Seasonal Dynamics of Macroinvertebrate Communities in Offshore Mussel Aquaculture in the Southern Black Sea: Implications for Diversity

This study investigates the taxon composition, seasonal variations, and diversity dynamics of macroinvertebrate communities associated with Mytilus galloprovincialis cultivated in mussel 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%) and Stenothoe monoculoides (28%). Individual abundance peaked in autumn, whereas taxon richness reached its highest levels in summer. ANOVA results revealed significant seasonal differences in diversity indices (p < 0.05). Multivariate analyses, including NMDS and RDA (PCA proxy), indicated distinct seasonal clustering, with pH (41%) and salinity (35 g/kg) 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 diversity. The dominance of opportunistic and detritivorous amphipods, along with their sensitivity to environmental gradients, suggests their potential utility as bioindicators for ecological monitoring.