Patterns of gastropod assemblages differ along tidal salt marsh and mangrove forest habitats in a southeastern Australian estuary

Estuaries across the globe are commonly fringed with intertidal salt marsh and mangroves. Here we present a long-term comprehensive description of spatial and temporal patterns between gastropods and vegetation in salt marsh and mangrove forest habitats in southeastern Australia. There were 11 macroinvertebrate taxa and 38,243 individuals in the salt marsh and 17 macroinvertebrate taxa and 13,420 individuals in mangrove forests. The main species of macroinvertebrates were gastropods from Heterobranchia and Caenogastropoda, the subgroup Pulmonata, and the families Assiminiedae Hydrobiidae and Littorinidae respectively. Gastropods were differentially distributed across the salt marsh and mangrove forest habitats; were overall 786 ± 38.57 S.E. individuals/m 2 (mean ± S.E.) with 915.26 ± 39.88 individuals/m 2 (mean ± S.E.) in the salt marsh and 572.65 ± 77.13 individuals/m 2 (mean ± S.E.) in mangrove forest habitats. Relationships between gastropods and biomass of vegetation were found both in salt marsh and mangrove forest habitats. There are several explanations for patterns of gastropods. These include: 1). the biomass of salt marsh vegetation and algae in mangrove forests, which can reduce harsh abiotic and edaphic characteristics and modify predation 2). reproductive and larval life history stages depend on tidal inundation 3). migration of recently settled stages, and 4). complex interactions among the structural features of salt marsh and mangrove habitats i.e. pneumatophores, leaf litter, crab holes and predation. Understanding the regulatory roles of gastropods and the ecological services provided by blue carbon salt marsh and mangrove forest habitats in southeastern Australia is increasingly important as anthropogenic pressures accelerates habitat loss. 249 words • Salt marsh and mangrove forests gastropod assemblages differ in southern Australia. • Assemblages depend on habitat structure, vegetation biomass and tidal inundation. • Anthropogenic pressures impact gastropods and remove blue carbon habitat services.