Rio Negro: ecological, landscape, and biological perspectives from a nature-based expedition in the Brazilian Amazon

Beneath the shade of giant trees lies an almost invisible world. Dark waters glide slowly over white sandy bottoms, carrying leaves from the surrounding forest and nutrients that sustain a complex web of ecological processes. A small fish silently moves through a narrow forest stream; a tree frog lays its eggs on a leaf suspended above the water; a caiman remains motionless among submerged roots. Nothing in this discreet landscape appears particularly grand, yet it supports an essential part of Amazonian biodiversity. This paper presents the results of a scientific and nature-based field expedition conducted in July 2016 in the Rio Negro Basin, Brazilian Amazon. The study was based on direct field observations, photographic documentation, and in situ interpretation of the region's principal geomorphological, hydrological, ecological, and biological features, with particular emphasis on the dynamics of ecosystems associated with blackwater environments. Special attention was given to the upland terra firme forests, seasonally flooded igapó forests, blackwater streams (igarapés), and other habitats that compose the landscape of the Rio Negro Basin, highlighting their importance for maintaining Amazonian biodiversity and ecological processes. During the field expedition, numerous records of wildlife were obtained, with particular emphasis on avifauna, whose observations illustrate the remarkable biological richness and ecological complexity of one of the largest remaining continuous tracts of tropical rainforest on Earth.