The largest artificial water body in Lithuania is an important resting place for migratory water and wetland birds. This artificial water body contains 25 rare and endangered bird species listed in the Lithuanian Red Data Book. And the section of the Nemunas below Kaunas HPP that does not freeze during the greatest frosts is the most important wintering ground for waterfowl in the inland waters of Lithuania. 34 species of fish are found in Kaunas Lagoon, 20 of them are commercial. The territory of the regional park is one of the few areas in Lithuania, where, in a relatively small area, almost all species of rarer animals live in the republic. Gray and white hares live in the park.

Kauno Marios Regional Park, as well as the whole of Lithuania, is characterized by taiga and broad-leaved forest vegetation. This is dominated by broad-leaved forests and spruce forests (P.abies, Q.robur, F.excelsior) and spruce forests with broad-leaved forest elements. The territory of Kauno Marios Regional Park is an oasis of waters and forests, where water and forest vegetation predominates. Significant areas (in agricultural areas) are occupied by cultivated fields, segetal and ruderal communities. Aquatic vegetation is concentrated not in the vast expanses of the lagoon and not on the shores of these expanses, where due to waves, currents, considerable depth, there are no suitable conditions for aquatic plants to grow...