Nine Seattle-area high school students are finalists in the Intel International Science and Engineering Fair in Pittsburgh, Pa.

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When storms wash the residue left behind by cars off the Highway 520 bridge, some nasty chemicals end up in Lake Washington.

Scientists typically check water quality by looking for levels of contaminants high enough to kill a lot of fish — a crude measure that misses the more subtle effects that runoff can have on marine life, especially fish eggs.

Meera Srinivasan, a senior at Interlake High School in Bellevue, wanted to find a simple way to directly measure what was happening with the fish.

Her solution earned her a spot in the 2015 Intel International Science and Engineering Fair in Pittsburgh, Pa., this week, described as “the world’s largest international pre-college science competition.”

She and eight other high school students from the Seattle area are competing with about 1,700 other finalists from 78 countries, regions, and territories for the top prize of $75,000.

The other Seattle-area finalists are:

Gokul Gowri, Inglemoor High School, Kenmore;

Mahalaxmi Elango, Interlake High School, Bellevue;

Sonia Murthy, Ethan Perrin, and Sophia Tevosyan from Nikola Tesla STEM High School, Redmond;

Cameron Beardsley, Hyrum Bock, and Rosemichelle Marzan from the Northwest Nuclear Consortium, Federal Way. (The consortium is an after-school STEM program.)

Meera Srinivasan
Meera Srinivasan

Srinivasan, who is in the gifted program at Interlake and earned her International Baccalaureate diploma last year with a perfect score, will attend Stanford University this fall where she plans to study biology and computer science.

She used zebrafish bred in the laboratory for her experiment, a species favored by biologists because it creates see-through embryos, allowing scientists to observe the development of internal organs like the heart under a microscope.

She found that exposure to a common contaminant in storm water runoff slowed the embryo’s heart rate, which she had to measure by counting each beat ­­– a time-consuming task that requires some pretty good microscope skills.

But counting a tiny fish embryo’s heart beats isn’t very practical, so she searched for another biological marker in the fish that would tell scientists about the toxicity of the water.

That turned out to be the presence of a certain kind of metabolite, which are molecular substances created when a zebrafish breaks down the contaminants in its system and are typically excreted.

Metabolism is generally considered to be detoxifying, but she discovered that some of those metabolites are more toxic than the original unmetabolized compound she was studying — a surprising result. She found that the presence of those toxic molecules in a zebrafish embryo was strongly associated with the lower heart rate she had observed.

“You can predict that you’re going to see cardiac abnormalities in the fish,” she said. “That was the aha moment.”

That means labs could save time and effort by just testing embryos for those molecules, using a chemistry technique she adapted for her project.

The other students’ projects range from designing more efficient flu vaccines to reducing the impact of discarded household refrigerators on global warming. The winner will be chosen Friday.