Mamidala Harikrishna Prasad, Ganguly D, Purvaja R, Singh Gurmeet, Das Subhajit, Rao M Nageswar, Kazip Ys Armoury, Arumugam K, Ramesh R
National Centre for Sustainable Coastal Management, Ministry of Environment, Forest and Climate Change, Chennai, 600 025, India.
J Environ Manage. 2023 Feb 15;328:116902. doi: 10.1016/j.jenvman.2022.116902. Epub 2022 Dec 9.
Efficient nutrient cycling through decomposition of leaf litter often regulates the high productivity and subsequent carbon sequestration of mangrove ecosystems along the land-ocean boundary. To understand the characteristics and the potentials of mangrove leaf litter in supplying organic carbon and nutrients to the coastal waters, four major mangrove species (A. officinalis, R. mucronata, H. littoralis and S. apetala) of Bhitarkanika mangrove forest, Odisha, India, were examined in controlled environmental conditions. Half-life time (t.), estimated for decomposition of those mangrove leaf litter materials ranged from 18 to 52 days. During the incubation experiment, organic carbon from mangrove leaf litter was released primarily through physical processes and was available for heterotrophic respiration. Among the four species, leaf litter of S. apetala with the lowest initial C/N ratios, released organic carbon with low molecular weight (labile substances) that has a relatively higher potential to support the aquatic food web. On the contrary, leaf litter of R. mucronata released organic material with relatively higher molecular weight (humic substances, higher aromaticity), which revealed its superior non-labile characteristics in this unique environment. The mean total heterotrophic bacterial (THB) population in the incubation was around nine-fold higher than the control. THB population growth and Chromophoric Dissolved Organic Matter (CDOM) spectral data further suggested the rapid release of highly labile and recalcitrant carbon from S. apetala and R. mucronata (between 7th and 21st day of incubation), respectively. The mean litter fall from the Bhitarkanika mangrove forest was estimated to be 11.32 ± 1.57 Mg ha y and its corresponding carbon content was 5.43 ± 0.75 Mg C ha. The study revealed the role of leaf litter leachates as an important food source to microbial communities in the adjacent coastal waters, in addition to a potential carbon sequesterer through long-term burial in mangrove soil and export to the deep sea.
通过落叶分解实现的高效养分循环，常常调节着陆地 - 海洋边界红树林生态系统的高生产力及随后的碳固存。为了解红树林落叶向沿海水域供应有机碳和养分的特征及潜力，在可控环境条件下对印度奥里萨邦比塔卡尼卡红树林的四种主要红树林物种（药用海榄雌、尖瓣海莲、滨海木榄和无瓣海桑）进行了研究。这些红树林落叶材料分解的半衰期（t.）估计在18至52天之间。在孵化实验期间，红树林落叶中的有机碳主要通过物理过程释放，并可用于异养呼吸。在这四个物种中，初始C/N比最低的无瓣海桑落叶释放出低分子量的有机碳（不稳定物质），其支持水生食物网的潜力相对较高。相反，尖瓣海莲落叶释放出分子量相对较高的有机物质（腐殖质，芳香性更高），这表明其在这种独特环境中具有优越的非不稳定特性。孵化过程中异养细菌总数（THB）的平均值比对照高约九倍。THB种群增长和发色溶解有机物（CDOM）光谱数据进一步表明，无瓣海桑和尖瓣海莲分别在孵化的第7天至21天之间迅速释放出高活性和难降解的碳。比塔卡尼卡红树林的平均落叶量估计为11.32±1.57 Mg ha y，其相应的碳含量为5.43±0.75 Mg C ha。该研究揭示了落叶渗滤液不仅是相邻沿海水域微生物群落的重要食物来源，还可能通过长期埋藏在红树林土壤中以及向深海输出而成为潜在的碳汇。
