A water column which is unmixed or only partially mixed because the depth of the water body is greater than the depth of mixing. Salinity is reduced relative to the adjacent fully marine seawater. This habitat type is usually found in deeper coastal water situations and is the result of river inflow or ice melt. Note that some discretion should be used in the interpretation of “adjacent”, for example in the Baltic Sea, “adjacent” fully marine seawater is reached only in the Kattegat. Medium residence time is defined as changing over time preiods greater than daily and up to about 14 days (based on the time required for the phytoplankton population to double) and long residence time lasting longer than 14 days.