Gastropods are one of the most conspicuous group of sheltered sandy beaches. The gastropod Olivella minuta is widely distributed along the Brazilian coast and is a common species on beaches in Caraguatatuba Bay, São Sebastião Channel, and particularly abundant in Araçá Bay. However studies on the ecology of this species and on the macrofaunal community in the Araçá are scarce although there is a wide range of anthropogenic impacts in these sites, such as organic pollution by domestic sewage, oil spills, overexploitation of natural resources and alteration and remobilization of sediment. This project aims to characterize the spatial distribution of Olivella minuta linking its abundance to sediment characteristics (size, selection degree, and calcium carbonate and organic matter contents) which is heterogeneous in the study area, and biotic factors (presence / absence and abundance of other species of the community. A second objective is the characterization of the microscale distribution of this gastropod, checking for differences in the abundance of individuals within and outside tide pools present in the Araçá Bay. A year-round assessment of the density variation of O. minuta will also be done. The mesoscale distribution will be sampled at 16 stations along the intertidal zone. For each station eight 5 cm-deep sediment replicates will be randomly taken in a 0,25 m2 quadrat and processed through 1,0 and 0,5 cm sieves. The retained organisms will be identified. Each station will be sampled in three replicates for sediment analysis. The microdistribution of O. minuta will be assessed using a 15 cm diameter core in 50 points inside and 50 points outside the tide pools. The temporal variation of O. minuta will be sampled year-round with 5 transects perpendicular to the waterline randomly placed along the intertidal zone of the Araçá Bay.
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