Department of Geological & Atmospheric Sciences, Iowa State University, Ames, Iowa, USA.
Center for Applied Geoscience, University of Tübingen, Tübingen, Germany.
Microbiologyopen. 2022 Jun;11(3):e1287. doi: 10.1002/mbo3.1287.
Subsurface chlorophyll maxima layers (SCML) are ubiquitous features of stratified aquatic systems. Availability of the micronutrient iron is known to influence marine SCML, but iron has not been explored in detail as a factor in the development of freshwater SCML. This study investigates the relationship between dissolved iron and the SCML within the dimictic, ferruginous lake Grosses Heiliges Meer in northern Germany. The occurrence of the SCML under nonferruginous conditions in the spring and ferruginous conditions in the fall are context to explore temporal changes in the phytoplankton community and indicators of primary productivity. Results indicate that despite more abundant chlorophyll in the spring, the SCML sits below a likely primary productivity maximum within the epilimnion, inferred based on colocated dissolved oxygen, δ C , and pH maxima. The peak amount of chlorophyll in the SCML is lower in the fall than in the spring, but in the fall the SCML is colocated with elevated dissolved iron concentrations and a local δ C maximum. Cyanobacteria and Chlorophyta have elevated abundances within the SCML in the fall. Further investigation of the relationship of iron to primary productivity within ferruginous SCML may help to understand the environmental controls on primary productivity in past ferruginous oceans.
次表层叶绿素最大值层 (SCML) 是分层水生系统中普遍存在的特征。已知微量元素铁的可利用性会影响海洋 SCML，但铁作为淡水 SCML 发育的一个因素尚未得到详细研究。本研究调查了德国北部二型、高铁湖泊大赫利戈尔斯米尔湖 (Grosses Heiliges Meer) 中溶解铁与 SCML 之间的关系。在春季非高铁条件和秋季高铁条件下 SCML 的出现，为探索浮游植物群落和初级生产力指标的时间变化提供了背景。结果表明，尽管春季的叶绿素更为丰富，但 SCML 位于可能的表水层初级生产力最大值之下，这是基于共定位溶解氧、δ C 和 pH 最大值推断的。秋季 SCML 中的叶绿素峰值量低于春季，但在秋季，SCML 与升高的溶解铁浓度和局部 δ C 最大值共定位。秋季 SCML 中的蓝藻和绿藻丰度升高。进一步研究铁与高铁 SCML 内初级生产力的关系，可能有助于了解过去高铁海洋中初级生产力的环境控制因素。
