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LAKE RANAU |
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+Lake
Ranau has an inlet of Warkuk River at Kota Batu and an outlet at Surabaja
through the Komering River to the Bangka Strait. The drainage area is used for
agriculture. Lake Ranau is in the Indonesian conditions a high-altitude lake. It
is surrounded by rain forests and agricultural fields. There is also a spa at
the lake shore. It has been observed that the western end is four centigrades
warmer than the eastern end because of the influence of hot springs (Forbes
1885), but this kind of observations were not made in this study. It was weakly
stratified (RTR 57.7 and 64.7), and it had an anoxic hypolimnion. Oxygen
concentration was zero at about the depth of 70-100 meters. At the same depth
hydrogen sulfide could already be detected, and the highest concentration near
the bottom was 1.5 mg/l. The maximum depth is 229 meters. The nutrient
concentrations were; total nitrogen from 0.158 to 0.893 mg/l N and total
phosphorus from 0.055 to 0.411 mg/l P. Chlorophyll a concentrations varied from
1.21 to 1.28 mg/cu m. The highest carbon dioxide concentration in the
deeper hypolimnion was 12.0 mg/l and sulfate concentration 20.2 mg/l. The lake
is oligotrophic, having a biomass of 0.03 mg/l and transparency of 8.8 meters.
The most abundant taxa were in March 1992 Chodatella spp. and Planktonema
lauterbornii, and in August 1993 chlorophyte Botryococcus braunii and
diatom Aulacoseira granulata.
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