ABOARD KEXUE, Aug. 26 (Xinhua) -- Chinese scientists on board the research vessel Kexue have discovered coral gardens and sponge forests for the first time in an oligotrophic area of the western Pacific Ocean over the past two days.
The coral gardens and sponge forests have been observed in the east ridge of the Caroline Seamount, located in the south of the Mariana Trench, the deepest spot on Earth, said Xu Kuidong, chief scientist on board the ship, whose name in Chinese means "science."
Being representatives of high-biomass, coral gardens and sponge forests are often seen in sea areas from 30 degrees South and North Latitude to the two poles, and no coral gardens and sponge forests have been reported yet in the oligotrophic area of the Pacific Ocean.
The open sea areas of the Pacific Ocean, from 20 degrees South and North Latitude to the equator, are far from land and have few nutrient supplies. The upside and bottom seawater in these areas rarely exchange as the temperature is steady the whole year, therefore, the nutrients at the seafloor can't be brought up.
These sea areas are typically oligotrophic and many creatures can't survive here.
In the research currently carried out by Kexue, scientists saw a lot of corals, sponges, sea lilies, brittle stars and squat lobsters in the east ridge of the seamount, a typical oligotrophic area. On a stone, there are nine large corals, four large sponges and plenty of little creatures living among them.
One of the large corals is four meters long and two meters high, and scientists said it could be a thousand years old.
This ridge is part of a seamount, and ocean currents go up when they meet the seamount and bring nutrients at the sea bottom up as well, which support corals and sponges, Xu said.
Besides, the ridge has a steady geological environment and its bottom is made up of large rocks, which provide a stable base for the corals and sponges attached to them.