Resiliência de invertebrados aquáticos via propágulos dormentes em arrozais no sul do Brasil: uma perspectiva ecológica

Abstract

Wetlands are prioritary ecosystems for preservation due to their high biological diversity and productivity. As such, they are important ecosystems to protect biodiversity. Besides, they are a source of natural resources for mankind and have a great ecologically importance as ecosystems for the planet. Irrigated rice production is one of the main human activities which accounts for the disappearance of natural wetlands. The emergence of aquatic invertebrates via dormant propagules and their application in studies on the restoration of wetlands has not been investigated yet in irrigated rice fields. This study aims at the analysis of the resilience potential of aquatic invertebrates via dormant propagule banks in dry sediments of irrigated rice fields in southern Brazil by linking the community reactions to the system type and cultivation history; it also aims at the comparison of this biological community between natural wetlands and irrigated rice fields. The sediment samples were collected in rice fields with different cultivation systems and different cultivation histories. In the laboratory the dry sediment was treated with distilled water and kept under controlled conditions. The invertebrates were sampled the day before hydration of the dry sediment and on successive dates after hydration. A total of 2.364 individuals allotted among 23 taxons were found in the experiment on the different cultivation systems, and a total of 7,334 individuals allotted in 27 taxons were found in the experiment conducted with the varied cultivation histories. The richness, density and composition of aquatic invertebrates showed variation along the experiment. The different treatments showed a similar relationship between richness and density and cultivation type and history. Aquatic invertebrate composition varied mainly between rice fields and natural wetlands, and it was also different between the systems and the cultivation history. Our findings have increased the foundation for the development of management programs and restoration strategies of regional wetlands, which have largely been degraded or are at great risk of degradation.