Papers in Marine Biology and Oceanography, Suppl. to vol. 3 of Deep-Sea Research, pp. 212-223. 



Hypotheses connecting fluctuations in Arctic climate with biological 



productivity of the English Channel 



By L. H. N. Cooper 

 Marine Biological Laboratory, Plymouth, England 



Summary — An explanation of variations in nutrient content and biological productivity in the 

 English Channel in the last thirty-five years has been sought in terms of variations in Arctic climate. 

 To provide the connecting links a series of interlocking hypotheses has been erected. These are 

 summarized in the discussion. 



For many years at Plymouth we have been concerned with the large variations in the 

 phosphorus available for growth of plants and animals as represented by the amount 

 of phosphate present at the midwinter maximum (Fig. 1). This was high during the 

 nineteen-twenties, fell to a little more than half during the nineteen-thirties and forties, 

 and is now tending to increase again. There have been large associated changes in the 

 abundance and nature of the zooplankton in the English Channel. 



Fig. 1. Annual variations in inorganic phosphate available for plant growth at a position in the 

 English Channel, 22 miles south-west of Plymouth, as measured at the winter maxima. In 1922 and 

 1923 the maxima were probably missed; they were probably greater than shown. 



For some years we sought an understanding from studies on the continental shelf 

 within 200 miles of Plymouth (the Celtic Sea) and found none. The next step was to 

 examine the conditions over the continental slope of the Celtic Sea (Cooper, 1952 b). 

 Upwelling on the scale which occurs along the coasts of California, Peru and South- 

 west Africa has never been recognized, since the prevaiUng winds are unfavourable 



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