188 DEEVEY 



any other sulfide, whereas fertilizer sulfate is enriched; the isotopic label does 

 not label biogenic sulfur unambiguously. The other source is in the original 

 figures for the sulfur in continental runoff, which mainly turn out 1 to have been 

 jotted down on foolscap by contemporaries of Sir Humphrey Davy. So far as 

 these can be brought up to date, they suggest (to Berner 24 ) that Europe and 

 North America have far more excess sulfur than the unindustrialized continents. 

 Nevertheless, Berner is among those who agree that there is a great deal of excess 

 sulfur in circulation and that most of it is biogenic. He argues, however, that the 

 biogenic fraction has been increasing in the Northern Hemisphere along with the 

 industrial fraction owing to excessive organic loading of the seas around Europe 

 and North America. 



Welcoming Berner to the Institute of Ecology, we note that an expansion of 

 anaerobic environments accelerates the rate of recycling of all elements whose 

 cycles involve a biological reduction step. Eutrophication is then a general 

 phenomenon, potentially affecting the entire biosphere. It makes little 

 difference, at least in the early stages of acceleration, whether the limiting 

 nutrient is seen as phosphorus, carbon, nitrogen, or sulfur. In a lake, excess 

 phosphorus accelerates carbon fixation, shifts the phytoplankton composition in 

 favor of nitrogen-fixing blue-green algae, promotes anaerobiosis in deep water, 

 and so accelerates the formation of ammonia and sulfide. On land, the excess 

 nitrate and sulfate in rainwater and the direct absorption of excess carbon and 

 sulfur dioxide can accelerate organic production and nitrogen fixation; and 

 excess nutrients exported to sea, whether or not they include particulate or 

 dissolved carbon compounds, will eventually eutrophicate the oceans too. 



I have now to remind myself that we do not know that the biosphere is 

 increasing. If it is, we can guess that it will not increase indefinitely, despite 

 accelerated recycling. Some one of the newly accelerated rates will become rate 

 limiting on the rest, although I for one have no idea which one it will be. 



In principle, these ideas are testable in a number of ways. Every quantitative 

 deduction I can think of — such as the prediction that emissions of carbon 

 monoxide and nitrous oxide from the ocean should be increasing — stumbles 

 over a gross inadequacy of analytical data. One set of predictions, having to do 

 with the fractionation of nitrogen isotopes in nature, I intend to test in my own 

 laboratory. You will doubtless think of others. Meanwhile, there is a sort of 

 historical postdiction, posed by Holser and Kaplan's data on 3 S in marine 

 sulfates, 25 that I find fascinating (Fig. 1). 



We have had to give up H. G. Thode's attractive idea, on the basis of a first 

 look at these data, that isotopic fractionation of sulfur began with the first living 

 organisms. Changes in the volume of the oceans might account for these 

 remarkable variations, but that idea always falls before the razor of William of 

 Occam, alias Karl Turekian. There could have been changes in the mean 

 temperature of the oceans, but, in the simple form hinted at by Hitchcock and 

 Wechsler, 1 a theory of temperature dependence seems to predict minimal 



