Characterization of the primary productivity using a year-long high resolution sediment trap experiment in the southwestern part of the East/Japan Sea

Abstract

The southwestern East/Japan Sea is one of the worlds most productive fishing grounds that is readily visible from the space born satellites day-night band due to bright lights emitted from dense assemblage of fishing fleet. Traps were deployed to collect sinking particles in the depths of 1,020 m and 2,100 m at the inter-plain gap between Ulleung and Dok islands (37°25.77′N, 132°30.27′E, 2300 m) in 1999 with shorter than 10 days sampling interval. The water temperature and current at 350 m depth using RCM 7 at the site adjacent to the sediment trap mooring site were also utilized to aid our data analysis. This high resolution temporal observations showed many important characteristics related to the productivity of the southwestern East/Japan Sea: 1) Ulleung Warm Eddy enhanced primary productivity as evidenced by a simultaneous variation in water temperature at 100 m and particulate organic carbon fluxes at 1,020 m depth. 2) Siliceous phytoplankton species dominated spring and autumn blooms. The ratio of biogenic silica flux to particulate organic carbon flux increased during these two seasons 3) Calcareous productivity was observed during August when surface water temperature was the highest when the ratio of calcium flux to aluminum flux peaked its maximum 4) Small sized primary producers such as nano- or pico- plankton dominated in summer. Dissolution of sinking particulate organic carbon appearedeployed to collect sinking particles in the depths of 1,020 m and 2,100 m at the inter-plain gap between Ulleung and Dok islands (37°25.77′N, 132°30.27′E, 2300 m) in 1999 with shorter than 10 days sampling interval. The water temperature and current at 350 m depth using RCM 7 at the site adjacent to the sediment trap mooring site were also utilized to aid our data analysis. This high resolution temporal observations showed many important characteristics related to the productivity of the southwestern East/Japan Sea: 1) Ulleung Warm Eddy enhanced primary productivity as evidenced by a simultaneous variation in water temperature at 100 m and particulate organic carbon fluxes at 1,020 m depth. 2) Siliceous phytoplankton species dominated spring and autumn blooms. The ratio of biogenic silica flux to particulate organic carbon flux increased during these two seasons 3) Calcareous productivity was observed during August when surface water temperature was the highest when the ratio of calcium flux to aluminum flux peaked its maximum 4) Small sized primary producers such as nano- or pico- plankton dominated in summer. Dissolution of sinking particulate organic carbon appeared