Seasonal Dynamics of Macroinvertebrate Communities in Offshore Mussel Aquaculture in the Central Black Sea: Implications for Biodiversity

This study investigates the species composition, seasonal variation, and diversity dynamics of macroinvertebrate communities associated with Mytilus galloprovincialis (Lamarck, 1819) cultivated in offshore longline systems in the central Black Sea. Monthly sampling conducted between September 2023 and August 2024 yielded a total of 99,719 individuals representing 20 taxa. The communities were predominantly dominated by amphipods, particularly Jassa marmorata (71.3%) and Stenothoe monoculoides (27.8%). Individual abundance peaked in autumn, whereas species richness reached its highest levels in summer. ANOVA analyses revealed significant seasonal differences in diversity indices (p< 0.05). Multivariate analyses, including NMDS and PCA (RDA proxy), indicated distinct seasonal clustering, with pH (41%) and salinity (34.5%) identified as the primary environmental drivers of community composition. These findings demonstrate that offshore mussel longline systems function not only as aquaculture infrastructure but also as reef-like artificial habitats that support benthic biodiversity. The dominance of opportunistic and detritivorous amphipods, along with their sensitivity to environmental gradients, suggests their potential utility as bioindicators for ecological monitoring.