Comparisons of Salt‐marsh Fucoid Production Estimated From Three Different Indices¹

Production of Ascophyllum nodosum (L.) LeJolis ecads and Fuscus vesiculosus L. was calculated from measurements of in situ growth, seasonal variations in standing‐crops and seasonal variations in photosynthetic capacity. A computer model for predicting daily, monthly and yearly net production from photosynthesis data was constructed. This model used daily irradiation, actual biomass of algae/m 2 contributing to production and photosynthesis vs. light intensity relationships as data inputs. Comparison of production estimated from in situ growth, standing‐crops and photosynthesis indicated that both marsh fucoids turn over biomass twice per year. Total net production of both fucoids, estimated from photosynthesis data, was ca. 315 g C · m −2 · yr −1 . On the other hand, production of both fucoids calculated from standing‐crop data was only 155 g C · m −2 · yr −1 .