Vertical Flux Profiles of Particulate Material in the Sea of Sanriku

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Abstract
Sinking particulate material was collected directly using a particule collector system in the sea area off Sanriku (Japan) in June 1977 and May 1978. A series of collectors were set for a day at the depth range of 50-500 m along a suspension rope hung from a surface buoy system. Many particles collected were visible to the naked eye; microscopic observations revealed that > 90% of the particles above 125 .mu.m in diameter were either fresh fecal pellets of zooplankton or disintegrated loose clumps of possible fecal origin. These particles contained many skeletal remains, e.g., of diatoms. The maximum vertical flux of the sinking particles obtained in 1978 was 418 mg C m-2 d-1 [day] at 100 m. This corresponds to about 1/3 the daily primary production in the euphotic layer above. Below 100 m, the downward flux gradually diminished to a level of 300 mg C m-2 d-1 at 250 m. A sharp decrease was found between 250-400 m; the particulate flux was 28 mg C m-2 d-1 at 500 m. This profile is very different from the vertical variation in particulate organic C simultaneously observed, the latter having a sharp peak at the depth of 50 m. This indicates that sinking particles such as fecal pellets constitute most of the downward flux of materials and that the real flux of material is different both in quantity and quality from the conventional estimates based on observed C concentrations.