AQUATIC HABITAT

HABITAT (AQUATIC HABITAT)

Habitat is a place where organisms (plants, microorganisms and animals) are naturally found e. g. the habitat of tadpole is the bottom of fresh water ponds or streams. There are three main types of habitats, namely; aquatic habitat (in or around water), terrestrial habitat (in or on land) and arboreal habitat (in or on trees)

There are three kinds of aquatic habitat;

1. marine/salt water habitat e.g. ocean, seas
2. brackish water habitat (where salt and fresh water mix) e.g. delta, lagoon, bay
3. Fresh water habitat (contain little or no salt) e.g. lakes, rivers, streams.

 

MARINE HABITATS

Characteristics of marine habitats are as follow:

1. The marine habitats constitute the largest habitat in the biosphere (70% of the earth’s area)
2. They do not undergo sudden or rapid changes in physical factors such as temperature, PH and specific gravity. Hence they show the greatest stability of all habitats.
3. Chemical composition :- marine water consists of many kinds of dissolved ions including Na⁺, K⁺, Mg²⁺, Ca²⁺, Pb₄^3-, I^–, NO^3- t. c.
4. Hydrogen (H⁺) concentration (PH): – salt water is alkaline in nature with PH of about 8.0 – 9.0 near the surface.
5. Salinity (salt concentration of water). The seawater has a high salinity. The average salinity of seawater is 35 parts per thousand.
6. Density of marine water is high. It is about 1.028 while that of fresh water is 1.0. This allows many organisms to float in it.
7. The temperature of the sea changes less quickly than that of the land. However, the temperature falls with increase in the depth of the sea.
8. Oxygen concentration is highest at the surface where the atmospheric oxygen dissolved in water. The concentration of oxygen decreases with depth.
9. Waves are temporary movement of surface water of the sea which occurs in any direction. They are caused by wind blowing against the surface of water. They also bring about the mixing of seawater. Waves can also beat against the shore and sometime caused it to be eroded.
10. Tides are alternate rise and fall of the surface of the sea at least twice daily. Tides are caused by water distribution resulting from the combined gravitational pull of the earth by the sun and moon.

 

EVALUATION

1. What is a habitat?
2. With two examples each, state the three kinds of aquatic habitats.

 

ZONATION OF MARINE HABITAT

HORIZONTAL ZONATION

The marine habitat is made up of the sea shore and open sea. The major zones of the marine habitat are generally as follow

1. Supratidal or splash zone is the exposed zone with occasional moisture being the area where water splashes when waves breaks at the shore.
2. Intertidal or neritic zone is the planktonic zone which is exposed at low tide or covered by water at high tide. This zone has high photosynthetic activities because of abundant sun shine. Water temperature fluctuates.
3. Subtidal or littoral zone is about 200m deep, constantly under water, with abundant sunlight and nutrient.
4. Benthic zone is about 500m deep with low light penetration and low nutrients. The water is dark, cold and with little oxygen. Hence, it is unfavourable for life.
5. Abyssal or palegic zone is about 7000m deep with low light penetration, low temperature and high pressure. The low light leads to low photosynthetic activities. Hence food production is primarily by chemosynthesis.
6. Hadal or aphotic zone is the deepest, over 7000m deep. This forms the floor or the bed of the ocean. No light penetration or photosynthesis

 

VERTICAL ZONATION

Based on light penetration or depth, the marine habitat can be zoned into three ;

1. Euphotic zone is the area in direct contact with sun shine. Hence, there is enough light penetration for photosynthesis. Therefore producers, consumers and decomposer are all present.
2. Disphotic zone is a region of dim light. Light penetrate the water with low too intensity for photosynthesis to take place. Consumers and decomposers are found in this zone.
3. Aphotic zone is the bottom or bed of the seas and oceans. It is characterized by cold dark water without light penetration and very few living organisms.

 

EVALUATION

1. State the major zones of marine habitat
2. Differentiate between splash and hadal zones

 

DISTRIBUTION OF ORGANISMS AND ADAPTATION TO MARINE HABITAT

• Organisms of the splash zone include periwinkles; crustaceans e.g. ghost crab, seaweeds and sargassum (algae).
• Those of intertidal zone include starfish, sea anemones, sponges, sea urchin, annelids, mollusca and barnacles.
• In the subtidal zone are snails, crabs, lobsters and crayfish.
• The benthic zone is unfavourable for life. The producers are absent, only few saprophytic animals are present.
• The neritic zone house plankton (microscopic floating organisms e.g. diatom, algae, protozoa, crustacean and worms) and nekton (e.g. fishes, crabs, prawns and whales).
• Oceanic water house sharks, croaker, sea cat fish, mackerel, bonga fish e.t.c.

 

ADAPTATION OF ANIMALS TO MARINE HABITAT  

Animals including barnacles, fishes, crustaceans e.t.c. found surviving in marine habitat do so with the following adaptive features;

• Barnacles have i. protection mantle for attachment to rock shore and water retention ii. Cilia for feeding. Iii. Shell that prevents dessication (drying up)
• Fishes possess i. reduced or no kidney to retain urea in their body to cope with high salinity e.g. cartilaginous fishes like shark, dogfish etc. ii. Salt secreting glands in their gills or eyes for maintaining osmoregulation (salt balance) e.g. bony fishes like tilapia, herring etc. iii. Tube feet which enable them to hold on to rock shores and hard shell to prevent desiccation e.g. starfish, whales.
• Whale has i. fins for stability in water ii. An organ in front of the nostril for detecting pressure changes in water. Iii. A thick layer of dermal fat insulation or food reservoir.
• Shrimps possess powerful claws for holding food or prey.
• Periwinkles possess lungs for breathing and foot for attachment.
• Crabs burrow fast into the mud to protect them against predators, strong waves or hide.

 

ADAPTATION OF PLANTS TO MARINE HABITAT

Plants such as seaweeds, algae, sesuvium and diatoms are naturally found in marine habitat with the following adaptive features;

• Seaweeds have i. hold–fast for attachment. ii. mucillagenous cover to prevent desiccation. iii. Divided leaves or floating devices for buoyancy.
• Algae (e.g sargassum) have i. chlorophyll for photosynthesis. ii. Small size or large surface area for floating in water.
• Planktons (e.g. diatoms) possess; i. air space in their tissues ii. Rhizoid for attachment to rocks iii. Air bladder for buoyancy (floating).

Examples of food chain in a marine habitat include

1. Diatom → crabs → tilapia
2. Diatom →zooplankton → tilapia →shark

 

EVALUATION

1. Mention two organisms in the following zones: i. Splash, ii. Neritic, iii. Littoral, iv. Benthic
2. Using 3 plants and 2 animals, explain adaptation in marine habitats.

 

ESTUARINE HABITATS (BRACKISH WATER HABITATS)

An estuary is a body of water formed at the coast where fresh water flowing towards the sea mixes with sea (salt water) flowing inland. Estuarine habitats include deltas, lagoons and bays.

 

CHARACTERISTICS OF ESTUARINES

1. The salinity fluctuates.
2. The specific gravity is less than that of the sea.
3. They have high turbidity due to frequent disturbances. Hence rate of photosynthesis and respiration by organisms reduces.
4. The water is shallow.
5. They have low diversity of species compared to marine habitat.
6. They have high level of nutrients
7. They have low oxygen content, hence anaerobic activities are common.

 

PLANTS DISTRIBUTION AND ADAPTATION IN ESTUARINES

Plants found in estuaries include planktons, algae, red and white mangrove and they have the following adaptive features;

• Planktons (diatoms) have; i. air spaces in their tissues ii. Rhizoid for the attachment to rock shores iii. Air bladder for buoyancy
• Algae have: i. chlorophyll for photosynthesis ii. small size or large surface area for floating in water
• Red mangrove has; i. stilt roots with rootlets that have air-spaces for air conduction to the root tissues and support to prevent washing away of the plant by the tide ii. Seeds which germinate while they are still on the parent plant, thus preventing the carrying away of the seedlings by water current.
• White mangrove has pneumatophores (breathing roots) for gaseous exchange.

 

ANIMALS DISTRIBUTION AND ADAPTATION

Animals including mosquitoes, crustaceans, mollusca, worms, fishes e.t.c. found in estuaries survive possessing the following features;

• Mosquito larvae and pupae possess breathing trumpets for gaseous exchange
• Crustaceans and water snails burrow into the mud against predators, strong waves or tides.
• Worms have strong protective and impermeable covering against high salinity.
• Mudskippers have fins for crawling on land and swimming in water.
• Fishes have fins for movement and swimming bladder for buoyancy.

 

FOOD CHAIN IN ESTUARINE HABITATS

1. Detritus → worms → snails → birds
2. Diatoms → shrimps →fishes
3. Diatoms → small fish → sharks → man

 

EVALUATION

1. What is estuarine?
2. List five characteristics of estuarines

 

FRESH WATER HABITATS

This is a body of water formed mainly from inland waters and it contain very low or no salt. Fresh water is of two types based on its mobility;

1. Lotic fresh waters: – These are running waters flowing continuously in a specific direction e.g. rivers, springs, streams
2. Lentic fresh waters: – These are stagnant waters which do not flow e.g. lakes, ponds, puddles, swamps and dams

 

CHARACTERISTICS OF FRESH WATER HABITATS

1. It contains little or no salt. Salinity is 5 parts per thousand i.e. 0.5%.
2. It is small in size.
3. Oxygen concentration is high, being available in all parts of the water body, especially at the surface.
4. The water is shallow, hence sunlight penetrate to the bottom.
5. The temperature varies with seasons and depth.
6. It has seasonal variation; decreasing or drying up in dry season and increasing in rainy season
7. Water currents affect distribution of organisms, salts and gases, especially in lotic fresh waters

 

PLANTS DISTRIBUTION AND ADAPTATION IN FRESH WATER

Plants of fresh water include water lily, spirogyra, water lettuce, water weeds e.t.c. and they have the following adaptive features;

• Water lily has i. air bladder ii. Expanded tips and light weight which keep it afloat.
• Spirogyra has mucillagenous cover for protection
• Water lettuce has hairs in leaves to trap air and keep it afloat
• Water weed (elodea) has a long and flexible petiole for swinging with water currents.

 

ANIMALS DISTRIBUTION AND ADAPTATION

Animals of fresh water habitats include protozoa, duck, pondskatters, hydra, fishes e.t.c. their adaptive features include

• Protozoa have contractile vacuole for osmoregulation in water.
• Duck has webbed feet for locomotion and serrated beak for sieving food in water into its mouth.
• Hydra has slippery surface, hooks and suckers for attachment to water particles.
• Pondskatters has long legs for skating on water surface
• Fishes have swim bladders for buoyancy and gills for respiration

 

FOOD CHAIN IN FRESH WATER HABITATS

1. Diatoms → fish fry →tilapia
2. Spirogyra → tad poles → carps → king fish
3. Algae → mosquito larva → small fish

EVALUATION

1. State five characteristics of freshwater habitats
2. With three examples each describe plants and animals adaptation to freshwater habitats

 

GENERAL EVALUATION

1. Give two examples of food chain in marine habitats
2. How do organisms adapt to life in estuary?
3. What is a fresh water habitat?
4. Differentiate between lotic and lentic fresh water habitats
5. Differentiate between waves and tides.
6. According to light penetration, zone marine habitat.

 

WEEKEND ASSIGNMENT

1. Buoyancy in salt water is ensured by the following except A. divided leaves B. chlorophyll C. floating devices D. air bladder
2. The mucilaginous cover in sea weed and spirogyra is mainly for A. protection B. osmoregulation C. avoiding desiccation D. feeding
3. Which of the following is not a fresh water habitat? A. puddle B. swamp C. stream D. sea
4. Which of these is not an adaptive feature in a marine habitat? A. bladder for floating B. hold fast for attachment C. fur to prevent water loss                           D. rhizoid for attachment to rock
5. The following are characteristics of fresh water habitats except A. low salt content B. high salinity C. shallow water D. can be stagnant or running water

 

THEORY

1. In a tabular form, state five differences between fresh water and a marine habitat
2. State three adaptive features each of plants and animals to fresh water habitat

 

See also

NUTRIENT CYCLING IN NATURE

FOOD PRODUCTION AND STORAGE

DEVELOPMENT OF ZYGOTE IN FLOWERING PLANTS

DEVELOPMENT OF NEW ORGANISMS

ORGAN OF HEARING