This study analyzes the relationship between the main environmental factors and the structure of the cladoceran community in the Malta Channel during late summer. Zooplankton samples were collected at 32 stations during the OUROBS2025 campaign, between August 31 and September 6, using a Bongo40 net (200 μm) and a CTD profiler to characterize the environmental factors.

The results indicate typical late-summer conditions. The water column was highly stratified, well oxygenated and characterized by low phytoplankton biomass. A clear hydrological gradient was recognizable: warmer, less saline and relatively less productive Atlantic waters on the western side of the study area and cooler, more saline and more productive Ionian waters on the eastern side.

Cladocerans occurred at 93.75% of the stations and showed a strong heterogeneous spatial distribution. The community was dominated by Evadne spinifera, followed by Pseudoevadne tergestina and Podon intermedius. Multivariate analyses (NMDS + envfit) and Spearman  correlation identified water-column stratification (Brunt–Väisälä frequency squared, N²) as the only environmental factor significantly associated with the community structure, influencing both total and species-specific abundances and species richness. Salinity also showed positive relationships with most of the abundances and richness, suggesting a complementary, but not decisive, role in shaping the community.

The highest abundances were mainly observed in a few highly stratified coastal stations, influenced by river inflows. Some offshore stations also showed relatively high abundances, related to a higher salinity.

The distributions of individual species agreed with previous reports from the Mediterranean: P. intermedius was mostly associated with coastal and continental shelf waters, P. tergestina preferred more saline offshore waters, whereas E. spinifera was found throughout almost the entire study area, confirming its oceanic affinity and its typical summer abundance peak.