The salinity tolerance of forty-six marine phytoplankton isolates

The acclimated reproduction rates of 46 marine phytoplankton isolates were measured in six salinities ranging from 0 to 45%. Estuarine species tolerated low salinity better than the oceanic species, coastal species being intermediate in their tolerance. The estuarine and oceanic species had salinity tolerances appropriate for their environments, but most of the coastal species tolerated salinity much lower than that from which they were isolated. This characteristic of coastal species may be a relict of selection pressure during the most recent glaciation or the result of gene flow being dependent upon central genetic populations located in bays and estuaries.