Changes in periphyton communities with land use in tropical mountain streams from Loja (Ecuador)

Abstract Riparian vegetation along a stream regulates the flow of sediments and nutrients. It also provides stability to the riverbanks and controls the watershed microclimate that ultimately influences the primary production of lotic environments. The degradation of terrestrial vegetation can also have an impact on the biotic component of rivers. Periphyton communities are altered in their composition, abundance, and diversity when the natural conditions in the watershed are modified. While widely studied in Europe and North America, studies on changes in periphyton community structure in mountainous tropical ecosystems are rare. In this study, we investigated if and how alteration of the riparian vegetation results in changes in the diatom community composition of seven streams in southern Ecuador. Streams were sampled in one or 2 zones, with 5 sub-samples each. The sampled streams show different levels of degradation within their watersheds. Temperature was higher in open (i.e. deforested) areas within a stream and open areas, e.g. pastures, had higher abundance of cyanobacteria filaments. Total algal cell abundances increased from forested to open and more fully degraded zones. Species richness was lowest in the forested areas. Microbial diversity was low across all habitats, but the highest values were documented in the degraded habitats. Diatom communities dominated at all sites, followed by filamentous bacteria. Gomphonema minutum (Agardh) Agardh, G. parvulum (Kütz.) Kütz., and Achnanthidium minutissimum (Kütz.) Czarnacki were the most common and abundant species. Diatom communities from zones with different land use within a stream were as different from each other as communities from different watershed streams.