Seasonal variation in the input of allochthonous matter in an Atlantic Rain Forest stream, Ilha Grande-RJ
REZENDE1, C.F. & MAZZONI2, R.
1 Programa de Pós Graduação em Biologia –Ecologia, Instituto de Biologia Roberto Alcântara Gomes, Universidade do Estado do Rio de Janeiro, Universidade do Estado do Rio de Janeiro. Av. São Francisco Xavier 524, RJ -20550-013, e-mail: carla.fr@terra.com.br.
2 Laboratório de Ecologia de Peixes, - IBRAG /UERJ / Ecologia - Av. São Francisco Xavier 524, RJ - 20550-013, e-mail: mazzoni@uerj.br.
ABSTRACT: Aspects of the seasonal variation of allochthonous matter input are discussed. Allochthonous matter was quantified in five sampling occasions between May 2002 and February 2003 in a covered site of Andorinha stream. At each sampling occasion four boxes (40 cm x 20 cm - 0,8 m2 each) were randomly exposed, during 48 hours, through a 100 m long stretch of the study site. Allochthonous matter was composed of arthropods (mainly insects and mites), leaves, flowers and vegetal parts. Considering the five sampling occasions altogether, vegetal input was 16x higher than animal input (t test; t= 3.50, P< 0.01). Seasonal analysis indicated that the input of allochthonous matter is higher during the wet season, both for vegetal (t test; t= -2.54, P< 0.01) and for animal (t test; t= -3.13, P< 0.01) matter. Arthropods biomass, as well as diversity was higher during rainy season. Acaridae, Odonata, Homoptera, Lepidoptera, Lepidoptera larvae and Diptera larvae were not found during the dry season, but Diptera adults and Hymenoptera predominated during both rainy and dry seasons. The obtained data indicated that input rates, as well as animal and vegetal matter diversity, vary seasonally.
Key words: Atlantic forest, Streams, Allochthonous matter input.