Relationship of Population Attributes of a Dominant Macrofaunal Species with Environmental Conditions in a Eutrophic Estuary (Guanabara Bay, Brazil)

Hydrobioid gastropods are abundant in coastal systems and ecologically important for ecosystem functioning. We aimed to unravel the relationship between usual and stress-related population attributes of the dominant macrofaunal species <i>Heleobia australis</i> with indicators of environmental quality and coastal pollution. Using Guanabara Bay (GB, Brazil) as a model of a multi-impacted coastal system, our hypothesis is that increased amounts of rainfall during the warm season reduce the bay’s environmental quality and induce shifts in snail population attributes. A suite of environmental variables, population attributes, and sediment quality descriptors was assessed by combining field and laboratory evaluations with literature compilation. Results indicate high organic pollution levels with environmental degradation and reinforce GB status as a severely contaminated system. Some environmental conditions can be applied as seasonal predictors of changes in warm-rainy (rainfall and salinity), intermediate (silicate), and cold-dry seasons (nitrite and nitrate). Three selected usual population attributes (snail density, fecundity, and recruitment) were not affected by changes in environmental conditions, but significant effects were detected on two stress-related attributes (relative penis length index and shell deformity). For the first time, shell deformity was recorded in <i>H. australis</i> snails. Low variation in usual population attributes highlight the high tolerance of <i>H. australis</i> to shifts in environmental conditions.