INTRODUCTION 



The Ocean Food and Energy Farm (OFEF) concept envisions large areas of open 

 ocean under cultivation utilizing solar energy input and the photosynthetic process to 

 produce high yields of marine algae. The proposed crop plant, the giant brown kelp 

 Macrocystis pyrifera, is expected to yield in excess of 270 wet metric tons (36 dry metric 

 tons) of harvested organic material per acre per year (Refs. 1 and 2). This material would 

 be harvested and processed to produce methane gas, food and feed products, fertilizer, 

 ethanol, and other organic products, many of which are currently produced from nonrenew- 

 able petroleum sources (Ref. 3). In addition, a mariculture subsystem would produce higli- 

 value finfish and shellfish products for human consumption. 



The economic success of any aquaculture system is dependent on the selection of an 

 appropriate site. Factors which must be considered in selecting potential sites include 

 various physical, chemical, biological, economic, and geopolitical parameters. 



Proper selection of a farm site requires that the needs and hmitations of the total 

 farm system be considered. Particularly important are the biological requirements of the 

 kelp Macrocystis pyrifera and the practical engineering and economic factors which affect 

 design of the farm substrate and artificial upwelling systems. 



Biological and chemical parameters of importance to site selection include the 

 availability and concentration of nutrients in both the near-surface mixed layer (directly 

 available to crop) and at intermediate depths (100 to 300 meters of depth and available to 

 the crop after artificial upwelling). Nutrient concentration and availability in combination 

 with light intensity and temperature are among the principal factors which will determine 

 the rate of OFEF primary productivity and therefore, economic return. Nutrient concentra- 

 tions are highly variable in both location and season with the principal determining factors 

 being the amount of wind-caused mixing, natural upwelling, and biological utilization. 



The cost of the substrate system will constitute a large part of the total cost of the 

 OFEF. The substrate therefore "represents a major investment in an ocean structure which 

 may be vulnerable to damage during periods of storm and adverse weather conditions" (Ref. 

 2). Selection of a farm site which minimizes the chance for environmental damage is 

 consequently of great importance. 



The location and intensity of prevailing currents are also important; areas of high- 

 speed currents may have to be avoided whereas weaker currents can act to remove waste 

 materials and replenish nutrient supplies. 



Other aspects important to the farm location include the amount of incident solar 

 radiation and degree of light penetration (both vary geographically), the ocean temperature 

 in relation to M. pyrifera tolerance, and the location and concentration of potential sources 

 of pollution. 



