ASM-401 ENVIRONMENTAL SCIENCE

UNIT-2

DR. MOHD. AAMIR MAZHAR

ASSISTANT PROFESSOR
DEPARTMENT OF CIVIL ENGINEERING
JAMIA MILLIA ISLAMIA, NEW DELHI

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ECOSYSTEM

• An ECOSYSTEM is a community of living organisms interacting with

each other and their physical environment.
• It includes both biotic (living) components, such as plants and
animals, and abiotic (non-living) components, such as soil, air, water,
and sunlight.
• The study of ecosystems is called ECOLOGY, which plays a crucial role
in understanding the complex relationships and interdependencies
between different living organisms and their environment.

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COMPONENTS OF AN ECOSYSTEM
1. Producers
2. Consumers
3. Decomposers

1. Producers:
• These are primarily plants and other photosynthetic organisms that
convert sunlight into energy through the process of photosynthesis.
• They form the base of the food web by providing energy for all other
organisms in the ecosystem.
• Producers are also known as autotrophs.

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COMPONENTS OF AN ECOSYSTEM
2. Consumers:
• These organisms depend on other organisms for their energy and food
supply.
• Consumers are classified into different groups:
Herbivores: Animals that eat plants.
Carnivores: Animals that eat other animals.
Omnivores: Animals that eat both plants and animals.
3. Decomposers:
• These organisms, including bacteria and fungi, break down dead plants
and animals into simpler substances.
• Decomposers play a crucial role in recycling nutrients back into the
ecosystem, making them available for producers to use again.
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TYPES OF ECOSYSTEMS
Ecosystems can be classified into various types based on their physical
characteristics, such as climate, temperature, and geography.

• Terrestrial Ecosystems: These include forests, grasslands, deserts, and

tundra. Each of these ecosystems has distinct flora and fauna adapted
to their specific environments.

• Aquatic Ecosystems: These can be freshwater (lakes, rivers, and

wetlands) or marine (oceans, coral reefs, and estuaries). Aquatic
ecosystems are characterized by the presence of water, which is the
primary habitat for the organisms living there.

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 FUNCTIONS OF AN ECOSYSTEM
1. Oxygen Production: Through photosynthesis, producers (mainly plants)
release oxygen into the atmosphere, which is essential for the respiration of
most living organisms.
2. Nutrient Cycling: Ecosystems facilitate the recycling of nutrients.
Decomposers break down organic matter, releasing nutrients back into the
soil, which are then taken up by plants.
3. Carbon Sequestration: Ecosystems, especially forests and oceans, play a
significant role in storing carbon, helping to regulate the Earth's climate.
4. Habitat Provision: Ecosystems provide habitats for various species,
contributing to biodiversity.
5. Food Production: Ecosystems are the source of food for many organisms,
including humans. They support agriculture, fisheries, and other food
production systems. 6
 FUNCTIONS OF AN ECOSYSTEM
6. Energy Flow: Energy enters the ecosystem through sunlight and is captured
by producers via photosynthesis. This energy flows through the food chain,
with each trophic level losing energy due to metabolic processes. Eventually,
decomposers release the remaining energy back into the ecosystem as heat.
7. Ecological Succession: This refers to the gradual change in the composition
of an ecosystem over time due to interactions between biotic and abiotic
factors. Primary succession occurs in previously uninhabited areas, while
secondary succession follows disturbances in existing ecosystems.
8. Ecosystem Services: Ecosystems provide essential services such as air and
water purification, climate regulation, and resources like food, fiber, and fuel.
These services are critical for human well-being but are threatened by activities
like habitat destruction and pollution.

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 HUMAN IMPACT ON ECOSYSTEMS
Human activities have a profound impact on ecosystems. Pollution,
deforestation, climate change, and overexploitation of resources are some of
the major threats. These activities can disrupt the balance of ecosystems,
leading to the loss of biodiversity and degradation of ecosystem services.

• Pollution: Contaminants from industrial, agricultural, and urban activities can

harm ecosystems. For example, water pollution can lead to the death of
aquatic organisms and disrupt the food web.
• Deforestation: The clearing of forests for agriculture, urban development, and
logging can result in habitat loss, soil erosion, and changes in climate.
• Climate Change: Changes in temperature and weather patterns can affect the
distribution of species and the functioning of ecosystems.
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CONSERVATION OF ECOSYSTEMS

To maintain the health and functionality of ecosystems, conservation

efforts are essential. These efforts include:
• Protected Areas: Establishing national parks, wildlife reserves, and
marine protected areas to safeguard biodiversity.
• Sustainable Practices: Promoting sustainable agricultural, fishing, and
forestry practices that minimize environmental impact.
• Restoration Projects: Initiatives to restore degraded ecosystems, such
as reforestation and wetland restoration.

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STRUCTURE OF AN ECOSYSTEM

1. Biotic Components:
• Producers: These are typically plants and algae that produce
energy through photosynthesis. They form the base of the food
chain and provide energy for other organisms.
• Consumers: These include herbivores, carnivores, and omnivores
that consume other organisms for energy. They are further divided
into primary, secondary, and tertiary consumers based on their
position in the food chain.
• Decomposers: These organisms, such as fungi and bacteria, break
down dead organic matter, releasing nutrients back into the
ecosystem.
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STRUCTURE OF AN ECOSYSTEM
2. Abiotic Components:
• These include non-living factors such as sunlight, water, air, soil, and
minerals. These factors are critical for the survival of living organisms
and influence the distribution and abundance of biotic components.
• Sunlight: Essential for photosynthesis, providing energy for
producers.
• Water: Necessary for all life processes and is a key resource for living
organisms.
• Soil: Provides nutrients and a habitat for plants and other organisms.
• Air and Minerals: Required for various metabolic processes.
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STRUCTURE OF AN ECOSYSTEM

3. Spatial and Temporal Structure:

• Spatial Structure: Refers to the physical arrangement of biotic and
abiotic components, such as the distribution of plant communities or
soil composition.
• Temporal Structure: Involves changes over time, such as seasonal
fluctuations and successional changes in vegetation.

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ENERGY FLOW IN THE ECOSYSTEM
• Energy flow is a fundamental process in ecosystems, describing how energy
moves from one organism to another.
• This flow of energy is unidirectional, beginning with the sun and ultimately
being released as heat.
• Understanding how energy flows through ecosystems is essential for
grasping their structure and function.
Primary Source of Energy
• The sun is the primary energy source for most ecosystems.
• Plants, algae, and other photosynthetic organisms, known as producers,
capture solar energy through photosynthesis.
• During photosynthesis, sunlight is converted into chemical energy stored in
organic compounds like glucose.
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ENERGY FLOW IN THE ECOSYSTEM

Trophic Levels and Ecological Pyramids

• Energy transfer in ecosystems is represented by ecological pyramids,
which illustrate the relative amount of energy at different trophic
levels.
• The base of the pyramid consists of producers, which are then
consumed by primary consumers (herbivores), secondary consumers
(carnivores), and tertiary consumers (top carnivores).
• Each step up the pyramid represents a transfer of energy from one
trophic level to the next.
• However, energy decreases as it moves up the pyramid because of
metabolic processes like respiration and digestion.

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ENERGY FLOW IN THE ECOSYSTEM
Laws of Thermodynamics
• The flow of energy in ecosystems is governed by the laws of
thermodynamics.
• The first law of thermodynamics states that energy cannot be created or
destroyed but only transformed from one form to another.
• For example, solar energy is transformed into chemical energy by
producers and then into kinetic and thermal energy by consumers.
• The second law of thermodynamics highlights that energy transfer is
inefficient.
• At each trophic level, a significant portion of energy is lost as heat.
• This inefficiency results in only a small fraction of the energy being passed
on to higher trophic levels, limiting the number of trophic levels an
ecosystem can support.

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ENERGY FLOW IN THE ECOSYSTEM
Energy Loss and Ecosystem Function
• The energy loss as heat is crucial in determining the structure and sustainability
of ecosystems.
• Because of this energy loss, there are fewer organisms at higher trophic levels.
• This loss also emphasizes the importance of conserving producers, as they form
the base of the food chain and support the entire ecosystem's energy flow.
Human Impact
• Human activities, such as deforestation and pollution, disrupt energy flow in
ecosystems.
• These disruptions can lead to a loss of biodiversity and degrade ecosystem
services.
• Understanding energy flow is critical for promoting sustainable management and
conservation of natural resources.

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FOOD CHAINS, FOOD WEBS, AND ECOLOGICAL PYRAMIDS

Food Chains
• A food chain is a linear sequence of organisms where each one is
eaten by the next member in the chain.
• Each level of the food chain represents a different trophic level,
starting with producers and moving up to various levels of consumers.
• Example 1: Grassland Ecosystem
Grass (Producer) → Grasshopper (Primary Consumer) → Mouse
(Secondary Consumer) → Snake (Ter ary Consumer) → Hawk
(Quaternary Consumer)

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FOOD CHAINS, FOOD WEBS, AND ECOLOGICAL PYRAMIDS

Food Webs
• A food web is a complex network of interconnected food chains.
Unlike a single linear food chain, a food web shows the multiple
feeding relationships that exist in an ecosystem.
• This complexity provides greater stability because if one species is
affected, other species can fulfill similar roles.
• Coral Reef Ecosystem: Phytoplankton (Producer) → Zooplankton
(Primary Consumer) → Small Fish (Secondary Consumer) → Large Fish
(Ter ary Consumer) → Shark (Quaternary Consumer)

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FOOD CHAINS, FOOD WEBS, AND ECOLOGICAL PYRAMIDS

Ecological Pyramids
Ecological Pyramids graphically represent the structure of an
ecosystem, showing the number of organisms, biomass, or energy at
each trophic level.
1. Pyramid of Numbers: Represents the number of individual
organisms at each trophic level.
Example: In a forest ecosystem, there may be many trees (producers),
fewer caterpillars (primary consumers), even fewer birds (secondary
consumers), and very few snakes (tertiary consumers).

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FOOD CHAINS, FOOD WEBS, AND ECOLOGICAL PYRAMIDS

2. Pyramid of Biomass: Represents the total mass of living matter at

each trophic level.
Example: In grassland, the biomass of grass (producers) is much greater
than the biomass of herbivores like grasshoppers, which is greater than
the biomass of carnivores like birds.
3. Pyramid of Energy: Represents the flow of energy at each
trophic level, typically decreasing as it moves up the pyramid.
Example: Energy captured by grass through photosynthesis is highest at
the producer level and decreases through each level of consumers
(grasshoppers, mice, snakes, hawks) due to energy loss as heat and
metabolic processes
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CHARACTERISTIC FEATURES OF FOREST ECOSYSTEMS
1. Diverse Plant Life:
Trees: Trees are the primary component, providing the structural basis for
the forest ecosystem. They offer shelter, food, and habitat for a wide range
of species.
Understory Plants: These include smaller plants that grow beneath the
canopy, such as shrubs, ferns, and young trees. They are adapted to lower
light conditions and provide food and shelter for smaller animals.
2. Variety of Animals:
Forest ecosystems are home to numerous animal species, from insects to
large mammals. These animals play crucial roles in processes like pollination,
seed dispersal, and nutrient cycling.
3. Rich Soil:
Forest soils are typically rich in organic matter and nutrients, supporting
plant growth and providing habitat for a variety of soil organisms.

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STRUCTURE OF FOREST ECOSYSTEMS
1. Biotic Components:
Producers: The green plants (mainly trees) that produce food through
photosynthesis.
Consumers:
Primary Consumers: Herbivores that feed on plants (e.g., deer, insects).
Secondary Consumers: Carnivores that feed on herbivores (e.g., birds, small
mammals).
Tertiary Consumers: Top predators that feed on secondary consumers (e.g., tigers,
eagles).
Decomposers: Organisms like bacteria and fungi that break down dead matter,
recycling nutrients back into the ecosystem.
2. Abiotic Components:
These include climatic factors (sunlight, temperature, rainfall), soil characteristics,
water availability, and other physical and chemical factors that influence the
ecosystem's functioning.

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FUNCTIONS OF FOREST ECOSYSTEMS

1. Carbon Storage: Forests act as carbon sinks, absorbing carbon

dioxide from the atmosphere and storing it in the form of biomass
(trees and plants) and soil.
2. Water Cycle Regulation: Forests play a critical role in the water cycle
by intercepting rainfall, reducing soil erosion, and regulating stream
flow. They help maintain the balance of water in the environment,
which is crucial for other ecosystems and human activities.
3. Biodiversity Support: Forests are among the most biodiverse
ecosystems on the planet. They provide habitat for a vast array of plant
and animal species, each contributing to the ecosystem's overall health
and stability.

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FUNCTIONS OF FOREST ECOSYSTEMS

4. Climate Regulation: By absorbing carbon dioxide and releasing

oxygen, forests help regulate the Earth's climate. They also influence
local weather patterns and temperatures.
5. Soil Formation and Maintenance: The decomposition of organic
matter in forests creates nutrient-rich soils that support plant growth.
This process is essential for maintaining soil fertility and structure.
6. Economic Benefits: Forests provide numerous economic benefits,
including timber, non-timber forest products, and opportunities for
ecotourism. They are a source of livelihood for many communities
around the world.

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EXAMPLES OF FOREST ECOSYSTEMS

1. Tropical Rain Forests: Located near the equator, these forests are
characterized by high temperatures, high humidity, and abundant rainfall.
They are incredibly rich in biodiversity, with distinct layers such as the
emergent layer, canopy, understory, and forest floor, each supporting
different forms of life.
2. Temperate Forests: Found in regions with moderate climates, these
forests experience distinct seasons. They include both deciduous forests,
where trees shed their leaves annually, and coniferous forests, dominated by
evergreen trees.
3. Boreal Forests (Taiga): Located in northern regions, these forests consist
mainly of coniferous trees. They have long, cold winters and short, mild
summers. Boreal forests play a significant role in carbon storage and are
critical for many migratory species.

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CHARACTERISTIC FEATURES OF GRASSLAND ECOSYSTEMS
1. Dominant Vegetation: Grasses are the primary vegetation in
grassland ecosystems, adapted to withstand drought and fire. They
vary in height from short grasses in temperate regions to tall
grasses in tropical savannas.
2. Climate: Grasslands typically have a semi-arid climate with
moderate to low rainfall. They experience distinct seasons, with a
wet season promoting grass growth and a dry season.
3. Soil: The soil in grasslands is often fertile and rich in organic matter,
supporting diverse plant life. However, it can also be subject to
erosion if not protected by vegetation.

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STRUCTURE OF GRASSLAND ECOSYSTEMS
1. Producers: The primary producers in grasslands are grasses and other
herbaceous plants. These plants convert sunlight into energy through
photosynthesis, forming the base of the food web.
2. Consumers:
Primary Consumers: Herbivores such as antelopes, bison, zebras, and
various insects feed on the grasses.
Secondary Consumers: Carnivores like lions, hyenas, and wolves prey
on the herbivores.
Tertiary Consumers: Apex predators, such as eagles and hawks, feed
on smaller carnivores and herbivores.
3. Decomposers: Microorganisms like bacteria and fungi break down dead
organic matter, returning nutrients to the soil and maintaining the nutrient
cycle.

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FUNCTION OF GRASSLAND ECOSYSTEMS
1. Carbon Storage: Grasslands act as carbon sinks, absorbing carbon
dioxide from the atmosphere and storing it in plant biomass and soil.
This helps mitigate climate change.
2. Soil Formation and Protection: The decomposition of organic matter
enriches the soil with nutrients, promoting plant growth. Grass roots
help bind the soil, preventing erosion.
3. Biodiversity Support: Grasslands support a wide range of plant and
animal species, contributing to overall biodiversity. This diversity ensures
ecosystem resilience and stability.
4. Water Cycle Regulation: Grasslands play a crucial role in the water cycle
by intercepting rainfall, reducing runoff, and enhancing groundwater
recharge.
5. Economic Benefits: Grasslands provide grazing land for livestock, raw
materials for industries, and opportunities for ecotourism, contributing
to local economies

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INDIAN EXAMPLES OF GRASSLAND ECOSYSTEMS
1. Terai Grasslands: Located at the foothills of the Himalayas, these
grasslands are characterized by tall grasses like elephant grass. They
support species like the Bengal tiger, Indian rhinoceros, and swamp
deer.
2. Shola Grasslands: Found in the Western Ghats, these grasslands are
interspersed with patches of shola forests. They are home to
endemic species like the Nilgiri tahr and the Nilgiri langur.
3. Banni Grasslands: Situated in Gujarat, these grasslands are part of
the Rann of Kutch. They support livestock grazing and are known for
the unique Banni buffalo breed.

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CHARACTERISTIC FEATURES OF DESERT ECOSYSTEMS
Deserts are primarily defined by their arid climate, receiving less than
250 mm of rainfall annually.
The main types of deserts include:
1. Hot Deserts: These are characterized by high temperatures, such as
the Thar Desert in India.
2. Cold Deserts: These experience cold winters, like the Gobi Desert in
China.
Adaptations: Plants and animals in deserts have developed unique
adaptations to survive in these conditions. For example, desert plants
such as cacti have deep roots, succulent stems, and spines to conserve
water. Animals like camels have humps to store fat and can go for long
periods without water.

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STRUCTURE OF DESERT ECOSYSTEMS
1. Abiotic Components:
Climate: High temperatures and low precipitation.
Soil: Often sandy or rocky, with low organic matter but rich in minerals.
2. Biotic Components:
Flora: Includes drought-resistant plants like cacti, acacias, and thorny
bushes. In the Thar Desert, common plants include Khejri (Prosopis
cineraria) and Cactus.
Fauna: Includes animals adapted to arid conditions, such as camels,
desert foxes, snakes, and insects. For instance, the Great Indian Bustard
and the Indian Gazelle are typical inhabitants of the Thar Desert.

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FUNCTION OF DESERT ECOSYSTEMS
1. Climate Regulation: Deserts play a crucial role in regulating the
Earth's temperature by reflecting sunlight and releasing heat into
the atmosphere.
2. Water Conservation: Plants and animals have developed efficient
ways to conserve water. For example, many desert plants store
water in their tissues.
3. Biodiversity: Deserts support a unique diversity of species that are
specifically adapted to survive in extreme conditions.
4. Cultural Importance: Deserts hold cultural significance for
indigenous people. For example, the Rajasthani culture in India is
deeply connected to the Thar Desert.

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CHALLENGES OF DESERT ECOSYSTEMS
1. Climate Change: Increasing temperatures and changing
precipitation patterns can exacerbate desertification, making
habitats even more inhospitable.
2. Habitat Destruction: Human activities such as urbanization, mining,
and agriculture can lead to habitat fragmentation and loss.
3. Overexploitation of Resources: Overuse of groundwater and other
resources can deplete the delicate balance of desert ecosystems,
threatening plant and animal life .

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CHARACTERISTIC FEATURES OF AQUATIC ECOSYSTEMS
1. Water Composition: Water is the fundamental component of aquatic
ecosystems. It serves as the habitat for a wide range of organisms, from
microscopic phytoplankton to large marine mammals.
2. Diversity of Life: Aquatic ecosystems are home to a rich diversity of life
forms, including plants, animals, and microorganisms. These ecosystems
support species that are adapted to life in water, such as fish,
amphibians, aquatic plants, and algae.
3. Temperature and Light: The characteristics of an aquatic ecosystem are
influenced by the temperature and the amount of light that penetrates
the water. These factors vary with depth and location, affecting the types
of organisms that can thrive.
4. Nutrient Availability: Nutrients in aquatic ecosystems come from various
sources, including the surrounding land, atmospheric deposition, and the
decomposition of organic matter. Nutrient levels can influence the
productivity of the ecosystem.

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STRUCTURE OF AQUATIC ECOSYSTEMS
1. Freshwater Ecosystems:
Ponds and Lakes: These are lentic (standing water) ecosystems. Ponds
are typically smaller and shallow, while lakes are larger and deeper.
Examples in India include the Dal Lake in Srinagar and Loktak Lake in
Manipur.
Rivers and Streams: These are lotic (flowing water) ecosystems. They
range from small streams to large rivers, supporting diverse aquatic life.
The Ganges and Yamuna are significant river ecosystems in India.

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STRUCTURE OF AQUATIC ECOSYSTEMS
2. Marine Ecosystems:
Oceans: Oceans are vast and deep, covering about 71% of the Earth's
surface. They are divided into different zones based on depth and light
penetration, including the intertidal zone, pelagic zone, and benthic
zone.
Coral Reefs: These are found in shallow, warm ocean waters and are
known for their high biodiversity. The coral reefs around the Andaman
and Nicobar Islands are notable examples in India.
3. Wetlands: These ecosystems are characterized by saturated soil
conditions and include marshes, swamps, and bogs. They play a critical
role in water purification and flood control.

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FUNCTIONS OF AQUATIC ECOSYSTEMS
1. Oxygen Production: Aquatic plants, especially algae, produce oxygen
through photosynthesis, which is vital for the survival of most aquatic
organisms.
2. Nutrient Cycling: Aquatic ecosystems play a crucial role in recycling
nutrients. Decomposers like bacteria and fungi break down organic
matter, releasing nutrients back into the water for use by plants and
other organisms.
3. Carbon Sequestration: Aquatic ecosystems, particularly marine
ecosystems, sequester significant amounts of carbon, helping to mitigate
climate change.
4. Habitat Provision: These ecosystems provide habitat for a diverse range
of species, supporting complex food webs and biodiversity.
5. Economic Resources: Aquatic ecosystems support fisheries, which are
vital for the economy and food security. They also provide recreational
opportunities and resources for tourism.

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INDIAN EXAMPLES OF AQUATIC ECOSYSTEMS
1. Dal Lake: Located in Srinagar, this lake is known for its houseboats
and floating gardens. It supports a variety of aquatic plants and
animals, including fish species that are vital for local fisheries .
2. Sundarbans: This is the largest tidal halophytic mangrove forest in
the world, located in the delta region of the Padma, Meghna, and
Brahmaputra river basins. It is home to a diverse range of species,
including the Bengal tiger and various fish species.
3. Loktak Lake: Situated in Manipur, it is famous for its floating islands
and supports a rich biodiversity, including the endangered sangai
deer.
4. Ganges River: This river is not only a vital water source for millions
of people but also supports a diverse range of aquatic life, including
the endangered Ganges river dolphin.
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