Macroalgae culture-induced carbon sink in a large cultivation area of China

Macroalgae culture-induced carbon sink in sediments has been little investigated. Here, total organic carbon (TOC), total nitrogen (TN), and delta C-13 were examined in sediments in a cultivation field of macroalgae (kelp and Gracilariopsis lemaneiformis) in Sansha Bay, Southeast China. Both proxies of C/N (TOC to TN ratio) and delta C-13 indicated a multisource of TOC. Based on a three-endmember model, macroalgae-derived TOC (TOCma) accounted for < 35% of the total TOC, averaging 16 +/- 9% (mean +/- SD). On average, terrestrial and phytoplankton-derived TOC showed much higher percentages of 24 +/- 17% and 60 +/- 20%, respectively (t-test, p < 0.02). A preliminary estimate suggested that TOCma represents a carbon sink of 8.2 x 10(3) tons per year, corresponding to about 22% of the sink associated with phytoplankton and macroalgae and 8 +/- 6% of the macroalgae carbon production in Sansha Bay. Considering its production magnitude, the macroalgae-induced carbon sink seems to be insignificant, on a national or global scale, to phytoplankton, though it should be taken into account given the small cultivation area.

Automated summary

The study examined the carbon sink and sources in sediments of a macroalgae cultivation field in Sansha Bay, Southeast China. The results showed that macroalgae-derived organic carbon accounted for less than 35% of the total organic carbon. A preliminary estimate suggested that macroalgae-induced carbon sink represented only 8.2 x 10^3 tons per year, which is relatively insignificant on a national or global scale. However, considering the small cultivation area, the impact of macroalgae culture on carbon sink should still be taken into account.