Marine diatoms grown in chemostats under silicate or ammonium limitation. III. Cellular chemical composition and morphology of Chaetoceros debilis, Skeletonema costatum, and Thalassiosira gravida

Abstract

A b~ Three marine diatoms, Skeletonema costatum, Chaetoceros debilis, and Thalassiosira g r a~d a were grown under no limitation and a m m o n i u m or silicate limitation or starvation. Changes in cell m o r p h o l o g y were d o c u m e n t e d with p h o t o m i c r o g r a p h s of a m m o n i u m and s i l i c a t e-l i m i t e d and n o n-l i m i t e d cells, and c o r r e l a t e d with observed changes in chemical composition. Cultures grown under silicate starvation or limitation showed an increase in p a r t i c u l a t e carbon, nitrogen and phosphorus and c h l o r o p h y l l a per unit cell volume compared to n o n-l i m i t e d cells; p a r t i c u l a t e silica per cell v o l u m e decreased. Si-starved cells were d i f f e r e n t from S i-l i m i t e d cells in that the former c o n t a i n e d more p a r t i c u l a t e carbon and silica per cell volume. The most sensitive indicator of silicate limitation or s t a r v a t i o n was the ratio C:Si, being 3 to 5 times higher than the values for n o n-l i m i t e d cells.

Silicon content of five marine plankton diatom species measured with a rapid filter method1

“…With another clone grown under corresponding conditions, Harrison et al (1977) obtained a still lower value of 2.1 pg Si * cell-l. These comparisons are permissible since the cell dimensions were about the same in all cases (cell diameter ca.…”

“…The Si : surface area ratios were in the range of 0.015-0.089 pg Si *PM-~, which is close to the 0.01-0.08 pg Si. prnm2 range found in other marine plankton diatoms grown in silicon-rich media (Durbin 1977;Harrison et al 1977;Furnas 1978) and somewhat less than the 0.04-0.17 pg Si . prnB2 reported for freshwater plankton diatoms (BaileyWatts 1976).…”

“…Within a given species, the Si content may vary as a function of cell size (Paasche 197%;Durbin 1977) as well as of external factors. When plankton diatoms are grown in media with low silicic acid concentrations, their Si content may be reduced by as much as 70% (Paasche 1973b;Tilman and Kilham 1976;Harrison et al 1977). The degree of silicification may decrease with increasing temperature (Durbin 1977) or may show a maximum at some intermediate temperature (Furnas 1978).…”

“…Although silicon in the form of polymerized silicic acid (biogenic silica) is a major component of the cell walls of all important plankton diatoms, there is considerable variation between species in Si content (Parsons et al 1961;Paasche 1973u;Harrison et al 1977). Within a given species, the Si content may vary as a function of cell size (Paasche 197%;Durbin 1977) as well as of external factors.…”

Effect of phosphorus limitation on elemental composition and stable carbon isotope fractionation in a marine diatom growing under different CO2 concentrations

“…Because q m was not measured under steady state conditions, these values cannot be used to calculate the storage pool (q m Ϫ q c ). Under nonlimited conditions Harrison et al (1977) reported a cell quota of 2.39 fg P m Ϫ3 in S. costatum. With our estimates of q c , this resulted in a maximum storage pool of 1.75 fg P m Ϫ3 .…”