Intertidal vermetid reef as a shelter for invasive bivalves in a tropical bay

Abstract

Vermetid reef building species play an important role as ecosystem engineers modifying the physical environment, creating microhabitats and affecting local hydro-sedimentary patterns. We explore the association of native vermetid reefs (Petaloconchus varians) with the invasive bivalves Isognomon bicolor and Leiosolenus aristatus. We also examined the different utilization of the reef habitat, since L. aristatus is a boring species, comparing their population structure on sheltered and exposed rocky shores. Ten sites (five sheltered, five exposed) were sampled at Ilha Grande Bay (Rio de Janeiro, Brazil). I. bicolor and L. aristatus were the most frequent with mean densities of 20,000 (±3400) and 2100 (±600) ind.m², respectively. There were no significant differences (t = 1.41; p = 0.17) between sheltered and exposed sites in relation to the densities of I. bicolor. However, there were significant differences (t = 3.14; p = 0.03) in relation to the densities of L. aristatus, with higher values at exposed sites. Mean size of both species was significantly (p < 0.01) higher in sheltered areas where the vermetid weight was significantly higher (t = 2.36; p = 0.02). Although native vermetid reefs act as a shelter for both invasive bivalves on sheltered and exposed rocky shores, they prevent the growth of I. bicolor which reaches smaller sizes in relation to populations outside of the reefs. Our results indicate that the two invasive bivalves might be differently affected by hydrodynamic processes.

Keywords:

• ecosystem engineer
• Isognomon bicolor
• Leiosolenus aristatus
• Petaloconchus varians
• Vermetidae

Acknowledgements

We thank the staff of Setor de Malacologia/MN, Laboratório de Benthos/UFRJ and Laboratório Integrado de Ficologia/UFRJ for helping in field work and Thomas Sprengers for the English revision.

Funding

We would like to thank Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) for the PhD scholarship granted to the first author; Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ) for the Project “Comunidades epilíticas fotófilas como indicadoras ambientais para a Baía da Ilha Grande, especialmente para a área de influência da Central Nuclear Almirante Álvaro Alberto (CNAAA)”; Instituto Estadual do Ambiente (INEA) for the authorization license n°050/2012 and Instituto Chico Mendes de Conservação da Biodiversidade (ICMBio) for the license n°17982–2.