Research Group for Aquatic Plants Restoration in Lake Nojiri.

Research Group for Aquatic Plants Restoration in Lake Nojiri.

The latest Photographs of the Aquatic Plants Restoration zone.(650KB)

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Fuyosou 2004. - Hotel Fuyosou in Lake Nojiri - Nojiri-ko Museum

The overview of the aquatic plants restoration

The Lake Nojiri
The Lake Nojiri is located on the northern part of Nagano Prefecture, central Japan. It has been famous for its beauty for international tourists as is called 'Fuyou (i.e., rase mallow) lake' and been appointed as a national park combined with Myouko and Kurohime heights. There is the site in the lake, inhabited by old people hunting large deer and elephants in the Palaeolithic age.

The profile of the lake is as follows: area 4.56 km2, altitude 654m, mean depth 21m (maximum 38.5m). And water quality of the lake is as follows: present state; COD 1.8mg/l, Total P 0.005mg/l, max. transparency >9m.

zVcNitellopsis obtusa

Aquatic plants of Lake Nojiri
Lake Nojiri had been famous for rich aquatic plants until 1970's. In the early 20th century, more than twenty of plant species were recorded during the ecological research on distribution and structure of aquatic plants in the lake. However, in 1978, five thousands grass carps were introduced in order to manage the aquatic plants, which sometimes interfere of the fishery and boat navigation. Three years after its introduction, most of aquatic plants including genus Nitellopsis obtusa (stonewort) were heavily damaged or extinct due to overgrazing by grass carps. During 1970-80, N. obtusa in other three Japanese lakes were extinct due to rapid degeneration of habitat and water. The loss of aquatic plants then caused the rapid decline in biodiversity , and finally the outbreak of freshwater red tide was found on July, 1988 in Lake Nojiri.

Start of research group for restoration of aquatic plants in Lake Nojiri.
Nitellopsis obtusa is now extinct in the wild in Japan, but living cultures of N.obtusa originating from Lake Nojiri has been preserved in the laboratory of Osaka Medical University. This information initiated activity for restoration in Lake Nojiri by Nagano Research Institute for Health and Pollution(NRIHP). In 1996, NRIHP activity for restoration had started with Nojiri-ko Museum, and local voluntary staffs. First project was to install experimental exclosures. On June 1996, six exclosures (10 cm mesh, 4 m square) were fixed at 1- 4.5m depth points, in which Typha (Cattail), Nitellopsis, Pharagmites(Reed), Vallisneria (Eelgrass)and others were transplanted.(see Map:Point 1) The growth of N.obtusa and other submerged plants like Vallisneria asiatica were observed through the pictures of underwater TV camera in 1999 and 2000.

These experiments have shown that biotic interactions between N.obtusa and other organisms were essential to the growth of N.obtusa in the lake.

On 2001, new exclosures were installed. One (area 450 u) was fixed at 1-2.5m depth point for restoration of aquatic plants zone consist of Phragmites australis, Typha angustifolia, Schoenoplectus validus, etc.(see Map:Point1) The other (6m square)in which cultures of N.obtusa were transplanted, was fixed at 7m depth point where the distribution of N.obtusa was recorded in 1950's.(see Map:Point2)
All of these activities were carried out in cooperation with voluntary stuffs and local people.
Our research and restoration project broadly supports environmental education for public such as in elementary school, local museum and local community by various ways (e.g., poster presentation, planning symposium on aquatic plants conservation).

The first change is visit of dragonfly. Dragonfly flew to the Aquatic Plants Restoration zone in June 2002. Dragonfly spawned an egg at leaf of the aquatic plant. People who visit the aquatic plant zone increased.

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