Does the management of sandbar openings influence the macroinvertebrate communities in southern Brazil wetlands? A case study at Lagoa do Peixe National Park – Ramsar site

This study assessed the influence of an artificial sandbar opening on the macroinvertebrate richness, abundance and composition of the Lagoa do Peixe floodplains in the only Ramsar site in southern Brazil. The Lagoa do Peixe has its connection with the sea artificially opened every year at the end of winter. However, this management intervention has been carried out without the evaluation of the impact of this opening in the aquatic biodiversity. Six samplings were carried out over two years (from March 2008 to October 2009) which encompassed two artificial sandbar openings. The mean richness and abundance were lower in the floodplain sites influenced by the artificial sandbar opening (opened wetlands) than in the floodplain sites not influenced by this event (natural wetlands). Water salinity was higher in opened wetlands than in natural wetlands during the open sandbar samplings. The richness was negatively associated with water salinity, and the abundance was positively associated with hydroperiod, and negatively associated with conductivity. The composition of macroinvertebrate taxa was different between opened and natural wetlands. Our results suggest that artificial sandbar openings have a negative impact on freshwater macroinvertebrate communities in southern Brazil floodplain wetlands. Hydrologic variation and increase of salinity related to this management may be the main factors of the change in the richness, abundance and composition in opened wetlands. We concluded that the artificial sandbar opening should be carefully re-analysed or forbidden, since this management practice may be jeopardizing the aquatic macroinvertebrate community in a National Park and Ramsar site, where the biodiversity conservation is a priority and protected by Brazilian laws.