Quick-guide to the major groups of freshwater algae
YES Chlorophyta GREEN ALGAE A large, diverse Microspora group, including:
Chlorophyceae YES Cells store starch: positive Mougeotia reaction to Charophyceae starch test
Chloroplasts usually grass Ulvophyceae green Cosmarium Ulothrix YES YES Euglenophyta EUGLENOIDS Highly motile with flagella. Cells motile and Many species colourless and may change or phagotrophic (ingest shape, many small particles) Cells contain chloroplasts organelles Phacus (e.g., chloroplasts; Chloroplasts some Ochrophyta: nucleus) other colour Cells may be filamentous, Xanthophyceae YELLOW-GREEN ALGAE many small chloroplasts NB. Difficult to distinguish from Chlorophyta. Vaucheria Placed in Ochrophyta because of pigments and food storage products, and phylogeny. Tribonema
No YES organelles Ochrophyta: DIATOMS Diatoms Chloroplasts brownish. Diatoma Ornamented silica cell walls. Definite Cells solitary or in filaments. geometric shapes. Often motile, but no flagella.
Shapes Navicula CONTINUED CONTINUED September 2012 Quick-guide to the major groups of freshwater algae (continued) Ochrophyta: Chrysophyceae GOLDEN-BROWN ALGAE Dinobryon Mixotrophic. YES Chloroplasts yellow to YES These two groups separated by pigments brown. Produce and structure of the stomatocysts (silica- flagella. walled resting stage with a characteristic collar and “mouth”) Synurophyceae Silica-scaled. YES Always photoautotrophic.
Synura Schematic of stomatocyst Dinophyta DINOFLAGELLATES Cells not Cell wall smooth or of containing No angular plates, sometimes organelles stomatocysts Brownish chloroplasts. YES with projections. (e.g., Cells with 2 furrows around chloroplasts; the cell, perpendicular to nucleus) each other. Peridinium ?
RED ALGAE Some other cell Olive or pinkish Rhodophyta arrangement chloroplasts. YES Batrachospermum Filamentous plants Compsopogon usually with a complex structure
Filaments (trichomes), Cyanobacteria “BLUE-GREEN” ALGAE single cells or gelatinous Nostoc colonies. Cell contents YES Tolypothrix diffuse; granules may be present
September 2012