Original paper
The effects of nutrient depletion on the sinking velocity and cellular composition of a freshwater diatom
Davey, Martin C.
Archiv für Hydrobiologie Volume 112 Number 3 (1988), p. 321 - 334
40 references
published: May 20, 1988
DOI: 10.1127/archiv-hydrobiol/112/1988/321
ArtNo. ESP141011203000, Price: 29.00 €
Abstract
The planktonic, freshwater diatom Asterionella formosa Hass was grown in batch culture until growth was limited by silicon or phosphorus availability. Limitation of growth by either nutrient led to an increase in colony sinking velocity and a decrease in colony density. In the case of silicon-limitation these effects occurred when ambient silicon was exhausted, but in the case of phosphorus-limitation they were delayed until the cellular reserves of phosphorus were exhausted. Lower sinking velocities and higher densities were recovered on addition of the limiting nutrient in excess. All such changes occurred rapidly (< 1 day) and following the initial changes no further variation occurred. Following limitation of growth by either nutrient photosynthesis appeared to continue leading to an increase in the cellular content of protein in silicon-limited cells or carbohydrate in phosphorus-limited cells. The decreases in colony density are explained by increases in cell volume, there being no decrease in the cell’s dry weight. The increase in sinking velocity may also have been partly caused by the increase in cell volume, but this cannot provide a full explanation. Variations in diatom sinking velocities in response to the prevailing nutrient regimes have important consequences for the vertical distribution of the diatom in the natural environment, in particular in the formation of midwater maxima.
Keywords
phosphorus • planktonic • silicon • photosynthesis