Abstract

GARCIA, Victoria J  and  RODRIGUEZ, Patricia. Beavers’ presence affects metabolism of periphyton and limnological variables in Fuegian rivers and streams. Ecol. austral [online]. 2018, vol.28, n.3, pp.593-605. ISSN 1667-782X.

The North American beaver (Castor canadensis) is an invasive species in Tierra del Fuego, which creates lentic systems in rivers and streams due to the construction of dams. Beavers influence hydrology and morphology of rivers, nutrient cycle, decomposition, riparian zone, and consequently communities. The aim of this work was to study the effect of beaver dams in subantarctic streams on limnological variables and, specially, on the metabolism (mass fractions and chlorophyll-a) of periphyton growing on rocks to evaluate its potential use as bioindicator of beaver activity. Six rivers and streams currently impacted and three streams that were impacted, but no longer have activity were studied during summer. Periphyton mass fractions and chlorophyll-a and physical, chemical, hydrological and morphological variables were estimated in each stream, upstream and downstream of current and abandoned dams. Sites similarity was analyzed through a cluster analysis based on morphological, hydrological and biological variables. Periphyton mass fractions upstream and downstream dams were analyzed using generalized linear mixed models. Upstream reaches were clustered regarding beaver activity and stream characteristics. Downstream reaches were similar among them, probably owing to beaver influence, which resulted in a homogenizing effect. Periphyton biomass show no significant differences in downstream reaches regardless beaver activity. Hence, our results indicate that in heterotrophic streams periphyton biomass and chlorophyll are not good bioindicators of beaver activity.

Keywords : Castor canadensis; Epilithon; Mass fractions; Periphyton chlorophyll; Patagonia; Beaver ponds.

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