科研之友
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摘要
The cause of a significant Coscinodiscus wailesii bloom that occurred in October 2013 at the eastern part of the Seto Inland Sea was investigated. C. wailesii is a harmful species that causes serious damage to Nori (Pyropia) culture. This bloom had seldom been observed since 1990, which was thought to be the result of the gradual decrease in nutrient concentrations in this area after 1970 and in particular, a decrease in dissolved inorganic nitrogen concentration after 1990. However, a large C. wailesii bloom occurred in October 2013, just after vertical mixing of the water column. At that time, nutrient concentrations of bottom water suddenly decreased, but those of surface water did not increase. This was probably due to the consumption of nutrients by the C. wailesii bloom. In September 2013, one month prior to its bloom, both rainfall and solar irradiance were particularly high. Moreover, the euphotic zone depth was notably deeper. It was thought that the large C. wailesii bloom was due to the combination of sufficient nutrient supply, sufficient light irradiation and deeper euphotic zone in the vertical mixing period. Our results suggested that the recurrence of these factors could cause C. wailesii bloom to occur again even under a low nutrient situation.
- 出版日期2015
