Sediment, carbon, and nutrient accumulation at two 10-year-old created riverine marshes

Abstract

Two 1-ha riverine wetlands at the Olentangy Wetland Research Park in Columbus, Ohio, USA were constructed in 1993 with a nearly identical geomorphology and have maintained an identical hydrology since their creation. The only initial difference was that one wetland was planted with native macrophytes in 1994 while the other was not. Sediment and nutrient accumulation was evaluated in May 2004, ten years after the wetlands were created. Higher mean sediment accumulation was detected in the deeper open water (OW) zones of both wetlands (6.1 ±0.6 and 7.3 ±0.5 kg m−2 yr−1) than in the emergent (EM) vegetation zones (3.7 ±0.2 and 3.9 ±0.3 kg m−2 yr−1). Directional spatial structure associated with sediment accumulation was detected in both wetlands and was attributed to the greater accumulation in the OW zones and the gradual decrease in accumulation from inflow to outflow. Despite several years of markedly higher productivity in Wetland 2, this wetland showed no evidence of greater organic C accumulation; however, the dense Typha established during those years may have elicited greater deposition and reduced re-suspension of sediment in the OW zones. Large accumulations of Ca (235 ±23 and 235 ±15 kg m−2 yr−1) and inorganic C (71.6 ±6.9 and 70.3 ±4.8 g m−2 yr−1) in the OW zones of both wetlands suggest that CaCO3 deposition has remained a critical process where alga productivity has been highest. Annual rates of sediment and nutrient accumulation for each wetland were lower than those calculated in previous years and typically fall between ranges seen for newly created wetlands and natural wetlands.