| Summary: | 碩士 === 國立東華大學 === 海洋生物多樣性及演化研究所 === 99 === Filamentous blue-green algae, Nostoc flagelliforme was tested for the presence of ultraviolet-absorbing mycosporine-like amino acids (MAAs). The aims of this study were to investigate the effects of long term exposure of different UVB intensities and salinity on chlorophyll a, MAAs both inside the cell and in culture medium, respectively. Results of chlorophyll a indicated that exposure to UVB irradiation and 20 mM NaCl enhanced the growth of N. flagelliforme, but in 260 mM NaCl, growth was inhibited. The increment of algal MAAs was proportional to the increment of UVB intensity and salinity. Releasing of MAAs in culture medium increased with the increasing of salinity, but not with UVB. Results of different concentrations of algae exposed to UVB revealed that higher concentration of N. flagelliforme adapted better to the irradiation. In low salinity, higher exposure of UVB increased growth in N. flagelliforme, but not under high salinity, which suggested that salinity was the main cause of the increment of chlorophyll a in N. flagelliforme. Synthesizing of MAAs in N. flagelliforme was the highest under simultaneous high UVB radiation and high salinity. Under different photoperiod with the irradiation of UVB resulted in less chlorophyll a and algal MAAs, but higher MAAs in the medium when exposed to 24 hr of light. It showed that the longer N. flagelliforme was exposed to the light, the more inhibition was on the growth, but at the same time it helped in releasing MAAs.
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