Science Diary: Beach Sand - Results: The Pulse of the Planet daily radio program offers free legal online mp3 downloads, exploring the world of sound in nature, culture and science, with audio adventures, world music, extraordinary sound portraits, science diaries, and nature ring-tones; an amazing sonic experience.

Airdate: Jun 17, 2008
Scientist: Adina Paytan

Science Diary: Beach Sand - Results

Science Diary: Beach Sand - Results
After heat sealing and incubating samples of ocean water, counting bacteria is a numbers game.

music; ambience

"Today we're going to look at our sand samples taking out of an incubator after about 20 hours."

Welcome to Pulse of the Planet's Science Diaries, a glimpse of the world of science from the inside. That's Ella and Rose, two middle school students collaborating on a science fair project on beach sand contamination. Their work caught the attention of Dr. Adina Paytan, an oceanographer at the University of California in Santa Cruz, who's helping to guide their research. Right now they're analyzing their latest test results.

"To read the total coliform levels, we count the big and small wells of yellow bacteria. And we have an MPN chart, or Most Probable Number, to see the amount of bacteria that is in each sample. And then to read the E. coli counts, we have a black light, and we count the number that are glowing."

Rose and Ella are looking at samples of water which they heat-sealed and incubated overnight. These ocean and groundwater samples were filtered through beach sand to understand how bacterial contaminants migrate between sand and water. Samples were taken from three California beaches which occasionally close when bacterial levels are high.

"Capitola AO, the sand filtered the bacteria in this one, because the ocean water was dirty, and it's completely clean now. Rio A6. Hey, look! It's clean!"

These latest results show little to no bacterial contamination in the water, while previous testing showed significantly high numbers. One theory is a recent rainstorm may have effectively purged the sands of contaminants.

Please visit our website,, and learn about our new project, the Kids' Science Challenge. Pulse of the Planet's Science Diaries are made possible by the National Science Foundation. I'm Jim Metzner.