3..r 



29 



limnology than cores taken in littoral areas. Although taxon 

 resolution varied with sediment core site, each core from Lough 

 Augher gave fundamentally the same record of eutrophication. Dixit 

 and Evans (1986) concluded that when time or financial constraints 

 are important, a sediment core from the deepest site on a lake will 

 provide a reliable indication of historical trends in pH. Because of 

 differences in pH inferences from various sites, however. Dixit and 

 Evans indicate that it is important to analyze several sediment cores 

 and demonstrate replicability for absolute inferences. 



Purpose 



The purpose of this study is to develop methods that would 

 permit quantitative assessment of historical macrophyte biomass in 

 lakes using sedimentary indicators. Macrophyte standing crop has 

 been documented to be high (Canfield et al. 1983a) in lakes such as 

 Fairview in Orange Co., Florida that appear oligotrophic and have 

 been used for calibration of diatom/trophic state models (Whitmore 

 1989). Conventional paleolimnological reconstructions of trophic state 

 have focused on inferring water-column nutrient concentrations 

 principally from planktonic diatom assemblages, but they have 

 ignored the often substantial component of primary production 

 occurring in macrophytes. 



Historical inferences of lower water-column nutrient 

 concentrations obtained with existing diatom predictive models don't 

 necessarily indicate that lakes were formerly less productive. A 

 negative correlation has been shown between water-column nutrient 

 concentration or phytoplankton biomass as measured by Chi a and 



