— 7 APPENDIX D: BRANDT 



compounds occurring in the waters of the North Sea and Baltic. 44 samples of surface- 

 water from the North Sea and Baltic contained on an average 0-08 mgr. of nitrogen 

 pr. liter in the form of ammonia, and 0189 mgr. of nitrogen in the form of nitrites and 

 nitrates, altogether 0'279 parts of fixed nitrogen in a million parts of water. 



In the investigations of Raben so far published, a difference according to the seasons 

 of the year is not clearly marked. We should expect, however, from general considerations, 

 that the nitrates especially, which are the most important, would show a regular decrease 

 or increase according to the seasons of the year. In the analyses made by Dr. Raben 

 of the water-samples collected in 1904, such a difference appears very clearly both in the 

 Baltic and in the North Sea, as is shown in the averages below. The number of the 

 various samples analysed is given in brackets. 



1 liter of surface-water from the open Baltic. 



Nitrogen as ammonia Nitrogen as nitrites and nitrates 



February (13) 0-068 mgr. 0-199 mgr. 



May (13) 0-Ü65 « 0-170 " 



August (13) 0-057 » 0-095 .. 



1 liter of surface-water from the open North Sea 



Nitrogen as ammonia Nitrogen as nitrites and nitrates 



February (12) 0-063 mgr. 0-216 mgr. 



May (15) 0-065 » 0-217 » 



August (13) 0-061 . 0-079 « 



It is of great interest, on the one hand, to see the agreement of the values for February 

 and May, and on the other hand, the very small amount of nitrates dining August, both 

 for the Baltic and North Sea. The great diminution in the nitrates and nitrites during 

 the warm period of the year 1904, 1 consider to stand in relation to the great decomposition 

 of the nitrates and nitrites by the so-called denitrifying bacteria, which are more active 

 in warmer than in colder water. 



Investigations are in progress at present, with the aim of reducing as much as possible 

 the size of the error still occurring, though closely determined, in the quantitative deter- 

 mination of nitrogen compounds. At the same time, it is also being determined why 

 and from what circumstances. Dr. Feitel and I obtained different results in our direct 

 examination of freshly obtained samples from Stettin harbour and mill-water in August 1904, 

 from those obtained by Dr. Raben, who examined thoroughly, some weeks later, sterilised 

 samples from the same regions. 



From the determinations of Raben, we may assess the average content of the water 

 of the North Sea and Baltic in organic nitrogen compounds, at 0-2 parts at least in 1,000,000 

 parts of water. The question is now, if this amount is sufficient to explain the quantity 

 of albuminous nitrogen in marine organisms. Earlier investigations ' have shown that 

 1,000,000 parts of sea-water from Kiel Bay contain on an average only 0-03 parts (0-0097 — 0-052) 

 of albuminous nitrogen. Consequently, about 7 times as much inorganic a's organic 



' K. Brandt, Beiträge zur Kenntnis der chemisclien Zusammensetzung des Planktons (Wiss. Meeresunt. 

 Bd. 3. Kiel 1898). Derselbe, Ueber die Bedeutung der SUckston'verbinduiigeii für die Prdduklioii im Meere 

 (Beihefte z. Botaii. Centralbl. XIV. 1904). 



