Production of the giant kelp, Macrocystis , estimated by in situ incorporation of 14 C in polyethylene bags 1

Incorporation of 14 C by the giant kelp Macrocystis pyrifera was measured in situ by enclosing individual blades within polyethylene bags in a kelp bed. Incorporation was highest in the tips of the blades in the canopy, about 0.315 mg C g −1 hr −1 on the basis of wet weight. In the densest part of the kelp bed, total wet standing crop of Macrocystis was about 5.9 kg m −2 , and production of Macrocystis blades in that area was estimated to be at least 6.8 g C m −2 day −1 , or about 17 g organic matter m −2 day −1 .