Fig. 2. Images of the Oder (Szczecin) Lagoon. Left to right, top: the beach near Ueckermünde on the southwestern coast, and a view over the Polish part of the lagoon and a beach near Wolin. Left to right, bottom: zebra mussel (Dreissena polymorpha) accumulation at the shore, and examples of discolouration and foam formation due to heavy blue–green algal blooms in August 2009.