Question

You have a set of data that you collected on a mid-summer oceanographic cruise at a location where the main phytoplankton species found was species X. Table 1, Daily irradiances (, PAR) at selected depths (Z) estimated from measurements of light extinction coefficients and daily incident solar radiation at a location inhabited by phytoplankton species X. Location A Z (m) IE m2 d 40 32.7 26.8 18 12 8.1 3.6 0.73 2.5 10 15 20 30 50 75 60 3. From the data for I vs Z in the table above, calculate the light extinction coefficient, k, rounding to three decimal places. Show your work. 4. Use the data in the P vs I graph from question 1 and the light attenuation data above to construct a graph showing how you would expect P to change with depth for species X at this location. Assume that the concentration of phytoplankton Species X is the same as in the experiment in part I and is constant with depth. Show your work. Briefly explain the vertical profile of P that you obtained. 5. Assuming that species X is representative of the phytoplankton assemblage, predict the critical depth for this site at the time period that you sampled. Show your work.

Answer 1

3) Calculate the light extinction coefficient k

The extinction coefficient K=(ln I_o- ln I_d)* D^-1

where, I_o is the light intensity at the surface

I_d is the light intensity at the depth and D is the depth.

Here I_o= 40 at the surface, I_d =0.1 at a depth of 75 m and depth=75m.

K=(ln40- ln0.1)*75^-1

K=5.99 * 75^-1

K=0.079