Use of native macrophytes for recovery of the habitat structure and complexity of a lowland stream affected by river engineering works: Implications for management

Abstract

Macrophytes were transplanted into a lowland stream affected by river engineering works. The aim was to analyse the feasibility of their reintroduction and potential to be used for the recovery of the structure and complexity of the lotic habitat. Macrophytes contribute heterogeneity to streams, modify the current velocity, affect sediment and nutrients dynamics, and provide a substrate for epiphytic biofilm. We transplanted specimens of Ludwigia peploides, Gymnocoronis spilanthoides, and Egeria densa into a stream located in the Pampean plain (Buenos Aires, Argentina). The growth and coverage of the transplanted macrophytes and the changes in the structure of the epiphytic biofilm were assessed. The results show that specimens of G. spilanthoides were negatively affected by the transplant and new conditions, E. densa decreased its coverage after the transplant, and L. peploides endured the transplant and adapted to the dredging site with successful establishment and expansion. There were no significant differences between the biofilm developed in L. peploides and G. spilanthoides. Additionally, the biofilm had similar features between the transplanted macrophytes and those from a site with no dredging. Considering this result, the selection between these macrophytes in relation to biofilm production is indifferent. However, as L. peploides adapts better to the new conditions generated by the river engineering works, its use in the rehabilitation project is recommended. Moreover, it is important to consider the ability of different species of macrophytes to survive the transplant and grow under new environmental conditions in order to include them in rehabilitation projects.