Freshwater habitat. A freshwater habitat is a body of water formed mainly from inland waters and contains very low levels of salinity.
Examples of freshwater habitats are:
rivers, ponds, streams, springs and lakes
Freshwater or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids.
Although the term specifically excludes seawater and brackish water, it does include non-salty mineral-rich waters such as chalybeate springs.
Fresh water may encompass frozen and meltwater in ice sheets, ice caps, glaciers, snowfields and icebergs, natural precipitations such as rainfall, snowfall, hail/sleet and graupel and surface runoffs that form inland bodies of water such as wetlands, ponds, lakes, rivers, streams,
as well as groundwater contained in aquifers, subterranean rivers and lakes. Fresh water is the water resource that is of the most and immediate use to humans.
Types of Freshwater habitat
Freshwaters are classified on the basis of their mobility. Based on this, two types are identified. These are:
Lotic freshwaters :
these include all running waters which can flow continuously in a specific direction. In other words, these are flowing or running waters, e.g. rivers, springs and streams.
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Lentic freshwaters :
these include standing or stagnant waters. These waters do not flow nor move. Examples are lakes, ponds, swamps and dams.
Characteristics of Freshwater Habitat
The following characteristics are associated with freshwater habitats:
1.
low salinity:
freshwater habitats normally contain very low levels of salts. It has about 0.5% salt compared to about 3.5% for seawater.
2.
small in size:
freshwater habitat is usually very small compared to ocean water which is about 75% of the earth\’s surface
3.
variation in temperature:
the temperature of freshwater habitats usually varies with season and depth.
4.
high concentration of oxygen content:
oxygen is usually available in all parts of fresh water especially in the surface of the water.
5.
the shallowness of water:
most freshwater habitats are very shallow hence sunlight can easily penetrate through the water to the bottom.
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6.
seasonal variation:
some freshwater habitats like streams and rivers normally dry up during the dry season while others have their volume reduced.
The volume of water in rivers also increases during the rainy season. Turbidity and fast flow of rivers are also high during the rainy season than in the dry season.
7.
currents:
currents can affect the distribution of gases, salts and small organisms in freshwater habitats such as rivers and streams.
MAJOR ECOLOGICAL ZONES OF FRESHWATER HABITAT
The zones of a lentic freshwater habitat, e.g. lake are similar to those of the marine habitats but there are no Supratidal and inter-tidal zones.
There are two major zones in a lentic freshwater habitat. These are littoral and benthic zones.
1.
Littoral zone:
it is the shallow part of the freshwater habitat. It contains several plants and animals. The littoral zone has rooted vegetation at its base.
It has the highest level of primary production because sunlight can easily penetrate the zone, hence photosynthetic activities are common.
Plants associated with this zone include spirogyra, Chlamydomonas, water lettuce, water fern, duckweed, diatoms and sedges.
Animals associated with this zone include water fleas, water snails, flatworms, frogs, toads, water skaters, ducks, snakes, crocodiles, tadpoles, hydrae, and hippopotamus.
Benthic zone:
the benthic zone is the deepest part of the lentic freshwater habitat. The benthic zone does not have rooted vegetation like the littoral zone although flowering plants may occur at its surface.
Plants associated with the benthic zone have well-developed root systems in the mud.
These plants include water lily, water arum, ferns, crinum lily, commelina and grasses, read more about weeds and their botanical names here.
Animals associated with the benthic zone include protozoa, rotifers, hydrae, tilapia fish, mudfish, catfish, leeches,
caddish fly larvae, larvae and pupae of mosquitoes, water snails, water spiders, crayfish, water scorpions, water boatmen and water bugs.
Lotic Freshwater Habitat
In a lotic freshwater habitat e.g. rivers, there exist two zones, these are:
1.
pool zone:
in this zone, water is relatively slow and calm.
2.
rapid zone:
in this zone, water is very fast. The lotic freshwater habitat is not as stratified as the lentic freshwater habitat.
ADAPTIVE FEATURES OF SOME ORGANISMS IN FRESHWATER HABITAT
some plants and their adaptive features
Water lily (Nymphaea):
the plant has air bladders, an expanded shape and is lightweight which keeps it afloat. It has long petioles attached at the centre of the leaf blade which prevent them from being drawn underwater by the current.
2.
Water hyacinth (Ipomea grassipis):
they have cavities and intercellular air spaces which give them the ability to float or maintain buoyancy on water.
Spirogyra:
the plant has a mucilaginous cover which protects them in water.
Water lettuce (pistia):
water lettuce has hairs on its leaves which help them to trap air and enable them to float.
5.
Hornwort (Ceratophyllum):
the plants have submerged or thin dissected leaves which increase their surface area to sunlight and gaseous exchange.
Water weed (elodea):
the plant has a long and flexible submerged petiole which enables it to swing with water currents.
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some animals and their adaptive features
1.
Protozoa:
these animals possess contractile vacuoles which enable them to carry out osmoregulation in water.
2.
Tilapia fish:
they have swim bladders which enable them to float (buoyancy) in water. They also have gills for respiration.
3.
Duck:
it has webbed digits on its feet for easy locomotion and a serrated beak for sieving food in water into its mouth.
4.
Lungfish (protopterus):
The animals obtain oxygen through the gills but when the water dries out during the dry season, they dig into the mud and breathe with their lungs until the rain comes again.
5.
Hydra:
it has a slippery surface, hooks and suckers for attachment to water particles.
6.
Pond skaters (gerris):
this animal has long legs with which he skates on the water\’s surface.
7.
Water boatman:
this animal can carry bubbles of air with it as it goes below the water surface to the bottom and uses these as its air supply (respiration) underwater.
Food Chain in Freshwater Habitat
Diatoms, spirogyra, detritus, water lily, and most of the flowering plants are the major producers in freshwater habitat. Some examples of food chains are:
i. Diatoms==fish fry==tilapia
ii. Detritus==worm==shrimps==birds
iii. Spirogyra==tadpoles==carps==king fishers.
energy flow in freshwater habitat
- Energy from sun/radiant energy/solar energy is received
- It is then absorbed/trapped by green plants/algae/phytoplankton (of freshwater/pond/stream/river, etc.).
- This is used in photosynthesis, to synthesize/manufacture organic substances.
- Zooplankton/fish/animals of the pond would now depend or feed on the green plants for food.
- The feeding is direct if they are herbivores as the plants are eaten by herbivores.
- The feeding is indirect if they are carnivores as herbivores are eaten by carnivores.
- When plants or animals/organisms die or when animals discharge their droppings/wastes, they are decomposed via the action of saprophytes/fungi/bacteria-decomposers/micro-organisms.
- By so doing, energy is lost.
Factors Affecting Freshwater Habitat
Factors which affect freshwater habitats are biotic and abiotic factors.
1.
Biotic Factors
a. Plant/producers
b. Animals/consumers
c. Parasites
d. Decomposers/saprophytes/micro-organisms
e. Predators
2.
Abiotic Factors
a. Temperature
b. Sunlight/light
c. Wind
d. Inorganic compounds
e. Turbidity/suspended particles/transparency
f. Topography
g. Dissolved oxygen
h. pH/dissolved CO
i. water current/currents
j. rainfall/precipitation
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Originally posted 2021-12-14 11:39:05.