FRESH WATER HABITAT
Fresh water habitat is a body of water formed mainly from inland waters and contain very low level of salinity.
Examples of fresh water habitats are:
rivers, ponds, streams, springs and lakes
Types of Fresh Waters
Fresh waters are classified on the basis of their mobility. Based on this, two types are identified. These are:
1.
Lotic fresh waters :
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.
2.
Lentic fresh waters :
these include standing or stagnant waters. These waters do not flow nor move. Examples are lakes, ponds, swamps and dams.
Characteristics of Fresh Water Habitats
The following characteristics are associated with fresh water habitats:
1.
low salinity:
fresh water habitats normally contains very low level of salts. It has about 0.5% of salt compared to about 3.5% for sea water.
2.
small in size:
fresh water habitat is usually very small compared to the ocean water which is about 75% of the earth surface
3.
variation in temperature:
the temperature of fresh water habitat 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.
shallowness of water:
most fresh water habitats are very shallow hence sunlight can easily penetrate through the water to the bottom.
6.
seasonal variation:
some fresh water 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 dry season.
7.
currents:
currents can affect the distribution of gases, salts and small organisms in fresh water habitats such as rivers and streams.
MAJOR ECOLOGICAL ZONES OF FRESH WATER HABITATS
The zones of a lentic fresh water 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 fresh water habitat. These are littoral and benthic zones.
1.
Littoral zone:
it is the shallow part of fresh water 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.
2.
Benthic zone:
benthic zone is the deepest parts of the lentic fresh water 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 system 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, mud fish, cat fish, leeches,
caddish fly larvae, larvae and pupae of mosquito
, water snail, water spider, crayfish, water scorpion, water boatman and water bugs.
Lotic Fresh Water Habitat
In a lotic fresh water 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 fresh water habitat is not as stratified as the lentic fresh water habitat.
ADAPTIVE FEATURES OF SOME ORGANISMS IN FRESH WATER HABITAT
some plants and their adaptive features
1.
Water lily (Nymphaea):
the plant has air bladders, expanded shape and light weight which keep it afloat. It has long petioles attached at the centre of leaf blade which prevent them from being drawn under water 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.
3.
Spirogyra:
the plant has mucilaginous cover which protect them in water.
4.
Water lettuce (pistia):
water lettuce has hairs on their leaves which help them to trap air and enable them to float.
5.
Hornwort (ceratophyllum):
the plants have submerge or thin dissected leaves which increase their surface area to sunlight and gaseous exchange.
6.
Water weed (elodea):
the plant has a long and flexible submerged petiole which enable it to swing with water currents.
some animals and their adaptive features
1.
Protozoa:
these animals possess contractile vacuole 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 digit on its feet for easy locomotion and serrated beak for sieving food in water into its mouth.
4.
Lung fish (protopterus):
he animals obtain oxygen through the gills but when the water dries out during dry season, hey dig into the mud and breathe with lungs until the rain comes again.
5.
Hydra:
it has slippery surface, hooks and suckers for attachment to water particles.
6.
Pond skaters (gerris):
this animal has long legs with which he skates on water surface.
7.
Water boatman:
this animal can carry bubbles of air with it as it goes below the water surface to the bottom and use these as their air supply (respiration) under water.
Food Chain in Fresh Water Habitat
Diatoms, spirogyra, detritus, water lily, and most of the flowering plants are the major producers in fresh water habitat. Some example of food chains are:
i. Diatoms==fish fry==tilapia
ii. Detritus==worm==shrimps==birds
iii. Spirogyra==tadpoles==carps==king fishers.
energy flow in fresh water habitat
1. Energy from sun/radiant energy/solar energy is received
2. It is then absorbed/trapped by green plants/algae/phytoplanking (of fresh water/pond/stream/river, etc.).
3. This is used in photosynthesis, to synthesize/manufacture organic substances.
4. Zooplankton/fish/animals of the pond would now depend or feed on the green plants for food.
5. The feeding is direct if they are herbivores as the plants are eaten by herbivores.
6. The feeding is indirect if they are carnivores as herbivores are eaten by carnivores.
7. 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.
8. By sodaing, energy is lost.
Factors Affecting Fresh Water Habitats
Factors which affect fresh water 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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