Colours of a Biome: Freshwater Edition


We are heading out from the Taiga’s pines and plunging into one of the most overlooked biomes. I hope you brought your waterproof shoes because things are about to get a whole lot wetter!

It’s easy to figure out if an area is freshwater, all you have to do is measure its salt concentration: if it is less than 1%, you have freshwater! The salt levels of water not only affect its taste, but also the types of plant and animal life it can carry. For example, species that are used to living in freshwater bodies (ponds, lakes, streams, rivers and wetlands) would not be able to survive in the oceans and coral reefs, where the salt levels are much higher.

Sockeye Salmon (Oncorhynchus nerka)

sockeye salmon, oncorhynchus nerka
Sockeye Salmon in their Freshwater Stage

Details: Sockeye are born into freshwater, but as they grow older, they make their way out to sea. After at least 2 years, they return to the freshwater where they spawn (mate) before reaching the end of their life. Adults can grow to 86cm averaging around 8 pounds.

My Hood: Sockeye live in freshwater and saltwater bodies along the Pacific coast of North America and Asia.

How I fit in: To survive the change from freshwater to seawater, sockeye’s gills and kidneys have to develop so they can process the salt efficiently. To help them blend into the environment in the sea, Sockeye salmon also have to change colour. The vertical bars and spots on their body that camouflage them in the freshwater disappear as they head for the ocean. On their way back to the freshwater they change colour again to show they are ready to mate. In this final stage they change their body to a bright red colour and their head a dull green.

Mexican dwarf crayfish (Cambarellus patzcuarensis)

mexican dwarf crayfish, cambarellus patzcuarensis
Mexican Dwarf Crayfish. Photo Credit: Veitw

Details: Dwarf crayfish have a strong shell that protects them from predators. However, when molting, their shell becomes very weak. During this time, they are very vulnerable and often stay hidden out of sight. These dwarf crayfish aren’t very big – they grow to less than 4cm long.

My Hood: Not surprisingly, the Mexican dwarf crayfish is native to Mexico. It is found in Michoacan’s Lake Patzcuaro but has also been spotted in the springs of Chapultepec, Opopeo, and Tzurumutaro.

How I fit in: The picture above shows an orange Mexican Dwarf Crayfish. Although this colouration may be seen in crayfish raised in captivity, it is rarely seen in the wild. The bright colour would make it easy for predators to spot them, putting them in danger. In the wild, they are more often tan, brown or rust. Unfortunately, they are threatened by habitat destruction from deforestation and water pollution caused by such things as the dumping of raw sewage.

Yellow Anaconda (Eunectes notaeus)

yellow anaconda, eunectes notaeus
Yellow Anaconda

Details: Although not as large as their green cousins, these snakes still get pretty big! On average, they grow about 3-4m long and weigh about 66lbs, but some have been recorded reaching 4.6m and 88lbs. Females tend to be larger than males, but all Yellow anacondas are big enough that they have few natural predators.

My Hood: In the swamps and marshlands of South America especially Paraguay, Southern Brazil, Northeaster Argentina, and Bolivia. Sometimes they visit forests when looking for large game to eat.

How I fit in: These yellowy-green snakes have black/brown bands that wrap around their bodies. This makes it easy for them to blend into murky water and forest vegetation.  As a top predator this species has an important role in this biome, helping to keep the populations of its prey under control. They are also very adaptable. During droughts they find wet caves to live in and in heavy rainfall, they travel to flooded areas to hunt aquatic animals.

Hydrilla (Hydrilla verticillata)

hydrilla, hydrilla verticillata
A Close up of Hydrilla

Details: Hydrillas are aquatic plants that grow up from the bottom of lakes. They tend to grow 2m tall, but some have been recorded reaching 7.5m. They cover the surface and can affect the water chemistry, zooplankton, fish populations, and other plants.

My Hood: Native to Africa, Australia, and Asia but was introduced to Florida in the 1960s and has since spread. It was also found in Esthwaite Tarn (a lake) in Britain, but was last seen in 1941.

hydrilla, hydrilla verticillata
Hydrilla. Photo Credit: J. M. Garg

How I fit in: This invasive plant has several advantages over other aquatic plants: it requires less light to grow and it is more efficient in absorbing nutrients. They also produce buds known as turions and tubers. Turions are dropped from the stem, while tubers are found at the roots. One square meter of Hyrillas can make 5000 tubers, which can produce new plants for more than 4 years. These buds can survive freezing, drying, herbicides, and even ingestion and regurgitation by birds. During the winter, hydrillas die back but with the help of tubers and turions sprout new shoots in the spring.

Blue-spotted Salamander (Ambystoma laterale)

blue-spotted salamander, ambystoma laterale, blue-spotted newt
Blue-Spotted Salamander

Details: Blue-spotted salamanders have dark blue or black skin covered in bluish-white spots. They can easily be mistaken for Jefferson Salamanders, but this salamander’s spots are more pronounced. Their bodies can grow to 10-14cm. 40% of this length is due to its tail, which is oval at the base and flattens out as it reaches the tip.  Females are larger, but males have flatter tails.

My Hood: They live by the forested ponds around the Great Lakes. They can be found in areas from Manitoba to the Atlantic Provinces and from James Bay Ontario to New England.

How I fit in: Blue-spotted salamanders are rarely seen. They stay hidden easily because blue spots break up the outlines of their bodies. They stay covered and hunt mainly at night so they can avoid direct sunlight. They eat small invertebrates, helping to keep these populations under control. If they are spotted and feel threatened, they release a noxious liquid from their tail and make their escape.

Ross D. MacCulloch, The ROM Field Guide To Amphibians and Reptiles of Ontario. Toronto: Royal Ontario Museum and McClelland & Steward Ltd., 2002: 46-48

Cape Blue Water lily (Nymphaea capensis)

nymphaea capensis, cape blue water lily
Cape Blue Water Lily. Photo Credit: Hацку

Details: This lily produces leaves and flowers that float on water, while its roots are found on the bottom. It grows sky or deep blue, pink or light purple flowers with yellowy-orange centers. These flowers can grow 150-200mm across.

My Hood: The Cape Blue Water lily is the only indigenous water lily in South Africa and grows in its ponds, wetlands, dams and pools.

How I fit in: There is more than just beauty associated with water lilies; they also have a deadly side. Sometimes pollinating insects like to skip the pollination and just drink a plant’s nectar. However, this doesn’t fly with the Cape Blue Water lily. This plant traps pollinating insects in liquid found in the center of the flower. When the insect drowns, the pollen it was carrying gets released and falls to the bottom of the flower where the stigmas are located. This ensures that the lily gets pollinated with or without the insect’s approval!

Bill Sheat and Gerald Schofield, Complete Gardening in Southern Africa. Cape Town: Struik Publishers, 1995: Page 185

Kristo Pienaar, Gardening with Indigenous Plants. Cape Town: Struik Publishers, 1994: Page 91

Thomas Johannes de Jong, Petrus Gerardus and Leonardus Klinkhamer, Evolutionary Ecology of Plant Reproductive Strategies. Cambridge: Cambridge University Press, 2005: Page 229

More splashes of colourful biomes are coming your way soon. In the meantime, find out what a biome is and the different types that can be found on Earth. Up next: the Grassland Biome!

To find out more about the freshwater biome check out these links:

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