SSS 1: Aquatic Habitat
Habitat
Habitat is the natural place where an organism lives successfully. A habitat meets all the environmental conditions an organism needs to survive.
Types of habitats
The two major types of habitats are:
1. Aquatic habitat
2. Terrestrial habitat
AQUATIC HABITATS
An aquatic habitat is a body of water where certain organisms live. Examples of aquatic organisms include: fish, toads, crabs, aquatic plants, etc
Types of aquatic habitat
There are three types of aquatic habitat:
(a) Freshwater habitat
(b) Marine (Salt) water habitat
(c) Estuarine (Brackish) water habitat
(A) Freshwater habitats
Freshwater habitat is a body of water formed mainly from inland waters. They contain a very low level of salt content (salinity). Examples of freshwater habitats are ponds, streams, lakes, rivers, and springs.
Organisms in freshwater habitats include snails, crabs, frogs, turtles, marsh birds, alligators, snakes, etc.
Types of freshwater habitats
Freshwater bodies are grouped based on their movement.
1. Lentic fresh waters: They are the stagnant waters. They do not flow e.g. ponds, lakes, dams, and dams.
2. Lotic fresh waters: They are the running waters e.g. rivers, streams, and springs.
Characteristics of freshwater habitats
1. Their salt content is very low (i.e. very low salinity).
2. They are small in size when compared with ocean
3. Their temperature varies with season and depth
4. They have a high oxygen content
5. Sunlight can penetrate to the bottom due to their shallowness
6. Volume changes with season
7. Water current can affect the distribution of gases, salts, and small organisms
Ecological zones of lentic freshwater
i. Littoral zone
ii. Benthic zone
Littoral zone
This is the shallow upper part of the lentic freshwater habitat. It has the highest level of primary producers. It has rooted vegetation at its base. Sunlight easily penetrates this zone thereby increasing photosynthesis activities. Examples of plants in this zone are water lettuce, duckweed, spirogyra, water weed(Elodea), etc
Examples of animals in this zone are water snails, toads, frogs, ducks, snakes, crocodiles, tadpoles, pond skaters, etc
Benthic zone
This is the deepest part of the lentic freshwater habitat. It doesn't have rooted vegetation like the littoral zone. Plants in this zone have a well-developed root system in the mud. Examples of plants in this zone are water lilies, ferns, water arum, grasses, etc. Animals found in this zone are protozoa, catfish, tilapia crayfish fish, water bugs, leeches, etc
Lotic fresh waters
Lotic fresh waters are characterized by flowing waters. Examples include rivers, streams, brooks, and springs.
The two zones in lotic fresh water are:
1. Pool zone: water is relatively slow and calm.
2. Rapid zone: water is very fast
EUTROPHICATION
Eutrophication is excessive plant and algae growth in the water bodies caused by an increase in organic nutrients leading to the death of aquatic organisms.
This process may result in oxygen depletion of the water body.
Causes of eutrophication
1. Overuse of fertilizer which drains into a water body
2. sewage discharge into an aquatic environment.
Food chain in freshwater habitat
- Algae ⇢ insects ⇢ fish ⇢ hawk.
- Spirogyra ⇢ tadpole ⇢ carps ⇢ shark
- Diatom ⇢ shrimp ⇢ small fish ⇢ kingfisher
Energy flow in freshwater habitat
Energy from the sun is trapped by green plants in the freshwater for photosynthesis. Smaller aquatic herbivores feed directly on the plants for food. Carnivorous aquatic animals feed on the herbivores. When plants or animals die or when animals discharge their waste, they are decomposed by the saprophytes. Energy is lost through this action.
Adaptive features of some plants in freshwater habitat
1. Spirogyra: It possesses a mucilage covering that protects it in water.
2. Water lettuce: water lettuce has hairs on its leaves which help it to trap air and also help it to float on water.
3. Waterweed (Elodea): it has a long and flexible submerged petiole which enables it to swing with water currents.
4. Water Lily: it has air bladders, an expanded shape, and is lightweight which keeps it afloat on water. It has long petioles attached at the center of the leaf blade which prevent them from being drawn under by the water current.
5. Water hyacinth: they have cavities and intercellular air spaces which give them the ability to float or maintain buoyancy on water.
Adaptive features of some animals in freshwater habitat
1. Protozoa: they possess contractile vacuoles which help them to carry out osmoregulation in water.
2. Hydra: it has a slippery surface, hooks, and suckers for attachment to water particles
3. Pond skaters: they have long legs with which they skate on the water's surface.
4. Tilapia fish: they have swim bladders which help them to float (bouyancy) in water. Presence of gills for respiration.
5. Duck: it has a webbed digit on its feet for easy movement and a serrated beak for sieving food in water into its mouth.
Factors affecting freshwater habitats
Factors affecting freshwater habitats are
1. Biotic factors: producers(plants), consumers(animals), parasites, saprophytes(decomposers), predators etc
2. Abiotic factors: Sunlight, temperature, wind, turbidity, topography, dissolved oxygen and carbon dioxide, pH, water current, rainfall(precipitation), inorganic compounds, etc
(B) Marine (Salt) water habitat
Marine habitats are aquatic habitats that contain salt water. Marine habitats include the oceans, lakes, shores, and the open seas. Examples of organisms in marine habitats include: sharks, whales, turtles, octopuses, seahorses, dolphins, seaweeds, jellyfish, starfish, etc
Characteristics of marine habitats
The characteristics of marine habitats are:
1. High salinity: Salinity is defined as the degree of saltiness or concentration of salt solution in the ocean.
2. High density: Many organisms can float in marine water due to high density.
3. High pressure: water pressure increases with depth at the rate of one atmosphere for every ten meters.
4. Large size: Marine habitats represent the largest of all the habitats. Examples of oceans are the Atlantic Ocean, Indian Ocean, Pacific Ocean (the largest), etc.
5. High water current at the surface of the ocean.
6. High tides: Tides are the alternate rise and fall of the surface of the ocean. Tides are due to the gravitational effect of the moon and the sun.
7. Oxygen concentration decreases down the ocean. Oxygen concentration is highest at the surface while it decreases with depth. There is practically no oxygen in the deepest part of the ocean.
8. High pH: Salt water is alkaline with a pH of about 8.0-9.0 near the surface.
9. High waves: waves are movement of surface waters of the oceans
10. Light penetration decreases down the water body. Penetration of light depends on turbidity.
Horizontal zones of marine habitat
The ecological zones of the marine habitats are:
1. Supratidal (Splash) zone
2. Intertidal (Neritic) zone
3. Subtidal (Litoral) zone
4. Benthic zone
5. Pelagic (Abyssal) zone
6. Aphotic (Hadal) zone
Supratidal (Splash) zone
This is the exposed zone of the marine habitat. It has occasional moisture. It is the area where water splashes when the waves break at the shore.
Intertidal (Neritic) zone
This zone is also called a euphotic or planktonic zone. It is exposed at low tide or covered by water at high tide. It has high photosynthetic activities because of the abundance of sunlight and nutrients.
Subtidal (Litoral) zone
The subtidal zone is about 200m deep. It is constantly underwater. It has abundant sunlight and nutrients.
Benthic zone
The benthic zone is also underwater and is about 500m deep. It has low light penetration and low nutrients.
Pelagic (Abyssal) zone
This zone is about 7000m deep.
•It has a low temperature.
•It has low light penetration
•It has high pressure
•It has low photosynthetic activities
•The primary production of food is by chemosynthesis
Aphotic (Hadal) zone
This is the deepest zone of the marine habitat. It is over 7000m deep.
•It forms the floor or bed of the ocean
•It has no light penetration
•It has no photosynthetic activities.
Vertical zones of the marine habitat
Based on depth or light penetration or vertical zoning of marine habitat.
Marine habitats can be divided into three major parts:
1. Euphotic zone
2. Disphotic zone
3. Aphotic zone
Euphotic zone
•This area is directly connected to sunlight
•The zone contains Producers, consumers, and decomposers.
•There is enough light penetration for photosynthesis activities
•It has abundant nutrients
Disphotic zone
•A region of dim light
•The zone contains consumers and decomposers
•Low light penetration for photosynthesis activities
• It has little amount of nutrients
Aphotic zone
•This is the bottom or bed of the sea or ocean
•It has cold dark water
•It has no light penetration
•It contains few living organisms.
General adaptation of plants in marine (salt) habitat
1. Presence of salt glands or bladder to regulate excess salt.
2. Presence of stilt root for anchorage
3. Presence of breathing root(pneumatophore) for breathing atmospheric oxygen
4. Good osmoregulatory mechanism to regulate water balance in the body
5. Presence of succulent stems and roots for easy water movement
6. Presence of viviparous seedlings to ensure survival and continuity
Adaptation of animals in Marine habitats
1. Cartilaginous fish e.g. Sharks and dogfish can retain urea in their bodies to cope with high salinity
2. Bony fish e.g. Tilapia possess salt-secreting glands in their gills or eyes to maintain osmoregulation
3. Starfish possess tube feet which enable them to hold on to rock shores and hard shells which prevent dedication or drying up
4. Periwinkles possess lungs for breathing and feet for attachment
5. Shrimps possess powerful claws or chelipeds for seizing or holding food or prey.
6. Barnacles have protective pads for attachment to rock shore, cilia for feeding, and shells that prevent desiccation.
Food chains in marine habitat
1. Diatom ⇢ zooplanktons ⇢Tilapia ⇢ shark
2. Diatom ⇢ crabs ⇢ Tilapia ⇢ hawk
Factors Affecting Marine Habitat
The factors include both the biotic and abiotic factors
(C) ESTUARINE HABITAT
Estuarine habitat is a body of water formed at the coast due to the action of tides which mix salt water from the sea and fresh water from the land resulting in brackish water. The brackish water is what is called estuarine.
Types of Estuaries
1. Delta
2. Lagoon
3. Bay
Delta
A delta is where a river divides into many channels before entering the ocean or sea. It is formed at the mouth of a river as it enters the sea.
Lagoon
This is the body of ocean water that enters into land through a canal thereby mixing with fresh water from rivers and streams.
Bay
This is a little or small portion of the seawater that enters the land and mixes up with fresh water from rivers and streams. A lagoon is bigger than a bay.
Characteristics of Estuarine habitat
1. Fluctuation in salinity: Salinity is lower at the mouth of a river and gets higher towards the sea. Salinity is affected by season. The rainy season reduces salinity due to the addition of fresh water, the dry season increases it.
2. Turbidity: Turbidity is the measure of the relative clarity of a liquid. The turbidity of estuarine habitat increases during the rainy season when lots of debris is brought down by rivers to the habitat. High turbidity also reduces the rate of photosynthesis and respiration by organisms.
3. Shallowness of water: The water in an estuarine habitat is very shallow compared to seawater.
4. Low species diversity: The estuarine habitat has a low diversity of species compared to the marine habitat.
5. Water is affected by tides: Sea water usually flows rapidly into estuaries at high tides and rushes back into the ocean at low tides.
6. High level of nutrition: It contains abundant nutrients, especially the organic detritus which form the bulk of producers in the habitat.
7. Low oxygen content: The oxygen content of estuarine habitats is generally very low and as a result, much of the microbial activities are anaerobic.
Adaptation of plants in Estuarine habitat
1. Planktons(diatoms): They possess air spaces in their tissues, rhizoid(false feet) for attachment to rock, and air bladder for buoyancy.
2. Algae: They possess chlorophyll for photosynthetic activities. Small size or large surface area for floating
3. Red mangrove (Rhizophora racemosa): It has silt root which has air spaces for conducting air to the tissues of the root
4. White mangrove(Avicennia nitida): It has pneumatophores or breathing roots for the exchange of gases.
Adaptation of animals in estuarine habitats
1. Mosquito larvae and pupa: They possess breathing trumpets for gaseous exchange
2. Crabs: They can burrow fast into the mud against predators, strong waves or tides
3. Water snails and shrimps: These animals can burrow into the mud when the tide is going out.
4. Worms: They have strong protective and impermeable covering against high salinity.
5. Mud skippers: These animals have fins adapted for crawling when on land and for swimming when in water.
6. Fish: Fish such as tilapia have fins for movement and swim bladder for buoyancy.
Food chain in estuarine habitat
1. Detritus ⇢ shrimps ⇢fish ⇢ bird
2. Detritus ⇢ worms ⇢snails ⇢ bird
3. Phytoplanktons ⇢ barnacles ⇢fish ⇢ bird
Factors affecting estuarine habitat
The factors include both the biotic and abiotic factors.
ASSIGNMENT
A.Explain the following and give two(2) examples:
1. Phytoplanktons
2. Zooplanktons
B. Define detritus and give two(2) examples of a detritus food chain
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