TY  - GEN
AV  - public
ID  - heidok34582
CY  - Heidelberg
Y1  - 2024///
A1  - Mocaer, Karel
UR  - https://archiv.ub.uni-heidelberg.de/volltextserver/34582/
TI  - Ultrastructural characterization of dinoflagellates from heterogeneous marine environmental samples
N2  - As a consequence of human impact, our planet is experiencing an alarming decline in biodiversity. However, estimating the extent of this loss is complex as many environments are still understudied to this day. While marine systems have been studied for decades, due to their incredible diversity and heterogeneity, our knowledge concerning their biology is still limited. 

Microplankton are widely distributed across the photic layer of the oceans and are responsible for an important fraction of CO2 absorption and O2 production on earth through photosynthesis (C. Field et al., 1998). Furthermore, these organisms play a crucial role in the equilibrium of the marine food web. They thus have a central ecological importance for climate and ecosystems regulation. Studying environmental microplanktonic cells populating our oceans is crucial to better assess the range in their biodiversity, as well as to investigate further their biology, physiology, and their response to changing environments. Additionally, thus far, it is only possible to preserve a small fraction of marine microorganisms in the laboratory, and setting large scale environmental investigations is difficult.

In my thesis project, I first focused on setting a workflow that would enable a detailed ultrastructural analysis of microplankton from the field. I collected microorganisms at sea in the early morning and afternoon, starting with an unsorted community of species taken from a 5 to 40 ?m size fraction. From such bulk samples, I focused on a subset of eukaryotic phytoplanktonic organisms, dinoflagellates, and studied their subcellular morphologies using Electron Microscopy (EM). 

Using unbiased 2D EM screens, I built an image atlas that gathers ultrastructural details of all species collected during our field expeditions across morning and afternoon conditions. From this Transmission Electron Microscopy (TEM) screen, I could annotate classes of subcellular structures which seemed to be associated to certain genera or trophic modes. Furthermore, this screen enabled me to observe variations, at the population level, in the occurrence of a subset of organelles. 

I then contributed in developing a light microscopy guided targeting strategy to perform volume EM imaging of a subset of organisms of interest from a heterogeneous environmental sample. Combining 2D and 3D EM modalities, I could work towards determining group-specific subcellular characteristics, and better understanding morphological variations existing in a mixed population, or in targeted organisms, across an ecological gradient (morning and afternoon).

My work has set the ground for some projects of the ongoing large scientific expedition called TREC and I am very excited to see how my results and also those from my colleagues in the lab will contribute to a better understanding of the marine ecosystems and their response to changing environments.
ER  -