POPULATION DYNAMICS OF CHIRONOMIDAE (DIPTERA) IN THE CENTRAL AMAZONIAN BLACK WATER RIVER TARUMÃ-MIRIM (AMAZONAS, BRAZIL)

Abstract

Data on the emergence of adult chironomids and on the colonization of submerged litter by larvae collected between 1984 and 1992 in benthonic habitat s of blackwater forest river Tarumã-­Mirim, joining the Rio Negro ca 25 km North-West of Manaus, are presented. Ali species (as yet unidentified) breed continuously. However, the rates of colonization (larvae/leaf/24h) and emergence (adults/0.25m²/24h), as well as the density of potential predators of larvae, are functions of the annual inundation cycle. There is a drastic depression during high water levels (April to August), when the aquatic fauna disperses into the inundation forest, and a minor depression between November and January, when the water is confined to the river channel; this latter depression appears to be a function of predation. Standing stock reserves, however, remain high the year round (minimal estimates = 2300 - 11,264/m²), with peak values between October and December. The ratios of chironomid larval prey/predator vary between 30 (April) and 201 (Dec.); chironomids, however, are not the only prey of the benthic macrofauna, composed mostly of small fish, shrimps and Odonata larvae. The annual mean of litter colonization by larvae is 1.377 larvae/m²/day, 155 (= 11.3%) of which emerge as adults.