Zonation in littoral macrobenthic assemblages in the Çanakkale Strait (Dardanelles)

This study presents an assessment of the benthic community structure in the supra-, medio-, and upper infralittoral zones along the Çanakkale Strait, Turkey. Replicated samples were collected with cores and quadrats from 16 stations during the summer months of 2019. The average density of zoobenthos was estimated at 20,626 individuals m⁻² and average wet mass of phytobenthos was 652 g m⁻². In total, the community comprised 160 zoobenthic and 35 phytobenthic species. Nine species were new records for the Turkish Strait System, and five were non-native to the area. The study revealed that Oligochaeta (sp.) were the dominant zoobenthos taxa, followed by the amphipod species Speziorchestia stephenseni (Cecchini, 1928). Additionally, the red alga Ceramium virgatum Roth, 1797 was identified as the most abundant phytobenthic taxon. No statistically significant differences were found in the biomass of the phytobenthic and the abundances of the zoobenthic assemblages among the supra-, medio-, and infralittoral zones, only zoobenthos community have a weak but significant difference with soft and hard substrates. Furthermore, a statistically significant but weak relationship between zoo- and phytobenthic species is also reported. The study also examined correlations between abiotic properties on community structure. It was revealed that the sediment in the structure of medium gravel, fine gravel, and fine sand affected the structure of the benthic community in the three zones. Also, the distance of the sampling area to the zone boundaries affects the distribution of zoobenthic communities in the medio- and infralittoral zones. The findings of this study offer fundamental data for the development of ecosystem-based marine management plans and extensive monitoring programs for the coastlines of the Çanakkale Strait. This area serves as the biological corridor of the Marmara Sea, which was designated as a Special Environmental Protection Area (SEPA) in 2021, facing pressures from anthropogenic activities and climate change.