ABSTRACT

Benthic invertebrates and aquatic vegetation were investigated in the volcanic Lake Monterosi in order to define the stage of development reached during progressive modifications occurring in this shallow lake. Increasing trophy and the introduction of an exotic plant (Nelumbo nucifera) were the key-factors responsible for the rapid qualitative reduction of the macrophyte population and its modification versus non rooted plants (Ceratophyllum demersum). The invertebrate fauna associated with macrophytes was found to be abundant, diversified (83 taxa) and characterized by high diversity and the presence of bioindicators of mesotrophy. Although the zoobenthic community appeared to be positively influenced by the macrophyte-dominated stage, certain negative effects of Nelumbo-colonization on the invertebrate fauna indicated that further growth of this plant would cause rapid a change in the lake

The paper presents the first European records of the copepod (Crustacea, Calanoida, Diaptomidae) Skistodiaptomus pallidus in shallow eutrophic waters indirectly connected with the Weser River, Northern Germany. Its original distribution is in the Mississippi basin of the United States of America. It is probable that this species entered the Weser River via ship ballast.