Image Analysis for Estimation of Biomass and Nutrient Removal of Duckweed Lemna aoukikusa, Spirodela polyrhiza, and Wolffia globosa in Lab-Scale Cultivation

Abstract

Image analysis was applied for the non-destructive measurement of the respective frond areas of three duckweed species. The dry biomass (y, mg) was found to be proportional to the frond area (x, cm²) measured by image analysis, y = 1.99x － 0.24 for lesser duckweed Lemna aoukikusa, y = 2.36x － 3.22 for giant duckweed Spirodela polyrhiza, and y = 1.17x + 0.91 for rootless duckweed Wolffia globosa. These duckweed species were cultivated separately for 7 days in the modified Hoagland medium under laboratory batch conditions. Biomass growth and nitrogen and phosphorus removal in the medium could be well predicted from change of the frond area and from typical biomass yields on nutrients without disturbing batch operations.