JPR Advance Access originally published online on February 15, 2006
Journal of Plankton Research 2006 28(6):563-570; doi:10.1093/plankt/fbi141
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A new hydrostatic pressure apparatus for studies of marine zooplankton
Department of Ecological Engineering for Symbiosis, Faculty of Engineering, Soka University, Tangi-Cho, Hachioji, Tokyo 192-8577, Japan
* Corresponding Author: tyoshiki{at}soka.ac.jp
Received April 1, 2005; accepted in principle February 1, 2006; accepted for publication February 13, 2006; published online February 15, 2006
Communicating editor: R.P. Harris
A new design of hydrostatic pressure apparatus for studying marine zooplankton is described. Zooplankton occur throughout the water column and are exposed to a range of hydrostatic pressures throughout their lifetime. The hydrostatic pressure apparatus developed in this study makes it possible to (i) increase pressure gradually from 1 to 200 atm, (ii) prevent corrosion of the pressure chamber by introducing a specimen holder that separates the pressure chamber from the surrounding seawater, and (iii) observe a wide size range of zooplankton including eggs (100–10 000 µm size range). The new apparatus is useful for the study of mesozooplankton throughout their life history from egg to adult. The effects of hydrostatic pressure on the eggs of the calanoid copepod, Calanus sinicus, were examined using the new hydrostatic pressure apparatus. Hydrostatic pressure did not affect C. sinicus egg development time, but egg-hatching success decreased significantly with increasing pressure. Most of the nauplii that hatched under high-pressure conditions (10, 50, and 100 atm) were deformed. Eggs of C. sinicus did tolerate pressures of 10 atm. This implies that eggs would not survive if they did not hatch within the upper 100 m.