In the southern Yellow Sea, researchers studied small sea creatures to see how healthy the ocean floor is. They found 134 different species, with worms being the most common. Some species were seen more in summer, while others were more common in autumn. The amount of creatures and their weight were measured, showing slightly more diversity in autumn. The depth of the water, temperature, and the amount of plant material in the sediment were important factors for the creatures living there. Overall, most areas in the southern Yellow Sea were found to have a moderate to good ecological status based on the types of creatures living there.