Nitrite utilization by Chaetoceros muelleri under elevated CO₂ concentration
2008
Hu, Hanhua | Zhang, Xu
Chaetoceros muelleri (Lemn.) was cultured with nitrite (NO ₂ ⁻) or nitrate (NO ₃ ⁻) as the sole nitrogen source and aerated with air or with CO₂-enriched air. Cells of C. muelleri excreted into the medium nitrite produced by reduction of nitrate when grown with 100 μM NaNO₃ as nitrogen source. Accordingly, NO ₂ ⁻ concentration reached 10.4 μM after 95 h at the low CO₂ condition (aerated with air); while the maximum NO ₂ ⁻ concentration was only around 2.0 μM at the high CO₂ condition (aerated with 5% CO₂ in air), furthermore, after 30 h it decreased to no more than 1.0 μM. NO ₂ ⁻ was almost assimilated in 80 h when C. muelleri was cultured at the high CO₂ condition with 100 μM NaNO₂ as sole nitrogen source. At the high CO₂ condition, after 3 h the activity of nitrite reductase was as much as 50% higher than that at the low CO₂ condition. It was indicated that enriched CO₂ concentration could inhibit nitrite excretion and enhance nitrite assimilation by cells. Therefore, aeration with enriched CO₂ might be an effective way to control nitrite content in aquaculture systems.
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