Pine pollen on the surface of Lake Tahoe. Photo/TERC

It is the time of year when the big blue turns yellow. Pine pollen can be seen blowing out of the forest in great clouds with much of it landing on Lake Tahoe’s surface.

When viewed from the air great swirls of yellow more than a mile long look like a giant hand finger painted on the surface. Despite the vast quantities, pollen does little to change Tahoe’s water clarity. Pine pollen grains (50-80 microns) are relatively large compared to the <10 micron particles primarily responsible for clarity loss.

In the water, the pollen grains stick together and settle to depth quickly. Once on the bottom they add to the historical record. Pollen grains recovered from sediment cores have been used by scientists to determine historic vegetation and provide clues to climate conditions thousands of years in the past.

— UC Davis, Tahoe Environmental Research Center