Common Phytoplankton and
Zooplankton in Carroll County Ponds
Some Examples
Phytoplankton
Kingdom Monera – The Blue-green “Algae”
Nostoc sp.
• Forms colonies composed of filaments of
moniliform cells in a gelatinous sheath
• Possess heterocysts (clear, thick-walled
cells) capable of nitrogen fixation
Phytoplankton
Kingdom Monera – The Blue-green “Algae”
Lyngbya sp.
• Filaments lack heterocysts
• Filaments with equal diameter
throughout whole length
• Rigid sheath that can extend beyond
the cells in the filament
Phytoplankton
Kingdom Monera – The Blue-green “Algae”
Merismopedia sp.
• Cells arranged in perpendicular rows one
cell thick to form rectangular colonies
• The colonies may be flat or slightly wavy
and are held together by colorless,
indistinct mucilage
Phytoplankton
Division Chlorophyta – Green Algae
Botryococcus sp.
• Cells form an irregularly shaped
aggregates, with thin filaments connecting
cells.
• Will bloom when in the presence of
elevated levels of dissolved inorganic
phosphorus
• Has potential as a producer of biofuels
Phytoplankton
Division Chlorophyta – Green Algae
Scenedesmus sp.
• Colonies with 4, 8, or 16 cells arranged in
a row.
• Spines and bristles make the colonies
more buoyant and allow them to uptake
the light and nutrients that are more
abundant near the surface, and may deter
predation by herbivores
• May be dense in nutrient- rich waters
Phytoplankton
Division Chlorophyta – Green Algae
Ankistrodesmus sp.
• Cells are long and needle- or spindleshaped, or sometimes curved or slightly
crescent-shaped.
• May be found individually, clustered,
twisted around each other, or in tufts
among other algae.
• The parietal chloroplasts sometimes have
pyrenoids
Phytoplankton
Division Chlorophyta – A Desmid
Staurastrum sp.
• Cells composed of two halves (semicells),
often almost divided from each other by
deep median incisions (True of all desmids)
• Often bear elaborate ornamentation
• Many small processes and arms tipped
with spines
Phytoplankton
Division Bacillariophyta – Diatoms
Fragilaria sp.
• Frustules rectangular to lanceolate, in
girdle view
• Frustules are joined by small marginal
spines to form ribbon like (band-shaped)
colonies.
Phytoplankton
Division Chrysophyta – The Golden Algae
Dinobryon sp.
• Loricate
• Lorica cylindrical and consisting primarily or
entirely of cellulose and protein; vase- or
Funnel-shaped and often with a slightly
broadened mouth
• Forming arbusculate (tree-like) colonies
(rarely solitary)
Phytoplankton
Division Pyrrophyta – Dinoflagellates
Peridinium sp.
• Motile, single, golden-brown cells
• Outer covering of rigid plates
• Two flagella
Phytoplankton
Division Rhodophyta – Red Algae
Porphyridinium sp.
• Cell with pink to red chloroplasts
• Cells solitary, but often grouped into
irregular colonies with ill-defined
mucilaginous matrix.
• Forms gelatinous coatings on surfaces in
freshwaters
Zooplankton
Kingdom Protista – Protozoans, Ciliates
Prorodon sp.
• Flexible ovoid body, round in cross-section
• Mouth apical
• Swims in large circles, revolving rapidly
around the long axis of its body.
• Eats bacteria, green algae, and small
nematodes. Cytoplasm typically filled with
food particles.
Zooplankton
Kingdom Protista – Protozoans, Ciliates
Didinium sp.
• Didinium are unicellular and have an oval
shape and two rows of cilia
• Front ends in a pointed snout (cytosome).
• Free-living carnivores
• Feed on other protists, dinoflagellates,
and green algae
Zooplankton
Kingdom Protista – Protozoans, Ciliates
Stentor sp.
• Among the largest aquatic protozoans.
Up to 2 mm long, they are larger than some
of the smallest multicellular organisms
• Usually attach to substrates and form a
trumpet shape.
• If they are free-swimming, they assume
an oval or pear shape.
• A major characteristic of Stentor is the
rapid contraction and extension of the cell
body.
Zooplankton
Phylum Rotifera – Rotifers
Keratella sp.
• A footless rotifer which possesses a
protective covering, or lorica, made up of
hexagonal plates
• Has a crown of anterior spines
• May or may not have a posterior spine
Zooplankton
Phylum Arthropoda, Class Crustacea,
Order Ostracoda – Seed Shrimp
Unidentified Ostracod
• Jointed appendages
• Body flattened from side to side and
protected by a bivalve-like, chitinous or
calcareous valve or "shell".
• They have a wide range of diets, and the
group includes carnivores, herbivores,
scavengers, and filter feeders.
Zooplankton
Phylum Arthropoda, Class Crustacea,
Order Copepoda – Seed Shrimp
Cyclopoid Copepod (likely Cyclops sp.)
• Jointed body and appendages
• With a teardrop shaped body and large antennae.
• Have a compound, median single eye, usually bright
red and in the centre of the transparent head
• Cyclopoid copepods have antennae shorter than
length of body
Zooplankton
Phylum Arthropoda, Class Crustacea,
Larval Stage
Unidentified Nauplius larva
• Jointed appendages
• Oval body with 3 pair of appendages
• Immature form of copepods, cladocerans,
and ostracods