Freshwater ferns along a river basin in northeast Brazil

Abstract

Despite their importance to the control of erosion on the banks of rivers, filtration and depollution of waters, shelter for fish, insects and mollusks and the cycling of nutrients in the aquatic environments, few studies have specifically addressed the composition and distribution of aquatic ferns in Brazil. The aim of the present study was to perform an inventory of these plants at 28 points along the Contas River in the state of Bahia, Brazil, distributed in five different environments (lake, river, tributaries, reservoir and delta), and record ecological aspects, such as frequency of occurrence, forms of life and seasonality. Sampling was performed six times between January 2008 and November 2010. Fourteen species of aquatic ferns belonging to seven genera and four families were recorded. The families with the highest species richness were Salviniaceae (5 species) and Pteridaceae (4 species). The highest richness was found in the rainy season (43% of the collection sites), although these plants exhibit adaptations for survival in dry environments and/or periods. Five collection sites had the greatest richness (three tributaries and two in the Funil Reservoir). Less than half of the species (43%) were infrequent. Free-floating and amphibious species were the most representative (36%). The aquatic fern flora in the Contas River is generally rich and exhibits a high degree of representativeness for northeastern Brazil (77.77%).

Keywords: aquatic plants, hydrographic basin, ecological aspects.