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Spatial and temporal distribution of Olivella minuta (LINK, 1807) (Mollusca, Gastropoda, Olividae) Barequeçaba Beach, North Coast of São Paulo

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Daniel Teixeira Tardelli
Total Authors: 1
Document type: Master's Dissertation
Press: São Paulo.
Institution: Universidade de São Paulo (USP). Instituto Oceanográfico (IO/DIDC)
Defense date:
Examining board members:
Alexander Turra; Roberto Munehisa Shimizu; Paulo Yukio Gomes Sumida
Advisor: Alexander Turra

Sandy beaches have typically abundant macrofauna, comprised of polychaetes, mollusks, and crustaceans. Among mollusks, gastropods comprise one of the most conspicuous groups. Nevertheless, data on this group for beaches are scarce and refer mainly to their occurrence in communities. The neogastropoda Olivella minuta is common and abundant on beaches along the Northern Coast of São Paulo. However, there are important gaps in the knowledge regarding the distribution of this species. Based on this scenario, the present study aims at analyzing the distribution of Olivella minuta in space and over time on Barequeçaba Beach, as well as the related environmental factors. To analyze the distribution of Olivella minuta along the intertidal zone of the beach, samples were obtained in October 2009 from twelve stations perpendicular to the waterline, comprised of three transects with six levels each. Abiotic (sediment characteristics) and biotic (macrofauna descriptors) factors that comprise each station were also sampled and linked to distribution. Results showed that there was higher density of individuals in the southern part of the beach, and in more humid environments, closer to the waterline. Calcium carbonate and organic matter were the most determining factors in the species\' distribution, as opposed to the hypothesis that both abiotic and biotic factors were influencing factors. To analyze the distribution of Olivella minuta over time in the vertical axis of the beach, samples were collected monthly in the intertidal zone, from five random transects set out perpendicularly to the waterline with nine sampling units. In addition, samples were also obtained quarterly with five random transects comprised of nine and six sampling levels in the intertidal zone and in the infralittoral zone, respectively. Results showed a distribution pattern for the species in the intertidal zone over time and confirm the hypothesis that O. minuta is distributed along the vertical axis of the beach according to the size of individuals, with smaller individuals occurring in the infralittoral and migrating to the intertidal zone throughout their ontogeny. Outcomes shown in the present study help improve the knowledge on population ecology of sandy beaches because they relate the distribution of a macrofauna species to environmental factors and mainly due to the fact that sampling covers also the infralittoral zone, since its distribution is not exclusive to the intertidal zone (AU)

FAPESP's process: 10/13589-4 - Spatial and seasonal distribution of Olivella minuta (LINK,1807)(Mollusca, Gastropoda, Olividae) at Baraqueçaba Beach,São Paulo-SP
Grantee:Daniel Teixeira Tardelli
Support type: Scholarships in Brazil - Master