Key Laboratory of Ministry of Education for Coastal and Wetland Ecosystems, Xiamen University, Xiamen 361102, China.
State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen 361102, China.
Sci Total Environ. 2018 Feb 1;613-614:548-556. doi: 10.1016/j.scitotenv.2017.09.140. Epub 2017 Sep 26.
Arbuscular mycorrhizal (AM) fungi produce a recalcitrant glycoprotein, (glomalin-related soil protein (GRSP)), which can contribute to soil carbon sequestration. Here we made a first study to characterize the spatial distribution of GRSP fractions in a mangrove forest at Zhangjiang Estuary, Southeastern China and to explore potential contributions of GRSP to sediment organic carbon (SOC) in this forest. We identified GRSP fractions in surface sediments, as well as those at a depth of 50 cm. The contents of easily extractable GRSP (EE-GRSP), total GRSP (T-GRSP), GRSP in particulate organic matter (POM-GRSP) and GRSP in pore water (PW-GRSP) ranged between 1.20-2.22mgg, 1.38-2.61mgg, 1.45-10.78mgg and 10.35-39.65mgL respectively, and these four GRSPs are significantly affected by sample sites and sediment layers. Carbon in GRSP accounted for 2.8-5.9% of SOC and its contributions can far exceed that of microbial biomass carbon (0.21-0.73%) in the 0-50cm sediment layers. Our data indicate that GRSP could be transported by pore water and accumulated in sediment profiles. The non-linear regression analysis revealed that as SOC and particulate organic carbon (POC) contents decrease, GRSP proportions increase, indicating the increase of the recalcitrant carbon offsetting the effects of mangrove carbon loss, especially labile C. Regression and ordination analyses indicated that GRSP fractions were mainly positively correlated with sediment carbon fractions and spore density but were negatively correlated with sand, pH. Strikingly, the unfavorable environmental factors for microbial organisms, especially AM fungi, prove to be able to promote the production or accumulation of GRSP. We propose that there are two different pathways for affecting the pool size of GRSP in mangrove ecosystems: (i) directly via indigenous AM fungi propagules; (ii) or via the GRSP transport and deposition by pore water and tides.
丛枝菌根（AM）真菌会产生一种抗降解的糖蛋白，即（Glomalin-related soil protein，GRSP），它有助于土壤碳的固存。本研究首次对中国东南部长江口的红树林生态系统中 GRSP 各组分在不同土层的空间分布进行了特征描述，并探讨了 GRSP 对该森林沉积物有机碳（SOC）的潜在贡献。我们鉴定了表层沉积物和 50cm 深处沉积物中的 GRSP 各组分。易提取 GRSP（EE-GRSP）、总 GRSP（T-GRSP）、颗粒有机 matter 中的 GRSP（POM-GRSP）和孔隙水中的 GRSP（PW-GRSP）的含量分别为 1.20-2.22mg/g、1.38-2.61mg/g、1.45-10.78mg/g 和 10.35-39.65mg/L，这四种 GRSP 均受到采样点和沉积层的显著影响。GRSP 中的碳占 SOC 的 2.8-5.9%，其贡献远远超过 0-50cm 沉积层中微生物生物量碳（0.21-0.73%）的贡献。数据表明，GRSP 可能通过孔隙水运输并在沉积层中积累。非线性回归分析表明，随着 SOC 和颗粒有机碳（POC）含量的降低，GRSP 的比例增加，这表明抗降解碳的增加抵消了红树林碳损失的影响，尤其是易降解碳。回归和排序分析表明，GRSP 各组分主要与沉积物碳组分和孢子密度呈正相关，而与砂、pH 值呈负相关。引人注目的是，对微生物生物，尤其是丛枝菌根真菌不利的环境因素，被证明能够促进 GRSP 的产生或积累。我们提出，在红树林生态系统中，有两种不同的途径可以影响 GRSP 库的大小：（i）通过土著 AM 真菌繁殖体；（ii）通过孔隙水和潮汐的 GRSP 运输和沉积。
