In Lake Shinji, Japan, periodic outbreaks of musty odour have occurred since mid-May 2007. Although the substance responsible for the odour was identified as geosmin, the odour-producing organism was unknown. We cultivated an axenic unialgal strain and determined that a species of Coelosphaerium (Synechococcales) was responsible for the production of geosmin in Lake Shinji. Our analysis was conducted using gas chromatography/mass spectrometry to determine the odorous compound. To determine the algae species, it was observed by optical microscopy to describe its morphological characteristics and the polymerase chain reaction was used to characterise the nucleotide sequence of the 16S rRNA gene and the 16S-23S rRNA internal transcribed spacer region. In addition, we explored the relationship between the number of cells of the Coelosphaerium sp. and the concentration of geosmin. In conclusion, geosmin, the cause of the musty odour in Lake Shinji in autumn 2009, was produced by Coelosphaerium sp., and to our knowledge, this is the first report of a geosmin-producing species in the family Coelosphaeriaceae.
Water, salt and phosphorus balance of the 19 years was calculated in Lake Shinji, a shallow brackish lake in Japan. Average annual freshwater inflow of 19 years into Lake Shinji was in the range of the 1.25 ~ 2.35 × 10 9 m 3 , the average was 1.77 × 10 9 m 3 . Reverse flow from the Lake Nakaumi located downstream of the Lake Shinji was in the range of 0.32 ~ 0.84 × 10 9 m 3 , the average was 0.49 × 10 9 m 3 , corresponding to 27.7% of the freshwater inflow. Retention time in consideration of the amount of freshwater inflow and reverse flow from the Lake Nakaumi were from 47.5 to 76.2 days, and 59.4 days on average. The percentage of annual deposition of TP to inflow TP was in the range of -23.6 to 69.3%, and 20.9% on average. In addition, there was a positive relationship (r = 0.71) between annual TP inflow and sedimentation rate, settlement amount was small drought year when inflow is low.Phosphorus concentrations peaked by released from the sediment in August-September around becomes a normal value almost in November-December. We calculated the ratio of phosphorus resettle to the sediment for the duration from the peak of the TP stock to become normal value, using water amount of outflow from Lake Shinji, inflow load and TP concentration of Lake Shinji. TP sedimentation rate was in the range of 8.8 to 65.6%, and 45.1% of phosphorus which released in summer was resettled to the bottom of the lake again in average, and it was considered to be involved in the release of the following year.In the process of phosphorus concentration decreases, SRP was greatly reduced, but the fact that changes in the PP was hardly seen. The SRP reduction occur when DO at the sediment surface increased at the same time. It was considered that reduction of phosphorus in the water column that released from sediment when there was anoxic is attributed to the SRP adsorption to the sediment surface where become aerobic. At this time sediment is deficiency state of phosphorus because it is after releasing SRP, it was believed to adsorb SRP easily.
close to the theoretical value for both compounds, and almost all organic carbons in each solution were detectable by TOC equipment. On the other hand, the COD oxidation rate in both the saccharide and amino acid solutions decreased according to the increase in the solutions' concentration, and there were also significant differences in the decomposition rate in each compound. The relationship between field data on COD and TOC in Shinji and Nakaumi lakes may be approximated by a quadratic expression, but the approximated curve did not pass the original point.This result indicates that there are some organic compounds that can be decomposed by TOC equipment but not by COD analytical methods, and the decomposition of COD was insufficient in high concentrations in environmental water. Therefore, we consider COD not to be an appropriate indicator of the organic compounds in public waters;instead, TOC should be used.
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