Abstract
To clarify the occurrence of upwelling and its effect on primary production in Shimanto
Canyon of western Tosa Bay, the vertical distributions of nutrients and chlorophyll a were
investigated seasonally in 2010. Maximum nutrient concentrations during each survey occurred
at the bottom layer in Shimanto Canyon. The vertical distribution of nutrients showed that
upwelling of the nutrient-rich deep waters of the sea bottom to the upper layers occurred only in
August. Simultaneously, the sharp chlorophyll a maximum, being the annual highest value,
appeared in the subsurface layer on the rim of Shimanto Canyon when the Kuroshio Current
flowed near the shore. This suggests that the upwelling occurrence in Shimanto Canyon is related
to the Kuroshio Current path, which plays an important role in supplying nutrient-rich waters of
the submarine canyon to the euphotic zone.
