Experimental Effects of Lime Application on Aquatic Macrophytes: 2. Growth Response versus Treatment Time and Lime Concentration

BACKGROUND: In addition to controlling sediment phosphorus in aquatic systems, lime (CaCO3 and Ca(OH)2) applications have been shown to be effective in both suppressing submersed macrophyte growth and changing species composition in a variety of ponds, small lakes, canals, and dugouts (Babin et al. 1992; Chambers et al. 2001; Prepas et al. 2001a, 2001b). The mode of action for controlling growth is believed to be temporarily induced inorganic carbon limitation of photosynthesis at high pH. Symptoms include pigmentation loss and arrested biomass development after treatment (Chambers et al. 2001, James et al. 2005). Other factors such as reduced light availability due to precipitation of calcite may also be involved in growth suppression. The lime dosage and exposure time requirement to suppress growth in this manner are not precisely known as dosage has primarily been targeted at phosphorus removal from the water column via precipitation with calcite rather than at macrophyte control. Another uncertainty is when to apply lime during the plants’ life cycle for most effective control. The objectives in Phase 2 of this research were to examine the effects of various lime application dosages during early and later stages of growth on the survivability of a test plant, sago pondweed, grown in experimentally controlled mesocosms.