm is XGBoost. The satellite-derived pCO2 achieved excellent performance in this complicated marginal sea, with low root mean square error (RMSE = 20 µatm) and mean absolute percentage deviation (APD = 4.12 %) for independent in situ validation dataset. During 2003-2019, the annual average CO2 sinks in the BS, YS, ECS, and entire study area were 0.16 ± 0.26, 3.85 ± 0.68, 14.80 ± 3.09, and 18.81 ± 3.81 Tg C/yr, respectively. Under continuously increasing atmospheric CO2 concentration, the BS changed from a weak source to a weak sink, the YS experienced interannual fluctuations but did not show significant trend, while the ECS acted as a strong sink with CO2 absorption increased from ∼10 Tg C in 2003 to ∼19 Tg C in 2019. In total, CO2 uptake in the entire study area increased by 85 % in 17 years. For the first time, we present the most refined variation in the satellite-derived pCO2 and air-sea CO2 flux dataset. These complete ocean carbon sink statistics and new insights will benefit further research on carbon fixation and its potential capacity.

Elevated pCO2 changes community structure and function by affecting phytoplankton group-specific mortality.

The rise of atmospheric pCO2 has created a number of problems for marine ecosystem. In this study, we initially quantified the effects of elevated pCO2 on the group-specific mortality of phytoplankton in a natural community based on the results of mesocosm experiments. Diatoms dominated the phytoplankton community, and the concentration of chlorophyll a was significantly higher in the high-pCO2 treatment than the low-pCO2 treatment. Phytoplankton mortality (percentage of dead cells) decreased during the exponential growth phase. Although the mortality of dinoflagellates did not differ significantly between the two pCO2 treatments, that of diatoms was lower in the high-pCO2 treatment. Small diatoms dominated the diatom community. Although the mortality of large diatoms did not differ significantly between the two treatments, that of small diatoms was lower in the high-pCO2 treatment. These results suggested that elevated pCO2 might enhance dominance by small diatoms and thereby change the community structure of coastal ecosystems.

Diagnosis of CO2 dynamics and fluxes in global coastal oceans.

Global coastal oceans as a whole represent an important carbon sink but, due to high spatial-temporal variability, a mechanistic conceptualization of the coastal carbon cycle is still under development, hindering the modelling and inclusion of coastal carbon in Earth System Models. Although temperature is considered an important control of sea surface pCO2, we show that the latitudinal distribution of global coastal surface pCO2 does not match that of temperature, and its inter-seasonal changes are substantially regulated by non-thermal factors such as water mass mixing and net primary production. These processes operate in both ocean-dominated and river-dominated margins, with carbon and nutrients sourced from the open ocean and land, respectively. These can be conceptualized by a semi-analytical framework that assesses the consumption of dissolved inorganic carbon relative to nutrients, to determine how a coastal system is a CO2 source or sink. The framework also finds utility in accounting for additional nutrients in organic forms and testing hypotheses such as using Redfield stoichiometry, and is therefore an essential step toward comprehensively understanding and modelling the role of the coastal ocean in the global carbon cycle.

Age prediction of children and adolescents aged 6-17 years: an epigenome-wide analysis of DNA methylation.

The DNA methylation age, a good reflection of human aging process, has been used to predict chronological age of adults and newborns. However, the prediction model for children and adolescents was absent. In this study, we aimed to generate a prediction model of chronological age for children and adolescents aged 6-17 years by using age-specific DNA methylation patterns from 180 Chinese twin individuals. We identified 6,350 age-related CpGs from the epigenome-wide association analysis (N=179). 116 known age-related sites in children were confirmed. 83 novel CpGs were selected as predictors from all age-related loci by elastic net regression and they could accurately predict the chronological age of the pediatric population, with a correlation of 0.99 and the error of 0.23 years in the training dataset (N=90). The predictive accuracy in the testing dataset (N=89) was high (correlation=0.93, error=0.62 years). Among the 83 predictors, 49 sites were novel probes not existing on the Illumina 450K BeadChip. The top two predictors of age were on the PRKCB and REG4 genes, which are associated with diabetes and cancer, respectively. Our results suggest that the chronological age can be accurately predicted among children and adolescents aged 6-17 years by 83 newly identified CpG sites.

Prevalence of and factors associated with myopia in primary school students in the Chaoyang District of Beijing, China.

PURPOSE: To determine the prevalence of and risk factors for myopia in primary school children in Chaoyang District, Beijing. METHODS: This cross-sectional prevalence survey was conducted in September to October 2011 in 4 schools randomly chosen from among the 126 primary schools in Chaoyang District. Students were assessed with autorefractometry under cycloplegia and checked with retinoscopy for accuracy. Questionnaires were completed by the students' parents. RESULTS: Myopia was present in 36.7 ± 0.7% of 4249 students aged 5-14 years old. The prevalence of myopia in girls (38.6 ± 1.1%) was significantly higher than in boys (35.0 ± 1.0 %) (p = 0.015) and increased with age (p < 0.001), with the highest prevalence observed in children aged ≥11 years (67.5 ± 1.8%). After adjustment, having a myopic parent (aOR 3.10; 95% CI 2.49-3.86), incorrect reading posture (aOR 2.09; 95% CI 1.75-2.50), reading a book at a distance of <20 cm (aOR 1.60; 95% CI 1.16-2.21), studying at home for >3 h daily (aOR 1.50; 95% CI 1.12-2.01), studying for >1 h continuously (aOR 1.21; 95% CI 1.02-1.45), and reading extracurricular books that utilize a font larger than that used in textbooks (aOR 0.74; 95% CI 0.59-0.94) were all significantly associated with myopia. CONCLUSIONS: The prevalence of myopia among primary school children in Beijing increased with age, and was significantly higher in girls ≥10 years old. Myopia was significantly associated with parental myopia, reading posture, distance between the eyes and the book being read, font size used in extracurricular reading material, time spent studying at home, and the duration of continuous study time.