Effect of Temperature, Nutrients and Diuron on Freshwater River Biofilms: A Statistical Approach

The influence of riverine physico-chemical factors on overall physiological status and
growth of river biofilms was established in a field data-based model. Two sampling stations were
located in the intermediate and downstream watershed areas of the river Morcille (France). Water
temperature, suspended matter (SM), dissolved organic carbon (DOC), nutrients (NH₄, NO₂ , NO₃ ,
PO₄ , Si) and toxicant (herbicide diuron) concentrations in the river were used as independent
variables for modeling their effect on biofilm photosynthetic (PS) yield and dry weight (dependent
variables). Basis function of 5^th degree polynomial to accommodate the non-linear associations
between the dependent variable and each of the independent variables followed by multiple linear
regression was applied to determine the two endpoints. Data from September 2008 to December
2011 were utilized for model development and 2011 data were used for model validation. Nutrients
and DOC, rather than diuron had a significant influence (p<0.05) on PS yield and dry weight. This
model, therefore, integrated the interaction between co-occurring physico-chemical factors and
pollutant to understand the dynamics of biofilm growth.