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短 報〔Note〕 天塩川水系岩尾内ダム直下流域におけるヒゲナガカワトビケラ (Stenopsyche marmorata Navas)の優占 岩舘知寛 1),3) ・程木義邦 1),4) ・大林夏湖 1),5) ・村上哲生 2) ・小野有五 1)

・Liping Zhu 5)Study of primary production magnitude under the thermocline (20-25 m) and the continuous supporting mechanism of production in Lake Pumayum Co, Tibetan Plateau AbstractTo study the primary production magnitude under the thermocline (20-25 m) and the continuous supporting mechanism of the production in Lake Pumayum Co (a high alpine lake) located on the southern Tibetan Plateau Thus, the subsurface primary production maximum appears to have formed in the 27-45 m water layer of the lake. Moreover, although this high alpine lake is generally classifi ed as oligotrophic and is located well above the forest line, primary production in the subsurface layer probably continued to exceed the mesotrophic magnitude.2) Because of the transport and supply mechanisms of nutrients supporting such high production under the thermocline, there can be deep intrusion of river water (5℃ ) colder than the lake epilimnion (10-13℃ ). This possibility is supported by the high average abundances of silt and clay, sinking terrestrial plant-derived organic carbon, and sinking soil-derived organic carbon in the 27-45 m water layer, as compared with the 0-27 m layer.The supply of nutrients in the 27-45 m water layer is believed to be several times higher than that of the 0-27 m

The morphological, chemical and biological features of small pools located in the high mountain region of the Hida Mountains in Toyama Prefecture, Japan, were redescribed for the first time in 50 years. Although these pools are in an interesting limnetic environment and they are noteworthy monitoring sites for long-term changes in regional temperature and precipitations, there is limited limnological information. The pools are called 'Ta (paddy fields)' or 'Gaki-ta (paddy fields for hungry ghosts)' in Japanese based on their resemblance to subdivided paddy fields. The pools were classified into two types based on morphology and topography: irregular-shaped pools on steep slopes and isolated round-shaped pools on gentle slopes or flat ground. Although both pool types are fed by snowmelt, the former develops through erosion along the temporal current to form irregular basins, while the shores of the latter are eroded by wind and develop into round basins.The pH in the water of the six pools was around 4.5, irrespective of the shape and size of the pool: the pH was about 0.7 lower than 50 years ago, perhaps due to recent acidic precipitation. Dissolved oxygen was undersaturated at midday in pools without submerged vegetation due to oxygen consumption of the sediment mud. Conversely, dissolved oxygen was oversaturated at midday in the pools with submerged Sphagnum. The rate of oxygen production by Sphagnum is dependent on water temperature; for example, at 17℃ it is 0.26±0.13 mgO 2 wet g -1 h -1 and at 27℃ it is 0.72 ± 0.29 mgO 2 wet g -1 h -1 .Filamentous Tribonema affinis (Xanthophyceae) and members of the acidophilous taxon of Diatomaceae, such as Frustulia rhomboides and Pinnularia spp. were dominant in the epipelic algal communities of the pools that were studied.