An integrative approach sheds new light onto the systematics and ecology of the widespread ciliate genus Coleps (Ciliophora, Prostomatea).

Species of the genus Coleps are one of the most common planktonic ciliates in lake ecosystems. The study aimed to identify the phenotypic plasticity and genetic variability of different Coleps isolates from various water bodies and from culture collections. We used an integrative approach to study the strains by (i) cultivation in a suitable culture medium, (ii) screening of the morphological variability including the presence/absence of algal endosymbionts of living cells by light microscopy, (iii) sequencing of the SSU and ITS rDNA including secondary structures, (iv) assessment of their seasonal and spatial occurrence in two lakes over a one-year cycle both from morphospecies counts and high-throughput sequencing (HTS), and, (v) proof of the co-occurrence of Coleps and their endosymbiotic algae from HTS-based network analyses in the two lakes. The Coleps strains showed a high phenotypic plasticity and low genetic variability. The algal endosymbiont in all studied strains was Micractinium conductrix and the mutualistic relationship turned out as facultative. Coleps is common in both lakes over the whole year in different depths and HTS has revealed that only one genotype respectively one species, C. viridis, was present in both lakes despite the different lifestyles (mixotrophic with green algal endosymbionts or heterotrophic without algae). Our results suggest a future revision of the species concept of the genus Coleps.

Molecular Data Reveal a Cryptic Diversity in the Genus Urotricha (Alveolata, Ciliophora, Prostomatida), a Key Player in Freshwater Lakes, With Remarks on Morphology, Food Preferences, and Distribution.

Species of the ciliate genus Urotricha are key players in freshwater plankton communities. In the pelagial of lakes, about 20 urotrich species occur throughout an annual cycle, some of which play a pivotal role in aquatic food webs. For example, during the phytoplankton spring bloom, they consume a remarkable proportion of the algal production. In ecological studies, urotrich ciliates are usually merely identified to genus rank and grouped into size classes. This is unsatisfying considering the distinct autecological properties of individual species and their specific spatial and temporal distribution patterns. As a basis for future research, we characterized in detail four common urotrich morphotypes, i.e., specimens identified as U. furcata and tentatively as U. agilis, U. pseudofurcata, and U. castalia, using state-of-the-art methods. We used an integrative polyphasic approach, in which morphological studies (in vivo observation, silver staining methods, scanning electron microscopy) were linked with a molecular approach exploiting four different gene fragments as taxonomic DNA barcodes with different resolution potential (SSU rDNA, ITS-1, ITS-2, hypervariable V4 and V9 regions of the SSU rDNA). We shed light on the diversity of urotrich ciliates as well as on their global distribution patterns, and annual cycles. Additionally, we coupled individual species occurrences and environmental parameters, and subsequently modeled the distribution and occurrence, using logistic regressions. Furthermore, for one strain putatively identified as U. castalia, we ascertained the optimal cultivation media and food preferences. Thereby, our comprehensive view on these important freshwater ciliates that frequently occur in environmental high throughput sequencing datasets worldwide will allow future studies to better exploit protistan plankton data from lakes.

Do the regular annual extreme water level changes affect the seasonal appearance of Anabaena in Poyang Lake?

BACKGROUND: Poyang Lake is an ecosystem experiencing annual variations in water level of up to 14 m. Water level changes were 8.03 and 11.22 m, respectively, in the years 2013 and 2014. The biomass and heterocyst frequency of Anabaena increased in the summers of recent years. METHODS: A weekly to bi-weekly monitoring from June to November 2013 and 2014 was set up to explain the variations of Anabaena appearance in different phases of the water level. RESULTS: Anabaena was present in the lake throughout the year. The average relative biomass of Anabaena in the present study was over 40%, being most abundant in summer. The average heterocyst frequency was 0.23% in 2013 and 0.76% in 2014. Correlation analysis indicated a positive trend of Anabaena biomass with water temperature and water level and a negative one with total nitrogen (TN), which is the reason for the increase of heterocyst frequency in 2013 and 2014. Heterocyst frequency of Anabaena was positively correlated with water temperature, water level and PO4-P, and negatively with dissolved inorganic nitrogen (DIN/DIP), NO3-N and TN. Moreover, water temperature and DIN/DIP were significantly correlated with water level, indicating that water level changes have a direct effect on Anabaena and heterocyst formation in Poyang Lake. CONCLUSIONS: The results of this study support the hypothesis that increasing biomass and heterocyst formation of Anabaena can be primarily caused by seasonal changes of the water level in Poyang Lake.

Variations in organic carbon, aggregation, and enzyme activities of gangue-fly ash-reconstructed soils with sludge and arbuscular mycorrhizal fungi during 6-year reclamation.

Mining activities can cause drastic disturbances in soil properties, which adversely affect the nutrient cycling and soil environment. As a result, many efforts have been made to explore suitable reclamation strategies that can be applied to accelerate ecology restoration. In this study, we reconstructed mine soils with fly ash, gangue, sludge, planted ryegrass, and inoculated arbuscular mycorrhizal fungi (AMF) in Pangzhuang mine of Xuzhou during 2009 to 2015. The soil aggregation process, enzyme activities (i.e., invertase, urease and acid phosphatase activities), soil organic carbon (SOC) as well as other soil nutrients such as nitrogen, phosphorus, and potassium contents of the reconstructed mine soils were monitored during 6-year reclamation. The integrated application of sludge and AMF led to a promising reclamation performance of mining areas, in which soil aggregate stability, enzyme activities, SOC, and ryegrass biomass were effectively enhanced. The micro-aggregates (< 0.25 mm) decreased with the increase of macro-aggregates (> 0.25 mm) during the reclamation, indicating that macro-aggregates were gradually formed from micro-aggregates during the pedogenesis of reconstructed mine soils. The correlation analysis shows that SOC contents in aggregate fraction of 0.25∼0.5 mm were correlated with aggregate distribution and enzyme activities. Enzyme activities, however, were not significantly correlated with aggregate distribution. The outcomes from the present study could enrich our understanding on soil property changes in pedogenesis process of reconstructed mine soils, and meanwhile, the employment of sludge combined with AMF is suggested to be an effective alternative for the mine soil reclamation.

[Phytoplankton community structure and its succession in isolated lakes of Poyang-Junshan Lake].

As one of the human activities that transform nature, construction of dams and dykes may impose significant effects on lake ecosystems. Due to lacking of comparative data for ecological monitoring, how the changes of phytoplankton community structure respond to altered hydrological connectivity between lakes and other water bodies is still unknown. This work chose Junshan Lake, the typical isolated lake from Poyang Lake floodplain, to investigate the succession in phytoplankton communities responding to altered connectivity. Phytoplankton samples were collected during the wet and dry seasons in Junshan Lake, to analyze the phytoplankton community structure. The results showed that, fifty three genera from six phyta were identified in Junshan Lake, with Chlorophyta (47.2%), Bacillariophyta (22.2%), Cyanophyta (14.8%) and Euglenophyta (9.3%) being the main phyta. The dominant species were Ceratium hirundinella (20.5%), Anabeana spp. (18.5%) and Microcystis spp. (12.9%) during the wet seasons. Cryptomonas ovate (38.4%), Aulacoseira granulata (15.2%) and Microcystis spp. (10.5%) dominated during the whole dry seasons. The total phytoplankton abundance was mainly composed of Cyanophyta (85.4% -87.0%). The total phytoplankton biomass was dominantly made up of Cyanophyta (45.0%), Dinophyta (21.1%), Bacillariophyta (15.6%) and Chlorophyta (11.5%) during the wet seasons. Cryptophyta (38.2%), Bacillariophyta (31.3%) and Cyanophyta (21.1%) were the main contributors of the total phytoplankton biomass during the dry seasons. The phytoplankton community structure changed from Dinophyta-Bacillariophyta type during the wet seasons of 2007-2008 to Cyanophyta- Dinophyta type during the wet seasons of 2012-2013, and changed from Dinophyta- Bacillariophyta type during the dry seasons of 2007-2008 to Cryptophyta- Bacillariophyta- Cyanophyta type during the dry seasons of 2012-2013. The abundance and biomass increased from 2.66 x 10(6) cell L(-1) during 2007-2008 to 6.77 x 10(7) cell x L(-1) during 2012- 2013, and from 0.72 mg x L(-1) during 2007-2008 to 12.30 mg x L(-1) during 2012-2013, respectively. The succession pattern of phytoplankton community in the Junshan Lake showed a decrease in the proportion of oligotrophic species as Chrysophyta and Dinophyta, and an increase in eutrophic species as Cyanophyta and Cryptophyta. Thus, being isolated from Poyang Lake might alter hydrologic factors so that the water exchange time became longer and the water flow became slower which could promote the growth and aggregation of phytoplankton eutrophication indicator species in Junshan Lake.