Sea of Marmara about 22 parts per thousand, which is slightly greater than that of the Black Sea, but only about two-thirds that of most oceans. The water is much more saline at the sea bottom, averaging salinities of around 38 parts per thousand, similar to that of the Mediterranean Sea. This high-density saline water, like that of the Black Sea, does not migrate to the surface. Water from the Susurluk, Biga (Granicus) and Gonen Rivers also reduces the salinity of the sea, though with less influence than on the Black Sea. With little land in Thrace draining southward, almost all of these
Tool use by sea otters blunt, and the post-canines are bunodont. Their flat and broad shape is useful for chewing a combination of soft invertebrates and the harder parts of tougher invertebrates, like shell fragments and sea urchin tests. Sea otters also have some of the largest lungs in the otter family, which may be helpful for buoyancy, especially because sea otters do not have blubber. Being buoyant along the length of the body allows otters to lie on their backs and manipulate food, tools, and young while on the surface of the water. Underneath the arm of each sea otter, at the axilla, is