aquatic ecosystem

ENTREPRENEURSHIPEnvironmental Studies, 2e © Oxford University Press 2011 All rights reserved
Environmental Studies, 2e © Oxford University Press 2011 All rights reserved
Aquatic Ecosystems
CHAPTER 4
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
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.
Gulf of Mannar Biosphere Reserve (GOMBR
The Story of Gulf of Mannar
Gulf of Mannar Biosphere Reserve, Tamil Nadu
World richest marine diversity region
Rich biodiversity, mangroves, coral reefs, turtles, dugongs, etc.
10500 sq Km area, 21 island, 3600 species flora and fauna
Destruction:
People’s livelihoods affected
What this story tells us
Unique natural environment, population pressure, people livelihood and conservation efforts
Value of oceans and human impact that is adversely affecting the ocean ecosystem
Kind of organism in aquatic zones
Plankton, nekton and benthos
Freely floating plankton are microorganism that can not swim freely and buffered by wave and currents
Plankton: Phytoplankton and zooplankton
Phytoplankton: Photosynthesis and form basis of ocean’s food web
Zooplankton: Primary consumer and feed on phytoplanktons
Zooplankton are food for newly hatched fish and small organism
Nektons are strong swimmers, include all the larger organism like fishes, turtle and whales
Benthos are bottom dwellers adopted to live on floor of water body
Some fix on one spot like sponges, oyster and barcles
Some move about floor like crawfish and brittle stars
The Global Ocean
Occupy 71% of earths surface
361 million sq km with an average depth of 3.7 km and total volume of 1347000 sqkm
35g salt per kg
Single ocean, great depths
Pacific ocean cover one third of earth surface and contain 50% of its water
Pacific also has deepest part of ocean Mariana Trench (11Km, 2200m more)
Importance of oceans
Largely unexplored
Provides many ecosystem services:
Regulation of climate and rain fall, cycling of nutrient, absorption of carbon dioxide, waste treatment, nursery for many species, storage of biodiversity and genetic resources
Economic benefit include food items(fish, sea weeds and other items)
Fishmeal, oil and gas, mineral, medicine and building material, transport and recreation
Zones of the Ocean
Coastal zone: Extend from high tide mark on land to edge of continent
Open ocean:
euphotic zone: Upper part (Phtoplankton, Large fish, shark and swordfish)
bathyal zone: Lacks sunlight, no producers, zooplankton and smaller fish
abyssal zone: (4-6 Km) Dark zone, producer organism that withstand a temp of 200 c
Figure 4.1 The Zones of the Ocean
Coral Reefs
Aesthetically appealing
formed by huge colonies of tiny organism polyps
Secrete calcium carbonate to form a protective crust around their soft bodies
When die outerskeleton remain as platform for others to continue building the coral
The colour of coral come from zooxanhtellae a tiny single cell algae inside tissue of polyps
In return to home provide by polyps, zooxanthellae produce food and oxygen through photosynhtesis
Importance of coral reefs
Perform many ecological services
They can be called as rain forest of oceans
Economic side: Provide fish, shellfish, building materials and medicine
Through tourism bring invaluable foreign exchange
Threats to coral reefs:
being lost all over the world
Vulnerable to damage as grow slowly, get disrupted easily and very sensitive to variation in temperature and salinity
coral bleaching: Loss of colour
When reef become stressed loses its colour and food and ultimately dies
Increase in temperature cause bleaching
60% are threatened by coastal development, pollution and overfishing and warmer temperatures
Southasia with most species of all coral reefs is most threatened region
Mangroves
Found inland wiht coral reefs
roots are nurseries for fishes
branches are nesting sites for birds
prevent sea erosion
Antarctica
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
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
Ocean Governance
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
Coastal Zone
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
Figure 4.2 The Coastal Zone
The coastal zone with its diversity is ecologically important, but it is being degraded due to population pressure, urban expansion, infrastructure development, and pollution.
The Story of Chilika Lake
Chilika lake in Orissa
Faced ecological and social problems: siltation, reduced salinity, water logging on shores, reduced fish catch
Chilika Development Authority took steps:
Fish catch increased
Pollution of the holy Ganga
Keywords & Phrases of Chap.4
coral reefs, zooxanthellae
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.

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