SECT. 4] GEOGRAPHIC VARIATIONS IN PRODUCTIVITY 361 



thermal gradient persisted throughout the year. This had a pronounced effect 

 upon the rates of organic production, which never attained values in these two 

 years as high as in 1958. Although analyses of data were not completed at the 

 time of this writing, it is clear that climatic variability causes considerable 

 year-to-year fluctuations in the seasonal pattern and the total annual primary 

 production of this region. 



C. Temperate and Sub-polar Waters 



As is true of productivity studies elsewhere in the world, most of those 

 conducted in temperate and sub-polar seas have been made as a part of general 

 oceanographic surveys of specific areas during restricted and often brief 

 periods of the year. The lack of data on a seasonal or annual basis need not, of 

 course, detract from the values of such investigations, most of which were 

 carried out for purposes quite outside the objectives of this discussion. How- 

 ever, the seasonal variability of primary production in this part of the ocean is 

 so great that regional comparisons, beyond the scope of the immediate in- 

 vestigation, are meaningless without knowledge of the cycle of production 

 throughout at least one and, preferably, several years. Therefore, two investiga- 

 tions of north temperate areas which were concerned with the seasonal cycle 

 of primary production will be emphasized, one in the Atlantic Ocean off the 

 northeast coast of the United States, the other in the North Sea. Other studies 

 of the same oceanic region may then be considered briefly in the light of the 

 seasonal studies. 



During the period September, 1956-May, 1958, primary production was 

 measured as part of a broad investigation of the plankton ecology of the 

 Continental Shelf waters off New York by the Woods Hole Oceanographic 

 Institution. This discussion will be restricted to these measurements made at 

 three stations located outside the 1000-fathom contour which are believed to 

 be representative of oceanic conditions. Most of the productivity estimates for 

 the area were made from chlorophyll and radiation data by the method of 

 Ryther and Yentsch (1957). Due, however, to the problematical relationship 

 of these data to those obtained by the 14 C method, only the relatively few values 

 obtained by the latter technique will be reported here. Measurements by both 

 methods during the investigation have been reported by Ryther and Yentsch 

 (1958). Although the area was visited at rather scattered intervals throughout 

 the year, care was taken to select those periods when the greatest contrast in 

 biological activity could be anticipated, and it is believed that a reasonably 

 accurate picture of the seasonal cycle of primary production resulted from these 

 efforts (Fig. 7). 



For the seventeen in situ 14 C measurements, the mean rate of production is 

 0.56 g carbon/m 2 /day, the standard deviation, 0.57, indicating the high degree 

 of variability in the data and the need for measurements throughout the year. 

 The weighted annual mean is 0.33 g carbon/m 2 /day, equivalent to a total 

 annual production of 120 g carbon/m 2 , twice the estimate for the Sargasso Sea 



