Photosynthesis sequesters more carbon than growth does

Abstract

Abstract Carbon sequestration by marine plants has traditionally been measured based on biomass from growth rates. However, our work hypothesis is that photosynthesis based sequestration should yield larger values. In the Northwestern Cuban shelf, our study area, the combined photosynthesis of six seaweeds genera Halimeda thalli, and turtle grass leaves resulted in an estimated 350 t CO2 km-2 y-1 sequestered, 3.4 times the 102 t C km-2 y-1 from growth, validating the hypothesis. Other existing CO2 sequestration estimates are at least threefold smaller meaning that the world growth average of 119 t C km-2 y-1 should be increased to 357 t C km-2 y-1, similar to sequestration in the study area. Because high salinity and water transparency benefit the studied species’ growth, they can be qualified as oceanic. Biomass growth rates are expressed as “t C km-2 y-1” to facilitate comparisons with that in other areas. Sequestration values in this study are based on turn-over-rates of species’ dry biomasses collected 50 years ago, so they can be used as a baseline for present and future studies.