La comunidad de coleópteros y hemípteros acuáticos de un arroyo costero cantábrico (norte de España): composición, variación estacional e influencia de los factores ambientales

Abstract

The aquatic Coleoptera and Hemiptera assemblages have been studied in a short Cantabrian coastal stream (La Llantada, Asturias, North Spain). We aim to know the assemblage composition and to detect the environmental factors that affected it, consideringseasonalchanges(samplings in spring and autumn during two annual cycles). Most(89%)of the identified species (thirty-three of Coleoptera and eleven of Hemiptera) shows a high range distribution. It is remarkable the presence of some Southern species (Hydrochus grandicollis, Dryops striatellus, Velia caprai bertrandi). Chaetarthria simillima (Coleoptera: Hydrophilidae) is recorded for the second time in the Iberian Peninsula. The results show a clear decrease of richness towards the mouth that seems to be related to the decrease of water quality. Seasonal changes of assemblage composition are related to organic pollution, particularly during the months of summer with low rainfall and greater anthropic impact. CCA shows that most species of both groups respond negatively to high nutrient pollution, mainly total nitrogen and ammonium. A small group associated to samples with a high load of nutrients is detected and can be considered tolerant to pollution, for instance the water beetles Hydroporus vagepictus, Stictotarsus duodecimpustulatus, Helophorus minutus, Helophorus brevipalpis and Octhebius dilatatus.