Freshwater Ecology - PCB 4301
Third Problem Set
Due: 5:00 PM, Friday 1 October
Stoke's Law describes the sinking velocity of small objects like phytoplankton. Diatom cells are
between 5 and 25 microns in diameter, with an average around 15 microns. These cells have a
density ranging from 995 - 1300 kg m-3, with an average of about 1100 kg
m-3. Form resistance of diatoms ranges from 0.8 - 5, with a mean of 2. Explore the
consequences of differences in these properties on the sinking velocity of diatoms by graphing
sinking velocity as a function of diameter, density and form resistance (3 graphs). In each of
these graphs, hold the other factors important in sinking velocity constant at the mean value (that
is, for example, figure out sinking velocity for cells of diameters between 5 and 25 microns,
assuming these sells have a density of 1100 kg m-3 and a form resistance of 2).
Graph these results in a spreadsheet, and email the spreadsheet to Dr. Fourqurean at
fourqure@fiu.edu.