Meeting Abstract
15.2 Sunday, Jan. 4 Solving a low-Reynolds number conundrum: How fast should diatoms sink? MIKLASZ, K.A.; Hopkins Marine Station kmiklasz@stanford.edu
Diatoms are one of the oceans primary producers. We would like to understand the movement and flux of diatoms through the water column, or how fast diatoms of different sizes should sink. Fluid dynamic theory (Stokes law) predicts that for small objects such as diatoms, the relationship between size (r) and sinking speed (V) should be V~r2. Unfortunately, empirical data collected for diatoms over the last fifty years suggests an exponent much lower (between 1 and 1.5). This discrepancy can be solved if one realizes two facts: first, most of the diatom’s mass is in its frustrule, and second, the frustrule scales like a surface area. Through expressing these two ideas mathematically, a modification can be made to Stokes law such that it agrees with the empirical data. This modification solves a problem that has persisted for over fifty years and finally allows accurate modeling and prediction of diatom sinking speeds for oceanographic nutrient flux.
