Despite extensive studies of the terrestrial plant flora of Indiana, aquatic plant communities have only been superficially examined. Lakes of Indiana are small and shallow and most suffer from eutrophication problems from agricultural non-point source pollution. Over the past five years we have surveyed over 130 ponds and lakes, primarily throughout the Northern Lakes district of Indiana, with the goal of providing a better understanding of aquatic plant communities in Indiana. Specific objectives of this research are to identify populations of rare aquatic plant species and to develop conservation strategies for these species before they become lost due to the direct effects of eutrophication or from related impacts such as aquatic herbicide application. During the course of these surveys we have recorded over 100 new records for rare aquatic plant species in the state. Several of these species are particularly noteworthy because they either represent first records for the state (Ceratophyllum echinatum), records for species thought to be extirpated (Cabomba caroliniana, Lemna valdiviana, Potamogeton bicupulatus) or records for endangered species (Bidens beckii, Najas gracillima, Potamogeton epihydrus, Potamogeton pulcher). The geographic affinities of these species vary from coastal plain elements to those with more northeastern distributions to those at the northern extent of their range. The ecology of each species will be briefly discussed relative to their affinities, habitat preferences and fidelities, and community associations.

Key words: Ceratophyllum, Aquatic plants, Bidens, Indiana, Najas, Potamogeton.