Li Zhichun, Zhao Yanping, Xu Xiaoguang, Han Ruiming, Wang Mingyue, Wang Guoxiang
School of Geography Science, Nanjing Normal University, Nanjing, Jiangsu Province, China.
School of Environment and Surveying Engineering, Suzhou University, Suzhou, Anhui Province, China.
PeerJ. 2018 Nov 7;6:e5922. doi: 10.7717/peerj.5922. eCollection 2018.
The decomposition processes of accumulated cyanobacteria can release large amounts of organic carbon and affect the carbon cycling in shallow eutrophic lakes. However, the migration and transformation mechanisms of dissolved carbon (DC) require further study and discussion. In this study, a 73-day laboratory microcosm experiment using suction samplers (Rhizon and syringe) was conducted to understand the migration and transformation of DC during the cyanobacteria decomposition. The decomposition of cyanobacteria biomass caused anoxic and reduction conditions, and changed the acid-base environment in the water column. During the early incubation (days 0-18), a large amount of cyanobacteria-derived particulate organic matter (POM) was decomposed into dissolved organic carbon (DOC) in the overlying water, reaching the highest peak value of 1.82 g L in the treatment added the high cyanobacteria biomass (470 g). After 18 days of incubation, the mineralization of increased DOC to dissolved inorganic carbon (DIC) maintained a high DIC level of overlying water in treatments added cyanobacteria biomass. The treatment added the medium cyanobacteria biomass (235 g) presented the lower DOC/total dissolved carbon ratio than the high cyanobacteria biomass associated with the lower mineralization from DOC to DIC. Due to the concentration differences of DIC at water-sediment interface, the main migration of DIC from pore water to overlying water occurred in the treatment without added cyanobacteria biomass. However, the treatments added the cyanobacteria biomass presented the obvious diffusion of DOC and the low migration of DIC at the water-sediment interface. The diffusive fluxes of DOC at the water-sediment interface increased with the cyanobacteria biomass added, reaching the maximum value of 411.01 mg/(m·d) in the treatment added the high cyanobacteria biomass. In the overlying water, the group added the sediment and medium cyanobacteria biomass presented a faster degradation of cyanobacteria-derived POM to DOC and a higher mineralization level of DOC to DIC than added the medium cyanobacteria biomass without sediment. Therefore, during accumulated cyanobacteria decomposition, the biomass of accumulated cyanobacteria and sediment property can influence the migration and transformation of DC, playing an important role in carbon cycling in shallow eutrophic lakes.
积累的蓝藻分解过程会释放大量有机碳，并影响浅水富营养化湖泊中的碳循环。然而，溶解碳（DC）的迁移和转化机制仍需进一步研究和探讨。在本研究中，进行了一项为期73天的实验室微观实验，使用抽吸采样器（Rhizon和注射器）来了解蓝藻分解过程中DC的迁移和转化。蓝藻生物量的分解导致缺氧和还原条件，并改变了水柱中的酸碱环境。在孵化初期（第0 - 18天），大量蓝藻衍生的颗粒有机物（POM）在上覆水中分解为溶解有机碳（DOC），在添加高蓝藻生物量（470 g）的处理中达到最高峰值1.82 g/L。孵化18天后，增加的DOC矿化转化为溶解无机碳（DIC），使得添加蓝藻生物量的处理中，上覆水的DIC水平保持在较高水平。添加中等蓝藻生物量（235 g）的处理比添加高蓝藻生物量的处理呈现出更低的DOC/总溶解碳比率，这与从DOC到DIC的较低矿化程度相关。由于水 - 沉积物界面处DIC的浓度差异，DIC从孔隙水向上覆水的主要迁移发生在未添加蓝藻生物量的处理中。然而，添加蓝藻生物量的处理在水 - 沉积物界面处呈现出明显的DOC扩散和较低的DIC迁移。水 - 沉积物界面处DOC的扩散通量随着添加的蓝藻生物量增加而增加，在添加高蓝藻生物量的处理中达到最大值411.01 mg/(m·d)。在上覆水中，添加沉积物和中等蓝藻生物量的组比未添加沉积物的中等蓝藻生物量组呈现出更快的蓝藻衍生POM降解为DOC以及更高的DOC矿化转化为DIC的水平。因此，在积累的蓝藻分解过程中，积累的蓝藻生物量和沉积物性质会影响DC的迁移和转化，在浅水富营养化湖泊的碳循环中发挥重要作用。
