Sheyla R. M. Couceiro

Deforestation and sewage effects on aquatic macroinvertebrates in urban streams in Manaus, Amazonas, Brazil

In the last few years, awareness in developed countries has increased regarding the importance of urban watercourses as essential natural resources for human well being. Macroinvertebrates have been used as bioindicators to complement physico-chemical evaluation of water quality after environmental perturbations. The city of Manaus is closely associated with the Amazonian rain forest and with its dense hydrographic network. Any perturbation, such as deforestation and/or water pollution in the city’s streams, therefore causes changes in the local ecosystem as the population increases. In this study, 65 streams were sampled in October and November 2003. Samples were taken from stream-bed sediment in the center of the channel and litter/sediment at the edge of the stream. Deforestation, total Nitrogen (TN), total Phosphorus (TP), depth, width, electrical conductivity, temperature and dissolved Oxygen (DO) were measured. A total of 115,549 specimens were collected, distributed among 152 taxa. Oligochaeta, Chironomus, Psychodidae and Ceratopogonidae were the taxa with the greatest frequencies of occurrence and the highest total abundances. Higher deforestation, TN and TP were correlated with lower DO and greater electrical conductivity, pH and water temperature. Deforestation, TN and TP were not associated with water velocity and stream width. Depth was the only variable correlated (negatively) with deforestation and not correlated with TN and TP. Greater deforestation, TN and TP were correlated with lower richness of taxa; but these variables did not affect abundance. Canonical Correspondence Analysis ordenated the streams into two groups; the majority of the streams were in the group with high levels of deforestation and with high values of TP, TN, pH, electrical conductivity and temperature, where the macroinvertebrates were reduced to a few taxa. The other group was composed of streams that were well oxygenated and deep, where richness of taxa was higher. These results indicate changes in community composition in response to changes in environmental conditions. The highest taxa correlation was with streams that were well oxygenated and had the greatest depth and water velocity. Species Indicator Analysis identified 29 taxa as indicators of nonimpacted streams, 16 as indicators of deforested streams and three as indicators of streams impacted by deforestation and domestic sewage. Of the total sampled streams, 80% were impacted by deforestation and water pollution and had fauna tolerant of these perturbations. Water pollution, represented by TN and TP, affected the macroinvertebrate fauna in a way similar to deforestation, i.e., causing reduction in taxa richness, simplifying the insect community composition without changing abundance. Use of the taxa suggested in this study as environmental indicators could improve the evaluation of water quality in the streams in Central Amazonia.

An illustrated key to nymphs of Perlidae (Insecta, Plecoptera) genera in Central Amazonia, Brazil

An illustrated key to nymphs of Perlidae collected in streams of Central Amazonia, Brazil is provided. Three genera are reported for this region: Macrogynoplax Enderlein, Anacroneuria Klapalek and Enderleina Jewett. Additional diagnostic characters are provided for Enderleina nymphs.

Effects of an oil spill and discharge of domestic sewage on the insect fauna of Cururu stream, Manaus, AM, Brazil

Assemblages of aquatic and edaphic insects in three streams in Central Amazonia were used to evaluate the impact on one of the streams (Cururu) caused by an oil spill that occurred in August 1999. The Cururu stream had already been impacted by domestic sewage. These three streams were evaluated during four different periods of the regional hydrological cycle (falling-, low-, rising- and high-water), from September 2000 to May 2001. An Eckman dredge, an aquatic entomological net and a manual auger were used to collect insects, which were used to estimate the taxonomic richness (at the family level) and insect density in each stream. Anoxic and eutrophic conditions were determined in each stream based on the mean concentration of dissolved oxygen, total nitrogen and phosphorus. Richness and abundance of insect fauna were higher in the Cristalino stream (not impacted) than in the Bom Jardim stream (impacted by domestic sewage) and in the Cururu stream, with the exception of samples collected along the stream banks (littoral fauna). The mean dissolved oxygen was lower in the Cururu stream than in the other two, while the mean concentrations of total nitrogen and phosphorus were higher. These elements showed intermediate values in the Bom Jardim stream, while the opposite pattern was observed in the Cristalino stream, with higher concentrations of dissolved oxygen and lower concentrations of total nitrogen and phosphorus. The concentrations of these variables reflect the modifications resulting from anthropogenic eutrophication caused by the discharge of domestic sewage into Bom Jardim and Cururu and by the oil spill in Cururu, which negatively affected the richness and abundance of insects in these streams.

Species of Oukuriella Epler (Diptera, Chironomidae) inside freshwater sponges in Brazil

Larvae of Oukuriella Epler, 1986 (Diptera, Chironomidae) inside freshwater sponges are reported for the first time in Brazil.

Female and immature stages of Oukuriella epleri Messias & Fittkau, 1997, a freshwater sponge-dwelling Chironomidae

Abstract Female, pupa, and larva of Oukuriella epleri Messias & Fittkau, 1997 are described and figured. The larvae were collected in freshwater-sponges from Amazonia. We also provide an emended diagnosis for the genus.

Black-fly assemblage distribution patterns in streams in disturbed areas in southern Brazil

Black flies (Simuliidae) are considered to be pests in rural and in some urban areas in the south of Brazil due to the bites of females. Little information exists on the factors that contribute to Simuliidae distribution in these areas. We sampled 39 streams in the state of Rio Grande do Sul in September 2004 to address ecological aspects. Of the 18 species collected, those that occurred in more than 50% of the streams were: Simulium subnigrum Lutz 1910, Simulium pertinax Kollar 1882, Simulium subpallidum Lutz 1910 and Simulium incrustatum Lutz 1910. Species richness was not influenced by any of the environmental or geographical variables considered, and there was no pattern of species co-occurrence, corroborating the hypothesis of a stochastic distribution of the Simuliidae assemblage. When analyzed individually, only three of seven species with occurrence frequency >30% were related to any of the variables measured. The probabilities of occurrence of Simulium jujuyense Paterson & Shannon 1927 and S. pertinax were higher in streams with high values of water pH and electrical conductivity, whereas the opposite was observed for S. incrustatum. Therefore, due to stochastic distribution, the population studies of Simuliidae are more suitable for predicting the occurrence of species in rural areas than are studies of assemblages.

Bionomics of the black fly Simulium guianense (Diptera: Simuliidae) in northeast Brazil

Abstract Simulium guianense Wise (Diptera: Simuliidae) is the main vector of the nematode Onchocerca volvulus (Leuckart) (Spirurida: Onchocercidae), which causes onchocerciasis in the Amazonian focus of the disease. We present the first report of the presence of S. guianense in the Parnaíba River basin, its oviposition behavior, and its number of instars. Immatures were found in high density on bedrock, on leaves of Podostemaceae and other aquatic plants, and on branches and leaves of riparian vegetation. Larvae and pupae were collected in 9 rivers: 8 in the state of Piauí and 1 in the state of Ceará. Six instars were determined for a population in Piauí. Oviposition behavior was of the dabbing type. Ants (Solenopsis sp.; Hymenoptera: Formicidae) preyed on larvae and pupae stranded when the river receded.