摘要
The extracellular dissolved organic, carbon (DOC) and algal cell particlutate organiccarbon (POC) of a marine nanoplanktonic diatom Chaetoceros sp. were determined in this study. Thedaily rhythm and the influence of light and temperature on the production rate of DOC and POC were stud-ied by growing the diatom under different laboratory controlled conditions of light and temperature. Theresults showed that the production of DOC and POC varied with light and temperature and were generallyhigher at daytime than at night. Under culture conditions of 24L:0D light cycle and 3500 lx light intensi-ty, the DOC and POC reached maximum (DOC: 17. 27 mgC/L; POC: 103. 10 mgC/L). While
The extracellular dissolved organic carbon (DOC) and algal cell particJuiate organic
carbon (POC) of a marine nanoplanktonic diatom Chaetoceros sp. were determined in this study. The daily rhythm and the influence of light and temperature on the production rate of DOC and POC were studied by growing the diatom under different laboratory controlled conditions of light and temperature. The results showed that the production of DOC and POC varied with light and temperature and were generally higher at daytime than at night. Under culture conditions of 24L:0D light cycle and 3500 Ix light intensity, the DOC and POC reached maximum (DOC: 17.27 mgC/L; POC: 103.10 mgC/L). While without light, they kept decreasing (DOC: 7.16 - 9 .05 mgC/L; POC: 37.71 - 51 .14 mgC/L) . DOC and POC increased with temperature within the range of 16℃ to 30C℃(DOC: 7.45 - 12.66 mgC/L; POC: 28.52 -97.05 mgC/L), and reached relatively higher value when the temperature was 25℃ to 30℃ . It was found that generally about 10% - 25% of the photosynthetic organic carbon was excreted into the culture solution as DOC. The relationship between the diatom biomass and the production rate of DOC and POC was also studied. Our results suggested that absolute production of DOC and POC was nearly linear with diatom biomass expressed either as cell density or as dried weight and had similar time-course tendency under diverse levels of light intensity and temperature. In general, we suggest that optimal environmental conditions for diatom growth and biomass increase will facilitate the increase of absolute production of POC and DOC. On the other hand, extreme environmental conditions are responsible for the high percentage of DOC excretion although the absolute value of DOC is low.
基金
This work was supported by the MEE Key Laboratory of Ministry of Education,Xiamen University(Grant No.MEE9903)and by Ministry of Education Foundation for University Key Teacher
