Life cycle phenology, secondary production, and trophic guilds of caddisfly species in a lake-outlet stream of Patagonia

BRAND CECILIA; MISERENDINO MARIA LAURA

LIMNOLOGICA

ELSEVIER GMBH

Lugar: Amsterdam; Año: 2012 vol. 42 p. 108 - 117

0075-9511

Lake-outlets are transitional areas recognized as highly productive ecosystems in terms of density and biomass of aquatic insects. The knowledge of life histories, population dynamics, trophic relationships and environmental controls of freshwater species of these environments is crucial given that the number of undisturbed lake-outlets is rapidly decreasing on a global scale. Life cycles, secondary production, trophic guilds and environmental constraints of caddisfly assemblages were investigated on a natural lake-outlet stream (Nant y Fall, ~ 43° S) in Patagonia, Argentina. We visited the site monthly from May 2007 to April 2008. Environmental data were recorded at each visit and a sampling program was performed using a Surber sampler at riffle areas (n=36).  Mastigoptila longicornuta, Neoatopsyche brevispina, Neopsilochorema tricarinatum, Smicridea annulicornis, S. frequens, Brachysetodes quadrifidus and Parasericostoma ovale displayed well synchronized univoltine life cycles, although most of them had an extended recruitment, similar to those reported for non lake-outlet streams in the area. Annual secondary production per species varied from 8.22 (B. quadrifidus) to 3568.83 mg.m-2y-1 (P. ovale), being overall caddisfly production (4.8 g.m-2y-1). Shredder/collector-filterer ratio was 3.3/1 suggesting that our system was detrital based. Redundancy analysis indicated that seasonally dynamic variables such as discharge, benthic particulate organic matter and temperature, were the main predictors of caddisfly assemblage variation. We propose that the variety of food resources and the significant spatial heterogeneity at this lake-outlet stream contributed to sustain a rich caddisfly community.