A method for evaluating the impact of navigationally induced suspended sediments from the Upper Great Lakes Connecting Channels on the primary productivity

The impact of navigationally induced suspended sediments from the Upper Great Lakes Connecting Channels on the size-fractionated primary productivity was evaluated by the Carbon-14 technique. The method applied was on-site, rapid, sensitive, inexpensive, and provided dynamic-toxicological information essential for hazard assessment. Both enhancement and inhibition of the primary productivity was observed in various parts of the Upper Great Lakes Connecting Channels. These responses appear to depend on the type of natural plankton and their exposure to various contaminant/nutrient complexes generated by the disturbance of the bottom sediments during the passage of ships. Traditionally, only the inhibition of primary productivity has been monitored from a toxicity point of view, but it is important also to evaluate the implications of enhancement since it may result in increased eutrophication, propagation of nuisance blooms, and change of intricate food-web interactions. The procedure adopted in this study for the first time appears to possess considerable potential for a simple and rapid screening of environmental perturbations resulting from navigational activities.