The influence of modern living conditions on the human microbiome and potential therapeutic opportunities for allergy prevention.

Modern living conditions and the recent surge in global urbanization have transformed the human microbiome. This transformation is believed to be a significant factor in the recent spike of common chronic inflammatory diseases like asthma and allergies worldwide, evident in both developed and developing nations. Immigrants from less developed regions who settle in highly urbanized and affluent areas present an ideal demographic for research. Investigating immigrant populations can yield valuable insights, particularly when studying microbiome changes that occur as individuals transition from areas with low asthma prevalence to regions with a high prevalence of the condition. The application of prebiotics and probiotics as potential treatments for asthma and allergies faces challenges. This is due to the complex interplay of numerous factors that contribute to their aetiology. Exploring the interaction between the human microbiome and potential epigenetic changes in specific populations, such as immigrants adapting to new, urbanized environments, may offer crucial insights. Such research could underscore the role of prebiotics and probiotics in preventing allergic conditions. Recognizing the changes in the human microbiome in the context of a Western/modern environment might be essential in addressing the increasing prevalence of allergic diseases. Persistent research in this domain is pivotal for devising effective interventions such as dietary supplementation with prebiotics and probiotics.

Impact of environmental variables on the distribution of phytoplankton communities in the Southern Yellow Sea.

To gain a comprehensive understanding of the seasonal variation in the structure of phytoplankton communities in the Southern Yellow Sea (SYS), two research expeditions were conducted from 12 to 24 in April 2019, and from 12 to 22 in October of 2019. During the spring season, the phytoplankton community within the SYS was primarily comprised of diatoms and dinoflagellates, while in autumn, diatoms and cyanobacteria dominated. Thalassiosira rotula and Paralia sulcata were the dominant species in both seasons. In spring, P. sulcata displayed no obvious correlation with any environmental parameter, while in autumn, it exhibited negative correlations with environmental factors. According to the cluster and multidimensional scaling analyses, the phytoplankton community was stratified into three distinct ecological provinces in the SYS: the Western Yellow Sea, the Yellow Sea basin, and the southern coastal region. The phytoplankton community composition was predominantly affected by seasonal fluctuations in temperature and nutrient levels. Notably, the Yellow Sea basin exhibited the lowest phytoplankton abundance, largely because of the impact of the Yellow Sea Cold Water Mass. Furthermore, the presence of cyanobacteria, particularly prevalent in the Yellow Sea basin, may have been facilitated by transport mechanisms associated with the Kuroshio current. Aggregated boosted tree (ABT) and Generalized Additive models (GAM) suggested that temperature, DIN, salinity, and DIP were significant parameters of phytoplankton abundance in SYS. Additionally, the N:P nutrient ratio was a key parameter in governing the structure of phytoplankton communities during both seasons.

The relationship between air pollution and depression and anxiety disorders - A systematic evaluation and meta-analysis of a cohort-based study.

OBJECTIVE: To explore the correlation between air pollution and the onset of depression and anxiety disorders, to draw more comprehensive and integrated conclusions, and to provide recommendations for maintaining mental health and developing policies to reduce mental health risks caused by air pollution. METHODS: Meta-analysis of cohort study articles exploring the relationship between air pollution and depression or anxiety disorders included in Pubmed, Web Of Science, CNKI, and Wan Fang database before October 31, 2022, and subgroup analysis of the association between air pollution and depression and anxiety disorders regarding the air pollutants studied, the study population, and Publication bias analysis and sensitivity analysis. RESULTS: A total of 25 articles meeting the criteria were included in this study, including 23 articles examining the relationship between air pollution and depression and 5 articles examining the relationship between air pollution and anxiety disorders. The results of the meta-analysis were based on the type of pollutant and showed that there was a high degree of heterogeneity among the studies on the relationship between air pollution and depression and a significant heterogeneity among the studies on PM2.5 and the risk of anxiety disorders (I2 = 71%, p < .01), so a random-effects model was selected for the analysis. CO, O3, and SO2 and depression onset had combined RR values of 1.10 (1.00, 1.20), 1.06 (0.87, 1.29), 1.17 (1.06, 1.31), 1.19 (0.90, 1.58), 1.03 (0.99, 1.07), and 1.09 (0.97, 1.24), respectively, and PM2.5 and anxiety The combined RR value for morbidity was 1.10 (0.99, 1.22). The results of sensitivity analysis showed that the combined results were stable and reliable. The results of Egger regression method test showed that none of them had significant publication bias (p > .05). LIMITATION: Combined exposure to air pollutants on depression and anxiety, further studies by other researchers are needed in the future. CONCLUSIONS: PM2.5 and NO2 exposure, especially long-term exposure, may be associated with the onset of depression, and no association was found for the time being between PM10, CO, O3, SO2 exposure and depression and PM2.5 exposure and anxiety disorders.

Artificial Intelligence-Assisted Detection of Osteoporotic Vertebral Fractures on Lateral Chest Radiographs in Post-Menopausal Women.

Osteoporotic vertebral fractures (OVFs) are often not reported by radiologists on routine chest radiographs. This study aims to investigate the clinical value of a newly developed artificial intelligence (AI) tool, Ofeye 1.0, for automated detection of OVFs on lateral chest radiographs in post-menopausal women (>60 years) who were referred to undergo chest x-rays for other reasons. A total of 510 de-identified lateral chest radiographs from three clinical sites were retrieved and analysed using the Ofeye 1.0 tool. These images were then reviewed by a consultant radiologist with findings serving as the reference standard for determining the diagnostic performance of the AI tool for the detection of OVFs. Of all the original radiologist reports, missed OVFs were found in 28.8% of images but were detected using the AI tool. The AI tool demonstrated high specificity of 92.8% (95% CI: 89.6, 95.2%), moderate accuracy of 80.3% (95% CI: 76.3, 80.4%), positive predictive value (PPV) of 73.7% (95% CI: 65.2, 80.8%), and negative predictive value (NPV) of 81.5% (95% CI: 79, 83.8%), but low sensitivity of 49% (95% CI: 40.7, 57.3%). The AI tool showed improved sensitivity compared with the original radiologist reports, which was 20.8% (95% CI: 14.5, 28.4). The new AI tool can be used as a complementary tool in routine diagnostic reports for the reduction in missed OVFs in elderly women.

SRplot: A free online platform for data visualization and graphing.

Graphics are widely used to provide summarization of complex data in scientific publications. Although there are many tools available for drawing graphics, their use is limited by programming skills, costs, and platform specificities. Here, we presented a freely accessible easy-to-use web server named SRplot that integrated more than a hundred of commonly used data visualization and graphing functions together. It can be run easily using all Web browsers and there are no strong requirements on the computing power of users' machines. With a user-friendly graphical interface, users can simply paste the contents of the input file into the text box according to the defined file format. Modification operations can be easily performed, and graphs can be generated in real-time. The resulting graphs can be easily downloaded in bitmap (PNG or TIFF) or vector (PDF or SVG) format in publication quality. The website is updated promptly and continuously. Functions in SRplot have been improved, optimized and updated depend on feedback and suggestions from users. The graphs prepared with SRplot have been featured in more than five hundred peer-reviewed publications. The SRplot web server is now freely available at http://www.bioinformatics.com.cn/SRplot.

Analysis of coronary computed tomography angiography-derived pericoronary fat attenuation index characteristics in the diagnostic assessment of patients with Takayasu arteritis.

Background: The clinical value of pericoronary adipose tissue in assessing Takayasu arteritis (TAK) with coronary artery involvement (CAI) is yet to be determined. The purpose of this study was to investigate the characteristics of pericoronary fat attenuation index (FAI) derived from coronary computed tomography angiography (CTA) in patients with TAK. Methods: This is a retrospective study involving enrollment of 111 consecutive patients (mean age, 33.92±12.48 years) who were diagnosed as TAK, of which 52 patients had coronary artery involvement (TAK-CAI) and 59 patients without coronary artery involvement (TAK-nonCAI). Based on the extent of coronary artery lesion, the TAK-CAI group was further classified into localized group (n=25) and diffused group (n=27). Furthermore, patients with TAK were divided into active group (n=33) and inactive group (n=78). Meanwhile, 51 gender-matched individuals with normal appearance in coronary CTA examination were enrolled as the control group. The pericoronary FAI was quantitatively evaluated on each coronary CTA examination groups. The diagnostic value of pericoronary FAI was determined using the area under the curve (AUC) of the receiver operating characteristic. Results: A higher pericoronary FAI was found in TAK-nonCAI group than control group with normal coronary arteries (P<0.001). Multivariate analysis showed that the FAI is an independent risk factor for coronary involvement in TAK patients [odds ratio (OR): 1.23, 95% confidence interval (CI): 1.13-1.35, P<0.001]. With the best cut-off value of -86.50, the pericoronary FAI identified coronary involvement with 67.8% sensitivity and 74.5% specificity (AUC: 0.794, 95% CI: 0.713-0.875, P<0.001). Multivariate analysis showed that the pericoronary FAI is an independent risk factor for determination of active TAK patients (OR: 1.57, 95% CI: 1.25-1.97, P<0.001). With the best cut-off value of -79.50, the pericoronary FAI identified active inflammation with 93.9% sensitivity and 74.4% specificity (AUC: 0.911, 95% CI: 0.860-0.962, P<0.001). Conclusions: Coronary CTA-derived FAI is significantly increased in patients with TAK and can be used as a reliable biomarker to distinguish TAK patients from those with normal coronary arteries, and determine the extent of TAK inflammation.

Dissolved and particulate heavy metal pollution status in seawater and sedimentary heavy metals of the Bohai Bay.

Heavy metal contamination has been the focus of many studies owing to its potential risk on the health of coastal ecosystems. The Bohai Bay (BHB) is the second largest bay of Bohai Sea and subjected to serious anthropogenic perturbations. The aim of this study was to evaluate the distribution and pollution status of toxic heavy metals in seawater with two fractions (dissolved and suspended particulate phases) and surface sediments of this coastal system. Therefore, several hydrochemical parameters and concentration of seawater metals and sediment metals were measured at two cruises of 2020 summer and autumn. The spatial distribution and potential ecological risks were examined and their inter-element relationships were analyzed to identify potential geochemical processes. By comparing historical data since 1978, we find declining trends in contents of most trace metals in seawater and sediments, suggesting that recent pollution control in BHB have an effect on diminishing metal pollution. Dissolved metals showed no significant dependence on their particulate phase. The seawater posed a moderate to high level of ecological risk. The hydrochemical factors mainly had a greater impact on dissolved metals during summer, whereas they influenced suspended metals more significantly during autumn. These results provide fundamental information to support environmental quality management and ecological protection in coastal systems.

Genetic variants of TLR4, including the novel variant, rs5030719, and related genes are associated with susceptibility to clinical malaria in African children.

BACKGROUND: Malaria is a deadly disease caused by Plasmodium spp. Several blood phenotypes have been associated with malarial resistance, which suggests a genetic component to immune protection. METHODS: One hundred and eighty-seven single nucleotide polymorphisms (SNPs) in 37 candidate genes were genotyped and investigated for associations with clinical malaria in a longitudinal cohort of 349 infants from Manhiça, Mozambique, in a randomized controlled clinical trial (RCT) (AgeMal, NCT00231452). Malaria candidate genes were selected according to involvement in known malarial haemoglobinopathies, immune, and pathogenesis pathways. RESULTS: Statistically significant evidence was found for the association of TLR4 and related genes with the incidence of clinical malaria (p = 0.0005). These additional genes include ABO, CAT, CD14, CD36, CR1, G6PD, GCLM, HP, IFNG, IFNGR1, IL13, IL1A, IL1B, IL4R, IL4, IL6, IL13, MBL, MNSOD, and TLR2. Of specific interest, the previously identified TLR4 SNP rs4986790 and the novel finding of TRL4 SNP rs5030719 were associated with primary cases of clinical malaria. CONCLUSIONS: These findings highlight a potential central role of TLR4 in clinical malarial pathogenesis. This supports the current literature and suggests that further research into the role of TLR4, as well as associated genes, in clinical malaria may provide insight into treatment and drug development.

Strong variation in sedimental antibiotic resistomes among urban rivers, estuaries and coastal oceans: Evidence from a river-connected coastal water ecosystem in northern China.

Sediment is thought to be a vital reservoir to spread antibiotic resistance genes (ARGs) among various natural environments. However, the spatial distribution patterns of the sedimental antibiotic resistomes around the Bohai Bay region, a river-connected coastal water ecosystem, are still poorly understood. The present study conducted a comprehensive investigation of ARGs among urban rivers (UR), estuaries (ES) and Bohai Bay (BHB) by metagenomic sequencing. Overall, a total of 169 unique ARGs conferring resistance to 15 antimicrobial classes were detected across all sediment samples. The Kruskal-Wallis test showed that the diversity and abundance of ARGs in the UR were all significantly higher than those in the ES and BHB (p < 0.05 and p < 0.01), revealing the distance dilution of the sedimental resistomes from the river to the ocean. Multidrug resistance genes contained most of the ARG subtypes, whereas rifamycin resistance genes were the most abundant ARGs in this region. Our study demonstrated that most antimicrobial resistomes were highly accumulated in urban river sediments, whereas beta-lactamase resistance genes (mainly PNGM-1) dramatically increased away from the estuary to the open ocean. The relative abundance of mobile genetic elements (MGEs) also gradually decreased from rivers to the coastal ocean, whereas the difference in pathogenic bacteria was not significant in the three classifications. Among MGEs, plasmids were recognized as the most important carriers to support the horizontal gene transfer of ARGs within and between species. According to co-occurrence networks, pathogenic Proteobacteria, Actinobacteria, and Bacteroidetes were recognized as potential and important hosts of ARGs. Heavy metals, pH and moisture content were all recognized as the vital environmental factors influencing the distribution of ARGs in sediment samples. Overall, the present study may help to understand the distribution patterns of ARGs at a watershed scale, and help to make effective policies to control the emergence, spread and evolution of different ARG subtypes in different habitats.

Responses of biological traits of macrobenthic fauna to a eutrophication gradient in a semi-enclosed bay, China.

The impacts of eutrophication on benthic ecological functions are of increasing concern in recent years. In order to assess the response of macrobenthic fauna to increasing eutrophication, two field sampling surveys were conducted during the summer (July-August 2020) and autumn (October-November 2020) from offshore, nearshore to estuarine sediments in Bohai Bay, northern China. Biological trait analysis was employed for the assessment of macrofaunal samples. The results indicated that there was an increase in the proportion of benthic burrowering or tube-dwelling sediment feeders and taxa with higher larval dispersal ability, but a decrease in the proportion of taxa showing high motility in areas with higher nutrient levels. Seasonal differences were also noted in the shift in biological traits, with a significantly lower similarity among the sampling areas in summer and a higher proportion of carnivorous taxa in autumn. The findings suggested that long-term disturbance can lead to the dominance of smaller body-sized benthic species and reduced sediment quality, impeding ecological recovery of benthic organisms under such harsh environment.

Spatial and temporal changes in the assembly mechanism and co-occurrence network of the chromophytic phytoplankton communities in coastal ecosystems under anthropogenic influences.

As a typical semiclosed coastal sea area in China, the ecological environment of Bohai Bay has been significantly disturbed by human activities. As primary producers, the chromophytic phytoplankton are the basis of ecosystems, especially in coastal ecosystems, and changes in the chromophytic phytoplankton community can affect the stability of the entire ecosystem. In this study, we investigated the effects of the human activity-induced spatial and temporal environmental heterogeneity on the community composition, diversity, assembly mechanisms, and co-occurrence networks of chromophytic phytoplankton in Bohai Bay during the wet season and the dry season. The results showed that in both seasons, there was obvious environmental heterogeneity between the nearshore area and the offshore area, and the nearshore areas were more affected by human disturbance. Although higher diversity was supported by the abundance of nutrients in nearshore areas, co-occurrence network analysis revealed that the chromophytic phytoplankton were less closely connected to each other in nearshore areas than in offshore areas due to chemical oxygen demand (COD), eutrophication index (EI), and dissolved inorganic nitrogen (DIN). The nearshore network was less stable than the offshore co-occurrence network in both seasons, which was related to the concentration of dissolved oxygen and COD. Both stochastic and deterministic processes dominated the assembly of the chromophytic phytoplankton communities, with different importance rankings of stochastic and deterministic processes in the nearshore and offshore areas. Drift dominated the assembly of the communities in nearshore areas, while variable selection dominated the assembly of the communities in offshore areas. DIN, EI, and COD, rather than geographic distance, were the main environmental factors affecting the phylogenetic turnover of the chromophytic phytoplankton. Our study showed that environmental heterogeneity caused by human disturbance had a greater impact on the chromophytic phytoplankton communities in Bohai Bay than natural factors such as temperature and salinity.

Distribution, source identification and ecological effects of aerosol dissolved nutrients in the Bohai Bay.

The atmospheric aerosols around the Bohai Bay are affected intensively by the surrounding industrial, shipping and other human activities. Although atmospheric dry deposition is an important way for nutrients to enter the Bohai Bay, few studies explore the distribution patterns, source and deposition fluxes of typical nutrients in aerosols and their impacts on the marine ecosystem. This paper explored the spatial-temporal distribution of typical aerosol nutrients in summer and autumn, and their source and ecological effects were illustrated further. The mean concentration of dissolved total phosphorus (DTP), dissolved total nitrogen (DTN), dissolved organic nitrogen (DON), dissolved inorganic nitrogen (DIN), ammonium (NH4-N), nitrate (NO3-N), nitrite (NO2-N), silicate (SiO3-Si), phosphate (PO4-P), and dissolved organic phosphorus (DOP) were 31.22, 847.22, 288.19, 559.77, 288.19, 304.00, 253.65, 2.12, 15.74 and 15.48 nmol/m3, respectively, while their fluxes were corresponding to 0.61, 8.36, 2.52, 4.90, 1.41, 2.49, 0.02, 0.04, 0.19 and 0.26 mmol/(m2 month). Typical aerosol nutrient concentrations in autumn were mostly higher than those in summer, with high values occurring mainly in the central region. The potential sources of pollution were mainly concentrated in Shandong and Mongolia, and the sources of pollution were mainly agriculture, dust and industry. The large N:P and N:Si ratios in the dry deposition likely exacerbated Si and P limitation in the water column. These results provided the data basis for evaluating the pollution status and revealed that the dry deposition of aerosol nutrients should not be neglected by the ecological environment in the Bohai Bay.

Diversity, structure, and distribution of bacterioplankton and diazotroph communities in the Bay of Bengal during the winter monsoon.

The Bay of Bengal (BoB) is conventionally believed to be a low productive, oligotrophic marine ecosystem, where the diazotroph communities presumed to play a vital role in adding "new" nitrogen through the nitrogen fixation process. However, the diazotroph communities in the oceanic region of the BoB are still poorly understood though it represents most of the seawater volume. The present study investigated a detailed account of the bacterioplankton community structure and distribution in the oceanic BoB during the winter monsoon using high throughput sequencing targeting the 16S rRNA and nifH genes. Our study observed diverse groups of bacterioplankton communities in the BoB including both cyanobacterial and non-cyanobacterial phylotypes. Cyanobacteria (Prochlorococcus spp. and Synechococcus spp.) and Proteobacteria (mainly α-, γ-, and δ-Proteobacteria) were the most abundant groups within the bacterial communities, possessing differential vertical distribution patterns. Cyanobacteria were more abundant in the surface waters, whereas Proteobacteria dominated the deeper layers (75 m). However, within the diazotroph communities, Proteobacteria (mainly γ-Proteobacteria) were the most dominant groups than Cyanobacteria. Function prediction based on PICRUSt revealed that nitrogen fixation might more active to add fixed nitrogen in the surface waters, while nitrogen removal pathways (denitrification and anammox) might stronger in deeper layers. Canonical correspondence analysis (CCA) indicated that temperature, salinity, and silicate were major environmental factors driving the distribution of bacterial communities. Additionally, phosphate was also an important factor in regulating the diazotroph communities in the surface water. Overall, this study provided detailed information on bacterial communities and their vital role in the nitrogen cycles in oligotrophic ecosystems.

Deciphering the diversity and distribution of chromophytic phytoplankton in the Bohai Sea and the Yellow Sea via RuBisCO genes (rbcL).

Present study investigated composition and distribution of chromophytic phytoplankton in the Bohai Sea (BS) and the Yellow Sea (YS) by using rbcL genes. Bacillariophyceae, Haptophyceae and Pelagophyceae were the most abundant phytoplankton groups. Distinct phytoplankton communities were observed in the BS and the YS: offshore stations were dominated by bloom forming genera Thalassiosira and Skeletonema, while brown tide-forming species including Chrysochromulina spp. and Aureococcus anophagefferens were commonly found in the nearshore areas. Redundancy analysis showed that phosphate, temperature and silicic acid play key roles in structuring chromophytic phytoplankton, such as phytoplankton at nearshore stations were affected by nutrient runoff from adjacent rivers (Yellow River). Anthropogenic activities in the Bohai Sea and seasonal circulation of ocean currents may also contribute to shaping chromophytic phytoplankton communities. This study provides data support and foundational observations of chromophytic phytoplankton in the BS and the YS, and their responses to environmental gradients and human activities.

Water quality shifts the dominant phytoplankton group from diatoms to dinoflagellates in the coastal ecosystem of the Bohai Bay.

In this study, we conducted two cruises in the Bohai Bay (China) focusing on phytoplankton community and relation to water quality. The evaluation revealed that most of the open area was non-eutrophic, whereas the river inlet had severe eutrophication. Phytoplankton populations respond differently to different aquatic environments and are controlled by more than two factors, as revealed by aggregated boosted tree analysis. Notably, a shift in the phytoplankton community structure was observed during the seasonal transition, from the dominance of diatoms to the co-dominance of diatoms-dinoflagellates. However, the relative abundance of dinoflagellates increased by 14 % in autumn, when the harmful algae species Akashiwo sanguinea exclusively predominated; this was primarily linked to the nutrient ratios, temperature, and dissolved oxygen. The eutrophication and organic pollution had direct effects on phytoplankton abundance. Overall, our findings may provide further insights into the impacts of eutrophic environments on phytoplankton community structure in coastal systems.

Species and functional diversity of marine macrobenthic community and benthic habitat quality assessment in semi-enclosed waters upon recovering from eutrophication, Bohai Bay, China.

This study investigated the structure and function of macrobenthic community in Bohai Bay upon improvement of water quality due to pollution abatement. A total of 166 species were collected in the summer and autumn sampling, with an increase in sensitive species recorded as compared to data from previous studies. While historical variations in species richness indicated signs of improvement in community structure, results of functional diversity indices revealed that the macrobenthic community in Bohai Bay was still in an early stage of recovery. From BIO-ENV analysis, habitat instability may hinder how community responded to water quality improvement. Results of the benthic habitat quality assessment also indicated that the ecological status in most areas of Bohai Bay was classified as good, while a few estuarine regions were categorized in a poor status.

Exploring the dynamics of marine picophytoplankton among the Yellow Sea, Indian Ocean and Pacific Ocean: The importance of temperature and nitrogen.

Marine picophytoplankton (<2 µm) are the most abundant photosynthetic group and also important contributors to global primary production. However, it is still constrained to incorporate picophytoplankton into dynamic ecosystem models, as a result of our limited understanding of their global distribution and abundance. Here, we applied a large dataset consisted of 1817 in situ observations from the Yellow Sea, Indian Ocean, and Pacific Ocean to suggest that picophytoplankton abundance and distribution had a large variability among the three distinct regions. Based on the correlation analysis, aggregated boosted tree analysis, and generalized additive model, we proposed that water temperature and dissolved inorganic nitrogen (N) were key determinants in driving the large-scale variability of marine picophytoplankton. For example, we revealed that high temperature and low N would stimulate the growth of Prochlorococcus. Therefore, these results could provide some insights into the various environmental factors which affect the dynamics of picophytoplankton, as well as the dynamic ecosystem models.

Variation in biogenic calcite production by coccolithophores across mesoscale eddies in the Bay of Bengal.

Coccolithophore calcite production (CP) was investigated for the first time in the Bay of Bengal. Against expectation, calcite production was not fueled by the nutrient-enriched cold eddy because of the reduced light penetration. CP rate was observed to be higher at the anticyclonic eddy possibly benefited from rare species production. The adjoining river-induced shallow mixed-layer depth and eddy activity co-influenced CP rate. On average, the integrated CP rates were 0.04, 0.15, and 0.07 mmol C m-2 h-1 for the cyclonic eddy, anticyclonic eddy, and outer area, respectively. In the upper photic waters, CP rates showed a strong correlation with primary productivity (PP). However, a decoupling of CP and PP was observed in the lower photic zone due to differential light and nitrogen preferences in calcification and carbon fixation. Our findings could help to understand the biogenic response of eddy and inorganic-organic carbon association in the pelagic biogeochemical cycles.

Picophytoplankton in the West Pacific Ocean: A Snapshot.

Marine picophytoplankton have crucial ecological value and make an important contribution to marine primary productivity. While biomass of phytoplankton in general is projected to decline as a result of global warming, picophytoplankton will likely dominate in the future oceans due to their growth advantages in an oligotrophic environment. To better understand the biography of picophytoplankton, we undertook a comprehensive study of the distribution patterns of picophytoplankton, carbon biomass, and Chl a concentrations, etc. based on large-scale sampling in the tropical Western Pacific Ocean. In terms of cellular abundance, Prochlorococcus was the most abundant group (averaging [1.03 ± 0.40] × 104 cells/mL), followed by Synechococcus (averaging [1.31 ± 1.22] × 103 cells/mL) and then picoeucaryote (averaging [4.83 ± 2.84] × 102 cells/mL). The picophytoplankton size-fractionated chlorophyll a (Pico-Chl a) accounted for about 30% of the total Chl a, with Prochlorococcus and picoeukaryotes contributing 41 and 35%, respectively, of the Pico-Chl a-normalized carbon biomass, indicating the ecological importance of picophytoplankton as the primary producers. In terms of biogeographic distribution, the picophytoplankton communities exhibited contrasting patterns. The surface distribution of Prochlorococcus and Synechococcus was concentrated in the low latitude of the 142°E section, while picoeucaryote was more abundant near the 130°E and equator sections. Synechococcus was higher in the shallow layer at 25 m, and it was extremely tolerant of high-light irradiation, while Prochlorococcus and picoeucaryote were distributed in the deep Chlorophyll maximum layer (DCM) (about 100 m). From the carbon-to-Chlorophyll a ratios, which was derived from Prochlorococcus and picoeucaryote population groups, we found that the ratio varied widely, from 0.19 to 75.56, and was highest at the depth of 200 m. Of these, Prochlorococcus had an important contribution. The correlation analysis of environmental factors showed that Prochlorococcus, Synechococcus, and picoeucaryote were negatively correlated with nutrient concentration. We concluded that Prochlorococcus group was dominant in the WPO, both in abundance and biomass, and the various abiotic factors such as temperature, salinity, and nutrient concentrations were closely correlated with the spatial variation in the picophytoplankton community. These findings aid our understanding of how contrasting environmental conditions influence picophytoplankton community and the importance of picophytoplankton in contributing the carbon pool in the oligotrophic ocean.

Highly Diverse Synechococcus Pigment Types in the Eastern Indian Ocean.

Marine picocyanobacteria Synechococcus exhibit highly diverse pigment types (PTs) and hence possess great advantage to utilize different spectrum of light effectively and to occupy a wide range of light niches. In this study, we explored the diversity of Synechococcus PTs in the eastern Indian Ocean (EIO), surface water of Strait of Malacca (SSM), and coastal waters of Sri Lanka (SSL). All the detected PTs were phycourobilin (PUB) containing PT 3 and showed distinct distribution patterns. Low PUB PT 3a and partial chromatic acclimater PT 3eA dominated in coastal and shallow waters (SSM and SSL). In contrast, high PUB and chromatic acclimaters PT 3dA and PT 3c/3dB were mainly distributed in open ocean (EIO). PT 3dA and PT 3c/3dB occurred at similar depths of the lower euphotic layers but showed distinct distribution pattern that are partially exclusive, indicating that they compete with each other for the same light niche. Interestingly, the newly described PT 3f was detected with high relative abundances at all stations and particularly dominated in the upper euphotic layer in EIO, which was confirmed with PT-specific quantitative polymerase chain reaction (qPCR). The relative abundance of PT 3f was negatively correlated with nutrient level, implying that PT 3f is adapted to oligotrophic waters. Pronounced niche partition of different PTs was observed in the upper and lower layers of euphotic zone in EIO and SSM/SSL. Light, nutrients, and strong stratification may play important roles in the niche partition of different PTs. Further analysis about ecologically significant taxonomic units revealed high diversity within each PT at different locations, which provided insights for understanding specific PT with wide range of niches.