PART VIII — AQUATIC ECOSYSTEMS 



Figure VIM— 3 — SENSITIVITY OF PHYTOPLANKTON TO INSECTICIDES 



100 r- 



O 



0.01 0.1 1 10 100 1.000 



INSECTICIDE IN WATER (ppb) 



The left-hand charts show the uptake of ' 'C by phytoplankton as a function of 

 the concentration of several insecticides. At concentrations greater than one 

 part per billion (ppb) in three of the four species studied, the reaction in uptake 

 is great. The right-hand charts show the effect of adding 100 ppb of DDT and 

 endrin to water containing several types of phytoplankton. The insecticides were 

 added each day for 7 days and solvent was added in equal volume to the controls. 

 The insecticides significantly reduced production in three of the four species 

 under investigation. 



treatment applications. Through this 

 line of research, some of the results 

 of the intensive activity in biochem- 

 istry and molecular biology are being 

 incorporated into biological oceanog- 

 raphy, and satisfactory calculation 

 models for the absorption of nutri- 

 ents by phytoplankton are being de- 

 veloped rapidly. Since phytoplankton 

 production is limited in most regions 

 of the sea by the rate at which 

 nutrient-rich waters from below are 

 brought to the surface by hydrologi- 

 cal processes, the equations linking 

 phytoplankton production and basic 

 hydrological parameters of the ocean 

 circulation are virtually at hand. 



From this point on up the food 

 chain, the situation deteriorates. Little 

 useful information exists on rates of 

 grazing by the zooplankton, the small 

 animals intermediate between most 

 fish and phytoplankton. At this level, 

 animal behavior must be taken into 

 consideration and reproduction pat- 

 terns become important. Although 

 general patterns are known, the de- 

 tails remain to be filled in and are 

 largely lacking for modeling pur- 

 poses. The structure and behavior 

 of some fish populations is better 

 known as a result of the pressure of 

 economic value, and simulation mod- 

 els have been developed that are use- 

 ful in the management of specific 

 fisheries. These models, however, are 

 not linked in their present form to 

 the food chain supporting the fishery. 

 Efforts are currently under way to 

 form this link, using the Peru an- 

 chovy fisheries as a basis. In some 

 of the advanced simulation models, 

 the response of fishermen to various 

 regulation regimes is taken into con- 

 sideration. 



Future Requirements 



A library of simulation models of 

 oceanic productivity is needed to 

 deal with the problems posed by 

 man's intervention. Some models 

 should be designed to give large- 

 scale coverage without great detail — 

 for example, models of each of the 



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