nature.ca The Nature of the Rideau River HomeFrançais
The ProjectHistory and GeographyRiver HealthAnimals and PlantsWater QualityBiodiversityAction!ResourcesTeachers
 
Algae


Toxic Algae

 

Algae, the "Meadow" of the River

Microscopic algae, Pediastrum boryanum.
Microscopic algae, Pediastrum boryanum.

Microscopic algae comprise most of the life forms in fresh water, and they are the most productive. This aquatic "green slime" generates approximately 70% of the oxygen in Earth's atmosphere!

Algae grow in many forms; some are microscopic while others reach several metres in length.

Single-celled Algae
Microscopic varieties, which are single-celled, are phytoplanktons (from the Greek words for plant and wanderer). On average, fifty of these microscopic algae lined up end-to-end would measure one millimetre!

Phytoplanktons are the very beginning of the food chain. They are eaten by zooplanktons, which are a kind of tiny crustacean. Zooplanktons are eaten in turn by invertebrates, fish, molluscs, turtles and ducks. Phytoplanktons are called the "great meadow of the water" because like terrestrial meadows they are an important food source for other organisms.

Multicellular Algae
Most of the multicellular algae found in the Rideau River are green algae. Most multicellular algae can be easily distinguished from aquatic plants. Viscous in nature, multicellular algae grow in the water or on the surface, clustering together in a green mass that readily disintegrates at a touch.

Plant or Alga?
Multicellular green algae are the ancestors of our present-day terrestrial plants. Like plants, these algae are photosynthetic, that is, they need the sun's energy in order to convert water and carbon dioxide into sugar.

One of the major differences between plants and algae can be seen with a microscope. During the course of their adaptation to the terrestrial environment, plants developed conducting tissue that transports nutritive elements from the roots to the leaves and moves sap down to the roots. Algae do not have such tissue because every part of these organisms can absorb nutritive elements from water.

Further difference is found in their reproductive systems, which is more primitive in green algae.

One group of multicellular algae, the charophytes, bears a strong resemblance to aquatic plants. Even with a naturalist's eye, they can be mistaken for one another. Under a microscope, however, one can tell them apart because the internal structure of green algae is quite different from that of aquatic plants.

next page

 

 Algae
Bullet.
Bullet.
Arrow.
Arrow.
 Don't Overlook...
Arrow.
Arrow.
Arrow.
Arrow.


Microscopic algae, Gyrosigma acuminatum.
Microscopic algae, Gyrosigma acuminatum.


Microscopic algae, Diatoma tenuis.
Microscopic algae,
Diatoma tenuis.


Microscopic algae, Peridinium inconspicuum.
Microscopic algae, Peridinium inconspicuum.
A Project of the Canadian Museum of Nature
  
 Images: Linda Ley