琵琶湖南湖における2014年夏の沈水植物の現存量分布ならびに2002，2007，2012年との比較

摘要

琵琶湖南湖で2014年9月に沈水植物の現存量の平面分布をSCUBAサンプリングにより調査した。沈水植物は52地点中50地点に出現し，その分布範囲の面積は49.6 km~2と推定された。地点あたりの沈水植物の現存量(乾燥重量)の平均値と95%信頼限界は352±85 g m~2で，南湖全体の現存量は18173±4387tと推定された。沈水植物は14種が出現した。1地点あたりの出現種数と標準偏差は5.7±1.7だった。優占したのはセンニンモPotamogeton maackianusで，その現存量と95%信頼限界は，7275±2709tだった。以下，コカナダモElodea nuttallii(4937±2032t),クロモHydrilla verticillata(2927±757t)，オオカナダモEgeria densa(1481±949t)，ホザキノフサモMyriophyllum spicatum(825±562t)が続き，この5種で全体の現存量の96%を占めた。%The spatial distribution of submerged macrophytes, in terms of biomass and species composition, was surveyed in the southern Lake Biwa basin in September 2014， using SCUBA. Submerged macrophytes were observed in 50 out of 52 sampling stations. The average biomass (dry weight ± 95% confidence limits) of total submerged macrophytes per site was 352 ± 85 g m~(-2). The area with vegetation cover and the total biomass during the study period in the basin were estimated to be 49.6 km~2 and 18173 ± 4387 t， respectively. Fourteen species of submerged macrophytes were found in this study, and the number of species per site and S.D. was 5.7 ± 1.7. Potamogeton maackianus was dominant among them, with a biomass estimated to be 7275 ± 2709 t. Elodea nuttallii (4937 ± 2032 t), Hydrilla verticillata (2927 ± 757 t), and Egeria densa (1481±949 t), Myriophyllum spicatum(825 ± 562 t) followed. These species accounted for 96% of the total biomass of submerged macrophytes in this study.