Diversity and community composition of marine mollusks fauna on a mainland island of the coast of Paraná, southern Brazil

Farol Island is a continental island in the state of Paraná, southern Brazil. Due to its position in relation to the continent, three distinct environmental areas are observed: rocky shore area with open exposure to the sea (A) estuarine area (B); sandy beach area (C). Considering that the continental islands are excellent study models that reproduce the environmental conditions of the coastal zone in a smaller scale, the study aimed at surveying and researching the marine malacofauna on the Farol Island and comparing the diversity and shellfish composition. The sampling method was based on a monthly collection in three locations for two years (2011-2012). The survey found 91 species: 47 Gastropoda, 41 Bivalvia and three Scaphopoda. The highest abundance and species richness prevailed in environmental area A. The greatest equitability was observed in B and the highest dominance in C. There was a predominance of Gastropoda and Bivalvia in A, while the frequency of Scaphopoda did not vary among environments. The species composition of the three classes varied among the three areas. The variation of diversity and species composition in the three environments may be related to the natural characteristics of each side of the island, as salinity and wave action.