The researchers studied the distribution of small animals in the Watancheon estuary in Korea based on the saltiness of the water and the type of sediment. They found that different species prefer different levels of saltiness and types of sediment. Some species were more common in areas with lower salt levels and sandy sediment, while others were more common in areas with higher salt levels. The number of species and the amount of animals varied between different parts of the estuary. Overall, the distribution of these small animals in the estuary is mainly influenced by the saltiness of the water and the type of sediment.