Macrophytes, epipelic biofilm, and invertebrates as biotic indicators of physical habitat degradation of lowland streams (Argentina)

Abstract

Our objective was to assess the effect of the physical habitat degradation in three lowland streams of Argentina that are subject to different land uses. To address this matter, we looked into some physical habitat alterations, mainly the water quality and channel changes, the impact on macrophytes' community, and the structural and functional descriptors of the epipelic biofilm and invertebrate assemblages. As a consequence of physical and chemical perturbations, we differentiated sampling sites with different degradation levels. The low degraded sites were affected mainly for the suburban land use, the moderately degraded sites for the rural land use, and the highly degraded sites for the urban land use. The data shows that the biotic descriptors that best reflected the environmental degradation were vegetation cover and macrophytes richness, the dominance of tolerant species (epipelic biofilm and invertebrates), algal biomass, O2 consumption by the epipelic biofilm, and invertebrates' richness and diversity. Furthermore, the results obtained highlight the importance of the macrophytes in the lowland streams, where there is a poor diversification of abiotic substrates and where the macrophytes not only provide shelter but also a food source for invertebrates and other trophic levels such as fish. We also noted that both in benthic communities, invertebrates and epipelic biofilm supplied different information: the habitat's physical structure provided by the macrophytes influenced mainly the invertebrate descriptors; meanwhile, the water quality mainly influenced most of the epipelic biofilm descriptors.

Taxonomic, phylogenetic and functional diversity of leeches (Hirudinea) and their suitability in biological assessment of environmental quality

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Comunidades de macrófitas en ríos andinos: composición y relación con factores ambientales

“…La erosión y la compactación del suelo derivada de este uso generalmente modifican los hábitats, afectando la distribución de numerosas especies (Tilman et al, 1996;Murgueitio et al, 2003), y zonas riparias con un nivel de degradación alto pueden presentar una reducción de la diversidad (Cortelezzi et al, 2013). Sin embargo, en este estudio se evidenció que la riqueza de macrófitas aumentó en los ríos asociados a estos usos.…”

Feeding of Gymnogeophagus meridionalis (Osteichthyes, Cichlidae) in an urban stream

“…con el interés de mejorar el flujo de agua proveniente de intensas precipitaciones, es objeto de frecuentes limpiezas con remoción de vegetación acuática (principalmente palustre y flotante) y ribereña. Sus cabeceras se ubican en una zona con fuerte desarrollo de la actividad florihortíco-la; en su recorrido atraviesa un área suburbana, donde la agricultura, las zonas de recreación y de vivienda son los principales usos del suelo, por lo cual presenta aportes de desechos domiciliarios, basura y descargas industriales (cortelezzi et al, 2013;Ferreira, 2015). Sierra et al (2013) encontraron un incremento en la concentración de nutrientes, particularmente fosfato y nitrato, desde la naciente hasta la desembocadura del arroyo Martín, lo que repercute principalmente sobre el desarrollo de la biomasa algal y la actividad bacteriana.…”