Particulate matter sinking to the deep-sea floor at 2000 M in the Tongue of the Ocean, Bahamas, with a description of a new sedimentation trap

Abstract

A sedimentation trap for use just above the deep-sea floor was free-fallen to a depth of 2050 m in the Tongue of the Ocean canyon on January 3, 1974. On March 6, it was successfully recovered with the assistance of D.S.R.V. Alvin. The trap has a base 1 m square and a height of 30 cm. At the trap bottom are filters to retain falling particles. Two spring-powered sliding doors, each 1 m x 0.5 m, are used to close off the lower 2 cm of the trap during ascent to prevent disturbance of the particles collected on the filters. Total carbon on the filters as determined by high temperature combustion averaged 2301 mgC/m2 or an average on a daily basis of 36.5 mgC/m2. Similar filter aliquots were treated with cold phosphoric acid to eliminate the inorganic fraction. The resulting carbon values (X =: 5.7 mgC/m2/day) suggest 14% of the total carbon reaching the sea floor at 2000 m in this area is organic in origin. Fecal material is one readily identifiable component of the material contributing to the organic fraction. Counts of fecal pellets resulted in an estimate of an average of ~650 pellets/m2/day. Average pellet length was 241 μm and diameter was 109 μm. In laboratory experiments the pellets sank at rates varying from 50 m/day to 941 m/day (X at 5°C =159 m/day). Comparison of the sedimentation trap estimates of organic carbon input to the sea floor in this area with benthic energy requirements indicates that rapidly sinking small particulate matter could supply approximately 14% of the metabolic requirements of the benthos.