Epilithic chironomid larvae and water enrichment: is larval distribution explained by epilithon quantity or quality?

A. Maasri (1) , Stéphanie Fayolle (1) , Emmanuel Gandouin (2) , Robert Garnier (1) , Evelyne Franquet (1)

1 IMEP - Institut Méditerranéen d'Ecologie et de Paléoécologie
2 IRBI - Institut de recherche sur la biologie de l'insecte

The effects of nutrient enrichment of stream water on epilithic chironomid larval assemblages were examined during spring in a Mediterranean catchment. Three reaches that differed in degree of enrichment were selected for comparison. Water chemistry, epilithon biomass (as ash-free dry mass [AFDM]), epilithic algal biomass (as chlorophyll a [chl a]), algal biovolumes, and algal composition were analyzed to determine their association with density and taxonomic composition of epilithic chironomids. Kendall's s coefficient of rank correlations and canonical correlation analysis were used to evaluate correlations between the chironomid and algal assemblages. Significant correlations were found between chironomid larval densities and total algal cell densities and biovolumes. Chironomid larval densities were not significantly correlated with chl a or AFDM. Several contrasting trends were identified in the relationships between chironomid and algal assemblages. Densities of fixed-tube scrapers, such as Eukiefferiella claripennis and Cricotopus bicinctus, were strongly correlated with biovolumes of Rhodophyceae and Diatomophyceae, whereas densities of free-living scrapers, such as Thienemaniella, were slightly correlated with Chlorophyceae biovolume. Therefore, nutrient enrichment strongly influenced epilithic chironomid assemblage structure through its effects on biovolumes and cell densities of the epilithic algal assemblages.

Mots clés: Chironomidae; Eukiefferiella claripennis; Cricotopus bicinctus; water enrichment; epilithic al- gae; microhabitat scale study; food availability

Domaines: Sciences de l'environnement

A. Maasri, Stéphanie Fayolle, Emmanuel Gandouin, Robert Garnier, Evelyne Franquet. Epilithic chironomid larvae and water enrichment: is larval distribution explained by epilithon quantity or quality?. Journal of the North American Benthological Society, 2008, 27 (1), pp.38-51. ⟨10.1899/07-013R1.1⟩. ⟨hal-02959131⟩