Effect of an extreme flooding event on the infralittoral decapods of the Itajaí-Açu estuary, SC, Brazil

Abstract

Estuaries are coastal water bodies  with great economic and biological importance. The benthic organisms play a significant role in these environments as  regulators or modifiers of physical, chemical and biological processes. This study aimed to evaluate the spatial and temporal  distribution of the infralittoral decapods in the Itajaí-Açu estuary, investigating factors that influence their distribution and  possible effects of a flood event on the benthic community. Six sampling points were established along the longitudinal  gradient of the estuary. Monthly samples were taken with otter trawls between May 2008 and July 2010. The abundance  and biomass of the crustaceans were analyzed using descriptive statistics. Variations in the physicochemical data of the  water column, and its possible effects over the decapods, were also evaluated. The results showed that pH, salinity and  dissolved oxygen are related to the penetration of the salt wedge, while temperature shows a seasonal pattern. The estu-ary showed a low richness (14 species), mainly in the two months after the flood of November 2008, and high dominance.  It was possible to infer that many factors act on the estuary making it difficult to establish clear relationships between the  biota and environmental variables in particular. There was an increase in abundance and biomass between February and  July 2009, which suggests that the fauna was able to recover from the flood.