The Ecology of Benthic Diatom Assemblages in Saline Wetlands of the Ebro Basin, NE Spain

Benthic diatoms play a crucial role in aquatic ecosystems as indicators of environmental conditions and contributors to primary productivity. This study explores the ecology of benthic diatom assemblages in saline wetlands in NE Spain, focusing on the relationships between community parameters, species distributions, and environmental factors, particularly conductivity. Samples were collected from several wetlands representing a range of conductivity and trophic state. A total of 25 diatom taxa were identified, with assemblages dominated by halophilous species. Non-metric multidimensional scaling analysis revealed electrical conductivity (EC) as a primary factor shaping diatom communities, with nutrient levels as a secondary influence. Species exhibited varying responses to the EC gradient, with some showing overlapping niches and others clearly separated. The study found strong correlations between species abundance, occupancy, and their contribution to dissimilarity between sampling sites. More abundant and widespread species were key drivers of community structure and differentiation. Additionally, a significant relationship was observed between taxa occurrence and niche breadth, measured as EC tolerance. Species with broader tolerances tended to have higher occupancy rates, supporting ecological theories about generalist strategies in variable environments. Contrary to some previous research, rare taxa (3-5% in relative abundance) had a negligible effect on assemblage segregation among habitats. The findings suggest that both environmental filtering based on EC tolerance and species' inherent characteristics play important roles in shaping diatom community composition across these saline wetlands. This study contributes to our understanding of diatom ecology in saline habitats and highlights the importance of considering both local abundance and environmental tolerance in ecological studies of these communities. The insights gained can inform more accurate ecological models and improve our understanding of species distribution and community dynamics in saline aquatic ecosystems.