COMMUNITY ORGANIZATION: METABOLISM 



521 



energy, assuming an energy content of 740 

 gram-calories/gram of fresh raw fish, this 

 production is equivalent to 1.6 to 7.7 gram- 

 calories per square meter per day. In terms 

 of utilization of solar radiation, this rep- 

 resents an efficiency of 0.00005 per cent 

 to 0.00025 per cent. 



In summary, Clarke's data present the 

 following efficiencies on Georges Bank: 



per cent. These general relations are shown 

 in Figure 171. 



Several general principles may be sug- 

 gested, if the assumption is made that these 

 eflBciencies are relatively similar for com- 

 munities in general: (1) EfiBciency of pro- 

 ducers (Ai), whether diatoms or maple 

 trees, is low with respect to their utibzation 

 of the total radiant energy available; (2) 



LIGHT; 3000000 & CAL/DAY 



MIGRATION 

 CURRENTS 



Fig. 171. Productivities within a community as illustrated by a diagram of the relations 

 on Georges Bank. The values given are for the whole bank per square meter of sea surface. 

 Maximum and minimum values within the cogwheels are for the standing crop, those over 

 the wheels are for net production rate. (After Clarke.) 



average, incident fight, 100 per cent; dia- 

 toms, 0.3 per cent; zooplankton, 0.015 per 

 cent; fishes, 0.00025 per cent. 



These data accord with those of other 

 investigators. For example, Juday (1940) 

 calculated that fish production in Lake 

 Mendota was at the rate of 19 pounds per 

 acre per year, which is similar to the pro- 

 duction on Georges Bank of from 7 to 33 

 pounds per acre per year. Again, Riley 

 (1941) estimated the mean efiiciency of 

 net plant production in Long Island Sound 

 at 0.31 per cent, which is similar to the 

 diatom eflBciency on Georges Bank of 0.3 



rates of production decrease rapidly from 

 lower to higher trophic levels; (3) effi- 

 ciency of energy utifization decreases 

 rapidly from lower to higher trophic levels; 

 and (4) the extrapolation of the Lindeman 

 ratio. 



The subject of production is a basic one 

 in the metabofism of the community, and 

 deserves a great deal of future attention, 

 particularly with respect to species popu- 

 lations. Seldom do we have production rate 

 calculated in energetic terms for a single 

 species, as has been done for field corn 

 (Table 43). Instead our information is re- 



