The researchers studied the nutrients that limit the growth of algae in strip mine ponds. They used a test alga and natural phytoplankton to test for nitrogen, phosphorus, and iron as limiting nutrients. They also used a synthetic chelator to check for metal toxicants. Phosphorus was found to be the main limiting nutrient in both ponds, with nitrogen as a secondary factor. Iron was a limiting nutrient in only one pond. The presence of bacteria affected nutrient availability in one pond but not the other.