Ephemeroptera, Plecoptera and Trichoptera (EPT) trait-based biomonitoring of rivers within the northwestern Rif of Morocco: implications for determining riverine ecosystems ecological health in Africa

Abstract

Spatial pattern comprehension, dynamism of energy, and transfer of matter in running freshwater systems are significant for the functional composition of aquatic communities. Recently, the trait-based approach has become the center of functional assessment. The trait-based approach can complement structural bioassessment tools and has the advantage of combining ecological features and biological characteristics rather than only the use of a taxonomic-based approach. In the current study, we explored the differential responses of EPT (Ephemeroptera, Plecoptera, and Trichoptera) traits in selected stream sites in the northwestern Rif of Morocco. A Surber sampler with a 500-µm mesh size and dimensions of 20 × 20 cm was used to collect EPT samples at the sites. Physicochemical and hydromorphological parameters, including temperature, pH, BOD₅, NO_-3, Cl⁻, depth, and current velocity, were used to characterize the water quality of the sampled sites. We used 54 trait modalities belonging to 11 trait classes to describe the collected EPT at the family level. We conducted RLQ model and fourth-corner test to examine the interaction between the EPT traits assemblage and habitat predictors at the 36 sampled sites along the stretch of the study area. The RLQ ordination revealed that the distribution patterns of EPT traits differed significantly over the 36 sites. Thus, we expected that the EPT traits assemblage would reflect the degree of the detected environmental pressures. The RLQ model indicated that elevated nutrient levels and conductivity were the key factors explaining most of the variability in functional traits at the downstream sampled sites. EPT traits such as life cycle duration, food preferences, maximal potential size, and substrate preference were positively associated with sites exhibiting notable deterioration. Baetidae and Leptophlebidae in S2, S3, and S20 favored these trait assemblages. The fourth-corner test revealed that there was no statistically significant difference in the relationship between the EPT traits and selected physicochemical and hydromorphological parameters.