Diatom frustules

Individual diatom frustules are porous. The diatoms are highly variable in shape and size, having particles that range in effective diameter from 0.75 to 1000 pm, but most are 50 to 100 pm in diameter. Diatom shapes can range from simple cylinders and disks to complex, highly variable, but always punclaie, forms. 

CFSP Colony formation with seed particles In vitro observation of colony formation from solitary cells in P. pouchetii with diatom frustules Nejstgaard et al. (in press)... 

During the 2002 mesocosm study, an experiment was conducted to determine if in vitro P. pouchetii colony formation rates would be enhanced by the presence of diatom frustules added to culture medium detailed methods and results appeared in Nejstgaard et al. (in press). Colony formation rates were estimated using water from a nutrient-amended mesocosm that was filtered to remove Phaeocystis colonies but... 

Diatom frustules enhance P. pouchetii colony formation in vitro (Nejstgaard et al. 2006), a process that may therefore accelerate the in situ transformation of solitary motile cells into new colonies. This is the critical step in the formation of colony-based Phaeocystis blooms, and thus is essential in... 

Figure 17.4 A. SEM image of a residual, concentric diatom frustule that has been converted to a predominantly 7 A clay (synchrotron XRD). B). Superimposed EDS image showing density of K, Fe, Si, and Al in a residual frustule (all components present, S subtrated from Fe). Authigenic clays also can occur as cements agglutinating matrix clays. In some cases, the authigenic components are amorphous, 7 A, or 10 A phases (see Michalopoulos and Aller, In Prep., Michalopoulos et al. 2000).

The ongoing research into such specific N fractions is critical to address the fundamental issue of isotopic alteration of exported organic N in the water column and sediments. This work also raises a host of new questions. Consider the case of diatom frustule-bound N (Fig. 34.7). The organic N of diatoms exported from the surface layer could differ from the integrated sinking N, for instance, if the isotope effect of nitrate assimilation by diatoms differs from that of the entire phytoplankton population. Moreover, the of N trapped and preserved within the diatom... 

Diatom frustules and sponge spicules in terrestrial environments are derived chiefly from fresh and brackish water species and from unconsolidated fossiliferous sediments exposed to surface winds and water. 

As is the case with other forms of non-crystalline silica, the conversion to quartz of phytoliths, diatom frustules, and sponge spicules under sedimentary conditions on land can be expected to be accelerated by elevated temperature, elevated pressure, and the presence of an aqueous phase of high pH (>9) or containing electrolytes. 

Marine waters also receive some biogenic silica from the land. This material is transported to the sea as windblown dust and as part of the suspended load of rivers. Rivers also deliver about 0.43 Pg of dissolved silica annually to the oceans, and some fraction of this is undoubtedly derived from biological sources as well. Locally, terrigenous biogenic silica (in particulate form) may accumulate to significant concentrations on the sea floor. For example, Kolbe (1957) reported frequent occurrences of phytoliths and freshwater diatom frustules in deep-sea cores from the equatorial Atlantic, and one locahty contained diatom tests derived exclusively from freshwater species. 

Scanning electron micrographs of (A) a diatom frustule (opal), diameter c.20 pm ... 

Labyerie, L. Jr. 1974. New approach to surface seawater paleotem-peratures using 0/ 0 in silica of diatom frustules. Nature, 248 40-42. 

Figure 6.8 (A) Scanning electron microscopy image of diatom frustules within actively forming barrage tufas at Cwm Nash, Glamorgan. Scale bar 20 pm. (B) Detrital tufas from ancient barrage at Caerwys, North Wales. Micritic peloids within sparitic cement with much remaining pore space. Photographed under crossed nicols, width of image 2.5 mm.

Enhencement of diatom frustule dissolution by iron oxides. Marine Geology, 99 263-266. 

Ferrante, J. G. Parker, J. L, Transport of Diatom Frustules by Copepod... 

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