Contrasting chironomid assemblages in two high Arctic streams on Svalbard

Chironomid communities were investigated twice in summer 1997 in a glacier-fed (Bayelva) and a non-glacial stream (Londonelva), fed by snowmelt and rainfall near Ny-angstrom lesund (Svalbard Archipelago, 78 degrees N). Environmental conditions (discharge, water temperature, suspended sediment) were harsher for the fauna in the glacial system than in the non-glacial one. In all, 29 chironomid species were identified from larval, pupal and male adult material, including six species new to Svalbard. Diamesa was the best represented genus, showing contrasting distributional trends at the species level in the two streams: Diamesa aberrata and D. bohemani were more characteristic of the glacial stream, while D. arctica and D. bertrami colonised primarily the snowmelt-fed one. Total abundance of chironomid larvae was ten times greater in Londonelva than in Bayelva. The prevailing harsh conditions in glacial streams, such as high and fluctuating discharge, high sediment transport and substrate instability, strongly influenced the abundance of the chironomid fauna, demonstrating the key importance of water source in Arctic streams.