Department of Ecology and Ecosystem Modelling, University of Potsdam, Am Neuen Palais 10, Potsdam, Germany.
Department of Ecology and Ecosystem Modelling, University of Potsdam, Am Neuen Palais 10, Potsdam, Germany.
Sci Total Environ. 2018 Jun 1;626:1342-1349. doi: 10.1016/j.scitotenv.2018.01.188. Epub 2018 Feb 19.
The green microalga Chlamydomonas acidophila is an important primary producer in very acidic lakes (pH 2.0-3.5), characterized by high concentrations of ferric iron (up to 1 g total Fe L) and low rates of primary production. It was previously suggested that these high iron concentrations result in high iron accumulation and inhibit photosynthesis in C. acidophila. To test this, the alga was grown in sterilized lake water and in medium with varying total iron concentrations under limiting and sufficient inorganic phosphorus (Pi) supply, because Pi is an important growth limiting nutrient in acidic waters. Photosynthesis and growth of C. acidophila as measured over 5 days were largely unaffected by high total iron concentrations and only decreased if free ionic Fe concentrations exceeded 100 mg Fe L. Although C. acidophila was relatively rich in iron (up to 5 mmol Fe: mol C), we found no evidence of iron toxicity. In contrast, a concentration of 260 mg total Fe L (i.e. 15 mg free ionic Fe L), which is common in many acidic lakes, reduced Pi-incorporation by 50% and will result in Pi-limited photosynthesis. The resulting Pi-limitation present at high iron and Pi concentrations was illustrated by elevated maximum Pi-uptake rates. No direct toxic effects of high iron were found, but unfavourable chemical Pi-speciation reduced growth of the acidophile alga.
嗜酸绿藻 Chlamydomonas acidophila 是非常酸性湖泊（pH 值 2.0-3.5）中的一种重要初级生产者，其特点是铁浓度高（高达 1 g 总铁 L）和初级生产力低。先前有人认为，这些高铁浓度会导致铁的大量积累，并抑制嗜酸绿藻的光合作用。为了验证这一点，在灭菌的湖水和不同总铁浓度的培养基中，在限制和充足的无机磷（Pi）供应下培养藻类，因为 Pi 是酸性水中的一种重要的生长限制营养物质。在 5 天的时间内，光合作用和嗜酸绿藻的生长受高铁浓度的影响不大，只有当游离离子 Fe 浓度超过 100 mg Fe L 时，才会降低。尽管嗜酸绿藻相对富含铁（高达 5 mmol Fe：mol C），但我们没有发现铁毒性的证据。相比之下，许多酸性湖泊中常见的 260 mg 总铁 L（即 15 mg 游离离子 Fe L）的浓度会降低 50%的 Pi 同化率，并导致 Pi 限制的光合作用。高铁和 Pi 浓度下存在的 Pi 限制可以通过提高最大 Pi 吸收速率来证明。没有发现高铁的直接毒性作用，但不利的化学 Pi 形态会降低嗜酸藻类的生长。
