A study was made on the primary production of Lake Changjamot during the spring season of 1973 by means of the oxygen method.
The stratification of temperature and dissolved oxygen were formed in May with the stratified structure of Phytoplankton. The range of Secchi disc transparency was from 0.8m to 2.3m during the nine months of this investigation, which was begun in January, 1973. The value was lowest in early June when the phytoplankton blooming reached the peak.
The concentration of PO_4-P, NH_3-N, NO_3-N and NO_2-N was reduced at the beginning of the phyoplankton blooming and increased again after May except PO_4-P. It might have been caused by the inflow of the nitrogenous fertilizer from the surrounding agricultural area since May when farming was started.
The total amount of chlorophyll-a in the entire water column varied from 25㎎/㎡ to 277㎎/㎡ from January till September with the maximum value occurring in early June. These values show a considerable eutrophication of the lake in comparison with the data obtained in 1969.
The daily gross production in the lake varied from a low of 655㎎ C/㎡ to a high of 2,859㎎ C/㎡ during the spring season and this corresponds to the variation of the amount of chlorophyll. The total amount of daily respiration varies from 650㎎ C/㎡ in winter to 2,307㎎ C/㎡ in late spring and exceeds gross primary production especially in late May showing the negative balance of daily production and consumption of organic material at that time.
In conclusion, Lake Changjamot is a fairly productive and a moderately autotrophic lake and has been eutrophicated much during the past four years.
|