Spatial distribution of the biomass of submerged macrophytes in the southern Lake Biwa basin in September 2017

The spatial distribution of submerged macrophytes, in terms of dry weight and species composition, was surveyed in the southern Lake Biwa basin in September 2017, using SCUBA. Submerged macrophytes were observed at 40 out of 52 sampling stations. The average total biomass of submerged macrophytes per site was 54 g dry wt. m. During study period, the area covered by vegetation in the basin was estimated to be 39.7 km and the total biomass was estmated to be 2761 t. Thirteen species of submerged macrophytes were observed in this study, and the average number of species per site and its standard deviation was 4.5±3.0. Hydrilla verticillata and Elodea nuttallii dominated the observed submerged macrophytes, with biomass of 777 t and 776 t, respectively. Potamogeton maackianus (556 t), Egeria densa (283 t), and Myriophyllum spicatum (257 t) followed. Biomasses of other species were each less than 100 t. We also observed that a substantial amount of filamentous algae existed in the south basin, and its biomass (1161 t) is equivalent to about 40% of the total biomass of submerged macrophytes in the basin.