Estudo biogeográfico sobre algas diatomáceas como bioindicadores da qualidade ambiental dos igarapés de Manaus-AM

Abstract

Diatomaceous algae are a fascinating group of aquatic organisms that play an important role in marine and freshwater ecosystems. Characterized by their unique cell walls, composed of two silica compartments, they are one of the main sources of phytoplankton production. By composing fundamental structures in freshwater environments, they contribute to the health and balance of these ecosystems. Their ecological importance, as environmental indicators, highlights the need to protect and conserve these vital organisms. Diatomaceous algae also contribute to oxygen production and the carbon cycle on the planet. Their diversity and adaptability are impressive, with around 20,000 species identified to date, ranging from microscopic forms to species visible to the naked eye. For environmental monitoring, algae constitute indicators of water quality, as they are able to respond to environmental variations. In this sense, the present study aimed to perform a biogeographic analysis in the São Raimundo/Mindu hydrographic basin, mapping and analyzing biotic and abiotic variables, identifying geotopes suitable for diatomaceous algae colonies. The methodological approach included a bibliographic review for the theoretical framework, field observation and sample collection, as well as georeferencing of geotope types. In addition, morphometric and laboratory studies were carried out for genus identification, using manuals and other research in the same line. Twenty-four samples were collected over two years at nine points. The samples were treated and verified in the laboratory, where it was possible to identify the dominant genus in the basin (Pinnularia). This result can be incorporated into the most suitable geomorphological unit for the species, which was the valley floor, with altimetric quotients of 60 to 18 meters. The interpretation of climatic data from 2022/2023 made it possible to identify the average environmental temperature (28.22°C), relative air humidity (75.40%) and variations (0.22 mm). Following other physical variables, such as water temperature (25.97°C), water level (29 cm) and pH (5.6). The tested variables describe an ideal environment for maintaining colonies of diatomaceous algae of the genus Pinnularia. Regarding the distribution along the basin, there is uniformity. The strong human influence presents low diversity when compared to rivers in "natural" environments, however, lower anthropic interference, where a greater number of species is offered.