Seasonal and Vertical Changes in the Surface Area/Biomass Ratio of Potamogeton Lucens L. in a Clear and a Turbid Shallow Lake

To determine the influence of different growth conditions on the architecture of Potamogeton lucens L., we measured several morphological parameters of the plants from May to September 2001 in a clear macrophyte-dominated lake and a turbid phytoplankton-dominated lake in Central Estonia. The main difference between the lakes was the higher summer water transparency in the macrophyte-dominated lake. All size related parameters of P. lucenstended to be largerin the macrophyte-dominated lake, but only the total above-ground plant surface area and the surface area of leaves differed significantly (p< 0.05) between lakes. The relationship between surface area (A, in cm2) and dry weight (DW, in g) for the measured 25-cm sections of above-ground parts of the plants could be described as: A = 312.9 ± 9.4 DW + 26.5 ± 6.8 (± standard error) (R2= 0.649;n= 607;p< 0.001) Better light conditions in summer and shorter wind fetch in the macrophyte-dominated lake were likely factors stimulating further ramification on the plants in August and a more uniform vertical distribution of plant surfaces in this lake compared to the plankton-dominated lake.JRC.H.1-Water Resource