The Organic Budget 



177 



Much of the organic matter produced by 

 phytoplankton and sessile plants remains in 

 an intermediate stage before regeneration is 

 complete, as dissolved and suspended 

 organic detritus, or leptopel. According to 

 Fox (1957) this material is present in ocean 

 water in concentrations of at least 1 ppm. 

 At this concentration the waters in the area 

 of Chart I should contain about three times 

 the weight of organic matter annually pro- 

 duced by plants. The large size of this re- 

 serve should serve to soften the effects of 

 temporary variations in production of 

 phytoplankton on the food supply for ani- 

 mals. Because of the small grain size of the 

 particles, they are readily absorbed on 

 clayey sediments, but the proportion of 

 organic matter in the sediments that arrived 

 via adsorption is unknown. The role of 

 leptopel as an intermediate decomposition 

 product does not require its inclusion in the 

 organic budget of Figure 153. 



The primary grazers on phytoplankton 

 are small herbivorous animals such as 

 copepods. They in turn serve as food for 

 the large omnivorous and carnivorous spe- 

 cies of zooplankton and of pelagic fishes. 

 Much of the material eaten is excreted un- 

 digested to serve as food for other animals, 

 the scavengers. Digestion of the food re- 

 sults partly in its conversion into new animal 

 tissue but probably mostly in supplying 

 energy requirements. In the process of an- 

 imal use, as well as of simple chemical oxi- 

 dation, most of the organic matter is recon- 

 verted into the chemical nutrients that 

 originally were brought together by the 

 plants during photosynthesis. The tonnage 

 of nitrogen and phosphorus used annually 

 by phytoplankton is about 100 times the 

 amount annually contributed to the ocean 

 from land areas on a world-wide basis 

 (Emery, Orr, and Rittenberg, 1955). Under 

 steady-state conditions, the tonnage of nu- 

 trients annually lost to the sediments must 

 equal the amount annually brought to the 

 ocean from land, so it follows that about 

 100 times as much organic matter from 

 plants is regenerated in the water or the 

 bottom as is lost by permanent burial. Be- 

 cause the waters off southern California are 



shallower than the oceanic average, the 

 ratio of loss to regeneration in the water 

 column must be somewhat higher than the 

 world average. 



It is of interest to compare the standing 

 crops and annual production of zooplank- 

 ton, epipelagic fishes, marine mammals, and 

 bathypelagic animals so as to note the losses 

 involved during the conversion of organic 

 matter in each successive step of the food 

 chain. Unfortunately, however, too few 

 basic data exist to permit drawing up of es- 

 timates that are much more than guesses. 



Volumes of zooplankton have been 

 measured at 15 to 20 stations in the region 

 during monthly cruises since 1951 by the 

 California Cooperative Oceanic Fisheries 

 Investigations (1953-1956). Oblique tow 

 net hauls have been made usually to depths 

 of about 140 meters. Average zooplankton 

 volumes for 1952 to 1955 expressed in cubic 

 centimeters of displacement volume per 

 1000 cu meters ranged between 640 in June 

 to 121 in December. The annual average is 

 281, a third to half the average values found 

 on the shelf and in the bays of the East 

 coast (Deevey, 1956), although at least part 

 of the difference may result from the use of 

 different mesh nets in the two regions. By 

 using the conversion factor given by 

 Sverdrup, Johnson, and Fleming (1942, p. 

 929), the annual average corresponds to 3.56 

 grams dry plankton per 1000 cu meters of 

 water. This concentration taken through- 

 out the region of Chart I and uniformly to 

 an assumed depth of 200 meters yields a 

 standing crop of zooplankton amounting to 

 0.09 million tons. Work by Harvey (1950) 

 on food requirements suggests that zoo- 

 plankton increases in weight about 10 per 

 cent per day. This rate extrapolated over 

 a year gives an approximate ratio of 35 be- 

 tween annual productivity and standing 

 crop. From this ratio and the estimated 

 standing crop, the annual production of 

 zooplankton may be computed as 3,400,000 

 tons, about 7.5 per cent of the annual pro- 

 duction of plants (Fig. 153). 



The average annual commercial catch of 

 fishes for the five years 1947, 1950, 1952, 

 1953, and 1954 was 160,000 tons, according 



