Limnetica 38

Despite deforestation and population growth during the last 30 years in Esmeraldas (Northern Ecuador), there is no information about the impact of these changes on the coastal rivers. The Teaone is a 5^th order river located in Northern Ecuador that originates in the Mache-Chindul mountain range and flows into the Esmeraldas River near its mouth. It flows through a rural.

landscape that includes pastures, forestry plantations, and some remnants of humid forest. In this work, we have studied watershed land use indicators (percentages of agricultural and forest land in addition to road and housing densities), geomorphology (bed substrate composition and woody debris density and origin), water chemistry (pH, turbidity, conductivity, and oxygen, nitrate, nitrite, and ortho-phosphate concentrations) and benthic diatoms and macroinvertebrates along the river and in its main tributaries. The Teaone watershed has been severely modified and agriculture and forestry plantations occupy more than 50 % of the watershed area. The riverbed is dominated by fine sediment, but we could not establish whether an impact from land use changes had occurred because both natural and anthropogenic sources of fine sediment coexist in the watershed. Nitrate concentrations are high on the tributaries, but low concentrations in the main channel suggest the presence of a strong nitrate sink. On the contrary, phosphate concentrations are low in the tributaries and high in the main channel, which suggest that clothes washing and personal bathing in the river might be important sources of phosphate. The diatoms and macroinvertebrate communities respond in a similar way to environmental changes along the river. Both communities show a stronger relationship with watershed land uses than with water chemistry and in-stream habitat.