2024-10-082024-10-082022-02-16PINTO, Brenda Thays Barros. Assembléia de diatomáceas como indicadora da qualidade ambiental dos sedimentos do manguezal de Marapanim (Pará, Brasil). Orientador: José Francisco Berrêdo Reis da Silva. Coorientadora: Pryscilla Denise Almeida da Silva. 2022. 54 f. Trabalho de Curso (Bacharelado em Geologia) - Faculdade de Geologia, Instituto de Geociências, Universidade Federal do Pará, Belém, 2022. Disponível em:https://bdm.ufpa.br/jspui/handle/prefix/7309. Acesso em:.https://bdm.ufpa.br/jspui/handle/prefix/7309Diatoms are ornamented microalgae made up of polymerized silica and are excellent indicators of environmental gradients. The presence of these siliceous frustules are easily recovered in sedimentary profiles, and therefore are used as proxies to assess the environmental changes recorded in the geological layers. Therefore, the use of diatoms as biomarkers at the water/sediment interface in coastal environments such as mangroves constitutes an innovative research to evaluate the changes that have occurred in these environments. This work aims to evaluate the composition and abundance of diatoms in three sedimentary profiles of the mangrove and its relationship with the physical-chemical parameters and nutrients in the sediment. The study area is located in the municipality of Marapanim, on the northeast coast of the state of Pará. The northern portion of the Marapanim River estuary is characterized by a lobular structure in which mangrove vegetation developed, and three intertidal zones can be observed. (P1, P2 and P3). The collection of sediment cores was performed by inserting an acrylic tube into the mangrove substrate during low tide. The sediments were sectioned at standardized intervals to assess the temporal deposition of diatoms. Thus, 15 sample units representing the study area were obtained. The methodology used consisted of removing all the organic matter present and microscopic analysis. The environmental variables analyzed were salinity, pH and Eh, total phosphorus (PT) and total nitrogen (NT). The results showed that the sediments are slightly acidic (pH: 4.7 to 6.7), reductive (Eh: -350 to -35 mV), and with salinity values below those recorded in seawater (4 to 20). Profiles P2 and P3 showed similar values for NT and PT and point P1 showed the lowest values for these nutrients, which can be explained by its geographical position. N:P molar ratios <16 indicate that N is the limiting nutrient. As for the assemblage of diatoms, 32 species were found. The predominant genera were Coscinodiscus Ehrenberg (10 spp), Thalassiosira Cleve (4 spp) and Triceratium Ehrenberg (2 spp). These genera are characteristic of brackish and marine environments, which rarely occur in fresh water and are associated with environments with high productivity. No differences were found in the composition and spatial distribution of diatoms. The high abundance of planktonic diatoms indicates the transport of valves from the estuarine waters into the mangrove. The results suggest that there has been an enrichment of the mangroves in the last 30 years in a directly proportional relationship with the variations in the waters of the Marapanim River.Acesso AbertoPalinologiaDiatomáceasMicropaleontologiaPalynologyDiatomsMicropaleontologyCNPQ::CIENCIAS EXATAS E DA TERRA::GEOCIENCIAS::GEOLOGIATrabalho de Curso - Graduação - Monografia