# Microbial Community Dynamics in Early Tufa Biofilms

## TL;DR

Microbial communities in karst lakes stabilize tufa biofilms, with prokaryotes and microeukaryotes playing distinct roles in carbonate precipitation and structure.

## Contribution

This study reveals microbial succession patterns and functional roles in early tufa formation, highlighting site-specific environmental influences.

## Key findings

- Prokaryotic communities stabilize rapidly in tufa biofilms, dominated by genera linked to carbonate precipitation.
- Microeukaryotes like diatoms contribute to extracellular polymeric substances, aiding carbonate entrapment.
- Site-specific factors like hydrodynamics and organic input drive microbial community specialization.

## Abstract

Karst freshwater systems represent unique ecological niches where physicochemical and biological interactions promote intensive calcium carbonate precipitation and the formation of tufa barriers. Here, we studied the composition, diversity, and functional potential of prokaryotic and microeukaryotic communities involved in early‐stage tufa formation at two sites within the Plitvice Lakes National Park, Croatia. Over a 5‐day period in two different seasons, tufa and water samples were collected at Prošćansko Lake and Novakovića Brod to examine temporal and spatial microbial dynamics. High‐throughput sequencing revealed early stabilization of prokaryotic communities within tufa biofilms, dominated by genera, such as Bacillus, Delftia, Hyphomicrobium, and Methylobacterium–Methylorubrum, which are linked to carbonate precipitation processes. With biofilm maturation, shifts toward Acinetobacter and Rhodoferax indicated increasing heterotrophic activity and organic matter degradation. In contrast, microeukaryotic communities were more variable, with diatoms and Zygnemophyceae contributing to extracellular polymeric substance production, crucial for carbonate entrapment. Site‐specific patterns reflected environmental influences, such as hydrodynamics and terrestrial organic input. The results underscore the importance of microbial succession and community specialization in the formation and stability of tufa barriers, offering new insights into microbial contributions to biogeochemical processes in karst freshwater systems.

Microbial succession shapes the early development of tufa biofilms in karst freshwater systems, with prokaryotic communities stabilizing rapidly and microeukaryotes contributing to extracellular polymeric substance production and carbonate entrapment. Site‐specific hydrodynamics and organic inputs drive community specialization, ultimately influencing tufa barrier formation and stability.