The Influence of Field Site and Natural Sediments on the Growth and Tissue Chemistry of Vallisneria americana Michx

ABSTRACT

Rosettes of Vallisneria americana were transplanted into three upstate New York lakes, all on the same fertile lake sediment, at depths which received approximately the same quantum flux density. The lakes varied in pH and dissolved inorganic carbon (DIC) concentrations. In two of the lakes, Vallisneria was also planted on native sediment.

After ten weeks, dry matter accumulation for plants grown on the fertile sediment was approximately six-fold greater in the high pH, high DIC site, but concentrations of nitrogen (N), phosphorus (P), and potassium (K) were much lower in shoots of these plants. Greater DIC availability appears to have led to more rapid biomass gain, and effectively diluted the mineral nutrients in plant tissues. The highly significant site effect also led to greater total N, P, and K content in shoots in the high DIC site.

Sediment source had a significant effect in one of two cases. Growth was reduced ca. 60% on the sediment with the lowest pore water ammonium and soluble reactive phosphate concentrations, the lowest bulk density, and the highest organic content. Collectively these traits suggest that limited nutrient availability may have accounted for reduced growth. In contrast to trends observed among sites, smaller plants had significantly lower shoot concentrations of N and P, and no difference in K concentration occurred.

Both site and sediment effects were important regulators of biomass and nutrient accumulation by Vallisneria americana under natural conditions, but site effects—probably attributable to differences in DIC availability—had a greater impact in this study.