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Studies the chemical form of dissolved silicon taken up by marine diatoms. Kinetics of silicon use; Use of silicon tracer methodology to determine uptake rates; Variation in half-saturation constant.

Reports on the development of a [sup 32]Si autoradiographic technique using a liquid photographic emulsion for the study of diatom silica deposition in culture or in natural water samples. Use of the method in the Central North Pacific to study silica deposition by diatoms of the genus Rhizosolenia; Composition of the Rhizosolenia mats examined.

The relatively non-toxic dye, rhodamine 123 (R123), was incorporated into the frustule of Thalassiosira weissflogii Grun. clone ACTIN in direct proportion to biogenic silica (BSi). R123 was used together with the DNA stain propidium iodide to track and quantify Si deposition during the cell cycle of T. weissflogii using flow cytometry, Silicon deposition was not continuous through the cell cycle. Deposition of the valves occurred during M phase. The hypocingulum was largely deposited during G 1 with some suggestion of minor or girdle band deposition during G2. Silicon deposition did not occur during S phase. Assuming that a complete pustule consists of an epivalve, epicingulum, hypocingulum, and hypavalve, then 40% of cellular BSi was contained within the cingulum of T. weissflogii with 60% present in the valves. These percentages correspond to 0.38 pmol Si in the two cingula and 0.57 pmol Si in the valves. Temporal differences in the timing of silicic acid uptake and deposition during the cell cycle of T. weissflogii suggested that deposition of both the new valves and the cingulum is supported by an internal pool of dissolved Si acquired during G2. [ABSTRACT FROM AUTHOR]

Neutral lipids, consisting primarily of triacylglycerols, were found to be a major form of carbon reserve in zoospores of the giant kelp Macrocystis pyrifera (L.) C. Ag. The fluoreseent stain Nile Red revealed large lipid droplets in the posterior end of the cell, which comprised 20-41% of cellular carbon in newly released spores. Flow cytometric analysts of newly released spores stained with ,Vile Red revealed considerable variation in the neutral lipid content among spores that was independent of spore ha,. Lipid droplets were consumed during germination in spores maintained either under constant light or in continual darkness. The availability of light appeared to delay, but did not preclude, lipid use. The rate of lipid use during germination varied considerably among germlings with some cells consuming all of their lipid reserves within 5 h after release. In addition to zoospores, lipid droplets were observed in both male and female gametes. Numerous droplets were observed in eggs, while single lipid droplets were observed in sperm. Neutral lipid droplets were not observed in gametophytes or sporophytes except in developing gametes and spores. Large lipid reserves thus seem to be confined to the microscopic life history stages that presumably have relatively high energy demands. By serving as a supplemental fuel reserve, neutral lipids may be important in extending the effective range of zoospore dispersal. [ABSTRACT FROM AUTHOR]

The variability of marine diatom Si:C and Si:N composition ratio was examined to assess their utility as ecological under and 18:6 h LD cycle and sampled at the end of the light period gave mean ratios, by atoms, of 0.13 ± 0.04 and 1.12 ± 0.33 for Si:C and Si:N ratio, respectively (95% C.I. reported). The mean ratios, respectively under continuos illumination were 0.12 ± 0.03 for Si:C and 0.95 ± 0.23 for Si:N. the mean ratios of the clones grown under constant light were not statistically different from under constant light were not statistically different from those calculated for the same species grown under and 18.6 h LD photoperiod. The overall mean Si:C under an 18:6 h LD and continuous light experiments taken together, weighted by the number of species in each experiment, are 0.13 and 1.05, respectively. The average ratios for the nine nanoplandton species (<20 μm) examined were 0.09 ± 0.03 for Si:C and 0.80 ± 0.35 for Si:N. The eighteen netplankton species (>20 μm)had higher mean ratios, Si:C = 0.15 ± 0.04 and Si:N = 1.20 ± 0.37. Time course sampling throughout a 24 h period revealed twofold variations in both ratios for individual species grown on a 14:10 h LD cycle. Changes in irradiance can also produce factor of two variations, both ratios being higher under low light. Comparison of these data with those from the literature regarding the effects of temperature and nutrient limitation on diatom elemental composition suggest that use of these ratios to convert field estimates of biogenic silica production from [SUP14C] data, should yield results accurate to within a factor of three under most circumstances. [ABSTRACT FROM AUTHOR]