. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. AUTOTROPHIC FUNCTION IN Rll-TIA 139 ment, two worms ( and g) were run in their natural tubes in one chamber for 68 h. This experiment was started at °C without sulfide. After 6 h, sulfide was added continuously and 14 h later the animals showed net 2CO2 uptake (autotrophy). For the next 20 h the ef- fects of different sulfide concentrations on the fluxes of O2, 2H2S and 2CO2 were measured while maintaining O2 between 105 and 209 ^M (Fig. IB). After that time the temperature of the system was lowered to °C over
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. AUTOTROPHIC FUNCTION IN Rll-TIA 139 ment, two worms ( and g) were run in their natural tubes in one chamber for 68 h. This experiment was started at °C without sulfide. After 6 h, sulfide was added continuously and 14 h later the animals showed net 2CO2 uptake (autotrophy). For the next 20 h the ef- fects of different sulfide concentrations on the fluxes of O2, 2H2S and 2CO2 were measured while maintaining O2 between 105 and 209 ^M (Fig. IB). After that time the temperature of the system was lowered to °C over 2 h, and a similar set of measurements repeated at O2 concentrations between 72 and 211 nM during the next 24 h (Fig. 1A). The set of observations at °C started at 92 nAt 2H2S, decreased in steps to nM 2H2S, and then was then raised to 41-49 pM 2H:S for 6 h. As can be seen in Figure 1A, the lower 2H2S concentrations re- sulted in less uptake of 2CO2, and without added sulfide the 2CO2 balance was fully heterotrophic ( + /umoles 2CO2 g~'h~'). For the first three hours after the reintro- duction of sulfide, this balance remained heterotrophic (+ Mmoles 2CO2 g~'h~'. high point at 43 nM 2H2S in Fig. 1A), but autotrophy was reached in the next 3 h ( ' h~', at 49 ^/2H2S in Fig. 1A). The worms were then removed and their tubes replaced in the vessels. The tubes alone did not show significant 2CO2 flux (< /umole 2CO2 g ' worm h"') in the pres- ence of 130 ju/U 2H2S. When the worms were dissected after the experiment, S° was visible in their trophosomes. These data demonstrate that these worms were depen- dent on 2H2S levels greater than about 50 nM to break even on carbon flux and more than 90 nM was required for maximum uptake of 2CO2. They also show that the lag-time for changes in 2CO2 flux when 2H2S was re- moved was short, suggesting that use of stored S° was not quantitatively very important. In contrast, when sulfide was introduced
Size: 1877px × 1331px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
