TY  - JOUR
A1  - Spijkerman, Elly
A1  - Behrend, Hella
A1  - Fach, Bettina
A1  - Gaedke, Ursula
T1  - Decreased phosphorus incorporation explains the negative effect of high iron concentrations in the green microalga Chlamydomonas acidophila
JF  - The science of the total environment : an international journal for scientific research into the environment and its relationship with man
N2  - 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-1) 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 Fe3+ concentrations exceeded 100 mg Fe3+ L-1. 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-1 (i.e. 15 mg free ionic Fe3+ L-1), 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.
KW  - Chlamydomonas
KW  - Ecotoxicology
KW  - Extreme environment
KW  - Iron toxicity
KW  - Phosphate limitation
KW  - Phytoplankton
Y1  - 2018
U6  - https://doi.org/10.1016/j.scitotenv.2018.01.188
SN  - 0048-9697
SN  - 1879-1026
VL  - 626
SP  - 1342
EP  - 1349
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Spijkerman, Elly
T1  - The expression of a carbon concentrating mechanism in Chlamydomonas acidophila under variable phosphorus, iron, and CO2 concentrations
JF  - Photosynthesis research
N2  - The CO2 acquisition was analyzed in Chlamydomonas acidophila at pH 2.4 in a range of medium P and Fe concentrations and at high and low CO2 condition. The inorganic carbon concentrating factor (CCF) was related to cellular P quota (Q(p)), maximum CO2-uptake rate by photosynthesis (V-max; O-2), half saturation constant for CO2 uptake (K-0.5), and medium Fe concentration. There was no effect of the medium Fe concentration on the CCF. The CCF increased with increasing Q(p) in both high and low CO2 grown algae, but maximum Q(p) was 6-fold higher in the low CO2 cells. In high CO2 conditions, the CCF was low, ranging between 0.8 and 3.5. High CCF values up to 9.1 were only observed in CO2-limited cells, but P- and CO2-colimited cells had a low CCF. High CCF did not relate with a low K-0.5 as all CO2-limited cells had a low K-0.5 (<4 mu M CO2). High Ci-pools in cells with high Qp suggested the presence of an active CO2-uptake mechanism. The CCF also increased with increasing V-max; O-2 which reflect an adaptation to the nutrient in highest demand (CO2) under balanced growth conditions. It is proposed that the size of the CCF in C. acidophila is more strongly related to porter density for CO2 uptake (reflected in V-max; O-2) and less- to high-affinity CO2 uptake (low K-0.5) at balanced growth. In addition, high CCF can only be realized with high Q(p).
KW  - C3 photosynthesis
KW  - Micro-algae
KW  - Carbon concentrating mechanism
KW  - Phosphorus limitation
KW  - Iron toxicity
Y1  - 2011
U6  - https://doi.org/10.1007/s11120-010-9607-z
SN  - 0166-8595
VL  - 109
IS  - 1-3
SP  - 179
EP  - 189
PB  - Springer
CY  - Dordrecht
ER  -