Here is a link that may answer some of your questions....there are lot of different types of phytoplankton and zooplankton. Bottom line to your question though is: Don't expect a phytoplanton bloom in the winter unless the water in the area is warmed up artificially like around a power plant.

[url]http://www.chesapeakebay.net/plankton.aspx?menuitem=19401[url]