Cumulative effects of restoration efforts on ecological characteristics of an open water area within the Upper Mississippi River

Ecological restoration efforts in large rivers generally aim to ameliorate ecological effects associated with large‐scale modification of those rivers. This study examined whether the effects of restoration efforts—specifically those of island construction—within a largely open water restoration area of the Upper Mississippi River (UMR) might be seen at the spatial scale of that 3476 ha area. The cumulative effects of island construction, when observed over multiple years, were postulated to have made the restoration area increasingly similar to a positive reference area (a proximate area comprising contiguous backwater areas) and increasingly different from two negative reference areas. The negative reference areas represented the Mississippi River main channel in an area proximate to the restoration area and an open water area in a related Mississippi River reach that has seen relatively little restoration effort. Inferences on the effects of restoration were made by comparing constrained and unconstrained models of summer chlorophyll a (CHL), summer inorganic suspended solids (ISS) and counts of benthic mayfly larvae. Constrained models forced trends in means or in both means and sampling variances to become, over time, increasingly similar to those in the positive reference area and increasingly dissimilar to those in the negative reference areas. Trends were estimated over 12‐ (mayflies) or 14‐year sampling periods, and were evaluated using model information criteria. Based on these methods, restoration effects were observed for CHL and mayflies while evidence in favour of restoration effects on ISS was equivocal. These findings suggest that the cumulative effects of island building at relatively large spatial scales within large rivers may be estimated using data from large‐scale surveillance monitoring programs. Published in 2010 by John Wiley & Sons, Ltd.