Beyond biodiversity: the role of Paramuricea clavata forests in shaping taxonomic and functional diversity

Marine animal forests, composed of sessile suspension feeders such as gorgonians are known to host rich communities that support important ecosystem functions and services. These habitats are undergoing severe loss due to multiple pressures, with potential cascading effects on associated communities and their functions that remain poorly understood. To address this critical knowledge gap, we used fine-scale data to assess the role of Paramuricea clavata forests in supporting biodiversity and ecosystem functioning at multiple locations, in the Gulf of Naples (Italy, Western Mediterranean Sea). Through functional trait analysis, we compared taxonomic and functional diversity of benthic assemblages inside and outside P. clavata forests and investigated the loss of traits as a consequence of forest loss. Analyses revealed significant enhancements in both taxonomic and functional diversity within P. clavata forests, with observed increased species and functional richness. Trait-based investigations revealed a higher abundance of colonial heterotrophic species within forests, while outside, assemblages were dominated by low-longevity autotrophs, suggesting that P. clavata modifies environmental variables creating unique ecological conditions that favor specific traits. β-diversity measurements demonstrated increased compositional and functional turnover inside forests, indicating that P. clavata provides more available niches, supporting the replacement of species and functions. Our findings offer insights into how marine animal forests can structure marine communities, with broader implications for understanding biodiversity loss in changing marine ecosystems.