Table I 



Net organic production of various natural and cultivated systems in grams dry weight pro- 

 duced per square meter per day (from Ryther, in Press) . 



A. Theoretical potential 



average radiation (200 - 400 langleys/day) 

 maximum radiation (750 langleys/day) 



B. Mass outdoor Chlorella culture (Tamiya , 1957) 



mean 

 maximum 



C. Land (maxima for entire growing seasons) (Odum, 1959) 



sugar cane 



rice 



wheat 



spartina marsh 



pine forest (best growing years) 



tall prairie 



D. Marine (maxima for single days) 



coral reef (Odum and Odum, 1955) 



turtle grass flat (Odum, 1954) 



polluted estuary (Ryther, et al, 1958) 



Grand Banks (April) (Ryther and Yentsch, unpublished) 



continental shelf (May) (Ryther and Yentsch, 195 8) 



Sargasso Sea (April) (Ryther and Menzel, in press) 



8-19 

 27 



12.4 

 28.0 



18.4 

 9.1 

 4.6 

 9.0 

 6.0 

 3.0 



9.6 

 11.3 

 8.0 

 6.5 

 3.7 

 2.8 



values were compared with some of the highest 

 yields of organic matter which have been observed 

 in nature. The data are reproduced here as Table I 

 and they reveal that in cultivated crops and natural 

 communities, on land or in the sea, in algae or in 

 the higher plants, the maximum rate of production 

 is very nearly the same and may closely approach 

 the theoretical potential. As in laboratory quantum 

 yield experiments, organic production in nature ap- 

 pears to be species independent and determined 

 primarily by a photosynthetic potential common to 

 all plants . 



But the ideal conditions necessary for the 

 attairiment of this potential are seldonvmet in 

 nature. Rather than producing 5 kg/m /year, the 

 land averages no more than 10 - 20% of this, the 

 sea perhaps 2 - 3% . The low mean production of 

 the land is not hard to understand. Soils are fre- 

 quently poor in quality or essential nutrients . Ad- 

 equate moisture is often lacking. Carbon dioxide 

 is thought to be usually, if not always, limiting to 

 land plants, their yields being increased 2-3 fold 

 when this gas is artificially introduced in green- 

 house experiments (Maximov, 1930). Finally tem- 



perature, or climate, accounts for much of the dis- 

 crepancy between the potential and observed pro- 

 duction of the land . A large portion of the cultur- 

 able land on earth is found in temperate or semi- 

 tropical climates where the plants have a limited 

 growing season. An agricultural yield of 500 - 

 1000 g/m^ may be achieved in such regions in 4 to 

 6 months . 



But what of the ocean ? Here there are no 

 substrate problems; no lack of moisture. Carbon 

 dioxide is probably never limiting due to the great 

 reservoirs of dissolved carbonates and bicarbonates. 

 Oceanic temperatures are always favorable for the 

 growth of some species of phytoplankton . In the 

 words of Henderson (1913) "No philosopher's or 

 poet's fancy, no myth of a primitive people has 

 ever exaggerated the importance, the usefulness, 

 and above all the marvelous beneficence of the 

 ocean for the community of living things . " This 

 ideal environment yields an average crop of organic 

 matter which is almost two orders of magnitude less 

 than the biotic potential of its producers . Only be- 

 cause of its vast area does the ocean equal the 

 land in its over-all organic production. 



75 



