O papel da avifauna na transformação geoquímica de substratos na ilha da Trindade, Atlântico Sul

Abstract

Island environments always stir the human imagination and scientific curiosity, perhaps because of its geographic isolation, being land masses surrounded by water; by its strategic character, serving as a shelter, a place of renewal of supplies and expansion of marine activities; and being configured as natural fortresses, able to isolate any prisoner. It is reasonable to think that all the elements and geo-environmental phenomena such as variations in sea level and ocean currents, climate, lithological and geomorphological changes, geographic isolation and biological colonization, act together in the generation of the high degree of endemism on islands, both biological and the pedological, constituting true endemic ecosystems. In this context, there is Trindade, Brazilian oceanic island, that in addition to the factors discussed above, is also a place for other processes studied incipient. Oceanic islands are important nesting areas for several species of migratory birds, whose droppings (guano) are deposited on various substrates (rocks, sediments, soils). This interaction between the birds and the various lithological and pedological substrates allows the genesis of very diverse materials and features, with unique morphological and geochemical aspects that would not exist without the nesting of birds. In this sense, this work aims to study the products of the transformation from the interaction between excrement-substrates, as much soil as rocks, in the island of Trindade. They had their genesis discussed by mineralogical, geochemical and morphological analysis, considering that these attributes are indicators of how such interaction has transformed the substrates. In order to present the results and discussion obtained from the proposed objectives, the work was divided into two chapters. The first chapter deals with the Trindade excrement-soil process, considering soils derived from the three main groups of lithological materials on the island: alkaline volcanism, basic volcanism and bioclastic carbonate sediments. The second chapter deals with the excrement-rock process, with emphasis on alkaline and basic volcanic rock types.