RESULTS
The results of our experiment are summarized in the following graphs.
 

We took measurements on three different days.  These days were each three days apart.

PAR = photosynthetically available light
UVA = UV-A radiation
UVB = UV-B radiation
LL = algae grown under low light conditions
HL = algae grown under high light conditions

    In the interval between the first and second time measurements were taken, there was an increase in both the cell counts and the concentration of chlorophyll a.  Graph lines from both graphs show about the same slope.  However, the clustering that occurred when measurements were taken a second time do not show any significant differences between the three treatments (PAR, PAR + UVA, and PAR + UVA + UVB).  Possible explanations for this may be that the weather during this time was cloudy and overcast.  This might have resulted in lower ultraviolet radiation.  It was also noted that condensation occurred on the top of the boxes and that could have interfered with transmittance of ultraviolet radiation into the cultures.

    There was no significant change in either cell count or chlorophyll a concentration between the second and third interval.  Possible causes for this are the following: 1) the samples may have run out of nutrients; 2) there might have been a lack of carbon dioxide which could have been corrected by the addition of sodium bicarbonate to the cultures; 3) and, human error in counting and measuring chlorophyll a concentration and cell counts.

    A few cautions should be noted.  The bags were floating in different positions and in different places in the boxes causing uneven exposure to sunlight.  Also it is important to start with new materials on the box lids because over time mylar deteriorates.

    In conclusion, both cell counts and chlorophyll a concentration exhibit similar trends over time.  Therefore, both or either could be used to measure the growth of phytoplankton cultures.