Abstract
Mangrove ecosystem plays an important role in global cycling of nutrients. According to nutrient availability, microorganisms can optimize the allocation of C-, N- and P-degrading enzymes. Thus, in this study, enzymatic stoichiometry involved in C, N and P acquisition, and the microbial abundance were analysed in coastal mangrove sediments in two different seasons. Activities of β-1,4-glucosidase (GLU), N-acetyl-β-glucosaminidase (NAG), acid phosphotase (ACP) and phenol oxidase (PHO) were determined, and then applied to calculate the enzymatic C:N (GLU:NAG), C:P (GLU:ACP) and N:P (NAG:ACP) acquisition, respectively. Besides, GLU:PHO was applied as relative recalcitrance of sediment organic matter (SOM). The results showed the enzymatic stoichiometry and microbial abundance had strongly seasonal variations. Compared to other ecosystems, GLU:ACP and NAG:ACP ratios were largely lower, suggesting that sediments in this ecosystem might be microbial P-limitation. Moreover, the higher GLU:PHO ratio implied that SOM in this ecosystem might be more decomposable. Furthermore, the imbalance of nutrients for microbial abundance was revealed by the strong correlations relating sediment N:P to GLU:NAG, GLU:ACP, and GLU:PHO. On the other hand, microbial P limitation in this ecosystem may enhance C storage and sequestration because the higher C contents in sediments of March than November occurred with lower GLU:ACP and NAG:ACP ratios as well as bacterial abundance.
Published Version
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