Freshwater Phytoplankton Keyfor the Northeast
By: Rachael Brown, Sonya Carlson, and Diana Jackson Under the guidance of Dr. Alan Baker
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Introduction:This photographic key is intended to aid in identification of freshwater algae to the Genus level. Proceed through this key by clicking on the picture that most resembles your organism.
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Cells with definite chloroplasts and nuclei, not blue-green in color
Cells without definite chloroplasts and nuclei, blue-green in color
Vegetative cells usually grass-green in color and with a definite cell wall
Vegetative cells not grass-green
Vegetative cells yellowish to brown with a glass-like silica wall of two
overlapping halves
Vegetative cells yellow-green with a cell wall
Class: Chrysophyceae
Class: CyanophyceaeCommon Name: Cyanobacteria, blue-greens
Continue to Genus
Rectangular
Is the general contour of the specimen:
Elongate strands of cells Oblong, Circular, or Globular
Sperm shaped
Note: A filament is a strand of cells arranged end to end
Are the filaments:
Unbranched
Branched
Elongate filaments of cells
Genus: Microthamnion
Filaments are found alone
Unbranched:
Filaments form togetherin parallel colonies (rafts)
Option A: Oblong Option B: Circular
Option C: Globular
Oblong, Circular, or Globular
Head has thin membrane
Head has thick wavy membrane
Sperm-Shaped
Genus: Aphanocapsa
Genus: Aphanothece
Genus: Chroococcus
Genus: Coelosphaerium
Genus: Gloeocapsa
Genus: Microcystis
Genus: Merismopedia
Genus: Cylindrospermum
Genus: Gloeotrichia
Genus: Anabaena
Genus: Aphanizomenon
Genus: Calothrix
Genus: Chamaesiphon
Genus: Lyngbya
Genus: Nostoc
Genus: Oscillatoria
Filaments are joined at one
end
Filaments are parallel and are not joined together at any end
Filaments have elongate cells arranged end to
end
Filaments have horizontal cells that are stacked on top of each
other
Filaments Found Alone
Cells are round and are arranged in long
filaments (like strands of pearls)
Elongate unicells are found on a
substrate
unicells
Cell shape is rectangular
Cell shape is oblong
Filaments are spaced apart
from each other
Filaments are lumped together
Option A: Oblong
Cells float freely apart from each other
Cells join in even numbers and have a clear membrane
around them
Option B: Circular
Cells are free floating with thin clear membranes
Cells are congregated and encased in a round membrane
Encased CellsCells are
encased by a clear membrane
Cells are encased in a thick green
membrane
Order: BacillariophyceaeCommon Name:Diatoms
Continue to Genus
Is the shape of the organism rectangular?
Is the shape of the organism circular or oval?
Does organism have stalks?
Are there many rectangles joined together?
Are the rectangles separate from each other?
Do the rectangles make a line or stairstep formation?
Do the rectangles form a star? Do the rectangles form a box?
Genus: Tabellaria
Genus: Asterionella
Genus: Eunotia
Width (W) of individual cells is 1/10 of the length (L)
W
L
W
L
Width (W) of individual cells is 1/5 of the length (L)
Genus: Fragilaria
Genus: Fragilaria
Are there many small circles within the cells?
Is the end of the cell a long spike or is there a few large circles within the cells?
Genus: Melosira
Genus: Rhizosolenia
Is the middle of the cell wider than either end?
Is the end of the cell opposite of the stalk the
widest section?
Genus: Cymbella
Genus: Gomphonema
Are there smaller circles within the large circle?
Are there lines around the edge of the circle?
Is the shape of the organism oval?
Genus: Cocconeis
Genus: Cyclotella
Is the cell extremely long and skinny with the length (L) more than 15 times as much the width (W)?
Is the cell extremely long and skinny with the length (L) more than 15 times as much the width (W)?
Genus: Synedra
Are the ends of the cell pointed (p) or rounded (r) )?
Are the ends of the cell curved (c)? Are the ends of the cell flat (f)?
Genus: Gyrosigma
Genus: Amphora
Is the cell the same width in the middle as it is nearer to the ends?
(a is equal to b)
Is the cell the wider in the middle than it is nearer to the ends?
(a is larger than b)
Is the edge of the oval smooth?
Does the edge of the oval have a distinct bump?
Bump
Smooth
Is there a distinct line down the length of the cell?
DistinctLine
Is no distinct line visible in the center of the cell?
Is the center area of the middle line is wider than the ends of the middle line with a distinct
break in the center?
Is the middle line even in width with a distinct break in the
center? Is the middle line complete with no
distinct break in the center?
Genus: Navicula
Genus: Frustulia
Genus: Opephora
Is the cell long and skinny with the length (L) more than 5 times as much the
width (W)?
Is the cell short with the length (L) less than 5 times
as much the width (W)?
Genus: Diatoma
Genus: Amphipleura
Genus: Surirella
Are there distinct parallel lines extending from the middle of
the cell to the edge?
Is the interior of the cell a homogenous color without lines?
Lines
Genus: Achnanthes
Genus: Rhopalodia
Are the ends distinctly pointed?
Are the ends distinctly rounded?
Genus: Nitzschia
Genus: Pinnularia
Actinastrum
Ankistrodesmus
Apiocystis
Arthrodesmus
Bulbochaete
Carteria
Centritractus
Chaetophora
Chaetosphaeridium
Characiopsis
Characium
Chlamydomonas
Chlorella
Chlorococcum
Cladophora
Closterium
Coelastrum
Coelosphaerium
Coleochaete
Cosmarium
Crucigenia
Desmidium
Dictyosphaerium
Dimorphococcus
Docidium
Euastrum
Eudorina
Gloeocystis
Gonium
Haematococcus
Hormidium
Hyalotheca
Hydrodictyon
Kirchneriella
Micractinium
Micrasterias
Microspora
(Conjugating)
Mougeotia
Oedogonium
Onychonema
Oocystis
Palmella
Palmellocystis
Pandorina
Pediastrum
Planktosphaeria
Pleurotaenium
Scenedesmus
Selenastrum
Spirogyra
Staurodesmus
Tetraedron
Ulothrix
Volvox
Xanthidium
Zoochlorella
Zygnema
COLONIES (GROUPS OF CELLS)
FILAMENTS (LINEARLY)
CELLS ARE ARRANGED IN…
SINGLE CELLS
Class: Chlorophycae
COLONIES ARE…
FLAT (2-D) SPHERICAL (3-D)
CELLS IN FILAMENTS HAVE…
ONE CHLOROPLAST
TWO CHLOROPLASTS
MANY CHLOROPLASTS
SINGLE CELLS ARE…
UNICELLULAR HEMISPHERES
INDIVIDUAL CELL SHAPE IS…
SPHERICAL OR
ELLIPTICAL
LONG OR ROD SHAPED
SPIKEY
COLONIES HAVE…
TIGHTLY PACKED CELLS
SPACE BETWEEN CELLS
FILAMENTS ARE…
SINGULAR
BRANCHED
HEMICELLS ARE…
LONG AND NARROW SEMICIRCULAR
CHLOROPLASTS ARE…
CLUMPED
SPIRALED
ARE CELLS IN THE FILIMENT…
SHORT
LONG
Does your algae look like any of these?
Does your algae look like any of these?
Does your algae look like any of these?
Does your algae look like any of these?
Does your algae look like any of these?