Macrofauna community structure in extreme temperature and hypersaline waters: Khor Al-Adaid, Arabian Gulf

Abstract The Arabian Gulf experiences extreme seasonal fluctuations in temperature and salinity, imposing strong environmental filters on benthic ecosystems. This study examined the seasonal dynamics of macrobenthic communities in the hypersaline lagoon Khor‑Al‑Adaid, Qatar, to determine how physicochemical variability shapes species composition, diversity, and functional structure. Across four seasons, 108 macrobenthic taxa were recorded, with polychaetes representing the dominant group. Macrofaunal abundance peaked in winter (1774 ind. m −2 ) and it was lower in summer (703 ind. m −2 ), whereas species richness was higher in summer (47 species). Diversity indices varied seasonally (H′ = 1.23–1.52; d = 3.7–5.3; J′ = 0.40–0.46), reflecting shifts in community structure under extreme summer hyper salinity and temperature. Multivariate analyses (cluster analysis, SIMPER, k‑dominance curves, and RDA) revealed clear seasonal separation of assemblages, with winter communities associated with higher dissolved oxygen and chlorophyll‑a, and summer communities linked to thermal and salinity stress. Overall, the results demonstrate that extreme physicochemical conditions strongly regulate benthic community patterns in this lagoon system, providing an essential ecological baseline for monitoring and conservation in hypersaline environments of the Arabian Gulf.