1. CHAPTER 4 Environmental Studies, 2e
Aquatic Ecosystems
CHAPTER 4
Environmental Studies, 2e

2. Chapter Objectives
After studying this chapter, the reader should be able to:
Describe the main types of aquatic organisms
Appreciate the importance of the ocean with respect to the ecosystem services it provides
Explain the division of the ocean into zones
Understand the importance of coral reefs and mangroves
Appreciate the special features of Antarctica and its current state

3. Chapter Objectives (contd)
Recall the features of the UN Convention on the Law of the Sea and the importance of the Exclusive Economic Zone
Explain why the coastal zone is vital and what is happening to coastal areas of the world
Appreciate the importance of estuaries, coastal and fresh water wetlands
Describe the general characteristics of rivers and the spread of the river system in India.

4. The Story of Gulf of Mannar
Gulf of Mannar Biosphere Reserve, Tamil Nadu
Rich biodiversity, mangroves, coral reefs, turtles, dugongs, etc.
Destruction:
Bottom trawling
Coral mining
Pollution from industries
Many species facing threat of extinction
People’s livelihoods affected

5. Gulf of Mannar Biosphere Reserve (GOMBR

6. The Global Ocean Single ocean, great depths Largely unexplored
Greater biodiversity than on land
Provides many ecosystem services

7. Zones of the Ocean Coastal zone Open ocean: euphotic zone bathyal zone
abyssal zone

8. Figure 4.1 The Zones of the Ocean

9. Coral Reefs diverse and productive ecosystems formed by polyps
home for 25% of marine species
absorb carbon dioxide
protect coasts against storms
Threats to coral reefs:
being lost all over the world
coral bleaching

11. Mangroves salt-tolerant trees on coast roots are nurseries for fishes
branches are nesting sites for birds
prevent sea erosion
protect coast during storms
Threats to mangroves:
coastal development
logging
shrimp aquaculture

12. Antarctica fragile, sensitive, and unexploited ecosystem
contains 70% of world’s freshwater
mean temperature is rising, ice shelves are breaking off, leading to sea-level rise
seals and whales hunted to near-extinction
tourism creates problems

13. Inland Seas
Large saline lakes including the Caspian Sea, Dead Sea, Black Sea, Lake Victoria, and Aral Sea
Sensitive ecosystems, now being degraded
Aral Sea between Uzbekistan and Kazakhstan:
Once fourth largest freshwater lake
Lost 75% volume and 50% area over 40 years due to diversion of inflow for irrigation
Lake Victoria, East Africa:
Second largest freshwater lake
Fisheries collapse due to the introduction of a new predator species

18. Ocean Governance UN Convention on the Law of the Sea
Came into force in 1994
200 nautical miles of Exclusive Economic Zone for every country
UN control over ocean resources through International Tribunal for the Law of the Sea and the International Seabed Authority

19. Coastal Zone Area of interaction between land and ocean
Contains 90% of all marine species
Worldwide migration of population towards the coasts
Large cities, developmental activities on the coasts
Estuaries and coastal wetlands getting degraded

20. Figure 4.2 The Coastal Zone

21. The coastal zone with its diversity is ecologically important, but it is being degraded due to population pressure, urban expansion, infrastructure development, and pollution.

22. The Story of Chilika Lake
Chilika lake in Orissa
Largest brackish water lagoon in Asia
Rich in species of birds, fishes
Faced ecological and social problems: siltation, reduced salinity, water logging on shores, reduced fish catch
Chilika Development Authority took steps:
Fish catch increased
Flooding avoided

23. Pollution of the holy Ganga

25. Keywords & Phrases of Chap.4
aquatic life zone
plankton, nekton, benthos
phytoplankton, zooplankton
coastal zone
open ocean,
euphotic zone, bathyal zone, abyssal zone
coral reefs, zooxanthellae
mangroves
estuary, wetland
Common Heritage of Mankind
UNCLOS, EEZ

26. Key Points of Chap.4
The ocean is a treasure house of biodiversity and the provider of a range of ecological services.
Coral reefs and mangroves are vital organisms that are under threat.
The relatively unexploited Antarctica is now under pressure.
Many large inland seas and fresh water lakes face severe environmental problems.
The use of the ocean is now regulated by the UN Convention on the Law of the Sea.
The coastal zone with its immense biodiversity is being degraded by development and population pressure.