水温および日長が海産珪藻の発芽・復活および増殖に与える影響

抄録

In Hakozaki Harbor, Hakata Bay, Japan, diatoms bloom from June to August and decline from November to January, as typical cases of other temperate coastal waters. From November to January, nutrients tend to be sufficient levels for the diatom growth, although water temperature and photoperiod in this winter time decrease to the levels assumed to inhibit the growth and the abilities of germination/rejuvenation of diatoms. To clarify the effects of such lowering temperature and/or a short photoperiod in winter time, combinations of water temperature (25˚C, 15˚C)and photoperiods (14h L : 10h D, 11h L : 13h D) were examined on the growth of Skeletonema marinoi-dohrnii complex and germination/rejuvenation of several diatom species in the laboratory. The growth of S. marinoi-dohrnii complex under the low temperature and the short photoperiod condition (15˚C, 11h L : 13h D) was slightly lower than that under the high temperature and the long photoperiod condition (25˚C, 14h L : 10h D). On the contrary, germination/rejuvenation of the diatoms such as genus Skeletonema, Chaetoceros, and Thalassiosira were remarkably inhibited under low temperature and short photoperiod condition. These results suggest that the key mechanisms of diatoms decrease from November to January are most likely attributed to inhibition of germination/rejuvenation abilities under combination of low water temperature and a short photoperiod.