Detecting changes in ecosystem quality following long-term restoration efforts in Cootes Paradise Marsh

Abstract

Cootes Paradise Marsh is a large urban wetland of western Lake Ontario that has undergone major restoration as part of the Hamilton Harbour Remedial Action Plan. A key component of the restoration plan is exclusion of common carp ( Cyprinus carpio) via construction of the Cootes Paradise Fishway that became operational in 1997. Here, we evaluate the response of the marsh community to carp exclusion using three approaches. First of all we analyze changes in water quality parameters and the community composition of zooplankton, macrophytes and fish. Secondly, we use ecological indices based on water quality, zooplankton, macrophytes and fish communities to track changes in quality. Lastly, we evaluate changes in the wetland quality of Cootes Paradise over the past decade in comparison with two other coastal wetlands of the Laurentian Great Lakes for which long-term data exist (Matchedash Bay of Lake Huron and Long Point Marsh of Lake Erie). Our results show that there has been variable improvement in wetland quality at Cootes Paradise, but compared to the two other wetlands, it is still the most degraded in all aspects studied. The overall trend towards moderately better water quality conditions in Cootes Paradise over the past decade is not directly reflected in the zooplankton, macrophyte and fish communities. We believe that high nutrient levels and high turbidity are preventing the progression to a clear-water macrophyte dominated system. This is one of few long-term studies that tracks the progress of restoration in a degraded marsh. It underscores the difficulty in trying to restore a ‘novel ecosystem’ to its original biotic and abiotic characteristics.