http://www.co2science.org/data/mwp/studies/l1_lake4.php

“Because of this bloom-and-bust lifestyle, diatoms are believed to play a disproportionately important role in the export of carbon from oceanic surface waters[9][8] (see also the biological pump).” Wikipedia

“The first stable product of photosynthetic carbon fixation by land plants is either the three-carbon molecule phosphoglycerate (in C3 plants) or the four-carbon compounds malate or aspartate (in C4 and CAM (crassulacean-acid metabolism) plants). Reinfelder et al. infer that a C4 biochemical pathway of carbon fixation also operates in marine diatoms1, 2 on the basis of their discovery of the enzyme phosphoenolpyruvate (PEP) carboxylase and of their 14C-tracer results in the marine diatom Thalassiosira weissflogii. However, we consider that further analysis is called for to demonstrate that this marine diatom meets all the criteria for C4 photosynthesis.” Nature

e.g. A. Leynaert P. Tréguer, Christiane Lancelot and Martine Rodier 2000

It would appear that a study of long-term oceanic diatom population changes might be interesting.

JF

The top of a sediment pile is generally looser and more unconsolidated material than the more compacted material beneath. Mostly, the top needs casing to allow the drilling to continue.

However, in Kathan’s thesis, a comparison of core log with the acoustic scan of the hole showed the core losses to be at the bottom of the hole – perhaps because drilling cuttings (percussion) were settling in the bottom and making core recovery difficult. My post #17 notes this.

Kathan maintains that the BSi index is a measurement of the skeletal silicate remains of diatomaceous activity. Various laboratory examinations of the core samples and sediment traps (including some electron microsocopy) were used to decide the origin of the silica shards.

Again, Kathan’s contention is that increased levels of BSi in the area of study were a result of summer precipitation, not glacial meltwater (p.49)

I haven’t completed a full reading of McKay’s thesis as yet, but can find no direct comment on core recovery as yet.

I am finding this thread a bit confusing. Is it known for certain what the period of the Kaufman proxies actually was, in terms of the widely used “BP” scale? I can understand that scale readily enough. Steve’s plot in #8 uses “Ascribed year” as the x axis. When I read that Kaufman states the period of his work covers from 5600 to 3000 how do I reconcile Steve’s axis notation with this scale? The Excel file that I’ve downloaded and begun to examine uses Year as its first column, on a scale going from 5 to 2000 – if I’ve remembered correctly – in steps of 5. This confuses me a lot (

Is there a full list of Kaufman’s proxies somewhere? I fear I must have missed it.

Thanks for any help/advice.

Robin

RE Tag #27 and Steve’s reply to #28, If the organisms are diatoms, then they are photosynthetic, and at least candidates for controlling for CO2. Wikipedia has a nice article on diatoms.

A method for distinguishing between BSi and LSi has been suggested:
Olivier Ragueneau et al Continental Shelf Research 25, (2005) 697-710

The MSc thesis by Kathan makes no mention of LSi. In all likelihood because they use mildly basic conditions (Mortlock and Froelich (1989) ) which would not dissolve LSi.

However, things are not so simple. When looking at trapped sediments the sample is pretreated with 1M NaOH, here one might expect LSi to be dissolved as well.

As ever I suspect these questions arise only because we are not familiar with the laboratory background. Almost certainly there exists a background knowledge which is taken for granted in the MSc thesis and not thought to need referencing.

Is this due to the activity of taking the core?