Foam from eight streams in boreal and mixed-wood forests in Québec were sampled in early and late fall 2002 to evaluate the biodiversity of their aquatic hyphomycete communities. Two regions were studied: 53-54 degrees N and 46-49 degrees N. A total of 54 species were identified. Twenty taxa were found only in the northern region, and four were unique to the southern region. A new aquatic hyphomycete, Dwayaangam colodena sp. nov., was found mostly in northern streams. It is described along with its taxonomic position.