Freshwater Algae Key

A1. NONMOTILE ALGAE WITHOUT CHLOROPLASTS: CYANOBACTERIA

A2. NONMOTILE ALGAE WITH CHLOROPLASTS

B1. CELLS USUALLY SOLITARY

B2. NONMOTILE COLONIES WITH TWO OR MORE CELLS

C1. CELLS FLATTENED, FORMING RIBBON-LIKE CHAINS, SHORT CYLINDERS, OR PLATE-LIKE GROUPS OF CELLS

C2. COLONIES SPHERICAL OR OVAL

D1. CELLS SPHERICAL, OVAL, OR LEMON-SHAPED

E1. CELLS BRIGHT GREEN; CELLS WILL TEST POSITIVE FOR STARCH

E2. CELLS BRIGHT BLUE-GREEN, OVAL OR LEMON-SHAPED; SOLITARY OR ENCLOSED IN EXPANDED PARENT CELL WALL TO FORM SMALL OVAL COLONIES; OFTEN EPIPHYTIC: Glaucocystis

E3. CELLS YELLOWISH GREEN, SPHERICAL, WITH RED PIGMENT DROPLET; SOLITARY OR IN SMALL COLONIES WITH 2-8 CELLS: Chlorobotrys

E4. CELLS GOLDEN BROWN, SPHERICAL, SOLITARY OR IN SMALL 2-4 CELL COLONIES; COLONIES SURROUNDED BY STRIATED MUCILAGE: Gloeodinium

D2. CELLS CYLINDRICAL, FUSIFORM, OR NARROWLY ELLIPTICAL

D3. CELLS ASYMMETRIC, BLUNTLY CRESCENT-SHAPED OR SAUSAGE-SHAPED; COLONIES USUALLY CONTAINING 4-8 CELLS SURROUNDED BY GELATINIZED PARENT CELL WALL: Nephrocytium

D4. CELLS ANGULAR, WEDGE-SHAPED, OR IRREGULAR

C3. COLONIES VARIOUS SHAPES OTHER THAN FLATTENED AND SPHERICAL/OVAL

B3. FILAMENTOUS ALGAE (INCLUDING PSEUDOFILAMENTS)

B4. CELLS ATTACHED TO ZOOPLANKTON (EPIZOIC), LIVING INSIDE ZOOPLANKTON OR OTHER AQUATIC ANIMALS (ENDOZOIC), OR ATTACHED TO AQUATIC PLANTS (EPIPHYTIC)

A3. MOTILE ALGAE WITH CHLOROPLASTS AND FLAGELLA

A4. CELLS DIVIDED INTO MIRROR-IMAGE SEMI-CELLS: Desmids (see key at cedar.wwu.edu/cedarbooks/14/ )

A5. CELLS ENCLOSED IN GLASSY, ORNAMENTAL FRUSTULES: Diatoms (see key at diatoms.org)