Macroinvertebrate community structure in created wetlands of different successional stage

Abstract

We analyzed biogeochemical characteristics of two temperate constructed wetlands in early and late spring to evaluate the utility of the macroinvertebrate community as an indicator of ecosystem development. The wetlands were similar in area, hydrologic regime, and influent water quality, but one was younger (15 y) and supported an early successional plant community while the older system (45 y) was forested. To characterize structural habitat in the two wetlands we analyzed water and soil quality, plant community characteristics, coarse woody debris, topographic variance and hydrologic regime. The correlation of macroinvertebrate community characteristics with structural variables was compared among wetlands, and macroinvertebrates were compared temporally within wetlands. Despite differences in nutrient concentration, substrate conditions, plant cover, and microtopography, the overall macroinvertebrate guild structure in the two systems was similar in terms of taxa richness, Simpson diversity, tolerance, and trophic distribution. Total abundance of macroinvertebrates was significantly correlated with a number of structural wetland characteristics, but trophic distribution was correlated only with nutrient availability. Temporal changes were apparent in both wetlands. The two wetlands supported proportionally different guild biomass in early spring, with the forested wetland dominated by grazing herbivores and shredders and the non-forested system by detritivores and predators. In late spring, however, there was no statistical difference in trophic distribution among the two wetlands, as both were dominated by grazing herbivores. These results suggest that macroinvertebrate community characteristics have limited utility as an indicator of successional development in created wetlands, as community characteristics are readily influenced by nutrient availability and temporal changes.