Biodiversity and distribution patterns of benthic macroalgae on Horseshoe Island, Antarctica, with new records

This research was conducted at six sampling stations between February 12 and 24, 2023, during the 7th Turkish National Antarctic Science Expedition, surveying the benthic macroalgae of Horseshoe Island. A total of 17 macroalgal species were recorded, with Rhodophyta as the dominant group (53%), followed by Chlorophyta (35%) and Heterokontophyta (12%). Station A (Lystad Bay) had the highest number of species, while Station B (terrestrial puddles) had the lowest. The Sørensen similarity index indicated distinct differences between stations, supporting that environmental factors such as temperature, salinity, and dissolved oxygen are the primary structuring forces of macroalgal assemblages. Remarkably, six of these species including Prasiola crispa, Acrosiphonia arcta, Ulothrix sp., Sarcopeltis skottsbergii, Callophyllis atrosanguinea, and Georgiella confluens represent new records for the region, contributing to the area´s knowledge of biodiversity. The identification of new records and distributional species shifts in macroalgal assemblages suggests that Horseshoe Island functions as a dynamic ecological unit, possibly shaped by habitat availability and regional climate processes.