Expectations for the future

　This study revealed that although the two carnivorous copepod species that dominate the zooplankton fauna have the same timing of reproduction, the subsequent growth rate and mode of reproduction differ significantly among the species. Both species reproduced during the polar night, which is conventionally considered a time of low biological production due to the lack of sunlight. The results of this study indicate that the polar night in the Arctic Ocean is more biologically active than previously thought. Although the reproductive timing of both species is the same, the subsequent growth rates of the two species differ significantly. In the Arctic marine ecosystem, carnivorous copepods not only feed on fish, which are higher-order predators, but also prey on early-stage individuals of larger particle-eating copepods, playing an important role in the material cycle in the marine lower-order ecosystem. Therefore, which of these carnivorous copepods adapts and increases its population in response to future changes in the marine environment will determine how the material cycle within the lower marine ecosystem will change. The present study is positioned to clarify the ecology of zooplankton in the past environment, which is important as a control material for the current changing environment. 

　Through the results of this research, we can expect to be able to assess future changes in the marine ecosystem in the Arctic Ocean.