Exploring Biodiversity and Food Webs in Sulfur Cave in the Vromoner Canyon on the Greek–Albanian Border

Sulfidic caves support diverse and abundant subterranean communities, including numerous endemic species and complex food webs, though the full extent of species diversity and resource utilization in these ecosystems remains largely unexplored. This paper presents the results of biological surveys conducted from 2023 to 2024 in Sulfur Cave, located in the Vromoner Canyon on the Greek–Albanian border, focusing on microbial, vertebrate, and invertebrate communities and investigating the structure of the subterranean food web. The microbial communities from the different biofilms are dominated by chemosynthetic sulfur-oxidizing microorganisms, specifically filamentous bacteria such as Thiotrix and Beggiatoa. Two species of fish, an eel (Anguilla sp.) and a Cyprinid (Alburnoides sp.), and six bat species from three families (Rhinolophidae, Miniopteridae, and Vespertilionidae) were documented. The invertebrate fauna includes five aquatic species, 25 terrestrial species, and four amphibiotic species. Among these, eight species are endemic, and seven species exhibit troglomorphic traits. Stable isotope analysis showed light carbon and nitrogen values for the terrestrial and aquatic invertebrates, suggesting that subterranean communities rely on food produced in situ by chemoautotrophic microorganisms. Our results identified cave areas of significant biological relevance and provided reference data to inform conservation actions aimed at preserving the biodiversity of this sulfidic cave.