Macroinvertebrate communities and environmental conditions in recently constructed wetlands

We quantified macroinvertebrate community characteristics in nine temporary or permanent wetlands, and related these to environmental conditions. Macroinvertebrates inhabiting the water column and shallow sediment (42-cm depth) were sampled 20 months after wetland construction in June 2005. A total of 29 taxa were collected, and macroinvertebrate communities varied among wetlands. Total macroinvertebrate biomass (mean ± SE = 16.44 ± 4.72 g AFDW/m³) and densities (mean ± SE = 372,096 ± 124,972 individuals/m³) were positively related to coarse particulate organic matter abundance (living and nonliving plant matter; CPOM) and negatively related to turbidity. Density of ecologically sensitive EOT (Ephemeroptera, Odonata, Trichoptera) taxa was also positively related to CPOM and negatively related to turbidity. Total taxa richness was negatively related to turbidity, and percent of total macroinvertebrate density consisting of EOT (% EOT) was positively related to CPOM. These relationships were greatly influenced by 10 dominant taxa (nematodes, physid snails, mites, small squaregill mayflies, narrowwinged damselflies, biting midges, non-biting midges, ostracods, cladocerans, and cyclopoid copepods) that were positively associated with CPOM and negatively related to turbidity. Two wetlands inhabited by common carp (Cyprinus carpio) appeared to be in the poorest condition. These wetlands had the lowest macroinvertebrate biomass and densities and highest turbidity. Additionally, although net uptake of total nitrogen (TN) occurred in these high-turbidity wetlands, NH₃ concentrations were two-fold higher in outflow than inflow. Net uptake of total phosphorus (TP) occurred only in wetlands with low turbidity, high CPOM abundance, and high macroinvertebrate abundance and diversity. To enhance macroinvertebrate abundance and diversity and ecological functions (e.g., nutrient removal) in newly constructed wetlands, management efforts should be directed toward increasing plant abundance and reducing turbidity.