THE LAW OF THE MINIMUM IN THE SEA 207 



year, when the amount of nitrogen compounds in the water 

 is least, this foodstuff is in minimal proportion. 



What is the cause of the poverty of the warmer sea areas 

 in inorganic nitrogenous foodstuffs, and that of the relative 

 scarcity of these in the colder seas during the warmer months 

 of the year? It was suggested by Brandt 1 in 1899 that there 

 must be a considerable destruction of nitrogen compounds in 

 the sea, for they are continually being added to the latter by 

 drainage from the land, by electric discharges in the atmosphere, 

 and possibly to some extent by direct fixation of atmospheric 

 elementary nitrogen. The amount of this element which is 

 added to the sea in the course of a year in a large area such 

 as the North Sea and Baltic can be determined approximately, 

 as well as the amount of nitrogen, in the form of food fishes 

 and other animals, which is removed from this sea area in the 

 same period. When these values are compared, it is seen that 

 the nitrogen added to the sea is greatly in excess of that taken 

 from it. Some of the fixed compounds are therefore returned to 

 the atmosphere as elementary nitrogen. Now it has been known 

 for many years that there are bacteria on the land which can 

 break up nitrates, nitrites, and ammonia, and set free the ! nitrogen 

 in the elementary form. It was also suggested by Vernon 2 in 

 1898 that such denitrifying bacteria were also present in the 

 sea. But it was not until 1902 that the actual demonstration 

 of the presence and activities of these organisms was made 

 by Baur. 3 Gran 4 also wrote about them in 1902. Then Feitel 5 

 in 1903 made further investigations on the occurrence and 

 activities of these micro-organisms. 



Baur made use of a nutritive solution containing potassium 

 phosphate, magnesium sulphate, calcium chloride, magnesium 

 carbonate, ammonium sulphate, and sodium chloride to the 

 extent that this latter salt is present in the sea-water. This 



1 Brandt, " U. d. Stoffwechsel im Meere," Wiss. Meeresunters. Kiel. Komm. 

 Bd. 4, Abth. Kiel, 1899. 



2 Vernon, "The Relations between Marine Animals and Vegetable Life," 

 Mitth. Zool. Stat. Neapel, Bd. 13, 3 Heft, 1898. 



3 Baur, " u.d. zwei denitrificenden Bakterien aus der Ostsee," Wiss. Meeres- 

 unters. Kiel. Komm. Bd. 6, Abth. Kiel, 1902. 



4 Gran, " Studien u. Meeresbakterien ; I. Reduction von Nitraten u. Nitriten," 

 Bergens Museums Aar&og, Bergen, 1902. 



5 Feitel, " Beitrage zur Kenntniss denitrifizender Meeres Bakterien," Wiss. 

 Meeresunters. Kiel. Komm. Bd. 7, Abth. Kiel, 1903. 



