Epsilon Archive for Student Projects

Abstract

Both nitrogen and phosphorus may limit the algal biomass in lakes.
Phosphorus is generally considered to be the most limiting factor in fresh
waters, and therefore addition of that nutrient leads to enhanced algal
production; eutrophication. In recent years, the role of nitrogen as a
eutrophicating factor has come into focus, and some models have been
published describing the combined effect of phosphorus and nitrogen on
algal biomass. These published equations were applied on data for 103
Swedish reference lakes from the years 1996-97 to see their validity.
To further evaluate the eutrophicating effect of nitrogen in nutrient poor
lakes, new models were made based on the Swedish data. Multiple linear
regression using epilimnic data for the whole vegetation period
(May-September) revealed the best equation as:
log(Chl-a)=-1.243+0.710log(TP)+0.515log(TN)+0.251log(Abs_F)
r2=0.64, n=143, p<0.01
The results indicate that algal biomass (Chl-a) in nutrient poor lakes
depend not only on total phosphorus concentrations (TP), but also on total
nitrogen concentrations (TN) and water colour (Abs_F). The new models
were validated on independent data from 1998.