Department of Geography and Geosciences, GeoZentrum Nordbayern, Chair of Applied Geology, Schlossgarten 5, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Germany.
Department of Geography and Geosciences, GeoZentrum Nordbayern, Chair of Applied Geology, Schlossgarten 5, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Germany.
Sci Total Environ. 2022 Feb 10;807(Pt 3):151067. doi: 10.1016/j.scitotenv.2021.151067. Epub 2021 Oct 18.
Next to water quality deterioration, cyanobacteria blooms can affect turnover of aqueous carbon, including dissolved inorganic carbon (DIC), dissolved organic carbon (DOC), and particulate organic carbon (POC). We investigated interactions of these three phases and their stable isotopes in a freshwater pond with periodic cyanobacterial blooms over a period of 23 months. This helped to map turnover and sources of aqueous carbon before, during, and after bloom events. During bloom events POC isotope values (δC) increased up to -17.4‰, after aqueous CO (CO) fell below an atmospheric equilibration value of 412 μatm. Additionally, carbon isotope enrichment between CO and POC (ε) ranged from 2.0 to 21.5‰ with lowest fractionations observed at pH values above 8.9. The increase of δC and decrease of ε values at low pCO and high pH was most likely caused by the activation of the carbon concentrating mechanism (CCM). This mechanism correlated with prevalent assimilation of C-enriched HCO. Surprisingly, CO still contributed more than 50% to the POC pool down to pCO values of around 150 μatm. Only after this threshold the reduced ε suggested incorporation of C-enriched HCO.
除了水质恶化之外，蓝藻水华还会影响水相碳的周转，包括溶解无机碳（DIC）、溶解有机碳（DOC）和颗粒有机碳（POC）。我们在一个淡水池塘中进行了为期 23 个月的周期性蓝藻水华研究，调查了这三个阶段及其稳定同位素的相互作用，以绘制水相碳在水华事件前后的周转和来源图。在水华事件期间，POC 同位素值（δC）增加到-17.4‰，而水体 CO（CO）下降到低于大气平衡值 412 μatm。此外，CO 和 POC 之间的碳同位素富集（ε）范围为 2.0 至 21.5‰，在 pH 值高于 8.9 时观察到最低的分馏。在低 pCO 和高 pH 值下，δC 的增加和 ε 值的降低很可能是由于碳浓缩机制（CCM）的激活所致。该机制与富含 C 的 HCO 的普遍同化有关。令人惊讶的是，即使在 pCO 值降至约 150 μatm 时，CO 仍为 POC 池提供了超过 50%的碳。只有在这个阈值之后，ε 的降低才表明 C 富集的 HCO 的掺入。
