Inhibition of NO3-, NH4+, and PO4(3-) uptake in Anabaena doliolum exposed to a petroleum oil.

The aqueous extract of Assam crude inhibited the uptake of NO3-, NH4+, and PO4(3-) in Anabaena doliolum and the response was essentially concentration dependent. Inhibition was most severe for the uptake of NH4+ followed in decreasing order by PO4(3-) and NO3-. Uptake of nutrients was competitively inhibited as in all the cases oil extract did not change Vmax; however, apparent Km was increased. The nature of oil components competing with nutrient ions is not certain at present. Oil-induced inhibition of nutrient uptake in cyanobacteria might be reversed in eutrophic waters rich in nutrients.