10 



and Lodge 1986). Zooplankton are abundant in weed beds and the 

 habitat complexity also provides cover and protection for spawning 

 and young fish (Carpenter and Lodge 1986). Dense infestations of 

 submerged macrophytes, nevertheless, have been shown to have a 

 negative effect on the presence of sport fish (Shireman and Maceina 

 1981). 



Conflicting reports have been presented about the effects of 

 eliminating macrophytes in lakes through chemical or biological 

 control. Carpenter and Lodge (1986) stated that because of the 

 macrophyte role in enhancing sedimentary P recycling, an increase in 

 macrophyte standing crop will lead to an increase in phytoplankton 

 standing crop, whereas the long-term effect (>3 yrs.) of killing 

 macrophytes will lead to a decrease in water-column N and P and a 

 decrease in phytoplankton. This positive correlation between 

 macrophyte and phytoplankton standing crop is contrary to the 

 negative relationship reported by Canfield et al. (1984) between the 

 percent of lake volume infested with macrophytes and water-column 

 Chi a for 32 Florida lakes. An increase in water-column P 

 concentrations and phytoplankton standing crop has been shown 

 following herbicide application to macrophytes in Florida lakes 

 because of nutrient release by the decaying plant material (Richard 

 et al. 1984). An increase in water-column P was also reported 

 following biological control of macrophytes using the grass carp 

 Ctenopharyngodon idella because of nutrient release from feces, 

 although this increase seems less dramatic because of the retention 

 of P in the fish biomass (Richard et al. 1984, Canfield et al. l9S3h, 

 Canfield et al. 1984). 





