Seawater is a complex solution of many chemicals. Their concentration is, on average, 33-37 parts per thousand by weight. Ninety percent of this is common table salt, sodium chloride.
|Oxygen & salinity|
Salinity in the deep sea varies mostly only slightly and ranges between 34.69 % in the Pacific and 35 % in the northern Atlantic. Only in the Red Sea and Mediterranean salinity is significantly higher with about 39 %. This influences also the adjacent seas, as the heavy surface water flows in and sinks to deeper levels. This may affect also the species composition in the NE Atlantic.