Highlights
- DOC production rate of thallus was much higher than that of conchocelis.
- DOC production rate of thallus tends to increase with light intensity.
- Ocean acidification did not significantly change the DOC production rate of thallus.
Abstract
The large-scale cultivation of macroalgae has the potential to act as a carbon sink because macroalgae can release a large amount of organic carbon into the surrounding seawater. However, this needs to be evaluated on the basis of the entire life cycle under a background of changes in pH and light intensity. The present study investigated the difference in organic carbon release between conchocelis and thallus stages of the economically important red alga Pyropia haitanensis in response to three light intensities (10, 50, and 500 μmol m−2 s−1) and two pH conditions (current pH: 8.1, projected future pH: 7.5). The study found that regardless of the light intensity and pH values, the growth rates, production rates of tissue carbon, and dissolved organic carbon (DOC) of thalli tended to be higher than those of conchocelis, by more than 170%, 85%, and 106%, respectively. The DOC production rate was higher than the production rate of particulate organic carbon (POC) by at least two orders of magnitude. Positive correlations were found between growth rate and production rates of tissue carbon and growth rate and DOC production rate, but no clear relationship was found between growth and POC production. The DOC production rate of thallus tended to increase with light intensity but was not significantly influenced by ocean acidification. However, decay of tissue caused by exposure of the conchocelis to high light intensity resulted in increased POC and DOC production rates, indicating the complexity of organic carbon release by P. haitanensis. This study provides insights into the release of organic carbon during the complete life cycle of P. haitanensis, and the results can further our understanding of the carbon metabolism of this cultivated macroalgal species.
Xu K., Li M., Wang W., Xu Y., Ji D., Chen C. & Xie C., 2021. Differences in organic carbon release between conchocelis and thalli of Pyropia haitanensis and responses to changes in light intensity and pH. Algal Research 61: 102574. doi: 10.1016/j.algal.2021.102574. Article (subscription required).
