The Development of an Aquatic Vegetation Community in Pool 19, Upper Mississippi River

Abstract

ABSTRACT Sediments have accumulated in the main channel border area upstream of Lock and Dam 19 on the upper Mississippi River to the extent that water depth has decreased from 11.5 m to less than 2 m. Beginning in the 1950's, aquatic vegetation became established in the lower 3 km of the pool; community development through 1983 was primarily submersed vegetation (Potamogeton spp. and Vallisneria americana). Aerial photographs were used to document the expansion of plant beds from 19 ha (1956) to 80 ha (1978). In 1984, Nelumbo lutea invaded the plant bed and by 1987 occupied 26 of the 110 vegetated ha. Standing crop estimates showed that where N. lutea was present, standing crop biomass of V. americana was reduced by an average of 56%. Using existing conceptual models and estimated sedimentation rates, we predict that the study area will become a naturally leveed floodplain dominated by immersed vegetation. Species composition of the community will depend on elevation, nutrient status of the soils, and the degree of inundation, exposure, and disturbance.