Functional responses of aquatic insect feeding groups in permanent semi-arid and arid wadis of Algeria

This study reports the response of aquatic insect functional feeding groups (FFGs) to forest microclimatic conditions in a protected area and anthropogenic disturbance across four permanent wadis in the semi-arid and arid Aurès Region (north-eastern Algeria), comparing two wadis within a protected forested area with two exposed to domestic, agricultural, and industrial effluents. Aquatic insects and selected environmental parameters were sampled once per season. A total of 19,271 aquatic insects were collected, representing 58 taxa and 36 families distributed across seven orders. Across the recorded FFGs, the most abundant group was gathering collectors (67%), followed by filtering collectors (16.7%) and herbivore shredders (12.5%). Data were analysed using the Mann-Whitney U test, hierarchical clustering and canonical correspondence analysis. The FFGs indices were used as surrogates for stream ecosystem attributes to reveal functional changes of the studied wadis. The results indicate that the undisturbed wadis (Bouilef and El-Ma), located in a protected forest area under a semi-arid climate, showed higher functional diversity, characterised by the presence of all FFGs. The disturbed wadis (El-Hai and Gourzi), located in an arid region, display a low functional community, likely due to the degradation of water quality. This study showed that the forest microclimate, as well as the level of anthropogenic pressure, influenced the functional structure of the aquatic community. The autotrophy/heterotrophy index indicated that all studied wadis were heterotrophic. The shredder and filtering collector index were higher in forested wadis. The habitat stability index indicated that stable substrates were more abundant in undisturbed wadis. These results confirm the usefulness of the FFGs index as a relevant tool for understanding functional changes under a semi-arid to arid climate.