# The Microbial Ecology of Antarctic Sponges

## TL;DR

Antarctic sponges host unique microbial communities that play important roles in nutrient cycling and ecosystem resilience, despite the harsh polar environment.

## Contribution

This paper integrates culture-based and molecular data to reveal the taxonomic and functional diversity of Antarctic sponge microbiomes.

## Key findings

- Antarctic sponge holobionts host diverse symbionts spanning 63 bacterial, 5 archaeal, and 6 fungal phyla.
- A conserved core microbiome dominated by Proteobacteria and Bacteroidetes is found across Antarctic sponges.
- Microbial functions include nitrogen cycling, chemoautotrophic carbon fixation, and stress tolerance.

## Abstract

Microbial communities in Antarctic marine sponges have distinct taxonomic and functional profiles due to low temperatures, seasonal days and nights, and geographic isolation. These sponge holobionts contribute to nutrient cycling, structural habitat formation, and benthic ecosystem resilience. We review Antarctic sponge holobiont knowledge, integrating culture-based and molecular data across environmental and taxonomic gradients. Although microbiome data exist for only a fraction of the region’s 593 known sponge species, these hosts support diverse symbionts spanning at least 63 bacterial, 5 archaeal, and 6 fungal phyla, highlighting the complexity and ecological significance of these understudied polar microbiomes. A conserved core microbiome, dominated by Proteobacteria, Bacteroidetes, Nitrospinae, and Planctomycetes, occurs across Antarctic sponges, alongside taxa shaped by host identity, depth, and environment. Metagenomic data indicate microbial nitrogen cycling, chemoautotrophic carbon fixation, and stress tolerance. Despite these advances, major knowledge gaps remain, particularly in deep-sea and sub-Antarctic regions, along with challenges in taxonomy, methodological biases, and limited functional insights. We identify key research priorities, including developing standardised methodologies, expanded sampling across ecological and depth gradients, and integrating multi-omics with environmental and host metadata. Antarctic sponge holobionts provide a tractable model for investigating microbial symbiosis, functional adaptation, and ecosystem processes in one of Earth’s most rapidly changing marine environments.

The online version contains supplementary material available at 10.1007/s00248-025-02543-y.