There are many artificial ponds for irrigation in Higashi-Hiroshima. Himega-ike(pond) is famous for a local legend of Ayame-no-mae. To have an opportunity of finding the condition of natural environment around us we conducted a field observation program at Himega-ike as sedimentary basin on February 15, 2004. The program consists of plankton-collecting from pond water with plankton net which was handled by participants on a rubber boat and observation of plankton and a core of bottom sediment which was obtained by a piston core-sampler in the course of the program.