A Preliminary Study on the Eukaryotic Microbial Diversity in Croatian Geothermal Waters

Mitrović, Maja; Čačković, Andrea; Selak, Lorena; Marković, Tamara; Orlić, Sandi (2025) A Preliminary Study on the Eukaryotic Microbial Diversity in Croatian Geothermal Waters. Water, 17 (4). ISSN 2073-4441

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Abstract

Microbial eukaryotes have essential roles in aquatic ecosystems, yet their diversity and ecological functions in extreme environments remain understudied compared to prokaryotes. This study aims to thoroughly characterize the composition and diversity of microbial eukaryotic communities in 14 geothermal waters across Croatia. Physicochemical analysis revealed significant variations in temperature (36–55 °C), pH (6.5–8.3), and nutrient concentrations, with all sites displaying anoxic conditions except for one. Sequencing of the V9 18S rRNA gene identified 134 taxa, predominantly from the Alveolata, Stramenopiles, and Opisthokonta supergroups. The highest diversity and richness were observed in aquifer groups with moderate temperatures and nutrient levels, while extreme sites exhibited reduced diversity. Among the key environmental factors shaping these communities, temperature, pH, and nitrate concentrations were most significant. Photoautotrophic and mixotrophic taxa, such as Ochrophyta, Dinoflagellata, and Chlorophyta, were prominent, reflecting their roles in primary production and nutrient cycling. Decomposers, including Basidiomycota and Ascomycota, were linked to organic matter degradation. Microeukaryotes showed adaptations to extreme conditions, such as thermotolerance and evolutionary shifts from phototrophy to heterotrophy, highlighting their ecological versatility. These findings underscore the potential of microbial eukaryotes in biotechnological applications, such as bioremediation and biofuel production. Genera like Tribonema and Navicula demonstrated promising capabilities in nutrient removal and CO2 fixation. However, further research is necessary to investigate and confirm their suitability for these purposes. To summarize, our research provides new insights into understudied microbial eukaryotes in Croatian hot springs that represent a valuable model for exploring microbial diversity, ecological interactions, and industrial applications in extreme environments.

Item Type:	Article
Uncontrolled Keywords:	hot springs; microbial eukaryotes; 18S rRNA gene amplicon sequencing; microalgae
Subjects:	NATURAL SCIENCES > Geology NATURAL SCIENCES > Biology
Divisions:	Division of Physical Chemistry
Projects:	Project title Project leader Project code Project type Višefazni pristup za dešifriranje mikrobne ekologije i biotehnološkog potencijala geotermalnih izvora u Hrvatskoj-MAMEBio Sandi Orlić; Petra Pjevac; Marija Vuković Domanovac; Martina Sudar PZS-2019-02-7373 HRZZ
Depositing User:	Ana Zečević
Date Deposited:	28 Apr 2025 07:54
URI:	http://fulir.irb.hr/id/eprint/9759
DOI:	10.3390/w17040541

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