Seagrass biomass and production: A reassessment

The biomass and production of seagrass populations were reassessed based on the compilation of a large data set comprising estimates for 30 species, derived from the literature. The mean (±SE) above- and below-ground biomass in the data set were very similar, 223.9 ± 17.5 and 237.4 ± 28 g DW m^-2, respectively, indicating a general tendency for a balanced distribution of biomass between leaves and rhizomes + roots (mean ratio (± SE) = 1.11 ± 0.08). The biomass development and the ratio of above- to below-ground biomass varied significantly with latitude and was species-specific, with a significant tendency for large-sized seagrass species to develop high below- ground biomass. Maximum daily seagrass production differed significantly among species, but averaged 3.84 ± 0.34 and 1.21 ± 0.27 g DW m^-2 per day for above- and below-ground organs respectively, with an average ratio of above- to below-ground production of 16.4 ± 8.5. The biomass turnover rates averaged 2.6 ± 0.3 and 0.77 ± 0.12% per day for the above- and below-ground material respectively, and tended to be faster for temperate species. The average annual seagrass production found here, 1012 gDW m^-2 per year, exceeds previous estimates by 25%, because the average excedent carbon produced by seagrasses must be revised upwards to represent 15% of the total surplus carbon fixed in the global ocean.