Limited trait responses of a tropical seagrass to the combination of increasing pCO2 and warming

J Exp Bot. 2022 Oct 22;erac425. doi: 10.1093/jxb/erac425. Online ahead of print.

Abstract

Understanding species-specific trait responses under future global change scenarios is of importance when doing conservation efforts and to make informed decisions within management projects. The combined and single effects of seawater acidification and warmer average temperature were investigated by means of the trait responses of Cymodocea serrulata, a tropical seagrass, under experimental conditions. After a 35-days exposure period, biochemical, morphological and photo-physiological trait responses were measured. Overall, biochemical traits mildly responded under the individual exposure of high temperature and increasing pCO2 values. The response of C. serrulata was limited to a decrease in %C and an increase in the sucrose content in the rhizome under the high temperature treatment, 32°C. This suggests that this temperature was lower than the maximum tolerance limit for this species. Increasing pCO2 levels increased %C in the rhizome, and also showed a significant increase in leaf δ 13C values. The effects of all treatments were sub-lethal, however, small changes in their traits could affect the ecosystem services they provide. Particularly, changes in tissue carbon concentrations may affect carbon storage capacity, one key ecosystem service. The simultaneous study of different types of trait responses contribute to establish a holistic framework of seagrass ecosystem health under climate change.

Keywords: Cymodocea serrulata; Indo-Pacific; carbohydrates; carbon allocation; carbon dioxide concentrations; carbon stable isotopes; morphology; photosynthesis; temperature.