Resumo

VELASQUEZ, Stella M  e  MISERENDINO, M Laura. Allochthonous organic matter and functional organization of macroinvertebrates at habitat scale in Patagonian mountain rivers. Ecol. austral [online]. 2003, vol.13, n.1, pp.67-82. ISSN 1667-782X.

In this paper we examined the composition, structure and functional feeding groups of invertebrates in different habitats of four Patagonian mountain rivers (Blanco, Baguilt, Los Rifleros and Nant y Fall). At each river, a representative sector was selected and sampled during high and low water periods. Samples of macroinvertebrates, coarse particulate organic matter and fine particulate organic matter were obtained. Seven habitat types were analyzed: boulder, cobble, pebble, and gravel (in riffle areas), and sand, leaf-packs, and macrophytes (in pools). At each habitat, three samples were collected per river and date. Riffle areas had higher density and biomass of macroinvertebrates than pools. Collector-gatherers were the dominant functional group followed by collector-filterers. Shredders showed high density in boulder and gravel during the study. Filterers were dominant in macrophytes and gravel, and their biomass was high in boulder, macrophytes, cobble and pebble. Scrapers were common in boulder, pebble and cobble, but showed high biomass in gravel. Both shredders and collector-gatherers co-dominated in leaf-packs. Collector-gatherers were the only functional feeding group represented in sand. The coarse particulate organic matter in riffles was associated mainly with habitats of medium size substrates, while fine particulate organic matter was related to gravel and leaf-pack habitats. Local geomorphology and related physical parameters influenced the distribution and biomass of organic matter. The results suggest that community structure and functional organization are distinctive at habitat scale in low order streams of Patagonia, and they depend on the quality and availability of allochthonous organic resources.

Palavras-chave : Riffles; Pools; Leaf pack; Aquatic plants; Abundance; Biomass; Functional groups; Organic matter; Macroinvertebrates.

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