Assessing the environment–benthic fauna coupling in protected and urban areas of southern Brazil Original Research Article

Growing urbanization adjacent to aquatic systems may alter water, sediment and benthic community interactions. The ecological effects of urbanization on regional, local and site-specific spatial variations of benthic macrofauna and of sediment and water properties were investigated in relatively pristine rivers and in urban rivers of southern Brazil. The benthic communities were found to be different in urbanized and protected areas. Their predominant responses to environmental conditions were characterized as either a: (i) sensitive species assemblage, formed by polychaetes Nephtys fluviatilis and Heteromastus similis and the crustacean Kalliapseudes schubarti; or a (ii) tolerant species assemblage, formed by the polychaete Laeonereis acuta and by an unidentified oligochaeta Tubificidae. The relationships between fauna and environment differed between protected and urban rivers. In protected areas the fauna distribution was directly related to grain sorting and phaeophytin a in sediments; and to chlorophyll a, dissolved oxygen and phosphorus in water. In urban sites the strongest determinants of fauna distribution were the presence of lead, copper, dissolved phosphorus, chlorophyll a and phaeophytin a in sediments, and suspended particulate matter, dissolved phosphorus, nitrogen, and silicate in water. The comparison of animal–sediment–water interaction in natural and urban areas can be useful in planning environmental impact mitigation strategies for conservation even in rivers and estuaries with non-point sources of pollution.