著者

Shinji Shimode Takafumi Yamaguchi Kiyotaka Hidaka

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.3, pp.301-311, 2022-08-30 (Released:2022-08-30)

参考文献数

41

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Calanus sinicus is one of the most dominant planktonic copepods and plays a key role as a secondary producer in the mid-latitude coastal shelf areas of the Northwestern Pacific. In this study, we investigated seasonal changes in in situ egg production rate (EPR) of C. sinicus collected from March 2014 to February 2015 in Sagami Bay, Japan. Simultaneously, we collected formalin-preserved samples to measure reproductive index (RI), which was calculated as the proportion of individuals with matured gonad to total females in each sample. Monthly averages of EPR and RI varied from 2.4 to 44.9 eggs female−1 day−1 and 0% to 75.9%, respectively. RI showed a significant positive effect on EPR. Moreover, EPR decreased with increasing temperature, which was the inverse of the effect of temperature on EPR reported in a previous study in the Seto Inland Sea. The difference between the studies suggests that the local population may adapt to different temperature environments in each location. Using a stepwise multiple regression model, EPR estimates for C. sinicus in Sagami Bay were explained by the average water temperature and RI with high probability (R2=0.71). Although local water temperature ranges must be considered before applying our model to other areas, the model would be useful to reconstruct past secondary production of C. sinicus from preserved samples collected in other neighboring coastal areas.

著者

Taketoshi Kodama Kazutaka Takahashi Ken-ichi Nakamura Shinji Shimode Takafumi Yamaguchi Tadafumi Ichikawa

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.10, no.1, pp.75-79, 2015-03-25 (Released:2015-03-20)

参考文献数

25

被引用文献数

1 4

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Short-term variation in the ammonium excretion rate by Calanus sinicus during the post-capture period was evaluated in 1-h incubations. Incubation water volume (13 mL vs. 100 mL) did not significantly affect the excretion rate, and the overall mean excretion rate of C. sinicus was similar to reported values from congeneric species. However, the 24-h variations in the excretion rate denoted that acclimation stress decreased the excretion rates 1–2 h after introduction to a no-food condition. The effect of presence/absence of food was not significant up to 24 h after capture.