NPS photo

Marsh marigolds along a stream

The phytoplankton of the inland lakes of Pictured Rocks National Lakeshore include at least 51 taxa of blue-green algae (Cyanophyta), dinoflagellates (Pyrrhophyta), yellow-brown algae (Chrysophyta), diatoms (Bacillariophyta), and green algae (Chlorophyta). Seasonal fluctuations occur in the relative densities of these unicellular plants.

Dominant taxa include the diatoms Asterionella formosa, Fragillaria intermedia, Aulocoseira islandica, and Tabellaria fenestrata and the blue-green algae Aphanizomenon flosaquae, Aphanocapsa rivularia, Chroococcus limneticus, and Lyngbya birgei. The filamentous green alga, Bulbochaete sp., is found attached to submerged logs in softwater Legion Lake. Diatoms of this acidic lake are typically benthic, and, due to limited dissolved silica, are not preserved in the sediments.