48 BROECKER 



TABLE 7 



CHANGES IN RATIO OF TOTAL CARBON AND ALKALINITY 

 AS DEEP WATER IS BROUGHT TO THE SURFACE 



*In micromoles. 



content. The equilibrium constant for that temperature (1800) demands that the 

 speciation in the water be as follows: 232 micromoles of bicarbonate, 10 

 micromoles of carbonate, and 3 micromoles of dissolved C0 2 gas (Table 7). The 

 first thing that happens to that water when it reaches the surface is that the 

 plants take up all the nitrogen and phosphorus and an appropriate amount of 

 carbon, leaving the water devoid of the nutrients and deficient in carbon. If 

 there were no calcium carbonate production along with that, then the 10% 

 removal of carbon would drop the carbon value by 10%. There is no alkalinity 

 change associated with the formation of organic tissue, and the equilibrium 

 constant would not change. From these parameters we could calculate the new 

 distribution of species. What we see is that the carbonate ion goes up by a factor 

 of 3 and the C0 2 content goes down by around a factor of 4. So if we were to 

 have a Strangelove revolution, which wiped out all life, the surface ocean would 

 then assume the chemistry of the deep sea (90% of the ocean). The deep sea has 

 the chemical composition near the oceanic average, and the thin layer of water 

 at the surface has a highly modified chemistry that is modified by the life cycles 

 of the organisms. Interestingly enough, because of organic removal, the CO2 

 content of surface ocean water is four times lower than it was in the upwelling 

 water. It follows, then, that the C0 2 content of our atmosphere is four times 

 lower than it would be in the absence of life. So we see life exerting a strong 

 influence on the C0 2 -content difference between these two reservoirs. When we 

 add to this the effect of calcium carbonate removal, we find the opposite effect. 

 When plants or animals manufacture calcium carbonate, they use not only 

 carbon but alkalinity as well. They take out two plus charges (as Ca 2+ ) per 

 carbon atom, and the alkalinity drops from 252 to 236. If we say that, for every 

 10 units of organic carbon that fall, 3 units of carbonate fall, we see that the 

 C0 2 partial pressure is three times lower than it is in the deep sea because of life. 



