Virtual Museum of Canada

WATERS OF LIFE

LIFE UNDERWATER

PLANKTON - PHYTOPLANKTON - BIODIVERSITY

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Microscopic photo of the alga Oedogonium

Oedogonium = 0.02 to 0.04 mm

Green algae:
Green algae include a great variety of species of various shapes, both microscopic and visible to the naked eye.

Microscopic photo of the alga Cladophora

Mass of Cladophora = up to 15 m

This microscopic photo shows the cells of the alga Cladophora.

Microscopic photo of the alga Closterium

Closterium = 0.3 to 0.6 m

Chlorophyll gives them their green colour and allows them to photosynthesize.

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Microscopic photo of the alga Closterium (another view)

The alga Closterium is seen here from another angle.

Microscopic photo of the colonial alga Volvox

Volvox =
cell (0.004 to 0.008 mm) colony (up to 2 mm)

Green algae can be colonial (Volvox, Scenedesmus), filamentous (Spirogyra, Cladophora, Oedogonium) or unicellular (Closterium, Micrasterias, Cosmarium).

Microscopic photo of the alga Spirogyra

Spirogyra =
cell (0.01 to 0.1 mm)
and filament (few cm)

This photo shows the filamentous alga Spirogyra.

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Mass of filamentous algae floating among the aquatic plants.

Mass of filamentous algae floating among aquatic plants

Filamentous algae can form masses.

Several Cladophora algae

Cladophora

They sometimes resemble tangled hair.

Masses of green algae floating on the water.

Mass of green algae

Masses of green algae often float to the surface of the water.

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Microscopic photo of the alga Micrasterias

Micrasterias = 0.05 to 0.29 mm

The alga Micrasterias has a star shape.

Microscopic photo of the alga Cosmarium

The alga Cosmarium presents a more spherical shape.

Microscopic photo of the alga Scenedesmus

Scenedesmus = 0,04 mm

Some species of green algae have flagella that give them some motility.

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Video filmed under a microscope of several colonies of the alga Volvox

VIDEO - 0 min 20 s
Volvox is a colonial alga made up of between 1,000 and 3,000 individuals, each with two flagella. These individuals are connected to each other by strands of cytoplasm.

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Video filmed under a microscope of colonies of the algae Volvox moving.

VIDEO - 0 min 15 s
The connections hold the colony together and coordinate the motions of the flagella so the colony can move around.

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Video filmed under a microscope of a close-up of the colonial alga Volvox.

VIDEO - 0 min 07 s
In the centre, you can see the «daughter» colonies, which result from the division of cells from the «mother» colony.
Once they are fully developed, the «mother» colony disintegrates, freeing the «daughter» colonies.

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Microscopic photo of the alga Spirogyra

Spirogyra = 0.01 to 0.1 mm

Spirogyra is a filamentous green alga whose cells are organized into long ribbons.
This species is easily recognized by its long, chloroplasts arranged in spirals. Chloroplasts are the structures where photosynthesis takes place.

Microscopic photo of the alga Cymbella

Chrysophytes or golden brown algae:
Diatoms are small unicellular algae, easily recognized by their unique structure with two nested valves forming a resistant exoskeleton. Species are identified by the shape of their exoskeleton.

Microscopic photo of the alga Fragilaria

Fragilaria = 0.04 to 0.11 mm

The alga Fragilaria shows a yellow ocher color.

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Microscopic photo of the alga Fragilaria (from another angle)

Here, from another angle.

Microscopic photo of the alga Ceratium

Ceratium = 0.54 mm

Dinoflagellates:
Dinoflagellates are unicellular algae that are commonly encased in a theca, a protective calcareous enveloppe. They have two flagella of different lengths that allow them to move around.

Microscopic photo of the alga Anabaena

Anabaena = 0.01 mm

Cyanobacteria:
Cyanobacteria are bacteria. They are also known as blue-green algae because they contain both chlorophyll, which gives them a greenish colour, and phycocyanine, another pigment that gives them a bluish colour.

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Channel near Yamaska River

Channel near Yamaska River

Cyanobacteria are among the most ancient organisms on Earth. They are usually found in most lakes.

Cow drinking in the channel

These algae can produce toxins that create health problems in both humans and animals.

Traces of cyanobacteria on the Yamaska River’s bank

Yamaska River’s bank

Cyanobacteria are usually noticed only during algal blooms, but they are generally invisible to the naked eye.

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Mass of the alga Lyngbya full of amphipods and isopods

Lyngbya full of amphipods and isopods

Some species of cyanobacteria form mats on the lake bottom, while others live in the water column.

The greenish water of the Yamaska River

Yamaska River

Higher levels of nutrients, and especially of phosphorus, cause cyanobacteria to increase significantly.

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LIFE UNDERWATER

PLANKTON - PHYTOPLANKTON