Constructed wetlands increase the taxonomic and functional diversity of a degraded floodplain

Abstract

Numerous wetland restoration projects have been implemented in recent years to mitigate the increasing loss of global wetland surface area caused by human activities. Most of these projects have focused on the local recovery of habitats and species diversity, with little evaluation of functional recovery. We aimed at demonstrating that constructing wetlands on a degraded floodplain increases not only the taxonomic, but also the functional diversity of macroinvertebrate assemblages by providing greater water quality to the local fauna. We studied the macroinvertebrate community using taxonomic and functional diversity indices, and the physicochemical characteristics of three wetlands constructed 5–25 years ago, and three relict natural wetlands on the floodplain of a regulated river (Ebro River, NE Spain). Constructed wetlands demonstrated significantly greater taxonomic abundance and richness of macroinvertebrates than natural wetlands. At the functional level, the richness and Shannon diversity of biological traits relating to reproduction, respiration, dispersal and feeding were also greater in constructed wetlands, which is partly explained by low inorganic nitrogen concentration in these habitats. In contrast, a high content of phosphorus and water organic matter led to the lowest values of taxonomic and functional diversity found in natural wetlands. We conclude that it is essential to consider not only taxonomic but also functional aspects at all stages of a restoration project in order to optimize its long-term efficacy to provide and support key species and functions.