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|Title:||Interactions between macrophyte growth and sediment nutrient availability|
|Authors:||Aquatic Plant Control Research Program (U.S.)|
Barko, John W.
Smart, R. Michael.
Chen, Rex L.
McFarland, Dwilette G.
|Publisher:||Environmental Laboratory (U.S.)|
Engineer Research and Development Center (U.S.)
Abstract: Aquatic macrophytes rely primarily on sediment as a direct source of nitrogen (N) and phosphorus (P). The availability of these nutrients in sediments is affected markedly by sediment type, and is also influenced by macrophyte growth. On sediments planted with Hydrilla verticillata (L. f.) Royle compared with control (unplanted) sediment, reductions of > 90 percent and >30 percent in concentrations of exchangeable N and extractable P were measured during two 6-week periods of growth. Diminished N availability in sediments due to uptake by Hydrilla resulted in nutrient limitation of subsequent Hydrilla growth. Concomitant increases (>30 percent) in the concentration of exchangeable potassium (K) suggest that this element, obtained via foliar uptake from overlying water, may be exchanged by macrophyte roots for ammonium in sediment. Exchange of K for ammonium in sediments occurred only under conditions of N limitation in this species. Changes in sediment nutrient availability effected by hydrilla in this investigation appear to have been entirely a function of nutrient uptake, since this species had a minimal influence on sediment redox potential. In contrast, the emergent macrophyte Sagittaria latifolia Willd. effectively promoted sediment oxidation via oxygen evolution from its roots. Species such as Sagittaria, which can modify sediment redox potential, may have an effect on sediment nutrient composition exceeding that due to nutrient uptake alone. Variations in the abilities of different aquatic macrophyte species to deplete sediment nutrients and to contend with autogenic reductions in nutrient availability may have an important influence on successional development in aquatic macrophyte communities. Changes in sediment chemistry induced by aquatic macrophytes, in addition to influencing subsequent nutrient availability, also potentially affect element exchanges with overlying water.
|Appears in Collections:||Technical Report|