Biodiversity of soft-bottom macrozoobenthos along the Sinop coasts (southern Black Sea): influence of environmental drivers

Context The Black Sea faces continuous anthropogenic pressures, requiring updated baseline data to assess coastal benthic habitat resilience. Aims This study evaluates the seasonal taxonomic composition, diversity and community structure of soft-bottom macrozoobenthos along the Sinop coasts. Methods Benthic sampling was conducted at six stations (8–72 m) in May and November 2016 using a 0.1-m2 Van Veen grab. Community structure was analysed using diversity indices and the Turkish benthic index (TUBI). Key results In total, 101 macrozoobenthic species were identified, including Neanthes acuminata, a new record for the Turkish Black Sea coast. May samples yielded 95 species (2763 individuals, dominated by Mollusca), whereas November yielded 71 species (1619 individuals, dominated by Polychaeta). Key dominant species across seasons included Nereis zonata, Capitella capitata, Lentidium mediterraneum and Amphiura chiajei. Amphibalanus improvisus was the only alien species. Conclusions The region supports a diverse benthic community with clear seasonal shifts. However, the persistence of the opportunistic polychaete Capitella capitata suggests localised environmental stress. Implications These findings provide critical baseline data for ecological status monitoring. Continuous tracking is essential to detect biodiversity trends and non-indigenous species arrivals in this changing ecosystem.