# Phototrophs in Unique Habitats of Thermomineral Springs in Central Serbia

## TL;DR

This study explores unique microbial communities in Serbian thermomineral springs, highlighting their ecological significance and potential for biotechnology.

## Contribution

The study identifies unique cyanobacterial taxa and characterizes phototrophic communities in under-researched Serbian thermomineral springs.

## Key findings

- Submerged biofilms showed higher primary production compared to splash zone biofilms.
- Bacillariophyta was the most diverse phototrophic division, followed by Cyanobacteria.
- Ammonia, total nitrogen, and organic carbon were key factors shaping community composition.

## Abstract

Thermomineral springs are unique aquatic habitats characterized by high temperatures or mineral-rich water and often host specialized microbial communities. In Serbia, these springs represent an important but under-researched ecological resource whose diverse physicochemical properties are shaped by their geological context. In this study, the physical and chemical properties of Serbian thermomineral springs and their relationship with phototrophic communities in different substrates are investigated. Phototrophic biofilms were categorized into fully submerged and splash zone biofilms, with the former showing higher primary production. Cyanobacteria, Chlorophyta, and Bacillariophyta were recorded, with Bacillariophyta being the predominant division in terms of diversity, followed by Cyanobacteria. Among Cyanobacteria, coccoid forms like Aphanocapsa, Chroococcus, Gloeocapsa and Synechococcus dominated splash zones, while trichal forms such as Leptolyngbya, Oscillatoria and Pseudanabaena were abundant in submerged biofilms, forming thick mats. Unique cyanobacterial taxa, including Desertifilum, Elainella, Geitlerinema, Nodosilinea and Wilmottia, were identified through molecular analysis, underscoring the springs’ potential as habitats for specialized phototrophs. Diatom communities, dominated by Nitzschia and Navicula, exhibited site-specific species influenced by microenvironmental parameters. Statistical analysis revealed ammonia, total nitrogen, and organic carbon as key factors shaping community composition. This study enhances the understanding of these ecosystems, emphasizing their conservation importance and potential for biotechnological applications.