Table 5. Macrocystis pyrifera net primary productivity (see text for 

 discussion of technique). 



Technique 

 Location 



Wet kg/m 2 /year 



Source 



Field Growth 

 Santa Barbara, California 

 Monterey, California 

 Palos Verdes, California 

 Southern California 



Physiological Estimates 

 Paradise Cove, California 

 Santa Barbara, California 

 San Diego, California 

 Monterey, California 



Harvest Estimates 

 Southern California 

 Santa Barbara, California 



Based on Coon 1982; net primary productivity 

 respiration. 



For rough conversions to other units, dry wt. 

 gC(carbon) = (0.023) g wet wt. (Coon 1982). 



'Based on biomass of 7 wet kg/m 2 . 



gross primary production - 

 = 0.12 wet wt. (Coon 1982), 



ratio because, relative to plants like 

 Laminaria , Macrocystis diverts large 

 amounts of energy to respiration and 

 structural repair. We are unaware of any 

 data that show this diversion is greater 

 in plants like Macrocystis , and Gerard's 

 (1976) data discussed above show that this 

 P/B ratio can be similar to ratios given 

 for Laminaria (Mann 1982). Thus, Mann's 

 (1982) suggestion that the net production 

 of kelp beds is greater than kelp forests 

 is probably incorrect. 



Heine (1983) measured the hi situ 

 productivity of two common understory red 

 algae, Botryocladia pseudodichotoma and 

 Rhodymenia californica , in the Point 

 Cabrillo kelp forest in central 

 California. However, rates were expressed 



per gram dry weight of tissue and measured 

 over small time intervals so yearly 

 production per unit area of bottom cannot 

 be calculated. We thus have no estimates 

 of yearly understory algal production for 

 giant kelp forests. 



The summary of productivity suggests 

 that if total net macroalgal primary 

 productivity ( Macrocystis plus all 

 understory algae] Ts ever measured in a 

 densely vegetated giant kelp forest, it 

 may be the highest of any marine 

 community. This might be expected, 

 because most of the biomass of giant kelp 

 is near the surface where light is 

 highest, and carbon fixed at the surface 

 is translocated to parts of the plants at 

 lower light intensities below (see Chapter 



38 



