著者

Akira Ishikawa Yuta Takei Ken-Ichiro Ishii Mineo Yamaguchi

出版者

The Plankton Society of Japan, The Japanese Association of Benthology

雑誌

Plankton and Benthos Research (ISSN:18808247)

巻号頁・発行日

vol.17, no.4, pp.383-392, 2022-11-30 (Released:2022-11-30)

参考文献数

46

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The temporal changes in the behavior of vegetative cells and cysts of the noxious red tide flagellates Chattonella (C. antiqua and C. marina) were investigated in Ago Bay, central Japan, mainly in 2013. In this study, in situ germination flux (cells m−2 day−1) was measured in May, June, and October 2013, using a ‘plankton emergence trap/chamber (PET chamber)’. Vegetative cells occurred in April and increased from May, forming a bloom in July with cyst production, and subsequently decreased thereafter. This change in the occurrence of the vegetative cells was considered to be controlled primarily by temperature and secondarily by nutrients and biotic factors. The PET chamber experiment showed that cyst germination in May contributed largely to forming the initial vegetative population to initiate blooming. An experiment to elucidate the effect of storage temperature on the germinability of cysts in the sediment showed that newly produced cysts (immature dormant cysts) mature (acquire germinability) under low storage temperature (10°C) within at least one month, indicating that cysts need to experience a cold season in the sediment for their maturation. The PET chamber experiment conducted in October before a cold season also confirmed that cysts scarcely germinated from the cyst population, containing many immature dormant cysts, in the in situ sediment. However, these cysts could act as seeds to form the initial population of the subsequent bloom in the next season, since the cysts will mature by then. Consequently, Chattonella cysts were concluded to play crucial roles in the population dynamics.

著者

Ken-Ichiro Ishii Ryoma Kamikawa

出版者

日本プランクトン学会、日本ベントス学会

雑誌

Plankton and Benthos Research (ISSN:18808247)

巻号頁・発行日

vol.12, no.3, pp.164-170, 2017-08-22 (Released:2017-08-24)

参考文献数

42

被引用文献数

7

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The non-photosynthetic diatoms Nitzschia spp. are known to have evolved from photosynthetic species to heterotrophic species by the loss of photosynthesis. We investigated their ability to tolerate wide ranges of temperatures and salinities. Nitzschia spp. were capable of surviving or thriving even at 5°C and 35°C. In addition, these diatoms were also capable of surviving at salinities of 0.5 and 12.0, while thriving at those from 1.0 to 9.0. Such tolerance to a wide range of temperatures and salinities would allow these non-photosynthetic diatoms to thrive in mangrove estuaries, where environmental conditions often drastically fluctuate. Our experiments revealed that the growth rates of the non-photosynthetic diatoms were larger than those estimated based on cell volumes and temperature, suggesting that these non-photosynthetic diatoms may be an important group of organisms contributing to material circulation by growing heterotrophically in mangrove estuaries.