Biodiversity of Summer Ichthyoplankton Associated with Coastal Posidonia oceanica Beds at Gümüldür (Aegean Sea)

This study was conducted to determine species diversity, abundance dynamics, and variation in the summer ichthyoplankton assemblage along the Gümüldür coast (İzmir), a significant coastal habitat of the Aegean Sea. Sampling was conducted at five stations in a shallow coastal area characterized by Posidonia oceanica seagrass meadows during July and August 2024. As a result of the study, 27 taxa belonging to 18 families were identified. Among the identified taxa, 22 were represented as eggs and 9 as larvae. The taxa dominant in the plankton community were identified as Labridae (70.7%), Engraulidae (7.8%) and Sparidae (5.3%), respectively. The mean abundance was calculated as 7189 ind‧1000 m-³ for fish eggs and 351 ind‧1000 m-³ for larvae throughout the study period. The highest mean abundance was recorded for Coris julis eggs with 2544 ind‧1000 m-³ larvae with 78 ind‧1000 m-³. Engraulis encrasicolus eggs with 558 ind‧1000 m-³ and larvae with 13 ind‧1000 m-³. Among the sampling periods, species diversity reached its peak in the first half of July (Smax=13, J'max= 0.96, H'max=2.39). In contrast, during the first half of August, species diversity decreased as the Labridae species became increasingly dominant, even as total abundance peaked. A decline in spawning activity was observed in the second half of August. As the first ichthyoplankton study conducted in Gümüldür, this research emphasizes the importance of the regional seagrass meadows, particularly for ecologically significant demersal fish taxa.