Aquatic ecosystems cover the following :
- The Ocean
- Water bodies on land area including streams , rivers , ponds , lakes , wetlands and estuaries.
- Man-made reservoirs
- Coral reefs
HOW AQUATIC ECOSYSTEMS DIFFER FROM TERRESTRIAL ONES ?
The difference arises from the fact that : –
- air and water are very different environments.
The differences observed between aquatic and terrestrial ecosystems are :
- Density : – Water is much more denser than air that’s why all the aquatic organisms can float in the water but when they move water exerts a drag .
- This is the reason organisms that move fast in water have streamlined body shapes.
- Gravity : – The buoyancy of water offsets the force of gravity .
- Oxygen availability : – Oxygen is easily available on land.
- In water, oxygen dissolves in relatively low concentrations.
- The content of oxygen is not equal for every aquatic organism like large aquatic organism have gills to help them extract oxygen from water.
- Some organisms like sea turtles rise to the surface to breathe oxygen.
- Temperature : – There are greater variations of temperature on land than water.
- land organisms have more tolerance than aquatic organisms.
- Light availability : – There is enough sunlight on land for food processing like photosynthesis but water affects light.
- For example : – More life in water exists in shallow depths
- This is because as we move down the water the less is the light available due to penetration of light.
The terrestrial organisms need more energy to move about because :-
- They have to fight gravity and
- They need more bones in their body for support .
- For example : – Elephants have many more bones than whales.
In actual there is only one single connected ocean.
TYPES OF OCEANS
For our convenience we have divided the ocean into different parts and they are :
- Pacific ocean ( the largest of all )
- Atlantic ocean
- Indian ocean
- Antarctic ocean or Southern ocean
- Arctic ocean
Some of the basic facts about the ocean are : –
- The ocean covers around 68-70% of earths surface and
- 1-2% for rivers , ponds etc as total water is present nearly 71%.
- The average depth is around 3700 m .
- The deepest point ( 11,000 m) is the Mariana Trench in the Western Pacific.
- 97% of all the water on the earth is in the ocean.
- The ocean ridges form a mountain range almost 60,000 km long which is larger than any mountain range on land.
- By volume around 99% of Earth’s living space is in ocean.
# WHY IS OCEAN IMPORTANT ?
- Life itself began in the ocean and now it supports the largest variety of life on Earth.
- The biodiversity of the ocean is thought to be much greater than of land.
- The ocean absorbs a quarter of carbon that we put into the atmosphere every year.
- Fish from the oceans provides the necessary nutrition to millions of people.
- The ocean provides 70% of oxygen.
- It absorbs heat and move around the globe and regulates our climate system.
- The ocean enables us to transport goods and oils to other part of the world.
- Ocean provides livelihood to millions of people.
The ocean also contains : –
- Minerals and
- Metals which are not fully exploited yet.
# MAJOR THREATS TO THE OCEAN
The major threats to the ocean are : –
- Illegal fishing
- Lack of protection
- Impact of Industries and Tourism
- Impact of shipping
- Dumping of waste