Composition and abundance of zoobenthos in the profundal zone of Lake Oze-numa in central Japan.

Abstract

Composition and abundance of zoobenthos in the profundal zone of Lake Oze-numa (36°56'N, 139°18'E) were studied at two sites, Lake Center and Off Nushiri, from May to September 1986. Among the eight taxa recorded, three species (Tubifex sp., Limnodrilus hoffineisteri, and Chironomus sp.) accounted for more than 95.5% of the macrobenthos in number. Species diversity, density, and biomass of macrobenthos were lower at Lake Center (8.8 m deep in average) than those of Off Nushiri (6.8 m). Oxygen content was probably an important factor in these differences between the sites. At Off Nushiri, Tubifex sp. and L. hoffineisteri reproduced throughout the study period but with low proportions ; pupae of Chironomus sp. were found only in late June.

Disappearance of deep profundal zoobenthos in Lake Ikeda, southern Kyushu, Japan, with relation to recent environmental changes in the lake

“…The profundal Lake Ikeda is quite similar to such water in terms of oligochaete composition. Both Tubifex tubifex and Limnodrilus hoffmeisteri can reproduce all year around under favorable conditions (Kennedy 1966;Poddubnaya 1980;Ohtaka et al 1988). The present summer survey in 1998 found their mature worms and cocoons and confirmed their reproduction as deep as 100 m. On the other hand, neither mature worms nor cocoons of any tubificines were found at the bottom at the 120-m depth.…”

“…Identification of chironomid larvae was made on slide specimens mounted in gum-chloral solution after being cleaned in about 10% hot KOH, that of oligochaetes was made on specimens on slides mounted directly in CMCP-10 (Polysciences, Warrington, PA, USA), or specimens that had first been dehydrated in a graded series of ethanol and water solutions, cleared in methyl salicylate, then mounted whole on slides in Canadian balsam. Mature oligochaete individuals were distinguished by having a clitellum, and oligochaete cocoons were identified after Ohtaka et al (1988). Specimens used in the present study are deposited in the Faculty of Education, Hirosaki University, except for a part of copepods studied by Ishida (2000).…”

Mixing pattern and bathymetric distribution of zoobenthos in an interconnected lake system in the Tsugaru-Juniko Lakes, Aomori Prefecture, northern Japan

“…Distribution records compiled from April to December 1995 and May to August 2007. (Findenegg, 1937;Wetzel, 2001)にあた ると考えられる。これは，有機物の分解に伴って底層 に塩類が蓄積する湖沼で起こる生化学的部分循環の一種 で，面積が小さくある程度の深さを持つ北米やヨーロッ パの多くの湖沼で，長く厳しい冬にしばしば観測されて いる (Wetzel, 1966;Wetzel et al, 1972;Wetzel, 1973 (Aston 1973;Brinkhurst and Kennedy 1965;Milbrink, 1980) ，国内外を問わず湖底 が貧酸素になる多くの富栄養湖で優占することが知ら れている (Brinkhurst, 1974;Ohtaka et al, 1988;Ohtaka and Kikuchi, 1997;Milbrink et al, 2002；大高・佐藤，2005) 。 ユスリカ類のうち，落口の池，王池ともに 10 m 地点ま で出現したユスリカ属は，同様に貧酸素に対する耐性 が高い種を多く含み (Kawai et al, 2004) ，国内外の富栄 養湖の湖底で優占することが多い分類群の一つである (Thienemann, 1922;北 川 , 1973;Hirabayashi and Hayashi, 1994;Lindegaard, 1995…”

<strong>Profundal oligochaete faunas (Annelida, Clitellata) in Japanese lakes</strong>

“…Faunal records of lake profundal oligochaetes in Japanese lakes have been accumulated since 1980s in accordance with an increase in faunistic and ecological studies of lake zoobenthos (Ito 1978;Ito and Uno 1980;Ito et al 2002Ito et al , 2005Fukuhara et al 1987;Yasuda and Okino 1987;Ohtaka 1994Ohtaka , 1995Ohtaka , 2001aOhtaka , b, 2004Ohtaka , 2006Ohtaka , 2009aOhtaka and Kikuchi 1997;Ohtaka and Ito 2002;Ohtaka and Iwakuma 1993;Ohtaka and Martin 2011;Nishino 1995, 1999;Ohtaka et al 1988Ohtaka et al , 2006Ohtaka et al , 2010Nishino et al 1999;Fend and Ohtaka 2004;Hirabayashi et al 2007Hirabayashi et al , 2012Martin and Ohtaka 2008). Comparing these records, species composition of profundal oligochaetes in Japanese lakes can be basically explained by the scheme of Timm (2012), but faunal differences among respective lakes and the factors determining the species composition have not been well understood yet.…”