京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第22787号 / 農博第2430号 / 新制||農||1081(附属図書館) / 学位論文||R2||N5307(農学部図書室) / 京都大学大学院農学研究科森林科学専攻 / (主査)教授 井鷺 裕司, 教授 森 直樹, 准教授 大澤 直哉 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

Copepod species are distributed throughout the ocean by many factors, including chemical, biological, and physical effects. Turbulence in the ocean has been suggested as a factor that vertically partitions some species of copepod. Copepods may seek calmer waters by sinking to deeper levels as the surface waters become more turbulent, or may maintain their position in turbulent waters. The goal of this study is to determine the behavioral effects of turbulence on three species of copepod, Calanus finmarchicus, Acartia tonsa, and Temora longicornis. Experiments consisted of exposing each of the species to stagnant water plus four levels of turbulence intensity. The experiments were conducted in a laboratory apparatus that mimics oceanic turbulence. The turbulence characteristics have been previously characterized by particle image velocimetry (PIV), that show the turbulence to be nearly isotropic and homogeneous in the observation region. Behavior responses were quantified via several measures, including the number of animals phototactically aggregating per minute, the number of escape events, the swimming speed, and the net-to-gross-displacement ratio. There are important conclusions about the effect of laboratory turbulence on copepods. The size of the copepod has a significant effect on its aggregation and swimming capability with increasing turbulence. The smaller copepods had less ability to overcome a strong flow field, and they were more likely to be advected by the stronger flow fields. Swim style also can influence how a copepod reacts to increased turbulence. If the copepod is a hop and sink traveler, then the copepod continues to hop and sink more than its cruising counterparts as turbulence increases. The cruise and sink travelers did not alter the number of escapes in response to turbulence.