This study analyzed changes in phytoplankton and zooplankton on the Newfoundland and Scotian shelves from 1962 to 2003 in relation to changes in oceanography. Three categories of phytoplankton (color, diatoms, dinoflagellates) increased in abundance in the 1990s, and these increases generally persisted into 2001–2003. This is believed to be a response to the persistent freshening of the water column, probably due to increased stratification.