1903] Studier over naturforholdene i vestlandske fjorde. 47 



exception for that part of the coast where the animal downfall is 

 1000 mm. or more, — in other words, about up to Lofoten. 



The downfall as a factor in the biology of the flords. 



It is clear, from what has already been said, that the downfall 

 plays an important part in the distribution of heat in the fiords. 



In the winter of 1899, when observations were being made in 

 the northern fiords of Norway, it happened occasionally that tem- 

 perature and salinity were found to be almost constant from the 

 surface to the bottom. At such places it was possible to demonstrate 

 a considerable loss of heat in the course of the winter, and this 

 exerted an influence to a considerable depth. Nothing corresponding 

 has been noticed in the south-west fiords, and can scarcely occur, 

 for the downfall on the west coast is too great. 



But on account of the comparatively little fall in the counties 

 (amter) of Tromsø and Finmark, the fiords there will have a more 

 even salinity, and consequently the winter cold will exert an in- 

 fluence a good way down. One will, for instance, at a depth of 

 200 m. find that temperature is less than the annual average one 

 for the place, ancl the variations in temperature may be quite con- 

 siderable. 



There is reason to believe, that the penetration of the winter 

 cold towards the depth, has a destructive influence on most of the 

 boreal and lusitanian species of animals; while, on the other hand, 

 it seems likely that the great fall which descends on western Norway 

 has a beneficial influence on the life of southern species. 



If it be the case, that the different distribution of the down- 

 fall exercises a great influence on temperature and salinity, not only 

 on the surface but also on deeper layers of water, then it is also 

 evident that the downfall is an important factor in the biology of 

 the fiords. And changes in the amount of the rain, snow and 

 hail which falls at a given place will, without doubt, bring forth 

 changes in the marine fauna and flora. 



Lyse Fiord and Mo Fiord. 



These two fiords have many points of resemblance, and the 

 divergences in them may be accounted for by the fact that the Mo 

 Fiord has a much more shallow opening than the Lyse Fiord. 



Of such divergences, the following may be mentioned: — 



