60 



Chinese began to cultivate these plants on rafts (C 2). In 1957 new genetic strains 

 were selected that made it possible to greatly extend the range of cultivation (C 3). 

 Algal culture facilities were developed to produce seedstock. Continued selection and 

 improvements in culture techniques, in particular the development of methods for 

 applying fertilizer, has led to increased yields. High-iodine yielding strains were 

 developed in 1970 (C 4). Present production of Laminaria in China is in excess of 

 150,000 dry metric tons per year. 



In Japan, the traditional cultivation of Porphyra on sticks placed in shallow 

 water, started in the 1700s, and continued to about 1950 (J 1) when net culture was 

 introduced. In 1957 the application of recently discovered life-history phases (previ- 

 ously unknown) made it possible to artificially seed this plant for the first time, (J 2) 

 and a rapid increase in production followed. In 1963, it was found that seeded nets 

 could be frozen for long-term storage, and that this procedure also enhanced crop 

 production (J 3). Problems of pollution in coastal waters made it necessary to move 

 what had traditionally been near-shore farms, out into the open sea. This (J 4) also 

 produced a substantial increase in the production of Porphyra. 



The harvesting of the giant kelp, Macrocystis in California 



The giant kelp, Macrocystis, is the largest known marine plant, reaching lengths 

 of up to 140 feet. These plants produce forest-like communities, where individual 

 plants grow at rates of 3 percent per day, under optimum conditions. Measurements 

 of the standing crop in natural kelp beds range from 2 to 97 wet tons per acre. An 

 annual harvest of some 160,000 wet tons is collected by mechanized harvesters in 

 California. Unfortunately this is not adequate to meet the present demand and 

 additional kelp is imported from Argentina, South Africa smd elsewhere. 



Examples of harvests from a single bed of about 680 acres in area (bed number 26, 

 in Goleta Bay) range from 12 wet tons per acre in 1975 to 7.5 wet tons per acre in 

 1977. The amount of kelp harvested is only a small amount of the total produced. 

 From measurements of beach drift in Goleta Bay, we estimate that at least 9 tons 

 per acre per year are cast ashore. Additional kelp sloughs away, and is eaten, 

 degraded or dissolved. The standing crop in this kelp bed is between 30 and 40 wet 

 tons per acre, the plants being separated from one another. 



The potential yield of oceanic kelp farms, where Macrocystis or other float-bearing 

 kelps would be grown 



It is logical to assume that a farmed population of macro-algae would be planted 

 and managed in such a way as to minimize damage due to wave action, plant loss 

 due to sloughing, eind other adverse effects, like those seen in natural kelp forests. 

 Also, as in the Chinese farming effort, genetic selection for improved yield is likely 

 to increase the production over that seen in natural kelp forests. 



In making assumptions about yield, disputes commonly arise as to the amount 

 that can be produced per acre. It is important to remember here that in contrast 

 with land-based energy farming, a major cost factor (the cost of the land) is not 

 involved. Thus it does not really matter whether the yields are high or low, as long 

 as the unit costs for farming (both in terms of money and energy) are minimized. 



The most important factor, influencing the yield of natural kelp forests, is the 

 availability of nutrients. It is logical to assume that this would also be the case for 

 farmed areas of the sea, particularly the open sea where nutrient levels are low. 

 Thus, in my opinion, the potential future yield of oceanic kelp farms will depend on 

 how efficiently nutrients can be supplied to the plants, and whether or not these 

 nutrients can be recycled to the farm once methane is extracted from the harvested 

 crop. 



