Ecosystem studies in the Indian Ocean sector of the Southern Ocean undertaken by the training vessel Umitaka-maru

This special issue provides an overview of the ten voyages undertaken by the Umitaka-maru from the austral summers of 2002/2003 to 2014/2015 to promote the next phase of study of the ecosystems in the Indian Ocean sector of the Southern Ocean. The voyages by the Umitaka-maru have mainly targeted three areas in the Indian Ocean sector: off Dumont d'Urville Base (France, 140°E transect), off Casey Station (Australia, 110°E transect), and off Syowa Station (Japan, north of Lützow Holm Bay). The findings of Umitaka-maru's research on the krill-independent food web, animal assemblages, community structure and distribution patterns from the epipelagic to the deeper waters provide invaluable information for elucidating the material cycle and predicting future ecosystem changes. Further studies on assessing the influence of sea ice on food webs in the water column are required, which will provide crucial information for predicting ecosystem changes as a result of projected sea ice changes in the near future.