Seasonal and spatial variations of dissolved nitrogenous nutrient concentrations in hypertrophic shallow lake, with special reference to dissolved organic nitrogen

Oxidation of dissolved methane in a eutrophic, shallow lake: Lake Kasumigaura, Japan

“…In the nonstratified, shallow Lake Kasumigaura, DIN concentrations are sometimes <3 PM between mid-spring and autumn. Such low nitrogen concentrations there are mainly due to phytoplankton uptake, which is dominated by Oscillatoria (Takamura et al 1992;Otsuki et al 1993). DIN usually increases in late autumn after the end of the summer phytoplankton bloom (Fig.…”

“…1). The mean water renewal rate is 220 d (Otsuki et al 1993). Differences in water temperature between the surface and bottom are minimal (<2"C, except for a few calm days in summer) because winds are usually sufficient to cause daily turnover.…”

“…Comparison of methane consumption rates and diffusive fluxes to the atmosphere as sinks for water-column methane and calculated turnover time of dissolved methane in Lake Kasumigaura (values are means -C 1 SD of interannual variation). time of dissolved methane is very short relative to the renewal time of the lake water (220 d; Otsuki et al 1993). Hence, the concentration of dissolved methane in the water column was not controlled by the water budget of the lake.…”

Observations on the Effects of Caged Carp Culture on Water and Sediment Metal Concentrations in Lake Kasumigaura, Japan

“…The water temperature at the lake center is at its lowest, 43C, in February and highest, 303C, in August. The mean water renewal rate is 220 days (Otsuki et al, 1993).…”

Seasonal variations in dissolved nitrous oxide concentrations in a eutrophic shallow lake without anaerobic layer.

“…Many eutrophic lakes in the world are shallow and receiving huge amounts of nitrogenous nutrients by inflows from polluted rivers, effluents from wastewater treatment plants, and precipiation, which have caused eutrophication of the lakes. However, it seems that there is little report on the accumulation of nitrogenous compounds in these lakes, except for sediment surface layer (e.g., Otsuki et al, 1993). This suggests that a considerable portion of loaded total nitrogen to such lakes must be be ing removed into the atmosphere as nitrogen gas during denitrification processes as one of natural purification mechanisms, and consequently nitrous oxide as an intermediate would be pro duced (Koike et al, 1984;Seitzinger, 1988) and be emitted to the atmosphere.…”