The effect of short-term fluctuations in pH on NO −3 uptake and intracellular constituents in Skeletonemacostatum (Grev.) Cleve

Abstract

Measurements of uptake rates, intracellular nitrogen pools, and other key intracellular constituents were made during exponential growth in Skeletonema costatum (Grev.) Cleve under varying pH levels. An understanding of the overall effects of extracellular pH on the above mentioned cellular parameters is crucial in order to ascertain the degree to which pH must be regulated and monitored in laboratory experiments with marine phytoplankton. It was found that uptake rates and intracellular pool sizes of NO − 3 were directly influenced by the extracellular pH level, whereas, other cellular compounds remained relatively unchanged. Therefore, nitrogen uptake and intracellular nitrogen storage are dependent on key H + and OH − ion transport mechanisms that are associated with phytoplankton metabolism. These findings reiterate the fact that investigators examining nitrogen uptake and assimilatory mechanisms in marine phytoplankton must be conscious of cellular H + and OH − fluxes that contribute to intracellular pH regulation and changes in extracellular pH levels, both of which interact to affect phytoplankton metabolic processes.