Influence of potassium source (sediment vs. open water) and sediment composition on the growth and nutrition of a submersed freshwater macrophyte ( Hydrilla verticillata) (L.f.) Royle

• Published in: Aquatic botany Vol. 12; no. 2; pp. 157 - 172
• Main Author: Barko, John W.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 1982
• Subjects: Freshwater; Hydrilla verticillata
• ISSN: 0304-3770; 1879-1522
• DOI: 10.1016/0304-3770(82)90011-0

Potassium uptake by Hydrilla verticillata (L.f.) Royle from sediment versus overlying water was evaluated in relation to the K demands incurred by this species during an 8-week period of growth. The investigation was conducted on a heterogeneous assemblage of sediments and in two solutions differing fundamentally in the presence (2.3 mg l −1) and absence of K. Both biomass production and shoot morphology in Hydrilla varied significantly between solutions and among sediments. In contrast to N and P, which were readily mobilized from most sediments, K was mobilized from all sediments to only a minor extent by this species. Mobilization of K was proportional to interstitial water K concentration; yet on at least four of the six sediments examined, K supplied from sediments was insufficient to support the maximal growth of Hydrilla. The open water rather than the sediment appears to be the primary source of K supply to this species and perhaps to most other submersed freshwater macrophytes. Where K was supplied in solution, sediment-related differences in the growth of Hydrilla negatively correlated with sediment organic matter content over the range 0.2–56.2% dry sediment mass. It is tentatively suggested that the organic composition of sediments may influence the species composition of aquatic macrophyte communities.