Community structure and functional traits of mollusks associated with coastal reef macroalgae in Northeastern Brazil

Abstract

This study investigated the community structure and functional traits of the mollusk fauna associated with macroalgae with different thallus morphologies in a reef environment in Northeastern Brazil. A total of 15 individuals of each species of macroalgae adhered to natural substrate and 15 individuals of Padina gymnospora detached from the substrate were collected. The structural complexity of algal habitats was measured and the associated malacofauna screened and identified. All three macroalgae differed significantly in the complexity of their habitat, with Sargassum polyceratium being the most complex. A total of 823 specimens of mollusks belonging to 22 species and 11 families were recorded, of which Columbellidae was the most represented with six species. The functional trait "size" revealed that micromollusks smaller than 10 millimeters were predominant in the community; however, individuals of larger sizes (up to 24.54 millimeters) belonging to young stages of other species were also present. Eight functional trophic groups were identified, of which "carnivorous" stood out with seven species. Six functional groups of microhabitats were identified, with intra-specific variation in habitats, while habitat expansion was documented for species not yet recorded in association with macroalgae. The structure of the molluskan community differed among the three algae species with the greatest richness, abundance, and diversity of mollusks and functional traits occurring with S. polyceratium. Community structure differed between algae adhered to natural substrate and detached algae, with the latter having lower mollusk richness and diversity, but with greater abundance of some species that remained on algal fronds after release from the reef environment. This study reinforces the importance of algal habitat for marine invertebrate fauna, especially for micromollusks that spend their entire life cycle, or part of it, in association with macroalgae. K E Y W O R D SDictyopteris justii, malacofauna, Padina gymnospora, phytal ecosystem, Sargassum polyceratium

Asymmetric effects of changes in the habitat‐forming algae Sargassum on different associated mobile faunas along São Paulo coast, Brazil

“…Thus, higher biomass is usually associated with higher abundance of associated macrofauna (i.e., crustaceans, mollusks and polychaetes), as reported by Torres et al (2015) and by Chen et al (2020), that found higher abundances of the main associated groups with increasing biomass among different macroalgae species and in Sargassum beds, respectively. Studies evaluating the relationship between specific invertebrate groups and macroalgae morphological features also found similar results (Barbosa et al, 2019;Box et al, 2010;Carvalho et al, 2018;Chemello & Milazzo, 2002;Kodama et al, 2020).…”

“…Overall, increasing habitat size and structural complexity is known to have a positive effect on associated mobile macrofauna, which benefits from more available refuge areas and food sources (Christie et al, 2009;Norderhaug et al, 2007;Veiga et al, 2014). This general pattern is also consistent and has already been registered separately for each of the main associated groups: for mollusks, a higher abundance, species diversity, and functional diversity were observed for assemblages associated with morphologically more complex macroalgae (Chemello & Milazzo, 2002;Veiga et al, 2018;Barbosa et al, 2019 andDuarte et al, 2020); for crustaceans, similar results were found for amphipods in Sargassum beds, presenting higher abundance and diversity in association with higher biomass and/or more complex fronds (Carvalho et al, 2018;Kodama et al, 2020); and for polychaetes, a higher abundance and diversity was observed when in association with increased biomass of an invasive macroalgae (Box et al, 2010). These positive effects are also observed in smaller organisms, such as meiofaunal assemblages, which are influenced by the macroalgal cover (Ape et al, 2018;Hicks, 1980;Losi et al, 2018).…”

Rede Ecológica Dos Gastrópodes Associados Ao Banco De Algas Da Praia Da Ribanceira, Santa Catarina, Brasil

“…Particularmente, a assembleia de moluscos que vive em associação com as macrófitas parece se beneficiar da maior proteção fornecida por espécies de macroalgas mais complexas, como demonstra Chemello & Milazzo (2002), cujo estudo encontrou maior diversidade desses animais em algas maiores, mais ramificadas e com mais elementos de complexidade, como Sargassum vulgare C. Agardh, 1820 e Cystoseira spp. Da mesma forma, Barbosa et al (2019) verificaram maior riqueza, abundância e diversidade de espécies em associação com Sargassum polyceratium Montagne, 1837, considerada a alga de morfologia mais complexa.…”

“…Alguns trabalhos já demonstraram elevada diversidade de moluscos vivendo em associação a Sargassum spp. em função da maior complexidade da alga em relação a outras espécies de macrófitas (Chemello & Milazzo 2002, Barbosa et al 2019. Entre espécies do gênero Sargassum com níveis diferentes de complexidade estrutural, a diversidade de moluscos tende a ser maior nas algas de morfologia mais complexa (Veiga et al 2018).…”

“…A fauna encontrada foi composta predominantemente por microgastrópodes ou juvenis de espécies maiores, semelhante ao encontrado em outros estudos com moluscos associados a algas (Longo et al 2014, Queiroz & Diaz 2014, Barbosa et al 2019. As espécies mais dominantes, como os microherbívoros E. affine e B. varium e alguns carnívoros da família Columbellidae, foram predominantemente encontradas em associação com S. cymosum, sendo espécies características dos bancos de Sargassum (Longo et al 2014).…”