Single-entity coccolithophore electrochemistry shows size is no guide to the degree of calcification

Abstract

We report single-entity measurements of the degree of calcification of individual phytoplankton cells. Electrogenerated acid is used to dissolve the calcium carbonate (CaCO3) shell (coccosphere) of individual coccolithophores and the...

Quantifying the Extent of Calcification of a Coccolithophore Using a Coulter Counter

“…The newly presented technique is in excellent agreement with the range of values as reported in the literature for each species, and this remains to be the case despite encompassing any variation in calcite mass per cell which might be expected at different stages of the growth curve. 24 , 25 As can be seen from Figure 5 , the mass of calcite per cell differs by almost 2 orders of magnitude between the E. huxleyi and C. braarudii samples. Given the far greater mass of calcite associated with the C. braarudii sample, the experimental dissolution times were significantly longer, taking an average of 272 ± 24 s for the material to dissolve.…”

“…If the calcite shell surrounding the coccolithophore was a smooth sphere, then the roughness factor would have a value of 1; however, in the present case, the calcite surface that is accessible during the dissolution reaction is clearly greater than that of a smooth sphere, and hence, R f must have a value greater than unity. A roughness factor of 4 ± 2 24 has been previously advocated for in the literature on the basis of optical dissolution study experiments; hence, in the following analysis, we use this range of roughness factors. Furthermore, it should be commented that eq 5 varies as a function of the particle radius, and it is important to recognize that this radius refers to the geometric particle size as can be measured accurately by optical microscope and not the relative particle size as reported using the Coulter Counter.…”

“…A roughness factor of 4 ± 2 is applied for all three species. 24 Also overlaid is a comparison of the expected calcite mass per cell on the basis of the reported literature values (see Supporting Information Section S8). The newly presented technique is in excellent agreement with the range of values as reported in the literature for each species, and this remains to be the case despite encompassing any variation in calcite mass per cell which might be expected at different stages of the growth curve.…”

Rapid Opto-electrochemical Differentiation of Marine Phytoplankton

“…A schematic of the opto-electrochemical cell showing the threeelectrode setup is reported elsewhere. 28 Concentrated phytoplankton cells from the culture medium were drop-casted onto the surface of the working electrode. The plankton cells were allowed to sediment onto the electrode under gravity for 2 min before the excess culture solution was removed from the electrode surface by gently soaking it up with a tissue paper.…”

“…A glass slide was then placed at the top to seal the opto-electrochemical cell to leave at least 1 mm of electrolyte solution in between the working electrode and the coverslip. 28 Potentiostatic control and synchronization with the camera were provided by a previously developed in-house built device and current amplifier (Keithley 427) from Keithley Instruments Inc. In other experiments, a galvanostat as opposed to the potentiostat was used, the principal feature being that a galvanostat controls the electrode current while allowing measurement of the applied potential as a function of time.…”