Boyd Steven H.

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Steven H.

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  • Technical Report
    Limits of Nematoscelis megalops in the northwestern Atlantic in relation to Gulf Stream cold core rings. II, Physiological and biochemical effects of expatriation
    (Woods Hole Oceanographic Institution, 1979-01) Boyd, Steven H. ; Wiebe, Peter H. ; Cox, James L.
    Nematoscelis megalops, a cold water euphausiid commonly found in Northwestern Atlantic Slope Water, is frequently transported in the cores of Gulf Stream cyclonic rings into the Sargasso Sea. The inner core made of cold Slope Water gradually assumes physical and biological characteristics of the surrounding Sargasso Sea. These changes gradually lead to a localized extinction of this species in the core of the ring. Samples of N. megalops taken from the same ring at 6 and 9 months after its formation show a weakened physiological and biochemical condition. Deterioration of ring individuals is evidenced by an increase in body water content and a reduction in total body lipid, carbon, respiration rates, and nitrogen relative to Slope Water individuals. By 6 months it appears that ring N. megalops must supplement food intake by metabolizing some of their body protein and by 9 months they appear to use lipids as well. A shipboard starvation experiment involving 40 Slope Water individuals showed that physiological and biochemical states similar to those found in individuals from the 9 months old ring could be duplicated in 4 days of complete starvation.
  • Technical Report
    Limits of Nematoscelis megalops in the northwestern Atlantic in relation to Gulf Stream cold core rings. I, Horizontal and vertical distributions
    (Woods Hole Oceanographic Institution, 1979-01) Wiebe, Peter H. ; Boyd, Steven H.
    The hydrographic limit of the distribution of Nematoscelis megalops in the Northwestern Atlantic Ocean is usually marked by the abrupt changes in water properties across the Gulf Stream. There are, however, isolated but repeated occurrences of this species in the Sargasso Sea. In our study, individuals in the Sargasso Sea were expatriates from the Slope Water which had been transported to the collection site by Gulf Stream cold core rings with but two exceptions. The exceptional cases can be indirectly linked to the presence of rings. Expatriated populations do not persist. Extinction in a ring appears to take place in one or two generations, and for N. megalops it is related to changes in hydrographic properties, and in particular, the vertical temperature structure. Both in the Slope Water and in the ring 50% or more of the population is found in a restricted temperature regime centered about 10°C. As a ring ages, the preferred temperature regime and N. megalops along with it move deeper into the water column. The physiological and biochemical data given by Boyd, Wiebe and Cox (1978) combined with data given here indicate that withdrawal from the surface results in progressive deterioration of the nutritional condition of the population, a cessation of growth, a drastic reduction in the number of males relative to females, reproductive incapacitation, and ultimate extinction. It is conceivable that a process similar to that occurring in rings is responsible for the maintenance of the Gulf Stream as a hydrographic limit in the distribution of N. megalops.
  • Technical Report
    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
    (Woods Hole Oceanographic Institution, 1976-09) Wiebe, Peter H. ; Boyd, Steven H. ; Winget, Clifford L.
    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.