Chironomid taxocenosis in a South Mediterranean wadi, the Kebir-East (Algeria)

SUMMARY - Chironomid taxocenosis in a South Mediterranean wadi, the Kebir-East (Algeria) - A total of 37 chironomid species were recorded during a survey of the catchment of the Kebir-East wadi, northeast Algeria. Chironomids spatial and temporal distributions were investigated based on 23 sampling sites, situated mainly within the El Kala National Park, across 4 seasons. Chironomid assemblages in the Kebir-East were similar to the ones known from other Mediterranean areas and were composed mostly of tolerant species (Chironomus riparius, Cricotopus (Isocladius) sylvestris), but some intolerant species (Paratrissocladius excerptus, Parakiefferiella gracillima, Thienemanniella partita) were present in some samples. A coinertia analysis was carried out to match 21 environmental variables at different spatial scales with the 37 chironomid species recorded in 90 samples: A longitudinal gradient was found along the first axis, which accounted for 42 % of the total variance; the samples ordered along the second axis, which accounted for 13 % of the total variance, were separated according to water temperature, water chemistry and site’s morphometry. The influence of anthropogenic pressures was evaluated with different benthic quality indices based on species diversity and on species optima (i.e. mean value of environmental variables weighted for species abundance). Results showed that the trophic status index was influenced by water quality and habitat type (krenal, rhithral, potamal), while the biotic indices were more influenced by season. To improve knowledge on the response of intolerant species, we suggest the implementation of a regular, more intensive sampling program.