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ABSTRACT
An inventory of the gastropods associated with three species of reef macroalgae having different thallus structures are provided. We discuss how algal architecture influences diversity patterns, abundance and species richness. Fronds of the macroalgae Gracilaria domingensis (Kützing) Sonder ex Dickie, 1874, Padina pavonica (Linnaeus) Thivy, 1960, and Cryptonemia bengryi W.R. Taylor, 1960 were collected in coastal reefs of Cabo Branco Beach, João Pessoa, State of Paraíba, Northeastern Brazil. Thalli were sorted in the laboratory to remove the associated mollusks. The macroalgae Gracilaria domingensis and Cryptonemia bengryi presented the most heterogeneous thallus architecture. The mollusk community comprised 18 species of gastropods, belonging to 14 genera. In total, 402 specimens were recorded, of which micromollusks predominated. The most frequent species were Eulithidium affine (C.B. Adams, 1850) (80% of occurrence), Rissoina sagraiana (d'Orbigny, 1842) (60%), Astyris lunata (Say, 1826) (40%), and Phyllaplysia engeli Marcus, 1955 (33.3%), the latter representing a new record for the coast of Paraíba state. The algae C. bengryi and G. domingensis presented highest values of richness and diversity for the associated malacofauna (F^sub 1,6^= 10.14; p = 0.0001). Differences in the associated mollusk communities among the three species, as well as differences in the ecological descriptors for each alga, suggest that the algal architecture influences the richness, diversity, and composition of microgastropods in the marine phytal.
Keywords: algal banks, community structure, microhabitat, micromollusks, phytal, reef habitat.
INTRODUCTION
Among the diverse marine ecosystems, it is possible to list a range of habitats as heterogeneous, such as coral reefs, banks of marine seagrass and algal banks, as well as consolidated substrates (TOKESHI & ARAKAKI 2012). Communities associated with macroalgae are known as the phytal. These environments serve as a habitat for several taxa of invertebrates, including mollusks. According to Kovalenko et al. (2012), macroalgae may be key components in aquatic ecosystems, due to their capacity for providing tridimensional environments. In these environments, macroalgae promote increase in space availability, and thus in diversity and coexistence among species.
Algal fronds attenuate hydrodynamism, promoting higher stability of the mollusk chemical parameters, mainly temperature and salinity. However, until now, few studies have dealt with the role of marine algae in structuring faunal communities (CHEMELLO & MILAZZO 2002). Edgar (1983) states that different algal shapes are important in determining...