The scientists studied the types of small animals living in the coastal area of Inchon, Korea, from 1994 to 1995. They found 231 different species, with some being more common than others. The areas were divided into four regions based on the types of animals found there. The size of the sediment, the amount of heavy metals, and the oxygen levels in the water all affected where the animals lived. The researchers noticed that the environment in the areas was getting worse from one region to another.