Conclusion and Extensions
Lab did show that as percent light increase, simulating shallower waters and brighter days, both the net primary productivity and gross primary productivity increased. Instead of linear growth, the data showed a logarithmic growth. Originally it was thought that this relationship was because lowered measured concentrations of dissolved oxygen puts stress on the aquatic system, the change in gross and net primary productivity would be apparent in systems exposed to lower intensities of light. The range of positive net productivity would be bounded by average primary productivity at 100 percent light and minimum percent light to maintain levels of dissolved oxygen. ...view middle of the document...
82-95). Using a linear model, it obtained an R2 value of .82, showing that 82 percent of the changes in primary productivity could be explained by variability in percentage light.
Because the results for the class and group data did not follow a linear relationship, there would have been some errors. When filling up the bottles initially, the method of plunging the bottle into the culture and allowing the air bubble to rise up could have added various amounts of dissolved oxygen to the initial culture. A better method might have been to slowly tip the bottles in, allowing the culture to enter the bottles as air moves out, then capping it underwater.
Because dissolved oxygen might have diffused out of the water when the caps were opened, accurate reading would not have been acquired. Titration should have been started immediately after opening the cap, to allow the contents to come to a fixed state without altering levels of dissolved oxygen. Additionally, when adding the manganous sulfate and potassium iodide, some culture could have spilled. Gas is lighter than water so there could have been higher dissolved oxygen content near the top of bottle. Opening the bottle caps in a colder room could have prevented loss of dissolved oxygen.
Studies have shown that titration method of determining dissolved oxygen concentrations is not that sensitive or as accurate. Also, because the titrant was administered in small squirts, issuing the wrong amount of titrant will magnify the error in ppm dissolved oxygen by a factor of 10. If possible, the method of using radioactive carbon to measure primary productivity will yield better results.
Because nutrients and wastes cause eutrophication to occur, depleting levels of dissolved oxygen in water, further experiments can be done comparing the effect of wastes and different amounts of nutrients in fertilizers on primary productivity. By finding what chemicals affect primary productivity to what degree, efforts can be directed to raise awareness and curb eutrophication. In addition the bodies of water can remain healthy, allowing for a diversity of organism to thrive. Because chemical may act together to produce different effect, dangerous combinations can be identified and eradicated. It will prevent pollution of large...