Within-Bed Distribution of Myriophyllum spicatum L. in Lake Onalaska, Upper Mississippi River

Abstract

ABSTRACT The exotic species Myriophyllum spicatum L. has become a recent member of the submersed aquatic plant community within the upper Mississippi River system (UMRS). Notable for nuisance growth in many North American locations, its potential for creating problems in the river system is not known. To better understand its nuisance potential, within-bed-plant pattern and the relationship between plant biomass, water depth, sediment moisture, and sediment organic content were studied in Lake Onalaska, a backwater lake of UMRS Pool 7. These results were compared with studies of biomass distribution of M. spicatum in Lake Wingra, Wisconsin. Within-bed biomass from Lake Onalaska was not significantly correlated with depth, organic matter, or sediment moisture. Lake Onalaska milfoil beds produced biomass similar to other lakes in the region but were restricted to much shallower water depths. The shallow maximum growth depth is probably related to poor water clarity but the maximum growth depth could vary significantly from year to year because of the dynamic nature of water clarity in the UMRS. Because Mississippi River pools are shallow, the area occupied by milfoil could also vary considerably from year to year.