470 BULLETIN OF THE BUREAU OF FISHERIES 



the Kennebec only about 0.3 part of combined nitrogen per million at Augusta 

 (Whipple, 1907, p. 182). Perhaps 0.5 part per million would be a fair average for all 

 the rivers emptying into the gulf — that is, only about one-fourth to one-fifth as rich 

 as Rhine water. Nevertheless, this is a considerably higher concentration of total 

 nitrogen than Raben (1905a and 1910) found in the sea water of the North Sea, 

 where it ranged from 0.110 to 0.378 part per million, or in the Baltic (0.105 to 0.247 

 part per million). With a total annual runoff of not less than twenty-five hundred 

 billion cubic feet of water from the rivers and streams that drain the watershed of 

 the gulf, the latter must yearly receive at least 39,857 tons of nitrogen fixed in com- 

 binations readily assimilable by plants. This, roughly, is one-tenth the amount 

 (383,000 tons) given by Johnstone (1908, p. 282) for the North Sea from Brandt's 

 (1S99) oft-quoted calculation of the nitrogen discharged by the Rhine. But the area 

 of the Gulf of Maine, as inclosed by a line Cape Cod-Cape Sable, is only about one- 

 fifth that of the North Sea, hence its river waters contribute at least half as much of 

 nitrogen compounds yearly per unit of sea area as do those of the North Sea, and 

 very likely more than half, for the other rivers that drain into the North Sea may 

 not carry as heavy a load of nitrogen as does the Rhine. 



Whipple s (1907) analyses of the water of the Kennebec, which may be taken 

 as typical of the rivers tributary to the gulf, may not prove a definite seasonal 

 periodicity in the concentration of dissolved total nitrogen, the range being from 

 0.24 to 0.49 part per million of water for the months of January, March, April, May, 

 June, and August; but the highest concentrations (0.487 and 0.327) were in March 

 and April, just when the total outflow is swelling with the spring freshets. Therefore 

 it is safe to assume that the land drainage that empties into the gulf is at least as 

 rich in nitrogen in spring, when the discharge from the rivers is at its maximum, 

 as it is during the rest of the year, if not actually richer, as the analyses suggest. 

 With the concentration of dissolved nitrogen compounds probably at least twice as 

 high in river water as in the sea water of the gulf, the freshening of the latter, which is 

 caused in spring by river freshets, is probably accompanied by a considerable in- 

 crease in the concentration of nitrogen in the coastal zone over the values obtaining 

 there in winter, with the alteration greatest near the mouths of the larger rivers and 

 along the zones where their discharges have the greatest effect on salinity. 



Although the decomposition of dead animals and plants in the sea does not 

 actually add anything to the store of nitrogen preexisting in the water, simply trans- 

 forming it from one form to another, it must constantly be making available for the 

 use of the pbytoplankton large amounts of this foodstuff that was previously bound 

 up in other organic forms 82 — that is, in the bodies of animals and in attached plants, 

 such as eelgrass (Zostera) and the larger algae; and great though the amount of 

 nitrogenous fertilizer brought down to the Gulf of Maine by its affluent rivers is, 

 this source may rival it. 



As every seaside farmer knows, eelgrass (Zostera) rots much more slowly than do 

 the various algae such as the "rock weeds" (Fucaceae) and "kelps" (Laminariae) 



s! Johnstone (1908) gives an interesting chapter on the circulation of nitrogen. 



