Oscillations of algal cell quota: Considering two-stage phosphate uptake kinetics.

Elucidating the mechanism of effect of phosphate (PO43-) uptake on the growth of algal cells helps understand the frequent outbreaks of algal blooms caused by eutrophication. In this study, we develop a comprehensive mathematical model that incorporates two stages of PO43- uptake and accounts for transport time delay. The model parameter values are determined by fitting experimental data of Prorocentrum donghaiense and the model is validated using experimental data of Karenia mikimotoi. The numerical results demonstrate that the model successfully captures the general characteristics of algal growth and PO43- uptake under PO43- sufficient conditions. Significantly, the experimental and mathematical findings suggest that the time delay associated with the transfer of PO43- from the surface-adsorbed PO43- (Ps) pool to the intracellular PO43- (Pi) pool may serve as a physiologically plausible mechanism leading to oscillations of algal cell quota. These results have important implications for resource managers, enabling them to predict and deepen their understanding of harmful algal blooms.

The characteristics of trimethylamine N-oxide content in different classes of marine animals over the coastal and offshore areas of China.

Trimethylamine N-oxide (TMAO) is widely present in marine animals. However, the characteristics of TMAO content in different classes of marine animals are insufficiently understood. In this study, the TMAO content in 79 marine animals (48 species, 7 classes) collected in the coastal and offshore areas of China during year 2019-2022 was analysed. The results showed that the TMAO content of the total samples varied from 0 to 139.19 mmol kg-1. The TMAO content in the classes Bivalvia, Gastropoda, Polychaeta and Holothuroidea varied from 0.06 ± 0.09 to 0.38 ± 0.63 mmol kg-1, but it varied from 30.20 ± 24.20 to 75.90 ± 38.59 mmol kg-1 in the classes Crustacea, Cephalopoda, and Osteichthyes. The TMAO content in the latter 3 classes was 2-3 orders of magnitude higher than that of the former 4 classes. It was inferred that the significant difference was related to the food sources or physiological metabolic mechanisms of different classes.

Spatial distribution and potential ecological risk assessment of heavy metals in the sediments of fishing ports along the coasts of the Yellow Sea and Bohai Sea.

More than 1,154 fishing ports are widely distributed in China's coastal areas. To date, however, few studies on the pollution and ecological risks of heavy metals in these fishing ports have been reported. In this study, the heavy metals of 148 sediment samples collected from 37 fishing ports along the coasts of the Yellow Sea and Bohai Sea were detected. The results showed that the average contents of Cu, Pb, Zn, and Cd were 53.58 ± 44.53, 27.90 ± 18.10, 143.52 ± 74.72 and 0.28 ± 0.15 mg/kg, respectively. Based on the geoaccumulation index (Igeo) and the potential ecological risk index (RI), we found that fishing ports were the most severely polluted by Cu, but Cd had the highest ecological risk, and most of fishing ports were in moderate potential ecological risk. The positive correlation between heavy metals and total organic carbon indicated that heavy metals in fishing ports were mainly affected by anthropogenic activities.

High dimethylsulfoniopropionate concentrations in the surface seawater over the marginal seas of China and the Northwest Pacific Ocean during May-July of 2021 following La Niña.

The total dimethylsulfoniopropionate (DMSPt) concentrations over the surface seawater of China's marginal seas and the northwest Pacific Ocean (NWPO) in May-July 2021 (during the recessional period of La Niña) were analysed. The results showed that the DMSPt concentrations in the marginal seas of China varied from 4.73 to 775.96 nmol L-1, with an average value of 111.42 ± 129.30 nmol L-1 (average ± standard deviation). It was 2-12 times higher than those previously measured in the same seas and in the NWPO in this study. Significant positive correlations between DMSPt, chlorophyll-a and surface seawater temperature (SST) were observed in the SYS, the ECS and the NWPO. Moreover, their abnormally high SST was related to La Niña. These results suggested that high phytoplankton abundance was caused by abnormally high SST following La Niña, which further promoted DMSPt concentration increases. However, the increase of DMSPt was also related to other factors such as nutrients.

Identifying the key factors affecting the trimethylamine N-oxide content of teleost fishes collected from the marginal seas of China and the epipelagic zone of the northwest Pacific Ocean.

To identify the key factors influencing the trimethylamine N-oxide (TMAO) content of teleost fishes living in shallow seas and the epipelagic zone of the deep ocean, the muscle TMAO content was measured in 152 teleost fishes (21 species) collected from the marginal seas of China and the epipelagic zone of the northwest Pacific Ocean (NWPO) during May-July 2021. The results showed that the TMAO content in all fishes varied from 4.99 to 82.97 mmol kg-1, and it varied notably among different species, e.g., the highest average content (72.71 ± 8.22 mmol kg-1 in Argyrosomus argentatus) was 1 order of magnitude higher than the lowest one (Scomber japonicus), but the ratios of the highest content to the lowest content in each species varied from 1.29 to 3.28, suggesting that the interspecific variations in TMAO content were obviously greater than the intraspecific variations. Moreover, no correlation was observed between the TMAO content of the 152 fishes and the corresponding environmental factors of seawater depth, salinity and temperature, indicating that species played a more important role than environmental factors in driving TMAO accumulation. To exclude the influence of species, intraspecies correlations between TMAO content and environmental factors were analyzed. In the marginal seas of China, only ∼8 % of the TMAO content of teleost fishes (1 species) showed a positive correlation with salinity and depth, but ∼50 % of the TMAO content (5 species) was negatively correlated with temperature. Moreover, the TMAO content of the fish increased by 4.66 ± 1.38 % compared with their corresponding intraspecific average values for every 1 °C of temperature decrease. A similar phenomenon was also found in the TMAO content of pelagic teleost fishes in the NWPO, suggesting that temperature was a key environmental factor affecting the TMAO content of teleost fishes in shallow seas and the epipelagic zone of the deep ocean.

The characteristics of CDOM structural composition and the effect on indirect photodegradation of sulfamerazine.

Sulfamerazine (SM) is a commonly used antibiotic and have been widely used to control various bacterial infectious diseases. The structural composition of colored dissolved organic matter (CDOM) is known to be a major factor that influences the indirect photodegradation of SM, yet the influence mechanism remains unknown. In order to understand this mechanism, CDOM from different sources was fractionated using ultrafiltration and XAD resin, and characterized using UV-vis absorption and fluorescence spectroscopy. The indirect photodegradation of SM in these CDOM fractions was then investigated. Humic acid (JKHA) and Suwannee River natural organic matter (SRNOM) were used in this study. The results showed that CDOM could be divided into four components (three humic-like components and one protein-like component), and terrestrial humic-like components C1 and C2 were found to be the main components that promote SM indirect photodegradation due to their high aromaticity. The indirect photodegradation of SM was much faster in low molecular weight (MW) solutions, whose structures were dominated by greater aromaticity and terrestrial fluorophores in JKHA and higher terrestrial fluorophores in SRNOM. The HIA and HIB fractions of SRNOM contained large aromaticity and high fluorescence intensities of C1 and C2, resulting in a greater indirect photodegradation rate of SM. The HOA and HIB fractions of JKHA had abundant terrestrial humic-like components and contributed more to SM indirect photodegradation.

Eutrophication status assessment in the Laizhou Bay, Bohai Sea: Further evidence for the ecosystem degradation.

Laizhou Bay is plagued by many environmental problems (e.g., acidification and eutrophication) that are likely to increase in the coming decades along with social and demographic trends. We thus conducted 12 cruises from July 2019 to December 2021 in the Laizhou Bay to evaluate the potential influences of human activities on its eutrophication status. The results showed that the parameters of dissolved inorganic nitrogen (DIN) and oxygen (DO) exceeded the water quality standard in some cases during the past 3 years, suggesting DIN and DO were the crucial factors controlling water quality in the bay. Meanwhile, DIN was identified as a major pollutant in the region, and played an important role in driving the phytoplankton dynamics. Furthermore, with the increases in human-related nutrient inputs (especially DIN), the bay environment reached the mild eutrophication level and was probably at risk from excessive nutrient loads at present, further evidencing the ecosystem degradation.

The Effect of Leucine Supplementation on Sarcopenia-Related Measures in Older Adults: A Systematic Review and Meta-Analysis of 17 Randomized Controlled Trials.

Background: The role of leucine in sarcopenia prevention remains unclear. We aimed to summarize the published data from randomized controlled trials (RCTs) to estimate the effect of leucine supplementation on sarcopenia-related measures in older adults. Methods: A systematic literature search was performed using the electronic databases PubMed, Embase, and Web of Science with restriction to randomized controlled trials design from January 1, 2009 to March 19, 2022. Sarcopenia-related measures included handgrip strength, total lean mass, gait speed, leg press, 6-min walk test, short-physical performance battery, timed up-and-go test and 30-s chair-stand test. Fixed- and random-effects meta-analysis models were used to generate pooled weighted mean differences (WMDs) and 95% CIs. Heterogeneity was examined in subgroup and sensitivity analyses. Publication bias assessments were performed. Results: A total of 17 RCTs enrolling 1418 subjects were identified. Leucine-isolated supplementation showed no effect on total lean mass (WMD = 0.03 kg, 95% CI: -0.51, 0.57, P = 0.917), handgrip strength (WMD = 1.23 kg, 95% CI: -0.58, 3.03, P = 0.183) and leg press (WMD = -1.35 kg, 95% CI: -7.46, 4.77, P = 0.666). However, leucine-combined supplementation including vitamin D showed a significant improvement in handgrip strength (WMD = 2.17 kg, 95% CI: 0.24, 4.10, P = 0.027) and gait speed (WMD = 0.03 m/s, 95% CI: 0.01, 0.05, P = 0.008). Conclusion: Leucine-isolated supplementation did not improve muscle mass and strength in elderly. However, leucine-combined supplementation including vitamin D exhibited a significant benefit for muscle strength and performance including handgrip strength and gait speed in older adults. A combination of nutritional supplements would be a viable option for improving sarcopenia.

Dietary Intake and Biomarkers of α-Linolenic Acid and Mortality: A Meta-Analysis of Prospective Cohort Studies.

Background: The association between α-linolenic acid (ALA) and mortality is inconsistent and has not been summarized systematically. Objective: The purpose was to conduct a meta-analysis that synthesized the results of prospective cohort studies to investigate associations between ALA intake and mortality. Methods: We conducted a comprehensive search on PubMed, Embase, and Web of Science databases on May 1, 2021, for relevant prospective cohort studies which reported associations of ALA (assessed by dietary surveys and/or ALA concentrations in body tissues) with mortality from all-cause, cardiovascular disease (CVD), and other diseases. Multivariable-adjusted relative risks (RRs) were pooled by a random or fixed-effects model. Results: A total of 34 prospective cohort studies, of which 17 reported dietary ALA intake, 14 for ALA biomarkers, and the remaining 3 reported both of intake and biomarkers. The studies included 6,58,634 participants, and deaths were classified into all-cause mortality (56,898), CVD mortality (19,123), and other diseases mortality (19,061). Pooled RRs of ALA intake were 0.93 (95% CI: 0.86, 1.01, I 2 = 71.2%) for all-cause mortality, 0.90 (95% CI: 0.83, 0.98, I 2 = 22.1%) for CVD mortality, and 0.94 (95% CI: 0.83, 1.06, I 2 = 73.3%) for other diseases mortality. The two-stage random-effects dose-response analysis showed a linear relationship between dietary ALA intake and CVD-mortality and each 0.5% energy increment of ALA intake was associated with a 5% lower risk of CVD-mortality (RR: 0.95; 95% CI: 0.90, 1.00). Pooled RRs per SD increment of ALA biomarkers were 0.99 (95% CI: 0.96, 1.01, I 2 = 27%) for all-cause mortality, 1.00 (95% CI: 0.98, 1.03, I 2 = 0%) for CVD mortality and 0.98 (95% CI: 0.95, 1.01, I 2 = 0%) for other diseases mortality. Conclusions: This meta-analysis summarizing the available prospective cohort studies indicated that ALA intake was associated with reduced risk of mortality, especially CVD mortality. Our findings suggest that ALA consumption may be beneficial for death prevention. Systematic Review Registration: https://www.crd.york.ac.uk/PROSPERO; identifier: CRD42021264532.

Concentration and size distribution of water-extracted dimethylaminium and trimethylaminium in atmospheric particles during nine campaigns - Implications for sources, phase states and formation pathways.

In this study, we determined the concentrations of water-extracted dimethylaminium (DMA+) and trimethylaminium (TMA+) in size-segregated atmospheric particles collected during three inland campaigns and one sea-beach campaign in Qingdao and five marine campaigns in marginal seas of China and the northwest Pacific Ocean. The averages of DMA+ and TMA+ in PM0.056-10 (the sum of concentrations from 0.056 to 10µm) during each campaign ranged from 0.045 to 1.1nmolm-3 and from 0.029 to 0.53nmolm-3, respectively. The increased concentrations of DMA+ and TMA+ in PM0.056-10, particularly the 1-2 orders of magnitude increased ratios of DMA+/NH4+ and TMA+/NH4+, in the marine and sea-beach atmospheres indicated that the overwhelming majority was derived from marine sources. Size distributions of TMA+ and DMA+ were also investigated in terms of phase states and formation pathways, e.g., the dominant modes of particulate DMA+ and TMA+ in some samples were characterized by the mass median aerodynamic diameter at 0.1-0.2µm against the dominant mode of NH4+ and SO42- at 0.7-0.9µm, while the ratios of DMA+/NH4+ and/or TMA+/NH4+ in <0.2µm particles increased by 3-10 times from the corresponding lower values in >0.2µm particles. This strongly implied that the particulate DMA+ and TMA+ at <0.2µm size range overwhelmingly existed in the liquid organic phase as unprotonated TMA and DMA, but those at the >0.2µm size range mainly existed in the aqueous (or solid) phase where the dominance of gas-aerosol equilibria would cause the ratios to be almost size-independent. The size-dependent phase states corresponded to their various formation pathways.

Identification of Major Sources of Atmospheric NH3 in an Urban Environment in Northern China During Wintertime.

To assess the relative contributions of traffic emission and other potential sources to high levels of atmospheric ammonia (NH3) in urban areas in the wintertime, atmospheric NH3 and related pollutants were measured at an urban site, ∼300 m from a major traffic road, in northern China in November and December 2015. Hourly average NH3 varied from 0.3 to 10.8 ppb with an average of 2.4 ppb during the campaign. Contrary to the common perspective in literature, traffic emission was demonstrated to be a negligible contributor to atmospheric NH3. Atmospheric NH3 correlated well with ambient water vapor during many time periods lasting from tens of hours to several days, implying NH3 released from water evaporation is an important source. Emissions from local green space inside the urban areas were identified to significantly contribute to the observed atmospheric NH3 during ∼60% of the sampling times. Evaporation of predeposited NHx through wet precipitation combined with emissions from local green space likely caused the spikes of atmospheric NH3 mostly occurring 1-4 h after morning rush hours or after and during slight shower events. There are still ∼30% of the data samples with appreciable NH3 level for which major contributors are yet to be identified.

Characteristics of dimethylaminium and trimethylaminium in atmospheric particles ranging from supermicron to nanometer sizes over eutrophic marginal seas of China and oligotrophic open oceans.

In this study, we characterized dimethylaminium (DMA+) and trimethylaminium (TMA+) in size-segregated atmospheric particles during three cruise campaigns in the marginal seas of China and one cruise campaign mainly in the northwest Pacific Ocean (NWPO). An 14-stage nano-MOUDI sampler was utilized for sampling atmospheric particles ranging from 18µm to 0.010µm. Among the four cruise campaigns, the highest concentrations of DMA+ and TMA+ in PM10 were observed over the South Yellow Sea (SYS) in August 2015, i.e., 0.76±0.12nmolm-3 for DMA+ (average value±standard deviation) and 0.93±0.13nmolm-3 for TMA+. The lowest values were observed over the NWPO in April 2015, i.e., 0.28±0.16nmolm-3 for DMA+ and 0.22±0.12nmolm-3 for TMA+. In general, size distributions of the two ions exhibited a bi-modal pattern, i.e., one mode at 0.01-0.1µm and the other at 0.1-1.8µm. The two ions' mode at 0.01-0.1µm was firstly observed. The mode was largely enhanced in samples collected over the SYS in August 2015, leading to high mole ratios of (DMA++TMA+)/NH4+ in PM0.1 (0.4±0.8, median value±standard deviation) and the ions' concentrations in PM0.1 accounting for ~10% and ~40% of their corresponding concentrations in PM10. This implied that (DMA++TMA+) likely played an important role in neutralizing acidic species in the smaller particles. Using SO42-, NO3- and NH4+ as references, we confirm that the elevated concentrations of DMA+ and TMA+ in the 0.01-0.1µm size range were probably real signals rather than sampling artifacts.