Yes you really cant use Encarta or another general encyclopedia for information of this nature  Daniel has carefully qualified AlgaeBase to precisely what it is at present the best database for species names of algae  In addition its easy to use its readily searchable on the web by anyone and it lists its references so if you want to double check its data you can or if it cites an authority who is somewhat controversial you know itit is one of the best done organism databases on the web because of these reasons  However if you dont want to use AlgaeBase you may use a recent textbook on algae instead  Either way simply quote whatever source you use as this is something in serious flux and disagreement among phycologists  Cheers