AUTHOR=Luo Hongxue , Liu Songlin , Ren Yuzheng , Jiang Zhijian , Wu Yunchao , Zhang Xia , Li Jinlong , Huang Xiaoping 

TITLE=Eutrophication decreases Halophila beccarii plant organic carbon contribution to sequestration potential

JOURNAL=Frontiers in Marine Science

VOLUME=Volume 9 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2022.986415

DOI=10.3389/fmars.2022.986415

ISSN=2296-7745

ABSTRACT=Seagrass ecosystems rank amongst the most effective blue carbon sinks in climate change mitigation and greenhouse gases removal. Nutrient pollution has emerged as a leading threat to seagrass decline and has diminished the carbon sequestration potential in recent decades. Changes in nutrient regime can also impact the organic carbon compositions (labile and refractory organic carbon compositions) of seagrass tissues, with important implications for determining the quantity and quality of carbon sequestration. However, there is still little information of the impacts of nutrient loading on seagrass plant refractory organic carbon composition (ROC), which hinders our ability to reveal the driving mechanisms of anthropogenic factors decrease seagrass organic carbon sequestration capability. Here, a multidisciplinary approach was employed to investigate the organic carbon variations of Halophila beccarii at five seagrass meadows with contrasting nutrient loading levels. The results showed that H. beccarii plant nitrogen (N) content ranged from 2.21-5.65%, with well reflecting the external nutrient loading levels. High nutrient loading elevated labile organic carbon contents, like free amino acid and soluble sugars. Nevertheless, ROC contents (cellulose-associated organic matter) decreased with increasing nutrient loading, which presented a significant negative linear correlation with plant N content. These results provide the evidence that eutrophic conditions enhance H. beccarii plant quality (high N and labile organic carbon) and consequently decrease plant ROC sequestration potential. This suggests that reducing nitrogen input to seagrass meadows may aid in increasing seagrass carbon storage.