Inherent and apparent optical properties of Lake Peipsi, Estonia

Lake Peipsi on the border of Estonia and Russia is a large, shallow, biologically very productive lake. It is bordered by many wetland areas. On the basis of underwater radiation measurements and analyses of water samples we have shown that the optical properties of L. Peipsi are very variable both spatially and temporally, covering a large range of water types previously classified in Estonian and Finnish lakes. Inherent and apparent optical properties are compared with those of the two other large lakes, Vänern and Vättern in Sweden. Lake Peipsi has higher concentrations of optically active substances, which are known to influence satellite measurements and underwater light field. Therefore, the lake complements the continuum between L. Vänern and L. Vättern in terms of water optical properties and adds new data into the database about optical properties of turbid and humic lakes. Results obtained here can be used in bio-optical modeling to develop algorithms for remote sensing and calculations of underwater light field.