Dead Spots in the Ocean: HNLC Areas' Restriction to Phytoplankton's Uptake of CO(2)

Overview

Objectives/Goals A current solutions to global warming is to fertilize HNLC (High Nutrient Low Chlorophyll) ocean areas lacking iron with iron to increase CO2 absorption from phytoplankton. However, besides iron, some HNLC areas also lack silicate. The objective of this project is to determine if the absence of silicate or iron has a greater restriction to diatoms# uptake of CO2. I also want to determine if fertilizing HNLC areas with iron to decrease the rising levels of CO2 in the atmosphere is really the best solution, as opposed to fertilizing it with silicate, another needed but lacked nutrient. Methods/Materials Thalassiosira weissfloggi, a common diatom, was chosen to be used for the experiment. They were inserted into three different environments modeling after each of the two different HNLC areas and the standard culture that diatoms live in. After CO2 was inserted into the air tight vials, the Gas Chromatography was used to monitor the absorption of CO2 over time. The pH level was also tested at the beginning and end of the experiment to observe the CO2 uptake. To study the growth in diatoms, a cell count was conducted at the beginning and end of the experiment as well. Results Based on the results from the Gas Chromatography, diatoms in the culture without silicate had the least amount of CO2 absorption, at 7µl less than the standard culture. The results of the pH measurements corresponded with the Gas Chromatography results. Diatoms in the vials without iron were found to have the least cell growth, with a difference of approximately 6,800 cells/µl less than the standard culture. Conclusions/Discussion After the research and experiment, it is reasonable to presume that fertilizing the ocean with iron might not be the best choice. From the results, one can conclude that iron in the ocean doesn#t cause diatoms to have additional CO2 absorption but population increase instead. The extra phytoplankton would absorb more CO2 if it didn#t trigger zooplankton, a predator of phytoplankton, growth as well. The population increase in both of the organisms eventually evens out, because the extra zooplankton would consume the extra phytoplankton. On the other hand, the lack of silicate causes diatoms to have a decrease in CO2 uptake, so with the silicate stimulation, there will be more CO2 uptake without more population. Silicate fertilization also only triggers diatom growth and would not result in unwanted consequences.

Awards (1)

• Category Award

Competition history

• CSEF 2004 Environmental Engineering · Entry J0899

Resources

• CSEF project summary ↗

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