Oceanografia Ambiental

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http://repositorio.ufes.br/handle/10/17530
Programa de Pós-Graduação em Oceanografia Ambiental

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Navegando Oceanografia Ambiental por Assunto "Algas vermelhas"

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    Análise da composição e estrutura interna de rodolitos da Cadeia Vitória-Trindade
    (Universidade Federal do Espírito Santo, 2018-06-19) Menandro, Tarcila Franco; Amado Filho, Gilberto Menezes; https://orcid.org/0000-0002-6053-4915; http://lattes.cnpq.br/5734763044971419; Bastos, Alex Cardoso; https://orcid.org/0000-0002-1272-1134; http://lattes.cnpq.br/2951081353357019; https://orcid.org/0000-0003-1783-2607; http://lattes.cnpq.br/6958042160031234; Quaresma, Valéria da Silva; https://orcid.org/0000-0002-7470-6642; http://lattes.cnpq.br/9423011006200936; Pereira Filho, Guilherme Henrique; https://orcid.org/0000-0001-6078-2241; http://lattes.cnpq.br/1211745530577271; Brasileiro, Poliana Silva; https://orcid.org/0000-0001-5520-8907; http://lattes.cnpq.br/3652663799345776; Bahia, Ricardo da Gama; https://orcid.org/0000-0003-3274-8008; http://lattes.cnpq.br/3076005225100928
    Rodoliths are nodules composed mainly of calcareous algae and other subordinate encrusting organisms (SEO), formed by subsequent overlapping processes of incrustations. The rhodoliths of the Vitória-Trindade Seamount Chain presented as main builders the calcareous algae (genera Sporolithon, Mesophyllum, Lithothamnion, Hydrolithon and Titanoderma) and peyssonneliaceae (genus Peyssonnelia). The main groups of SEO were encrusting foraminifers (Homotrema rubrum, agglutinated foraminifera or encrusting foraminifera), bryozoans, serpulids and cirripids. In rhodoliths where the bioerosion is very high, obliteration of the morphological characters of calcareous algae occurs, and identification at the species level is impossible, making it difficult to characterize the environment since this must be done at the species level. The study of the composition of SEO is an alternative to the study of the algal assemblage in environments with high bioerosion index. The analysis of the composition of SEO was distinct between the seamount and the insular platform indicating local differences in these environments that would be influencing the establishment of organisms. The ichno-assemblage of the Vitória-Trindade Seamount Chain was composed of microperforations and macroperforations of the Entobia type (associated with perforating sponges); Gastrochaenolites (associated with bivalves) and Trypanites (associated with polychaetes and sipunculus worms). The study of the ichno-assemblage identified an environment with low sedimentation rate and low hydrodynamics that allowed the development for long uninterrupted period of bioerosion. The formation of empty spaces by the bioerosion process allows the deposition of sediment that can trap benthic macroforaminifera. In Jaseur the genus Amphistegina was more frequent in both collection sites and in Trindade it was the genus Archaias that presented greater contribution. The large number of perforations due to the intense bioerosion could lead to the collapse of the nodules; however, large rhodoliths were observed (larger diameters with a mean of 17.8 ± 3.8cm for Jaseur 74m, 15.92 ± 2.14cm for Jaseur 66m and of 11.74 ± 1.40cm for Trindade 65m). The filling material of the perforations of the rhodoliths internal structure presented a sedimentary texture and was lithified; integrating the rigid structure inside the nodules. The lithification due to the growth of carbonaceous cement crystals in the empty pores in the internal structure is fundamental for the maintenance of nodule integrity. The lithification of the filling sediment creates new rigid structures within the older inner structure and these become susceptible to new infestations of perforating organisms. The repetition of the processes of perforation, filling, cementation and new perforations replaces the original internal structure (composed mainly by encrusting organisms) by the structure resulting from the repetition of processes (composed of bioclasts and lithified sediment). The present study identified the importance of the integrated study of all components of the internal structure of rhodoliths as the best way to understand the dynamics involved in the development of nodules and as a tool to obtaining solid environmental indicators