Assembleias de nematoda como indicadoras de qualidade ecológica em nascentes

Abstract

Springs are important for supplying water systems, and are subject to various human impacts, such as deforestation of riparian forests, pollution and erosion of banks. In chapter I, the hypothesis was tested that agricultural activities alter the structure of Nematoda assemblages in river springs, reducing taxonomic and trophic diversity, leading to the dominance of disturbance-tolerant Nematoda. In chapter 2, the size spectrum of Nematoda assemblages in these springs was investigated, testing the hypothesis that the ratio total length/maximum body width (L/W) responds to changes in physical-chemical and biological characteristics of the environment, differing between springs with and without the influence of agricultural activities. Physical, chemical and biological parameters of water and sediments were measured in 16 springs: pH, temperature, salinity, concentration of dissolved oxygen and ammonia, nitrate, nitrite and phosphorus and the most probable number of total coliforms and Escherichia coli in the water, organic matter content, concentration of mercury and pigments and granulometry of the sediments. Nematoda were identified to taxonomic genus level, classified according to trophic guilds and life strategy and their total lengths (L) and maximum body widths (W) were measured. The springs without the influence of agricultural activities showed greater abundance and richness of genera, greater trophic diversity and dominance of persistent Nematoda, while the springs with pastures and sugar cane presented Nematoda assemblages of low density and diversity and dominance of colonizing Nematoda. The Nematoda L/W ratio showed differences between springs with and without the influence of human activities and environmental variables, proving to be useful in assessing environmental quality in freshwater environments.