Sediments act as major carbon storage and transformation in mangroves with different root structures

Mangroves play a vital role in carbon capturing, transforming and storage in coastalareas; however, their carbon storage and stability affected by environmental variables such as salinity, tidal change, and other biochemical factors. This study investigates how contrasting root morphologies—Avicennia marina (aerial pneumatophores), Rhizophora stylosa (supporting roots), and mixed-species stands—govern sediment carbon quantity and quality in the Haomeiliao mangrove forests in southwestern coastal areas of Taiwan. Field measurements were bi-monthly conducted across wet and dry seasons, including sediment organic carbon content, redox potential and   dissolved organic matter (DOM) concentration and optical indices (fluorescence index, biological index) in porewater. Results show that, in generally, seasonal rainfall patterns induced persistent anoxia in sediments, which suppressed oxidative enzyme activity, indicating a hydrologically mediated “enzymatic latch” mechanism that declined decomposition rates of DOM and thus benefited carbon preservation and storage. Root morphology further modulated these processes: Rhizophora stands (supporting roots) showed constantly stable anoxic conditions with higher humic-like substances observed, whereas Avicennia stands (aerial roots) experienced greater redox variations, elevated enzyme activity, and higher carbon storage originated from stronger endogenous microbial and algal productions. Mixed forests displayed highest carbon concentration in the sediment , however, the humidification level of OM were lower (i.e., lower stability) of comparing to the pure Rhizophora forest. Our findings demonstrate that the interaction between root structural traits, sedimentary chemistry and seasonal rainfall patterns plays a critical role in regulating sediment carbon quality and quantity in mangrove ecosystems. Results provide critical knowledge for predicting the resilience of mangrove blue carbon under future climate-driven changes in precipitation, salinity, and species composition.

Presentation Preference: Standard Oral (12 Minutes)

Primary Presenter: Ya Hsin Liu, National Pingtung University of science and technology (maxliu9134@gmail.com)

Authors:

Ya Hsin Liu, National Pingtung University of science and technology  (maxliu9134@gmail.com)

Jeng Wei Tsai, National Pingtung University of science and technology  (tsaijw@mail.npust.edu.tw)