Arcicella gelida sp. nov. and Arcicella lustrica sp. nov., isolated from streams in China and re-examining the taxonomic status of all the genera within the families Spirosomataceae and Cytophagaceae.

Three Gram-stain-negative, aerobic, rod-shaped, non-motile strains (DC2WT, DC25WT, and LKC2W) were isolated from streams in China. Comparisons based on the 16S rRNA gene sequences showed that these three strains share 16S rRNA gene sequence similarity values over 97.0 % with the species of genus Arcicella. There was confusion due to the fact that all species of genera Flectobacillus, Aquirufa, and Sandaracinomonas show 16S rRNA gene sequence similarity of over 90.0 % to the above three strains, but the genus Flectobacillus belongs to the family Spirosomataceae and the genera Aquirufa and Sandaracinomonas belong to the family Cytophagaceae. Observing the phylogenetic trees, strains DC2WT, DC25WT, and LKC2W cluster closely with the species of genus Arcicella, but some species within the families Spirosomataceae and Cytophagaceae are not monophyletic. The phylogenomic tree also showed a confused phylogenetic relationships among these non-monophyletic species. Combining the phylogenetic relationships and average nucleotide identity values, the current taxonomic status of all the genera within the families Spirosomataceae and Cytophagaceae were re-examined. The genera 'Chryseosolibacter', 'Dawidia', and Chryseotalea should belong to the new family Chryseotaleaceae fam. nov., the genera Arcicella, Flectobacillus, Pseudarcicella, Aquirufa, and Sandaracinomonas should belong to the new family Flectobacillaceae fam. nov., the genera Fluviimonas, Taeseokella, Arcticibacterium, Emticicia, Jiulongibacter, Marinilongibacter, Lacihabitans, and Leadbetterella should belong to the new family Leadbetterellaceae fam. nov., the genus Litoribacter should be reassigned to the family Cyclobacteriaceae, and the genera Arundinibacter and Tellurirhabdus should be reassigned to the family Spirosomataceae. Strains DC2WT and DC25WT are reported to represent two novel species of the genus Arcicella, for which the names Arcicella gelida sp. nov. (type strain DC2WT=GDMCC 1.3209T=KCTC 92559T) and Arcicella lustrica sp. nov. (type strain DC25WT=GDMCC 1.3210T=KCTC 92557T) are proposed.

Vogesella aquatica sp. nov. and Vogesella margarita sp. nov., isolated from rivers in Southwest China.

Eight Gram-stain-negative, aerobic, short rod-shaped and motile strains (DC21WT, LYT5WT, LYT10W, LYT16W, LYT22W, LYT23W, LYT24W and SH7W) were isolated from rivers in Southwest China. Comparisons based on the 16S rRNA gene sequences showed that strain DC21WT shared the highest 16S rRNA gene sequence similarity (99.6 %) with Vogesella mureinivorans 389T, strain LYT5WT shared 99.2 % with Vogesella fluminis Npb-07T, and the other isolated strains took Vogesella indigofera DSM 3303T as their most similar strain, respectively. The phylogenetic trees reconstructed based on the 16S rRNA gene sequences also supported that strains V. mureinivorans 389T, V. fluminis Npb-07T and V. indigofera DSM 3303T were the closest neighbours of the isolated strains. The phylogenomic tree showed similar phylogenetic relationships among these strains. The calculated OrthoANIu and digital DNA-DNA hybridization values among strains DC21WT, LYT5WT and other related strains were less than 93.7 and 53.7 %, respectively. The calculated OrthoANIu and digital DNA-DNA hybridization values among strains LYT10W, LYT16W, LYT22W, LYT23W, LYT24W, SH7W and V. indigofera DSM 3303T ranged from 94.8 to 97.2 % and from 59.8 to 74.9 %, respectively. Although these values were located in the transition region of species demarcation, their similar phenotypic, biochemical and genotypic characteristics supported that these six strains should be assigned to the species V. indigofera. Comparative genomic analyses showed that only V. indigofera DSM 3303T harboured 19 genes encoding the Type VI secretion system. Combining above descriptions, strains DC21WT and LYT5WT should represent two independent novel species of the genus Vogesella, for which the names Vogesella aquatica sp. nov. (type strain DC21WT=GDMCC 1.3220T=KCTC 92556T) and Vogesella margarita sp. nov. (type strains LYT5WT=GDMCC 1.3213T=KCTC 92549T) are proposed, respectively.

Asticcacaulis aquaticus sp. nov., Asticcacaulis currens sp. nov. and Asticcacaulis machinosus sp. nov., isolated from streams in PR China.

Three Gram-stain-negative, aerobic, rod-shaped, stalked and motile strains with a polar flagellum (BYS171WT, DXS10WT and LKC15WT) were isolated from streams in PR China. Comparisons based on 16S rRNA gene sequences showed that strains BYS171WT and DXS10WT had the highest 16S rRNA gene sequence similarities (98.1 and 98.6 %, respectively) to Asticcacaulis excentricus CB 48T, and strain LKC15WT showed 99.6 % similarity to Asticcacaulis endophyticus ZFGT-14T. These three strains showed 16S rRNA gene sequence similarities of less than 96.9 % to other species of the genus Asticcacaulis. A phylogenetic tree reconstructed based on 16S rRNA gene sequences also showed that strains BYS171WT and DXS10WT took A. excentricus CB 48T as their closest neighbour, and strain LKC15WT formed a tight cluster with A. endophyticus ZFGT-14T. The phylogenomic tree also showed that these three strains belong to the genus Asticcacaulis and form a distinct clade with the species of the genus Asticcacaulis. The major cellular fatty acids of these three strains were summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c), summed feature 8 (C18 : 1 ω7c and/or C18 : 1 ω6c), C16 : 0 and 11-methyl C18 : 1 ω7c. Their polar lipids mainly consisted of phosphatidylglycerol, unidentified glycolipids and nitrogen-containing phosphoglycolipids. The calculated OrthoANIu and digital DNA-DNA hybridization values among strains BYS171WT, DXS10WT, LKC15WT and other related strains were less than 87.2 % and 34.0 %, respectively, indicating that these three strains should represent three independent novel species of the genus Asticcacaulis, for which the names Asticcacaulis aquaticus sp. nov. (type strain BYS171WT=GDMCC 1.3226T=KCTC 92612T), Asticcacaulis currens sp. nov. (type strain DXS10WT=GDMCC 1.3224T=KCTC 92543T) and Asticcacaulis machinosus sp. nov. (type strain LKC15WT=GDMCC 1.3225T=KCTC 92544T) are proposed.

Land-use and climate controls on aquatic carbon cycling and phototrophs in karst lakes of southwest China.

Land-use and climate changes have been repeatedly identified as important factors affecting terrestrial carbon budgets, however little is known about how deforestation and catchment development affect aquatic systems in carbonate-rich regions. Multi-proxy analyses of 210Pb-dated sediment cores from two hard-water lakes with different land-use histories were applied for assessing carbon cycling and limnological changes in response to land-use changes over the past century in southwest China. Logging of primary forests in the catchment of Lugu Lake, starting in the 1950s, led to a significant increase of catchment erosion, as well as a consistent decline in inferred lake-water total organic carbon (TOC) levels and sediment carbonate accumulation. This process of recent deforestation may significantly reduce the role of lake systems to act as carbon sinks through hampering of both the soil organic carbon flux and the dissolution of catchment carbonate. The decline in lake-water TOC in Lugu Lake further increased algal production (i.e. tracked through sediment trends in chlorophyll a and its main diagenetic products) and changes in diatom composition. In comparison, there was little variation of sediment carbonate content in Chenghai Lake, which has a long history of catchment deforestation, while both primary production and lake-water TOC increased following cultural eutrophication during the last three decades. Furthermore, regional warming was associated with an increase in small-sized diatoms in both deep lakes, likely due to enhanced thermal stability. This study highlights the significant role of vegetation cover and land use in driving aquatic carbon cycling and phototrophs, revealing that deforestation can strongly reduce both inorganic and organic carbon export to lakes and thus aquatic carbon storage in karst landscapes.

[Long-term pattern of lake ecosystem in response to eutrophication and water regulation in Chenghai Lake, Yunnan, China]. / äº‘å—ç¨‹æµ·æ¹–æ³Šç³»ç»Ÿå“åº”å¯Œè¥å »åŒ–ä¸Žæ°´æ–‡è°ƒæŽ§çš„é•¿æœŸæ¨¡å¼.

In the context of catchment development and climate change, anthropogenic activities have significantly altered the succession and functioning of freshwater ecosystems. Combining the sedimentary records and modern survey data, we reconstructed a 250-year history of ecological changes in Chenghai Lake, aiming to assess the long-term ecological changes in Changhai Lake in response to multiple environmental stresses, such as eutrophication and hydrological fluctuation.Three stages were identified for the process of nutrient enrichment leading to a long-term increase in primary production. Nutrient level was relatively low before 1970, increased gradually between 1970 and 2000, with an accelerating increase after 2000. The water regulation project enhanced water turbulence and river flux during 1993-2000, which promoted the growth of turbulence-tolerant Aulacoseira and influx of benthic Nitzschia. The organic carbon cycling in Chenghai Lake was mainly driven by the autogenetic inputs. The eutrophication process dominated the long-term shifts of diatom assemblages followed by hydrological fluctuation. Our results illustrated that ecological restoration and catchment management of Chenghai Lake not only need to focus on the control of nutrient enrichment and pollutant input, but also should consider hydrological regulation and water level fluctuation.

Environmental legacy and catchment erosion modulate sediment records of trace metals in alpine lakes of southwest China.

Sediment records are widely used to infer impact of atmospheric metal deposition in alpine lakes, however, the legacy effect and catchment erosion of historical pollutants could potentially affect metal influx into lakes. Here, we collect data (including six trace metals and three lithogenic elements) from well-dated sediment cores of seven alpine lakes in southeast Tibet, which is adjacent to southwest China. This area has a documented history of preindustrial pollution. Metals such as cadmium (Cd), zinc (Zn) and arsenic (As) are found at relatively low concentrations until a clear increase is observed after 1950s across lakes. This result is consistent with accelerating atmospheric metal deposition due to socio-economic development in the region. We observe no synchronous trend across lakes in the changes of lead (Pb), copper (Cu) and silver (Ag), which show no significant increase after ∼1950 over the last two centuries in most of the study lakes. The historical trends of 206Pb/207Pb ratio reflect an important source of anthropogenic Pb associated with preindustrial mining and smelting in this study region, suggesting a substantial impact of legacy contamination from ancient mines. Furthermore, the temporal variations in these six anthropogenic metals are largely accounted for by terrigenous elements (e.g. aluminum (Al) and titanium (Ti)) in most of the study lakes, and to a lesser degree by sediment grain sizes and organic matter content, suggesting a significant role of catchment erosion in modulating sediment metal signals. In all, this study highlights the legacy effect of historical pollutants may have enhanced the forcing of catchment erosion in modulating the sediment signals of anthropogenic deposition in southeast Tibet.

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.

Assessing the impact of long-term changes in climate and atmospheric deposition on a shallow alpine lake from southeast Tibet.

Regional warming and atmospheric nitrogen deposition have been widely recorded to impact remote catchments and alpine lakes; however, their independent roles and interactions have rarely been identified. Here, we combined down-core analyses of sedimentary mercury (Hg) and aluminum (Al) with multiple proxies (i.e. nitrogen stable isotope, chlorophyll a pigments, diatoms) for a radiometrically-dated sediment core of an alpine lake in southeast Tibet to track the atmospheric deposition of pollutants, and to examine possible effects of climate and catchment forcing over the past three centuries. The sediment data revealed that airborne deposition of Hg was recorded from the ~1860s, with an accelerating increase in anthropogenic Hg flux since the ~1960s. A synchronous decrease in reconstructed lake-water TOC indicated that acid deposition may have affected lake-water carbon concentrations and impaired catchment export of decomposed organic matter (OM). A moderate depletion of bulk sediment δ15N started from the ~1820s, but was followed by an enriching trend after the ~1970s. This positive shift of δ15N was associated with elevated sediment OM and decreased catchment runoff of clastic materials (as inferred by Al). Sediment OM content displayed an accelerating increase from the ~1960s, with an increased input of autochthonous sources (i.e. lower bulk sediment C:N ratios), such as algae (as inferred by sedimentary chlorophyll a pigments). Meanwhile, climate warming and decreased lake-water TOC enhanced the production of algae, which was characterized by a more enriched δ15N signal than that of allochthonous OM. Furthermore, atmospheric acid deposition was significantly related to diatom assemblage changes, with an increase in acidophilous taxa. Our sediment evidence revealed the dominating impact of climate and catchment processes on lake-water chemistry and algal shifts in the context of atmospheric nitrogen deposition, and highlighted an increasing link of external forcing with in-lake processes in enriching sediment δ15N signal over the last few decades.

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.

Calciphytoliths (calcium oxalate crystals) analysis for the identification of decayed tea plants (Camellia sinensis L.).

The history of tea is poorly known, mainly due to the questionable identification of decayed tea plants in archaeological samples. This paper attempts to test the utility of calciphytoliths (calcium oxalate crystals) for the identification of tea in archaeological samples. It provides the first survey of the macropatterns of calciphytoliths in several species of Theaceae and common non-Theaceae plants. Crystals were extracted from 45 samples of tea, Theaceae and common non-Theaceae plants, and detected microscopically between crossed polarizers. In tea plants, druse and trichome base are the most distinctive crystals. Druses have the smallest diameter (11.65 ± 3.64 µm), and trichome bases have four distinctive straight and regular cracks, similar to a regular extinction cross. The results provide morphological criteria for distinguishing tea from other plants, specifically the presence of identifiable druses together with calcified trichome bases. The implications are significant for understanding the history of tea and plant exploitation, especially for plants for which the preservation of macrofossils is poor.