CARBON-DIOXIDE CONTENT OF SEA-WATER AT 

 TORTUGAS." 



By Roger C. Wells. 



INTRODUCTION AND SUMMARY OF RESULTS. 



It is generally considered that the carbon-dioxide content of sea- 

 water may be increased by accessions from the air, by animal life, 

 by the decay of organic matter in the sediments on the bottom or 

 elsewhere, by the solution of carbonate rocks, by the contributions of 

 rivers, and by gas vents beneath the sea. Although all rivers carry 

 carbon dioxide into the sea, most of them actually dilute the sea-water, 

 and should, therefore, as a matter of fact, not be classed as increasing 

 the concentration of the carbon dioxide in sea-water. On the other 

 hand, sea-water may lose carbon dioxide to the air, to plants, and in 

 the formation of carbonate rocks and the carbonaceous parts of 

 organisms. Mere evaporation and precipitation also alter the carbon- 

 dioxide concentration somewhat if other conditions remain un- 

 changed. It is obvious that the actual condition of the water at 

 any given time and place depends on a complex set of factors whose 

 evaluation requires many observations as well as a knowledge of the 

 previous history of the water, including information concerning the 

 currents, flora, fauna, and other agencies that may affect it. 



With the hope of gaining information on some of these points, the 

 writer has made determinations on sea- water from various localities, 

 which supplement to some extent the work of Schlosing (1880), 

 Dittmar (1884), Murray (1889), Fox (1909), McClendon (1918), 

 and Mayor (1919). 



Determinations were made at Tortugas, Florida, in June 1919,' on 

 water taken directly from the sea at various points about Loggerhead 

 Key, which reveal unmistakable diurnal variations, first noted by 

 McClendon in 1916.'^ The water has sufficient contact with plants 

 and sea-weeds to show the effect of photosynthesis on its CO2 content. 

 There is a loss of CO2 by day and a gain by night. The respiration of 

 the animals is not sufficient to keep the equilibrium steady during the 

 day. It is impossible to say to what extent the balance is maintained 

 by the atmosphere, but in this locality, at least, where the water is 



' Published by permission of the Director, United States Geological Survey. 



» Carnegie Inst. Wash. Year Book for 1919, p. 195. 



• Carnegie Inst. Wash. Publication No. 252, p. 216 (1918). 



