Carbon storage in mollusk shells: An overlooked yet significant carbon sink in terrestrial ecosystems.

Mollusks, the second largest animal family, are found in a variety of ecosystems. As they grow, their shells absorb carbon and form calcium carbonate, making them an important storage place for carbon. However, the amount of carbon deposited in the carbonate shells of terrestrial mollusks throughout modern and geological history has not been quantified. In this study, we first conducted an investigation of carbon deposits in shells from various mollusk species at 470 modern surface soil sample sites across diverse terrestrial ecosystems in China. The deciduous broadleaf forest and shrublands exhibited a higher carbon deposition rate of ∼1.37 ± 2.15 and ∼1.56 ± 2.92 g C m-2/yr-1, while croplands and grasslands displayed a rate of ∼1.11 ± 1.95 and 1.07 ± 1.78 g C m-2/yr-1, respectively. Using geostatistical methods, we estimated the total shell carbon deposition of grassland, forest, shrublands, and croplands in China to be ∼3.39-5.45 × 106 t C yr-1, constituting ∼1.68-2.71 % of China's terrestrial carbon sink, an overlooked portion in previous studies. Additionally, we provided quantitative data on shell carbon fluxes spanning a remarkable 20,000-year period through over ten fossil sequences from loess deposits. The results underscore the continuous and abundant carbon deposition in mollusk shells across various locations for at least 20,000 years, highlighting the persistence and substantial accumulation of shell carbon deposits over time. Remarkably, we estimated that the total shell carbon deposition of loess sediments in China and the world over the past 20,000 years may reach 1.10 × 108 t C and 1.29 × 109 t C, roughly equivalent to an afforestation area of 2.32 × 106 km2 and 2.72 × 107 km2, respectively.

Seasonal climatic instability in the western Chinese Loess Plateau during Marine Isotope Stages 12-10.

Because of similar astronomical background, Marine Isotope Stage (MIS) 11 is viewed as an analogue of the Holocene, but the evolution of seasonal climatic instability during MIS 11 has not been well investigated. Here we present a time series of land-snail eggs-a recently-developed proxy of seasonal cooling events-from the Chinese Loess Plateau (CLP) to investigate seasonal climatic instability during MIS 11 and adjacent glacials. Due to the impact of low temperatures on egg hatching, egg-abundance peaks document seasonal cooling events. A total of five egg-abundance peaks were recorded in the CLP during MIS 12, MIS 11 and MIS 10. Three peaks are strong and occur close to glacial inception or interglacial-to-glacial transition; two weaker peaks occur during MIS11. These peaks imply seasonal climatic instability intensifies mainly during glacial initiation or transition. All these events correspond to ice-sheet growth and the loss of ice-rafted debris at high northern latitudes. Moreover, they occurred at the minima of local spring insolation during the MIS 12 and MIS 10 glacials, but at the maxima during the MIS 11 interglacial. This may contribute to the difference in the intensity of seasonal cooling events between low-eccentricity glacials and interglacials. Our results provide new evidence for understanding low-eccentricity interglacial-glacial evolution.

Fast response of vegetation in East Asia to abrupt climatic events during the last deglaciation.

Climate changes had major impacts on the vegetation of East Asia during the last deglaciation. However, the rate and pattern of vegetation succession in response to large-scale climatic events during this interval are controversial. Here, we present well-dated decadal-resolution pollen records from annually laminated Maar Lake Xiaolongwan during the last deglaciation. The vegetation changes were rapid and near-synchronous with millennial-scale climatic events, including Greenland Stadial 2.1a (GS-2.1a), Greenland Interstadial 1 (GI-1), Greenland Stadial 1 (GS-1), and the early Holocene (EH). The vegetation responded in different ways to the different rates of climate change. Vegetation change was gradual [∼1 thousand years (kyr) response time] during the transition between GS-2.1a and GI-1, but it was faster (∼0.4 kyr response time) during the transitions between GI-1, GS-1, and the EH, resulting in different patterns of vegetation succession. Additionally, the amplitude and pattern of vegetation changes resembled those in the records of regional climate change based on long-chain n-alkanes δ13C and stalagmite δ18O, as well as in the mid-latitude Northern Hemisphere temperature record and the Greenland ice core δ18O record. Therefore, the rate and pattern of vegetation succession in the Changbai Mountain of Northeast Asia during the last deglaciation were sensitive to the characteristics of changes in the regional hydrothermal conditions and mid-latitude Northern Hemisphere temperature, which were linked to both high- and low-latitude atmospheric-oceanic dynamics. Overall, our findings reveal a close relationship between ecosystem succession and hydrothermal changes during these millennial-scale climatic events in East Asia during the last deglaciation.

The Holocene temperature conundrum answered by mollusk records from East Asia.

Seasonal biases (the warm-season contribution) of Holocene mean annual temperature (MAT) reconstructions from geological records were proposed as a possible cause of the mismatch with climate simulated temperature. Here we analyze terrestrial mollusk assemblages that best reflect seasonal signals and provide quantitative MAT and four-season temperature records for northern China during the past 20,000 years. The MAT estimated from the seasonal temperatures of a four-season-mean based on mollusks shows a peak during ~9000-4000 years ago, followed by a cooling trend. In general, the contribution of summer and winter temperature to MAT is significantly greater than that of spring and autumn temperatures. The relative contribution of each season varies over time and corresponds roughly with the seasonal insolation in each season. This independent evidence from mollusk records from the mid-latitudes of East Asia does not support the Holocene long-term warming trend observed in climate simulations and the seasonal bias explanation.

Clinical Analysis of Severe Radiation Pneumonia.

OBJECTIVE: The present study aims to discuss the clinical characteristics, factors, and treatment methods affecting the prognosis in patients with severe radiation pneumonia (RP). METHODS: The radiotherapy status, clinical features, imaging characteristics, laboratory examination results, treatment methods, and prognoses of 34 patients with severe RP treated in our department between January 2011 and July 2017 were retrospectively analyzed. The severe RP grading was based on the Common Terminology Criteria for Adverse Events version 4.0; patients who scored Grade ≥3 were considered to have a severe case of RP. RESULTS: The results of the present study showed that 22 patients had lung cancer, 6 had esophageal cancer, 5 had breast cancer, and 1 had colon cancer with lung metastasis. The total radiation dose was 37.5-66 Gy, and the overall average dose was 53 Gy; the average dose in the patients who died was 52.9 Gy. A total of 28 patients presented with a cough and sputum as the initial symptom, and 24 presented with wheezing as an accompanying symptom; of the 24 patients, 8 experienced fever, 2 experienced wheezing as the only symptom, 1 had chest pain, and 1 had chest tightness. In 26 patients, the changes were in the radiation field, and in 8 cases, the changes appeared both inside and outside the radiation field. After the use of glucocorticoid methylprednisolone, respiratory support, and anti-infection treatment, 18 patients were cured, 8 showed a condition improvement, and 8 died. CONCLUSION: The prognosis of severe RP was not significantly correlated with the administered radiation dose; however, lung cancer, a high Acute Physiology and Chronic Health Evaluation score, and delayed diagnosis were risk factors for patient death. However, a combination of antibiotic therapy, ventilator-assisted respiration, and steroid therapy could improve patient prognosis.

Seasonal drought events in tropical East Asia over the last 60,000 y.

The cause of seasonal hydrologic changes in tropical East Asia during interstadial/stadial oscillations of the last glaciation remains controversial. Here, we show seven seasonal drought events that occurred during the relatively warm interstadials by phytolith and pollen records. These events are significantly manifested as high percentages of bilobate phytoliths and are consistent with the large zonal sea-surface temperature (SST) gradient from the western to eastern tropical Pacific, suggesting that the reduction in seasonal precipitation could be interpreted by westward shifts of the western Pacific subtropical high triggered by changes of zonal SST gradient over the tropical Pacific and Hadley circulation in the Northern Hemisphere. Our findings highlight that both zonal and meridional ocean-atmosphere circulations, rather than solely the Intertropical Convergence Zone or El Niño-Southern Oscillation, controlled the hydrologic changes in tropical East Asia during the last glaciation.

Development and Evaluation of a Loop-Mediated Isothermal Amplification Assay for Rapid and Specific Identification of Carbapenem-Resistant Acinetobacter baumannii Strains Harboring blaOXA-23, and the Epidemiological Survey of Clinical Isolates.

Acinetobacter baumannii is an important nosocomial pathogen in hospital-acquired infections, and carbapenem resistance has been increasingly observed worldwide. Oxacillinase production by blaOXA-23 is a predominant and prevalent carbapenem resistance mechanism of A. baumannii, especially in China. Rapid and specific detection of blaOXA-23 may offer valuable insight for administration of directed antimicrobial therapy. In this study, we aimed to develop a loop-mediated isothermal amplification (LAMP)-based method for identifying carbapenem-resistant A. baumannii (CRAB) harboring the blaOXA-23 gene. High-specificity primers for screening blaOXA-23 were designed and synthesized, and the LAMP reactions were performed. Clinical A. baumannii strains isolated from the Former 307th Hospital of People's Liberation Army were used to determine the sensitivity and specificity of this method compared with those of phenotypic antimicrobial susceptibility testing and the traditional PCR method. Multilocus sequence typing (MLST) was performed to investigate the epidemiology of the A. baumannii bacterial population. Compared with antimicrobial susceptibility testing, the sensitivity and specificity of LAMP in detecting blaOXA-23 were 88.4% and 97.7%, respectively. However, the LAMP method is much simpler and less time-consuming (within 60 minutes) than conventional PCR and phenotypic susceptibility testing. The 113 isolates could be clustered into 30 sequence types, and most strains (83/113) belonged to clonal complex (CC) 92, which is also the dominant CC in China. The LAMP-based method detected blaOXA-23 in a simpler manner and could provide rapid results for identifying CRAB. Consequently, blaOXA-23 may serve as a surrogate marker for the presence of CRAB in patients with serious infections in clinical practice.

Synchronous 500-year oscillations of monsoon climate and human activity in Northeast Asia.

Prehistoric human activities were likely influenced by cyclic monsoon climate changes in East Asia. Here we report a decadal-resolution Holocene pollen record from an annually-laminated Maar Lake in Northeast China, a proxy of monsoon climate, together with a compilation of 627 radiocarbon dates from archeological sites in Northeast China which is a proxy of human activity. The results reveal synchronous ~500-year quasi-periodic changes over the last 8000 years. The warm-humid/cold-dry phases of monsoon cycles correspond closely to the intensification/weakening of human activity and the flourishing/decline of prehistoric cultures. Six prosperous phases of prehistoric cultures, with one exception, correspond approximately to warm-humid phases caused by a strengthened monsoon. This ~500-year cyclicity in the monsoon and thus environmental change triggered the development of prehistoric cultures in Northeast China. The cyclicity is apparently linked to the El Niño-Southern Oscillation, against the background of long-term Holocene climatic evolution. These findings reveal a pronounced relationship between prehistoric human activity and cyclical climate change.

Influence of monsoonal water-energy dynamics on terrestrial mollusk species-diversity gradients in northern China.

Climate-related factors (e.g. environmental energy, water availability and climatic seasonality/variability) and habitat heterogeneity have long been considered as the main drivers of species diversity on a broad spatial scale. However, it is controversial whether the above environmental factors can explain observed diversity patterns in varied communities such as invertebrate taxonomic group, especially mollusks. Moreover, there are until now few systematic assessments of the relative roles of different factors in determining the patterns of mollusk species diversity in monsoon-dominated regions. Here, we depict variations in terrestrial mollusk diversity based on a dataset comprising 282 assemblages collected from surface soils along an ~800-km climatic gradient from subtropical to warm temperate and mid-temperate regions in northern China. The results show that mollusk species diversity increases significantly from ~3-4 species to ~17-19 species when annual temperature and precipitation increase up to ~12 °C and ~700 mm, respectively; however, at or above these values the rate of increase is reduced. These indicate that the relationships between mollusk species diversity and climatic factors are nonlinear. Statistical analysis suggests that water availability (relative humidity) and temperature seasonality (January temperature and annual temperature range) dominate the observed pattern of mollusk species diversity. Moreover, habitat factors such as vegetation condition and soil types were also important in determining mollusk species diversity. They may be an indirect reflection of the effects of monsoonal water-energy dynamic on mollusk communities. Our results suggest that more attention should be paid to water availability and temperature seasonality in predicting future biodiversity changes, especially in the environmentally stressed northwestern part of the East Asian monsoon region.

Time-Transgressive Nature of the Magnetic Susceptibility Record across the Chinese Loess Plateau at the Pleistocene/Holocene Transition.

The loess stratigraphic boundary at the Pleistocene/Holocene transition defined by the magnetic susceptibility (MS) has previously been assumed to be synchronous with the Marine Isotope Stage (MIS) 2/1 boundary, and approximately time-synchronous at different sections across the Chinese Loess Plateau (CLP). However, although this assumption has been used as a basis for proxy-age model of Chinese loess deposits, it has rarely been tested by using absolute dating methods. In this study, we applied a single-aliquot regenerative-dose (SAR) protocol to the 45-63 µm quartz grain-size fraction to derive luminescence ages for the last glacial and Holocene sections of three loess sections on a transect from southeast to northwest across the CLP. Based on the 33 closely spaced optically stimulated luminescence (OSL) samples from the three sections, OSL chronologies were established using a polynomial curve fit at each section. Based on the OSL chronology, the timing of the Pleistocene/Holocene boundary, as defined by rapid changes in MS values, is dated at ~10.5 ka, 8.5 ka and 7.5 ka in the Yaoxian section, Jingchuan and Huanxian sections respectively. These results are clearly inconsistent with the MIS 2/1 boundary age of 12.05 ka, and therefore we conclude that the automatic correlation of the Pleistocene/Holocene transition, as inferred from the MS record, with the MIS 2/1 boundary is incorrect. The results clearly demonstrate that the marked changes in MS along the southeast to northwest transect are time-transgressive among the different sites, with the timing of significant paleosol development as indicated by the MS record being delayed by 3-4 ka in the northwest compared to the southeast. Our results suggest that this asynchronous paleosol development during the last deglacial was caused by the delayed arrival of the summer monsoon in the northwest CLP compared to the southeast.

Late miocene-pliocene paleoclimatic evolution documented by terrestrial mollusk populations in the western Chinese Loess Plateau.

The Neogene eolian deposits in the Chinese Loess Plateau (CLP) are one of the most useful continental deposits for understanding climatic changes. To decipher Late Neogene paleoclimatic changes in the CLP, we present a terrestrial mollusk record spanning the time interval between 7.1 and 3.5 Ma from the western CLP. The results indicate four stages of paleoclimatic evolution: From 7.1 to 6.2 Ma, cold and dry climatic conditions prevailed as evidenced by high values of the total number of cold-aridiphilous (CA) mollusk species and by low values of all of the thermo-humidiphilous (TH) mollusk indices. From 6.2 to 5.4 Ma, the climate remained cold and dry but was not quite as dry as during the preceding phase, as indicated by the dominance of CA mollusks and more TH species and individuals. From 5.4 to 4.4 Ma, a warm and moist climate prevailed, as indicated by high values of the TH species and individuals and by the sparsity of CA species and individuals. From 4.4 to 3.5 Ma, all of the CA indices increased significantly and maintained high values; all of the TH indices exhibit high values from 4.4 to 4.0 Ma, an abrupt decrease from 4.0 Ma and a further increase from 3.7 Ma. The CA species of Cathaica pulveraticula, Cathaica schensiensis, and Pupopsis retrodens are only identified in this stage, indicating that the CA species were diversified and that the climate was becoming drier. Moreover, the CA mollusk group exhibits considerable diversity from 7.1 to 5.4 Ma when a cold, dry climate prevailed; whereas the diversity of the TH group was high during the relatively warm, wet interval from 5.4 to 4.4 Ma. This indicates that variations in the diversity of the CA and TH mollusk groups were closely related to climatic changes during the Late Miocene to Pliocene.

Mid-Neolithic exploitation of mollusks in the Guanzhong Basin of Northwestern China: preliminary results.

Mollusk remains are abundant in archaeological sites in the Guanzhong Basin of Northwestern China, providing good opportunities for investigations into the use of mollusks by prehistoric humans. Here we report on freshwater gastropod and bivalve mollusks covering the time interval from about 5600 to 4500 cal. yrs BP from sites of Mid-Late Neolithic age. They are identified as Cipangopaludina chinensis and Unio douglasiae, both of which are currently food for humans. The shells are well preserved and have no signs of abrasion. They are all freshwater gastropods and bivalves found in pits without water-reworked deposits and have modern representatives which can be observed in rivers, reservoirs, and paddy fields in the studied region. Mollusk shells were frequently recovered in association with mammal bones, lithic artifacts, and pottery. These lines of evidence indicate that the mollusks are the remains of prehistoric meals. The mollusk shells were likely discarded into the pits by prehistoric humans after the flesh was eaten. However, these mollusk remains may not have been staple food since they are not found in large quantities. Mollusk shell tools and ornaments are also observed. Shell tools include shell knives, shell reaphooks and arrowheads, whereas shell ornaments are composed of pendants and loops. All the shell tools and ornaments are made of bivalve mollusks and do not occur in large numbers. The finding of these freshwater mollusk remains supports the view that the middle Holocene climate in the Guanzhong Basin may have been warm and moist, which was probably favorable to freshwater mollusks growing and developing in the region.