The researchers developed a method to accurately measure nitrate in seawater even when there are high levels of nitrite present. They used an ozonation technique to convert nitrite to nitrate, and created an equation to adjust for both nitrite and nitrate in the sample. By comparing the initial nitrite amount with the nitrate produced, they could estimate the original nitrate level. This method is useful for studying nitrogen levels in algae or bacteria cultures, where accurate nitrate measurements are crucial.