The Biota (Flaura and Fauna) of the St. Lawrence

St. Lawrence Hydrographic Regions Flora Plankton Benthic Organisms Fish, Amphibians and Reptiles Birds Mammals

The St. Lawrence River can be divided into four hydrographic zones. Each zone has diverse and unique flora (plants) and fauna (animals). The biota of the St. Lawrence include algae, plants, plankton, bottom dwellers (benthic organisms), fish, amphibian, reptiles, birds, and mammals. The biota found in each hydrographic zone will be discussed in turn. The information provided is based on current knowledge. The identity and presence of many biota is unknown, data on microorganisms is particularly scarce.

The St. Lawrence River includes four hydrographic zones.

The St. Lawrence River can be divided into four major hydrographic regions.

1. The Fluvial Section is a freshwater ecosystem at the base of the river. It extends from Kingston to Trois Rivières. In this area, the river is calm and has a large flood plain.
2. The Fluvial Estuary flows east to Ile d'Orleans. The estuary water is deep, bordered by steep cliffs and turbid.
3. The Upper Estuary spans east to Tadoussac. The river is turbid, brackish and narrow in this section.
4. The Lower Estuary and Gulf of St. Lawrence is a marine environment.

Fresh and salt water plants grow in different sections of the river.

Salt marshes, Iles-de-la-Madelaine

Here flora is used to refers to photosynthetic organisms (primary producers) that use solar energy to fix carbon dioxide. The energy is then used for plant life activities or stored as starch. Plants are an important food source for species in higher trophic levels. They also create important habitats for many organisms.

Algae are single or multi-cellular photosynthetic organisms. They may be micro or macro-scopic. The algae that are found in the Fluvial Section and Estuaries are mostly Chlorophyta (green algae). The algae found in the Lower Estuary and Gulf are mainly Fucus, Kelp and Ascophyllum. Non-vascular plants are plants that lack a true vascular system. The main non-vascular plants that grow along the St. Lawrence River are Byrophytes (e.g, moss) and Lichens.

There are about 1,300 vascular plant species that grow along the St. Lawrence River. Wetland plant communities along the river are particularly important to filter organic matter and metals, and recycle nutrients from water. The four hydrographic regions of the St. Lawrence River contain unique flora. Different plant communities tend to grow parallel to the water in zones called hydroseres. The type of plants found in a specific zone may depend on water levels, soil composition, solar radiation and neighboring plant communities.

The Fluvial Section has extensive macrophyte beds in the littoral zone. Landward from this zone are fresh water wetlands. The wetlands include marshes, wet meadows and swamps. Similar plant communities are found in the Fluvial Estuary. However, the macrophyte bed is diminished significantly and more brackish water species are found. The Upper Estuary consists only of wetlands. The plant species are a mixture of fresh and salt water flora. The Lower Estuary consists of salt water plants that grow in salt marshes and meadows. In the Gulf of St. Lawrence the salt meadows are the dominate vegetation type and aquatic plants grow in sheltered sandy areas near shore.

A diversity of phytoplankton inhabit the river.

Many bacteria and yeast species inhabit the river.

A diversity of phytoplankton inhabit the river.

Zooplankton, such as, rotifers and fish larvae frequent the St. Lawrence River.

Plankton are organism that drift in the water column. They are non-motile or have limited mobility. Planktonic organisms include bacteria, yeast, phytoplankton, and zooplankton. Bacteria and yeast are prokaryotic organisms that lack many cellular organelles. Phytoplankton are floating microflora that fix carbon dioxide via photosynthesis. Zooplankton are single and multicellular micro-animals. Many zooplankton are the larvae of fish and other larger organisms. Planktonic organisms form the base of aquatic and decomposer food chains in the St. Lawrence River.

A diversity of bacteria and yeast inhabit the St. Lawrence River. The main bacteria identified in the river are Acinetobacter calcoaceticus, Aeromonas hydrophila, Clostridium botulinum, Enterobacter cloacae, Flavobacterium menigosepticum, Klebsiella pneumoniae, Legionella pneumophila, Listeria monocytogenes, Plesiomonas shigelloides, Pseudomonas aeruginosa, Vibrio cholerae, Vibrio parahaemolyticus and Vibrio vulnificus. The main yeast identified in the St. Lawrence River are species of the genus Rhodotorula, Candida, Debaromyces, Pullularia and Torulopsis.

The dominant phytoplankton that inhabit the Fluvial Section and Estuary are Diatoms, Cryptophycea, Zygophycea, Chlorophycea, Cyanobacteria and Dionophycea. Many of phytoplankton cells produced in the fluvial section are exported down stream. Phytoplankton diversity is greatest in the estuary. The Upper and Lower Estuary contains Dinoflagellates, Diatoms and Microflagellates. Due to environmental stresses phytoplankton are less abundant in the Upper Estuary and Gulf.

The main zooplankton found in the St. Lawrence River are identified below.

• The Fluvial Section and Estuary has Rotifers, Cyclopoids, Copepods and Cladocera. In the Fluvial Estuary zooplankton inhabit sheltered bays.
• The Upper Estuary has the lowest diversity and abundance of zooplankton. Some zooplankton found in the estuary are Harpacticoids, Cyclopoids, Mysids, Capelin and Atlantic herring larvae, and several endemic Copepoda.
• Many zooplankton species migrate to and from the Lower Estuary and Gulf. Some of the zooplankton in the zone are Copepods, Ostracods, Euphausiids, Ctenophora, Larvaceans and Coelentrates. There are also many fish larvae in the Lower Estuary and Gulf, such as, Cod, Redfish, Sand lance and Herring.

Benthic organisms in the St. Lawrence include gastropods, amphipods and molluscs.

Benthic organisms dwell on the bottom of the river. Benthic species include filter feeders, predators and herbivores. They are important for recycling organic matter from the river bottom, particularly in deep areas where light does not penetrate. They also provide a food source for many predator species, including humans. Some bottom dwellers found in each section of the St. Lawrence River are identified below. In addition, a table indicates some common benthic species in the St. Lawrence River and their preferred substrate.

• The Fluvial Section has Molluscs (e.g., clams), Crustaceans (e.g., crabs), Oligocheate worms, Diptera larvae, Amphipods, Gastropods (e.g., snails) and Tubificids.
• Tubificids, Gastropods, Sphaeriids, Glososcolecids and Chironomids inhabit the Fluvial Estuary.
• The Upper Estuary contains mostly Amphipods.
• Hydroids, Barnacles, Gastrpods, Urchins and Mussels are found in the Lower Estuary and gulf.

Common benthic organisms and their preferred substrate
	Mud	Sand	Rock	Gravel
Blue Mussel
Razor clam
Whelk
Star fish
Sea cucumber
Sand dollar
Barnacles
Hermit crab
Shrimp
Sponge
Anemone

Source: St. Lawrence Center. 1996. State of the Environment Report on the St. Lawrence River. Volume 1: the St. Lawrence ecosystem. Environment Canada -- Quebec region, Environmental Conservation, and editions MultiMondes, Montreal. " St. Lawrence UPDATE" series.

Fresh and salt water fish inhabit the St. Lawrence River.

Salamanders, snakes and frogs are found along the river.

The main fish species that inhabit the St. Lawrence river are identified below.

• Freshwater fish species inhabit the fluvial section of the river. The main species found are Bullhead, Carp, Bass, Pumpkinseed, Walleye, Stickleback, Sturgeon, Pike, Burbot, Muskellunge, Sucker, Perch, Shiner, Trout, Mudminnow, Charr and Redhorse.
• The freshwater fish in the fluvial estuary are Bass, Shad, Eel, Bullhead, Stonecat, Perch, Carp, Pumpkinseed, Shiner, Quillback, Sauger, Walleye, Smelt, Sturgeon, Killfish, Alewife, Pike, Whitefish, Mooneye, Sea lamprey, Sucker, Gar, Burbot, Drum, Crappie, Muskellunge, Chub, Charr, Fallfish, Bowfin, Redhorse and Trout.
• In the upper estuary there are salt and fresh water fish. The freshwater species are Eel, Bullhead, Bass, Carp and Sucker. The saltwater fish are Capelin, Shad, Alewife, Lumpfish, Sea lamprey, Cod, Smelt, Hake, Tomcod, Spiny lumpsucker, Shark, Sturgeon and Threespine stickleback.
• The saltwater fish in the lower estuary and gulf are Cod, Skate, Halibut, Shad, Poacher, Dogfish, Goosefish, Capelin, Sculpin, Hooker, Sea lamprey, Lumpfish, Smelt, Flounder, Salmon, Sand lance, Snailfish, Mackerel, Sunfish, Hagfish and Redfish.

A range of amphibians inhabit the St. Lawrence River, including: salamanders, newts, mudpuppies and frogs. A diversity of reptiles also frequent the area, such as turtles and snakes. Reptiles and amphibian are important secondary consumers in the food chain. They may be carnivorous or herbivorous. For example, most frogs eat insects.

Many species of birds inhabit the fresh water and marine ecosystems of the St. Lawrence River.

Birds are also important in the food chain. They may be carnivorous, herbivorous or omnivorous. Most birds inhabit the wetlands in the Fluvial section and/or Estuaries of the St. Lawrence River. Many of the birds migrate to the St. Lawrence region each spring in search of food and breeding grounds. The main bird species found in the Fluvial Section and Estuary are Blue heron, Water fowl, Canada geese, Mergansers, Goldeneye, Snow geese, Moorhen, Wood duck, Green heron, Pied billed geese and Peregrine falcon. Also some rare birds are seen in this portion of the river, such as Eagles, Redheads and Yellowtails. Many of these birds are wading birds or diving duck.

The Upper Estuary has the greatest diversity of water birds. Some of the birds found in the estuary are Snow geese, Black ducks, Merganser, Gadwall, Purple sand piper, Sparrows and Razorbills. There are over 20 different species of shore birds seen in this area.

In the Lower Estuary and gulf there are mainly sea birds. Many of these birds feed on open water and breed in large coastal or island colonies. Some of the birds found in the Lower Estuary and Gulf and their foods are identified in the table below.

Birds found in the Lower Estuary and Gulf of St. Lawrence and their foods
	Plankton	Green sea urchins	Molluscs	Crustaceans	Fish	Insects
Herring gull
Black legged kittiwake
Atlantic puffin
Razorbill,
Common Eider
Dovekie
Leach's storm petrel
Shearwaters
Shorebirds

Source: St. Lawrence Center. 1996. State of the Environment Report on the St. Lawrence River. Volume 1: the St. Lawrence ecosystem. Environment Canada -- Quebec region, Environmental Conservation, and editions MultiMondes, Montreal. " St. Lawrence UPDATE" series.

The St. Lawrence River has marine and fresh water mammal species.

In the freshwater portion of the St. Lawrence river mammals, such as mink, muskrats, otters, beaver and raccoons, can be found. These species are mainly found in the wetlands of the Fluvial Section and Estuary. The species seen in the Upper Estuary are Beluga, Longfinned pilot whales, Minke whales, Harbour seals, Harbour porpoises, Grey seals and Harp seals. Many of the species that were once common in the Lower Estuary and Gulf are now extinct or rare. For example, the Narwhal and Sperm whales. The main species that inhabit the Lower Estuary and Gulf are Whales, Dolphins, Pinnipeds, Harp seals, Beluga, Hooded seals and Grey seals.

• St. Lawrence Center (1996) State of the Environment Report on the St. Lawrence River. Volume 1: the St. Lawrence ecosystem. Environment Canada -- Quebec region, Environmental Conservation, and editions MultiMondes, Montreal. " St. Lawrence UPDATE" series.

Related Web Sites

The Zebra Mussel Page Beluga Whales Dinoflagellates Diatoms Phylum