JpGU-AGU Joint Meeting 2020

Presentation information

[E] Poster

A (Atmospheric and Hydrospheric Sciences ) » A-OS Ocean Sciences & Ocean Environment

[A-OS24] Exploring new frontiers of oceanic mixing research in the next decade

convener:Toshiyuki Hibiya(Department of Earth and Planetary Science, Graduate School of Science, University of Tokyo), Ichiro Yasuda(Atmosphere and Ocean Research Institute, The University of Tokyo), Lakshmi Kantha(Aerospace Engineering Sciences, University of Colorado, Boulder, Colorado, USA)

[AOS24-P18] Variations in egg production rates of Calanus sinicus (Copepoda: Calanoida) estimated by gonad morphology

*Kiyotaka Hidaka1, Shinji Shimode2, Takashi Fushima2 (1.Japan Fisheries Research and Education Agency, 2.Yokohama National University)

Keywords:ocean mixing, copepoda, egg production, Calanus sinicus

Ocean mixing brings nutrients to surface layer, which in turn enhance phytoplankton production. Phytoplankton can increase in number and biomass in a short time by cell division, hence increase of cell abundance or chlorophyll concentration can be seen nearby the area of nutrient supply. In contrast, multicellular zooplankton, e.g. copepods, takes time to increase in number, as improvement of food condition brings increase in egg production first. It takes several days to weeks for the development of the eggs to the adults and thus biomass increase in multicellular zooplankton would occur away from the area of nutrient supply, which makes it difficult to be distinguished. Here, we developed a method to estimate egg production rate (EPR) of Calanus sinicus, one of the dominant copepods around Japan, based on the observation of gonad morphology. Niehoff and Runge (2003) first established the method for C. finmarchicus and EPR can be estimated without culture experiment. The method was applied to the time series sample collected around the Tosa Bay and we found the long-term fluctuation of the EPR of C. sinicus, which was different to its abundance fluctuation.