Biology subjects

Jeppesen, E.

Publications and source records attributed to Jeppesen, E..

4 recordsLinked to original sources

bioRxiv2023

Species-level classification provides new insights into the biogeographical patterns of microbial communities in shallow saline lakes

Saline lakes are rapidly drying out across the globe, particularly in Central Asia, due to climate change and anthropogenic activities. We present the results of a long-read next generation sequencing analysis of the 16S rRNA-based taxonomic structure of bacteriomes of the Tengiz-Korgalzhyn lakes system. We found that the shallow endorheic, mostly saline lakes of the system show unusually low bacterioplankton dispersal rates at species-level taxonomic resolution. The major environmental factor structuring the lakes microbial communities was salinity. The dominant bacterial phyla of the lakes with high salinity included a significant proportion of marine and halophilic species. In sum, these results, which can be applied to other lake systems of the semi-arid regions, improve our understanding of the factors influencing lake microbiomes undergoing salinization in response to climate change and other anthropogenic factors. Our results show that finer taxonomic classification can provide new insights and improve our understanding of the environmental factors influencing the microbiomes of lakes undergoing salinization in response to climate change and other anthropogenic factors.

ecology↗

bioRxiv2023

Dynamics of associated microbiomes during algal bloom development: to see and to be seeing

Our understanding of the interactions between bacteria and phytoplankton in the freshwater phycosphere, including the development of algal blooms, is very limited. To identify the taxa and compositional variation within microbial communities, we performed 16S rRNA amplicon sequencing research on samples collected weekly through summer from mesocosms that differed in temperature and mixing regimes. We investigated, for the first time, the abundance diversity of microalgae, including Chlorophyta, Cryptophyta, and Cyanobacteria species, using visualization-based FlowCAM analysis and classification of microbial communities to species level by nanopore next-generation sequencing. We found that nanopore metagenomics, in parallel with complementary imaging flow cytometry, can depict the fine temporal dynamics of microbiomes associated with visually identified Microcystis morphospecies, Chlorophyta, and Cryptophyta during algal bloom development. Our results showed that the temporal characteristics of microbiomes combined with a visual approach may be a key tool to predict the metacommunity structure and dynamics of algal blooms in response to anthropogenic effects and climate change.

microbiology↗

bioRxiv2023

From colonial clusters to colonial "sheaths": analysis of Microcystis morphospecies in mesocosm by imaging flow cytometry

The alarming increase in the frequency of blooms of Microcystis in freshwater lakes and reservoirs occurs worldwide, with major implications for their ecosystem functioning and water quality. We applied FlowCAM-based imaging flow cytometry together with PCR and sequencing to get a comprehensive picture of the seasonal development of Microcystis community in a long-term running lake mesocosm experiment. The IFC analysis with manual taxonomic classification confirmed early findings with a machine learning algorithm that some Microcystis morphospecies completely disappeared and re-appeared along the mesocosm experiment timeline. This observation supports the hypothesis of the main transition pathways of colonial Microcystis. For the first time, colonial mucilaginous envelopes or sheaths were reported as separate entities, and not as a part of Microcystis colonies. The colonial sheaths may contain a few single Microcystis cells and reach significant numbers (thousands) during a cyanobacterial bloom. We also found that non-identifiable colonial small clusters of Microcystis cells are an important stage in the complex mosaic of a Microcystis bloom and are associated with the development of colonial forms. Our findings were validated by the principal component analysis coupled with the constructed associative matrices. We hypothesize that colonial sheaths may be crucial at Microcystis spp. dispersal and represent one of the stages of colonies development.

ecology↗

bioRxiv2020

Morphological and physiological response strategies of Vallisneria natans at different water depths and light conditions

Phenotypic plasticity is an important adaptation to spatial and temporal environmental variations. For submerged macrophytes, adaptation to water depth and light variation is particularly important. To determine the morphological and physiological adaptive strategies of Vallisneria natans at different water depths and light conditions, we combined field investigation, light control experiment and in situ physiological response experiment. In the field investigation and the light control experiment, both water depth and light intensity had prominent effects on the morphological of V. natans, especially in fresh weight and leaf length. The leaf length elongated more rapidly at intermediate water depth sites with lower light intensity. In the in situ experiment, the survival boundary of V. natans is 5.5 m in Lake Erhai. Below this depth, the chlorophyll-a content increased gradually with increasing water depth. Our results demonstrated that V. natans can adapt to water depth and light availability by changing morphological, physiological and resource allocation. At low light condition, V. natans invested more resource for light acquisition, simultaneously, changing the photosynthetic pigment content to compensate for light attenuation; conversely, more resource was directed towards reproduction. These results will provide new insight for species selection when conducting aquatic plants restoration in freshwater ecosystem. HIGHLIGHTSO_LIWater depth and light availability affect the morphology, physiology, and resource allocation of V. natans. C_LIO_LIAn alternative resource allocation pattern of V. natans could shift between light acquisition and reproduction. C_LI

ecology↗