The Effect of Ultraviolet (UV-B) Radiation on Spirogyra

Overview

Objectives/Goals The goal of my project was to determine if low-intensity radiation exposure in addition to normal sunlight effects a simple unicellular organism. My experiment uses a UV-B light in addition to normal sunlight to demonstrate that increased UV-B radiation reaching the Earth#s surface through the hole in the ozone layer might have a similar effect on unicellular organisms. Methods/Materials Spirogyra samples from a laboratory supply store were put in petri dishes filled with rainwater. Half the samples were placed on a table in the sun and half were placed on the same table but also exposed to a five watt UV-B light. I took extreme care to prevent my exposure to any radiation. Every five hours I looked at individual spirogyra strands under a microscope to count any changes in the number of cells. In the next part of the experiment I weighed new spirogyra samples on an electronic balance and then repeated placing the samples on the table in equal groups. At various times I measured the amount of light passing through the spirogyra samples. I used a data logger with a light sensor attached and downloaded the data to my computer. The experiment was repeated numerous times and a statistical analysis was conducted. Results When compared to spirogyra in sunlight, the samples exposed to both sunlight and UV-B radiation developed a weaker pigmentation and exhibited reduced growth. Longer exposure made these differences more noticeable. In the first part of the experiment the sunlight spirogyra strands increased in cell count or remained constant while the samples exposed to sun and UV-B radiation decreased. In the main part of the experiment more sunlight consistently passed through the sunlight and UV-B samples, indicating less chlorophyll, while less sunlight went through the sunlight only spirogyra, indicating more chlorophyll. A #Student T Test# statistical analysis of this data shows that the differences between the samples were significant, and not due to chance. Conclusions/Discussion Spirogyra in only sun continued to thrive but samples exposed to sun and UV-B radiation showed weaker pigmentation and reduced growth. Since pigmentation indicates the amount of chlorophyll present it appears that UV-B radiation effects spirogyra's photosynthesis process. The experiment#s statistical evidence is strong. Low intensity UV-B radiation has a detrimental effect on the unicellular organism spirogyra.

Competition history

• CSEF 2002 Pharmacology/ Toxicology · Entry S1403

Resources

• CSEF project summary ↗

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