Testate amoebae (Protozoa) in lakes of the Qinghai-Tibet Plateau: Biodiversity, community structures, and protozoic biosilicification in relation to environmental properties and climate warming.

The Qinghai-Tibet Plateau (QTP) is characterized by a vast number of frozen and unfrozen freshwater reservoirs, which is why it is also called "the third pole" of the Earth or "Asian Water Tower". We analyzed testate amoeba (TA) biodiversity and corresponding protozoic biosilicification in lake sediments of the QTP in relation to environmental properties (freshwater conditions, elevation, and climate). As TA are known as excellent bio-indicators, our results allowed us to derive conclusions about the influence of climate warming on TA communities and microbial biogeochemical silicon (Si) cycling. We found a total of 113 TA taxa including some rare and one unknown species in the analyzed lake sediments of the QTP highlighting the potential of this remote region for TA biodiversity. >1/3 of the identified TA taxa were relatively small (<30 µm) reflecting the relatively harsh environmental conditions in the examined lakes. TA communities were strongly affected by physico-chemical properties of the lakes, especially water temperature and pH, but also elevation and climate conditions (temperature, precipitation). Our study reveals climate-related changes in TA biodiversity with consequences for protozoic biosilicification. As the warming trend in the QTP is two to three times faster compared to the global average, our results provide not only deeper insights into the relations between TA biodiversity and environmental properties, but also predictions of future developments in other regions of the world. Moreover, our results provide fundamental data for paleolimnological reconstructions. Thus, examining the QTP is helpful to understand microbial biogeochemical Si cycling in the past, present, and future.

Distribution and ecological risk assessment of heavy metals in sediments of Dajiuhu Lake Wetland in Shennongjia, China.

The rapid development of modern society has resulted in discharge of large, heavy metal quantities into wetlands that have been continuously accumulating, causing severe pollution. Dajiuhu, located in the Shennongjia Forest District of Hubei Province in China, is a wetland of significant value internationally, serving as a model wetland ecosystem with heightened scientific research value. In this study, 27 surface sediment samples from nine sub-lakes in Dajiuhu were collected in August 2020. The concentrations of Cd, Cr, Cu, Ni, Pb, and Zn in the sediments were determined. The heavy metal occurrence and speciation characteristics were analyzed by an improved BCR (European Community Bureau of Reference) extraction method. Four methods were used to evaluate heavy metals' pollution degree and ecological risk. The possible source of heavy metals was inferred using correlation analysis and principal component analysis. The heavy metal content in the lake sediments of Dajiuhu wetland was from the highest to the lowest concentration as follows: Zn [Formula: see text] Cr [Formula: see text] Ni [Formula: see text] Pb [Formula: see text] Cu [Formula: see text] Cd. The average Cd content exceeded the national nature reserve threshold values, while the other heavy metals measured were below their respective threshold values. However, due to the occurrence of Pb and Cd in different forms, they still pose certain pollution and ecological risk to the lake wetlands. On the other hand, Zn, Cr, Ni, and Cu do not pose an ecological risk in the lakes of the Dajiuhu wetland. The spatial distribution of heavy metal content in the nine sub-lakes did vary significantly. Regarding the heavy metal sources in the lake sediments, Ni, Cr, and Cu originate from natural factors, and Cd and Pb have mainly anthropogenic origins. In contrast, Zn has both natural and anthropogenic origins. This study provides further insights into the study of heavy metal pollution in lake wetlands. It provides a framework and a direction for managing heavy metal pollution in the Dajiuhu wetland.

The elemental enrichments at Dajiuhu Peatland in the Middle Yangtze Valley in response to changes in East Asian monsoon and human activity since 20,000 cal yr BP.

Here we present multiproxy inorganic geochemical records from a peat core (ZK5) from the Dajiuhu Basin in central China to investigate peatland deposition processes and atmospheric metal pollution and to explore their relationships with East Asian monsoon change and human activities in the Middle Yangtze Valley since 20,000 cal yr BP. The peat physicochemical data including total organic carbon (TOC), trace elements, and grain-size show that the site has changed from a lake during the cold-wet Last Glacial Maximum (LGM; 20,000-18,000 cal yr BP), to a marshy wetland during the mild last deglaciation (18,000-11,500 cal yr BP) and a peatland during the mostly warm and dry Holocene (11,500 cal yr BP-present). This general sequence corresponds with changes in East Asian monsoon indicated by stalagmites δ18O records and boreal summer insolation. Marked decreases in trace element concentrations correspond to two periods of peatland expansion during the abrupt hydroclimatic transitions from the LGM to the last deglaciation and from the last deglaciation to the early Holocene. Warm-dry mid-Holocene might induce high organic matter decomposition in peat sediments. Increasing natural element concentrations since the late Holocene are correlated with the weakening of the summer monsoon and elevated atmospheric dust deposition. Increasing Cu and Pb concentrations in peat record indicate large-scale Cu smelting during the Bronze Age and excessive coal burning during the 10th century or so. The anthropogenic heavy metals were transported by prevailing East Asian summer monsoon and deposited in the Dajiuhu Basin during periods of heightened human activities. Our compilation of heavy metals records across China confirmed the noticeable impacts of the historical human activity on deposition environments during the late Holocene. Consequently, trace elements from the Dajiuhu Basin are reliable proxies for capturing monsoon climate-induced peatland deposition response and present important evidence for a historical atmospheric heavy metal pollution in the Middle Yangtze Valley. Our results offer useful references for peatland evolution and protection under the background of global change.

Response of carbon cycle to drier conditions in the mid-Holocene in central China.

The nature and extent to which hydrological changes induced by the Asian summer monsoon affected key biogeochemical processes remain poorly defined. This study explores the relationship between peatland drying and carbon cycling on centennial timescales in central China using lipid biomarkers. The difference between peat n-alkane δ2H and a nearby stalagmite δ18O record reveals that intervals of prominent peatland drying occurred during the mid-Holocene. Synchronous with these drier conditions, leaf wax δ13C values show large negative excursions, with the utilization of CO2 respired from the peatland subsurface for plant photosynthesis being a possible mechanism. Crucially, successive drying events appear to have had a cumulative impact on the susceptibility of peat carbon stores to climate change. Concurrently, bacterially derived hopane δ13C values suggest the occurrence of enhanced methane oxidation during the drier periods. Collectively, these observations expand our understanding of how respiration and degradation of peat are enhanced during drying events.

Screening for Autochthonous Phytoextractors in a Heavy Metal Contaminated Coal Mining Area.

In order to protect public health and crops from soil heavy metal (HM) contamination at a coal mining area in Henan, central China, HM pollution investigation and screening of autochthonous HM phytoextractors were conducted. The concentrations of cadmium (Cd), lead (Pb), copper (Cu) and zinc (Zn) in surface soils exceeded the corresponding local background values and the China National Standard (CNS). The maximum potential ecological risk (RI) was 627.30, indicating very high ecological risk. The monomial risk of Cd contributed the most to the RI, varying from 85.48% to 96.48%. The plant community structure in the study area was simple, and was composed of 24 families, 37 genera and 40 species. B. pilosa, A. roxburghiana, A. argyi, A. hispidus were found to be the most dominant species at considerable risk sites. Based on the comprehensive analysis of Cd concentration, bioconcentration factor, translocation factor and adaptability factor, B. pilosa and A. argyi had potential for phytoextraction at considerable risk sites. A. roxburghiana had potential for Cd phytoextraction at moderately risk sites and A. hispidus seemed suitable for phytostabilization. The results could contribute to the phytoremediation of the similar sites.

Nebela jiuhuensis nov. sp. (Amoebozoa; Arcellinida; Hyalospheniidae): A New Member of the Nebela saccifera - equicalceus - ansata Group Described from Sphagnum Peatlands in South-Central China.

Hyalospheniids are among the most common and conspicuous testate amoebae in high-latitude peatlands and forest humus. These testate amoebae were widely studied as bioindicators and are increasingly used as models in microbial biogeography. However, data on their diversity and ecology are still very unevenly distributed geographically: notably, data are lacking for low-latitude peatlands. We describe here a new species, Nebela jiuhuensis, from peatlands near the Middle Yangtze River reach of south-central China with characteristic morphology. The test (shell) has hollow horn-like lateral extensions also found in N. saccifera, N. equicalceus (=N. hippocrepis), and N. ansata, three large species restricted mostly to Sphagnum peatlands of Eastern North America. Mitochondrial cytochrome oxidase (COI) data confirm that N. jiuhuensis is closely related to the morphologically very similar North American species N. saccifera and more distantly to N. ansata within the N. penardiana group. These species are all found in wet mosses growing in poor fens. Earlier reports of morphologically similar specimens found in South Korea peatlands suggest that N. jiuhuensis may be distributed in comparable peatlands in Eastern Asia (China and Korea). The discovery of such a conspicuous new species in Chinese peatlands suggests that many new testate amoebae species are yet to be discovered, including potential regional endemics. Furthermore, human activities (e.g., drainage, agriculture, and pollution) have reduced the known habitat of N. jiuhuensis, which can thus be considered as locally endangered. We, therefore, suggest that this very conspicuous micro-organism with a probably limited geographical distribution and specific habitat requirement should be considered as a flagship species for microbial biogeography as well as local environmental conservation and management.

[Distribution Characteristics of Polycyclic Aromatic Hydrocarbons in Different Environmental Media from Qingbang Island, Zhoushan, China].

Eleven soil, three seawater and three passive air samples were collected from Qingbang Island in July, 2013, and 16 polycyclic aromatic hydrocarbons (PAHs) were analyzed. The distribution characteristics, possible sources and ecological risk assessment were investigated. The results showed that the concentrations of total 16 PAHs ranged between 60.30 and 123.34 ng x g(-1) with a mean value of 105.49 ng x g(-1) in soil, 45.96-101.08 ng x L(-1) with a mean value of 66.45 ng x L(-1) in seawater and 5.09-5.41 ng x d(-1) with a mean value of 5.35 ng x d(-1) in air samples, respectively. The PAHls concentrations of soil samples in tidal zone were higher than those in other areas. The highest PAHs concentrations in seawater were detected in complicated hydrological sea area. PAHs concentrations in air were equally distributed around the island. 2-4 rings PAHs were dominant species in soil, water and air samples. Ratio method and factor analysis were used to identify the possible sources of PAHs. The result suggested that PAHs in soil were mainly originated from combustion of coal, wood, diesel and petrol, while the possible sources of PAHls in water and air were mixed. The ecological risk assessment indicated that PAi s in different environment media posed little risk to people.

[Distribution and enrichment characteristics of organochlorine pesticides in water and halobios from Qingbang Island in Zhoushan, China].

A total of 14 biological samples and 3 water samples were collected from the Qingbang Island. The concentrations of OCPs in the samples were determined by GC-ECD to investigate the distribution, composition, source and potential health risks of these compounds in the study area. The results showed that OCPs were detected in all samples. The detection ratios of OCPs were 100%. Concentrations of HCHs and DDTs ranged from 0.09 ng x g(-1) to 11.51 ng x g(-1) and 0. 02 ng x g(-1) to 56.15 ng x g(-1), respectively. Compared with other regions, the pollution of OCPs in Qingbang Island stayed at a low level. Distribution characteristics of OCPs in halobios from Qingbang Island indicated that changes in the upwelling and fronts were the main factors that affected the distribution of OCPs. Source analysis showed that HCHs and DDTs in halobios were mainly originated from the external. In addition, OCPs residues were far below the National Food Safety Standard. The estimated daily intake of OCPs from the halobios tested was also below the acceptable daily intake(ADI) recommended by FAO/WHO, indicating little health risk in halobios consumption for local residents.

Diversity, distribution and biogeography of testate amoebae in China: implications for ecological studies in Asia.

Testate amoebae are a group of shelled protozoa that occur in high density populations in wet environments. More than 1900 testate amoebae species or subspecies have been reported in published literature over the last 200 years, from many regions of the world. Testate amoebae are classified as Lobosea or Filosea respectively, according to the presence of lobose or filiform pseudopodia. Testate amoebae have proved an interesting group of indicator organisms in palaeoenvironmental studies and have also been used as bioindicators of human impact on ecosystems. Until recently, the testate amoebae of China were unknown to most western scientists, but our knowledge has improved greatly over the past 20 years. This paper summarizes the testate amoebae research in China along with relevant data from other countries in Asia, and provides the necessary context for future research.

Pentagonia zhangduensis nov. spec. (Lobosea, Arcellinida), a new freshwater species from China.

The morphology of a new testate amoeba Pentagonia zhangduensis nov. spec. was investigated using light and scanning electron microscopy. The new species was discovered in the sediments of Lake Zhangdu, Hubei Province, China. The low coefficients of variation and normal size frequency distribution suggest that P. zhangduensis is a size-monomorphic species. P. zhangduensis differs from the one other species in this genus (P. maroccana), by its larger size and its quadrangular cross section with two parallel longitudinal ridges on each of the two flattened sides of the test.

[Determination of Cd in sediment samples by flow injection on-line anion exchange combined with vapour generation-atomic fluorescence spectrometry].

In the present work, a method was developed for the determination of ultra-trace levels of Cd in sediment samples by atomic fluorescence spectrometry (AFS). A flow injection on-line separation and preconcentration technique coupled with an intermittent injection vapor generation technique was employed in the study. The instrument operating parameters and chemical conditions were optimized. In a 2.0 mol x L(-1) HCl solution, Cd (II) was adsorbed on 717-strong alkaline anion exchange resin, while Cu (II) and Pb (II) passed throngh. Then Cd (II) was eluted by 0.5 mol x L(-1) HNO3. The eluting solution was determined directly by intermittent injection vapor generation atomic fluorescence spectrometry. It was showed that Cd (II) can be preconcentrated effectively and the interference can be completely eliminated by this improved method. The Cd atomic vapor generation efficiency could be greatly enhanced in the presence of Co (II) and 1, 10-phenanthroline. The linear range of the determination was 0-12 microg x L(-1) with a detection limit of 0.058 microg x L(-1). The RSD (5 microg x L(-1), n=7) was 1.09%. The method was convenient, rapid and successfully validated by using national water sediment standard reference materials.