Biodiversity report of the Bryozoans of Helgoland in 2025

Bryozoans are important members of the benthic fauna, contributing to shaping benthic ecosystems through habitat formation, filtration, and carbonate deposition. The waters surrounding Helgoland, a rocky island in the German Bight of the North Sea, contain one of the few extensive natural hard-bottom habitats in this otherwise predominantly sandy region. These hard substrates, often colonized by dense macroalgal communities, provide ideal conditions for bryozoan settlement and growth. The Helgoland area is therefore ecologically significant as it supports high biodiversity, serves as a refuge for hard-substrate species, and represents a key site for studying benthic community dynamics in the southern North Sea. This study aimed to assess the diversity of bryozoan species in this unique and biologically important habitat. Different hard substrate samples were collected from the intertidal zone as well as an approximately 30m-deep trench. Species identification was performed in subsequent days using stereomicroscopes and standard identification keys. Overall, 21 species were identified, comprising 15 species belonging to the order Cheilostomatida, 5 to Cyclostomatida, and 1 to Ctenostomatida. Compared to previous records from 2023, nine species are present in both datasets, while several taxa were unique to either survey, including Watersipora subtorquata, indicating changes in species composition and colonization patterns.