Water chemistry provides important parameters for the study of river ecology and management options of rivers and connected wetlands. Sioli, in the 1950s, established three water types (whitewater, blackwater and clearwater) for explaining limnological characteristics of the large Amazonian rivers, and related the physico-chemical parameters of these water types with the geological properties of their basins; a landscape ecology approach. Today, an increasing amount of hydrochemical data indicate that the chemical composition of Amazonian water bodies varies much more than assumed by Sioli. Nonetheless, due to its simplicity for describing the natural physico-chemical variability of Amazonian rivers, his classification is still valid. Our analysis, based in literature and field work, allowed to distinguish well among the three classical water types and to provide new preliminary insights about the limnological classification of Amazonian rivers in order to subsidize the sustainable management of water resources and wetlands.

In the last years, deforestation constitutes a threat for the aquatic ecosystems. This paper aims to characterize the water quality of the Purus river in the Brazilian Amazon, and investigate the relations between water quality and deforestation of the Purus river basin over a 9-year period, as well as to quantify the Purus river basin's land cover changes (%) in a 5-year period. Sampling data from upstream to downstream show a decrease in pH-value, dissolved oxygen, electrical conductivity, and total suspended solids. Correlation analysis revealed a significant negative correlation of the accumulated total deforestation values (km 2) with the pH-value (in all the study sites), and a significant positive correlation with temperature (only in two sites). However, the deforestation rates (km 2 /year) did not present, in none of the study stations, any significant correlation with water quality parameters. It seems that the effects of deforestation on water quality are related not with the rate but with the total area deforested. It was estimated that the basin's forested area decreased by 5.17%. Since similar attributes are common in other basins of the whitewater systems of the Brazilian Amazon, this results may be seen as a warning on the effects of deforestation on water quality (reduction in pH and increment in temperature values), in larger areas than those of our study sites. To maintain the conservation and preservation status of the Purus river basin, it is necessary, the implementation of a transboundary watershed management program that could serve as a conservation model for Brazil and other countries of the Amazonian region.

As herbáceas aquáticas são indicadoras da composição nutricional dos corpos de águaamazônicos e de suas áreas alagáveis, pois sua riqueza e abundância refletem as características físicas e químicas da bacia onde estão inseridas. Elas possuem diversas funções ecológicas, como proporcionar abrigo e alimento para organismos aquáticos e terrestres. Neste estudo, foi analisada a riqueza, diversidade e composição de espécies de herbáceas aquáticas e sua distribuição em nove igapós de água preta na Amazônia brasileira, dentro e fora de unidades de conservação (UCs). Os resultados foram obtidos por meio de inventários realizados entre os anos de 2009 e 2017, nos rios Negro, Jaú, Aracá, Cuiuni, Uatumã e Abacate. Foram amostradas 148 parcelas retangulares de 100 x 1m, distribuídas em nove pontos amostrais (6 a 29 parcelas por ponto). O levantamento florístico revelou 174 espécies, distribuídas em 99 gêneros e 46 famílias botânicas, predominando as famílias Cyperaceae (43 ssp.), Poaceae (33 ssp.) e Marantaceae (10 ssp.). As áreas apresentaram baixa similaridade florística, sendo que nenhuma espécie ocorreu em todas as áreas amostradas. As espécies Montrichardia arborescens (L.) Schott (Araceae) e Scleria secans (L.) Urb (Cyperaceae) foram as mais frequentes, ocorrendo em seis das nove áreas amostradas. Apenas 49,2% das espécies de herbáceas aquáticas amostradas estão presentes nas UCs inventariadas, indicando que estratégias de conservação que envolvam mais áreas de igapó de águas pretas precisam ser consideradas para a proteção desse importante grupo de plantas.

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