SECT. 4 J IDEOGRAPHIC VARIATIONS IN PRODUCTIVITY 375 



Steemann Nielsen (1958) and Riley (in lift.) have both suggested that the mid- 

 summer peak in production may be related to high water temperatures and to 

 the role of this factor in the bacterial regeneration of nutrients, particularly 

 from the bottom. 



According to Steemann Nielsen and Jensen (1957): "It was found during 

 the [Galathea] expedition that the rate of organic production is high practically 

 anywhere in the tropics in shallow water." The productivity of ten shallow 

 stations in the Indo-Malayan region ranged from 0.24-1.08, averaging 0.61 g 

 carbon/m 2 /day, almost an order of magnitude greater than offshore waters of 

 the same region. 



It is less evident that the average rate of production of shallow, temperate 

 regions is appreciably higher than that of the deep ocean. Annual net produc- 

 tion (roughly comparable to the 14 C values reported elsewhere) for Long Island 

 Sound was estimated at about 180 g carbon/m 2 . Values for Danish inshore 

 waters averaged about 75 g carbon/m 2 . These estimates are not appreciably 

 different from those reported earlier for offshore waters of comparable latitudes. 

 The reasons for this are not entirely clear. One undoubtedly important factor 

 is the preponderance in shallow environments of light absorbing, non-living 

 particulate matter which may compete seriously with the phytoplankton for 

 the available light (see page 350). Another factor is simply the limitation of 

 depth. If production is considered on a volume basis, as carbon fixation per 

 cubic meter, there is no question of its far greater magnitude in shallow regions. 

 Values of 10-100 mg carbon/m 3 /day are common for the latter, whereas a 

 range of 1-10 is typical of oceanic water. This advantage, however, is offset by 

 a disadvantage of equal magnitude. Plant growth in the open sea may occur 

 over depths of 50-100 m, while in estuaries and embay ments the depth of the 

 euphotic zone, if not the bottom itself, seldom exceeds 5-10 m. Production 

 integrated over the entire water column is thus comparable for the two situa- 

 tions. A rather dramatic example of this compensatory effect is the comparison 

 between production in a shallow, extremely rich, sewage oxidation pond and 

 the Sargasso Sea during the spring flowering (Fig. 14, from Ryther, 1960). 

 In this case, a difference of two orders of magnitude between rates of produc- 

 tion per unit volume is countered by an equal but opposite difference in euphotic 

 zone depths. Production per square meter differed by less than 20%. 



The question of which of the two regions is the more fertile or the more 

 productive is one of definition. Although equal areas may produce equal 

 amounts of organic matter, the advantage to herbivores and succeeding 

 trophic levels of having their food concentrated in a small volume is perhaps a 

 matter of somewhat greater significance to the animals in question. 



9. Production of Benthic Plant Communities 



Discussion of the productivity of coastal waters would not be complete 

 without consideration of the contribution made by the benthic plants, both the 

 algae and phanerogams. Studies of their rates of production are disappointingly 



