Impact assessment of seasonal variations on the biodiversity of marine benthos from the Red Sea coast

The Red Sea hosts highly diverse marine ecosystems that face increasing natural stressors and anthropogenic stresses. Despite its ecological significance, the seasonal dynamics of benthic macrofauna along the Egyptian coast remain weakly understood. This study aimed to assess the influence of seasonal variation and environmental factors on marine benthic macrofaunal biodiversity at three distinct sites along the Red Sea Coast: the front of the National Institute of Oceanography and Fisheries (NIOF), the front of Magawish Village, and El-Hamrawin. Benthic macrofauna were surveyed seasonally (spring, summer, autumn 2021 and winter 2022) using line transects, with simultaneous measurements of environmental factors. A total of 2,942 individuals, representing 60 species from seven phyla, were identified. Cnidaria and Mollusca were the dominant groups, exhibiting marked seasonal and spatial variation in abundance. Two-way ANOVA indicated highly significant differences among seasons and sites for most taxa. Canonical correspondence analysis (CCA) showed strong associations between environmental factors (temperature, salinity, dissolved oxygen) and benthic community composition. These results reveal the sensitivity of benthic assemblages to environmental fluctuations and emphasize the combined effects of seasonal changes and site-specific conditions as key drivers of biodiversity patterns along the Red Sea Coast.