Nitrogen nutrition of Myriophyllum spicatum: variation of plant tissue nitrogen concentration with season and site in Lake Wingra

Abstract

SummarySamples of water, sediment and Myriophyllum spicatum were collected from four weedbed sites in Lake Wingra, a small hypereutrophic hardwater lake in Madison, Wisconsin, several times during the 1972 and 1973 growing seasons, and analysed for various forms of N. The concentrations of inorganic N in the lake water were quite similar at all sites. The differences in the total N content of the Myriophyllum tissue from site to site directly related to the levels of available sediment N, indicating a dependence upon the sediment as a N source. Myriophyllum tissue N concentrations (ash and moisture‐free basis) were highest in spring, decreased steadily during the summer, and increased again in the fall. Myriophyllum apparently grows very little during the winter, but continues to accumulate N. The death and decay of a considerable portion of the Myriophyllum in the fall contributes insignificant amounts of N directly to the lake water. Nitrogen does not appear to be limiting Myriophyllum spicatum growth in Lake Wingra.