COUNCIL — SEPT. 1910 — APPEND. E — 78 — 



inorganic nitrogen compouuds in sea-water and explained the importance of such 

 investigations for comprehension of the metabolism of the sea. 



Approximately 400 samples of North Sea and Baltic water which had been 

 collected on the seasonal cruises of the years 1904—06 had been examined by Dr. Raben 

 of Kiel with regard to their ammonia, nitrite and nitrate contents. Further, his 

 methods had also been used in Kiel for the similar examination of about 200 

 samples from the 3 oceans, the Antarctic, Mediterranean etc. The ammonia is 

 apparently but little different everywhere and at all times, amounting to about 

 0.06 mgr. per litre of sea-water. On the other hand, the amount of the nitrites -|- 

 nitrates, which varies between 0.06 and about 0.5 mgr. per litre, shows a distinct 

 dependence on the temperature. This is most clearly seen when we calculate for 

 the open ocean the average amount of nitrites and nitrates for each degree of 

 temperature and further for the temperature intervals 0° — 5°, 5° — 10° and so on. 

 This dependence of the amount of nitrites and nitrates on the temperature can 

 only be indirect, and arises from the fact that the growth of the everywhere 

 occurring bacteria is favoured by warmth, so that their disturbing activity increases 

 with the rise of temperature. 



This dependence can also be seen in the North Sea and Baltic on arranging 

 the samples in series according to the temperature, but in these shallow regions 

 of the sea, where the influence of the coast is so considerable, the differences in 

 the amount of nitrites and nitrates at low and high temperatures are not so great 

 as in the open ocean, and they are least in the Baltic. Comparing the averages 

 from the 4 seasons of the 3 years investigated we find, that the cruises of February 

 and May gave higher values than those of August and November. That the values 

 are lower in November than in the warmer August can be understood, when we 

 remember that in the warmer period of the year the denitrifying bacteria have so 

 greatly increased in number that even on the temperature decreasing they can 

 still further reduce the amount of nitrites and nitrates in spite of a gradual slacking- 

 off in their activity. In winter the temperature falls so far that the denitrifying 

 bacteria are scarcely active any longer. Then an increase in the amount of nitrites 

 and nitrates again takes place by means of other bacteria — either nitrogen- 

 producing or nitrogen-collecting bacteria. The optimum for these bacteria, which 

 increase the amount of the nitrites and nitrates, lies in all probability between 5° 

 and 7°, both in the open ocean and in our home waters. 



H. M. Kyle 



