ZOOLOGY 



MARINE ZOOLOGY 



THE marine fauna of Norfolk, as of East Anglia in general, 

 presents several distinctive features of interest, in comparison 

 with the fauna of other parts of the British coasts. The 

 shore and sea bottom have an unusually uniform character, 

 while the sea in this region is subject to an exceptional annual range of 

 temperature. These two factors exert a marked influence in determining 

 the character of the local fauna, both by limiting the number of common 

 North Sea species fitted to live under these conditions, and by favouring 

 the development of certain species to an unusual degree. 



The basin of the North Sea is geologically a great bight of the 

 Norwegian Sea, and the great mass of its waters is still derived by tidal 

 and drift currents from the northward, mixed with the cold waters which 

 escape from the Baltic in spring after the melting of the winter ice and 

 snow, and to some extent with the warm waters of the English Channel. 

 The general North Sea fauna is, however, modified on the Norfolk 

 coast by the shallowness of the bottom in the adjacent region of the 

 North Sea. The North Sea is in fact cut obliquely into two portions by 

 the Dogger Bank and its extensions towards the Yorkshire coast in the 

 west and towards the Danish promontory in the north-east. This line, 

 which may be called the Dogger ridge, separates a northern deep region 

 (from 30 to 100 fathoms deep) from a southern shallow region, every- 

 where less than 30 fathoms in depth. The trough of the deeper region is 

 filled in summer with cold water, the temperature of which, in the height 

 of summer, may be 1 2° or 1 3° F. less than that of the surface water in 

 the same region, and even 15° or 16° F. below that of the water south 

 of the Dogger. The presence of this underlying mass of cold water 

 serves to moderate the temperature of the surface and coastal waters 

 north of the Dogger, while the absence of such a layer south of the 

 Dogger subjects the sea in this region to greater seasonal alternations of 

 warmth and cold. The shallow shelving shores of East Anglia intensify 

 this effect by exposing the coastal waters to the full influence of winter 

 frosts and summer heat. 



Thus it results that the water along the coast of East Anglia is 

 colder in midwinter and hotter in midsummer than along any equal 

 stretch of coast in the British Isles. This feature must be a most im- 

 portant factor in the physical conditions which determine the peculiar- 



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