This document discusses food chains, food webs, and the impact of human interactions on aquatic ecosystems. It provides examples of biotic and abiotic components of marine ecosystems and describes typical food chains and food webs. Human activities like overfishing, pollution, coastal development, and tourism are negatively impacting marine ecosystems by disturbing food webs, damaging habitats, and accumulating toxins. The document also examines water demand and supply in Bangalore, India, given its population growth. It analyzes Bangalore's water sources and consumption trends, the existing shortfall, and recommends strategies like conservation, wastewater recycling, and groundwater recharge to close the growing gap between demand and supply.

1. ENVIRONMENTAL MANAGEMENT
CENTER FOR CONTINUTING EDUCATION,
INDIAN INSTITUTE OF SCIENCE,
BANGALORE.
by
MAYURESH SURESH AMRALE
22/09/2016
based online chat session co-ordinated by
Mr. Abdul and Mr, Abhay
on 15-16th Sept., 2016

2. Assignments based on discussion Page 2
FOOD CHAINS AND FOOD WEBS
EFFECT OF HUMAN INTERACTIONS ON FOOD CHAIN AND FOOD WEB
Land, Atmosphere, Oceans, Ice Cover control the Environment by mutual interaction and
interdependence through Ecosystem. Oceans act a global thermostat, absorbing atmospheric
heat energy through surface streams, rivers and distributing to Glaciers by undergoing various
cycles of Water, Caron, Nitrogen and nutrient recycling. As Oceans cover almost 70% the Earth's
surface; it is the largest ecosystem (Marine Ecosystems).
Subcategories of Marine Ecosystems:-
• Open Ocean
• Ocean Bottom
• Coral Reefs
• Mangrove
• Salt Marshes and Estuaries
Every living thing depends on energy. Food chain is Food & Energy flow pattern through
interdependence of various Biotic Components & their interaction, transformations with
Abiotic Components.
As in most ecosystems, organisms can get food and energy from more than one source, and
may have more than one predator. Such inter and intra interaction or dependence with
each other is in general called as Food Web. Through these food webs interacting with
multiple food chains balance the ecosystems well and healthy.
Let me take example of Marine Ecosystems to explain various components.
Biotic Components of Marine Ecosystems:
o Autotrophs (Producers): Microbes, Phytoplankton
Harnesses the energy of inorganic substances by Photosynthesis or
Chemosynthesis to convert into organic substances (Life Building
Blocks)
Simply, act as food for next trophic level.
• Heterotrophs:
o Primary Heterotrophs: Zooplankton, Small Fish, Prawns, Crabs
Simply, feeds on Autotrophs
o Secondary Heterotrophs: Large Fishes, Seagulls, Sea Snakes, Turtles
o Tertiary Heterotrophs: Sharks, Marine Mammals, Sea Eagles, Humans
consume other organisms for energy
o Decomposers: Detritus bacteria
consume debris, such as decaying leaves or dead animals

3. Assignments based on discussion Page 3
keep streams clean and clear by filtering and recycling nutrients
Abiotic Components of Marine Ecosystems:
Temperature, Precipitation, Geology, Soil, Sunlight, Water chemistry (minerals and salts)
General Food Chain in Open Ocean: Biomass and Energy Flow
Food chains are often represented as food pyramids with different trophic levels.
• General Food Web in Mangrove Systems: Biomass and Energy Flow
Food webs represent patterns of energy and biomass transfer between inter and intra trophic
levels of multiple food
chains.
The marine (in general
aquatic) ecosystems play a

4. Assignments based on discussion Page 4
crucial role in maintaining Human and other life in following ways:-
Regulates the global water cycle through Evaporation and Precipitation with Sun Energy
Recycles carbon, oxygen & other nutrients through Photosynthetic activity by Planktons
Provides nutrition to most life forms as sea food acts as major protein supply
Its coral reefs, mangroves, marshes act as shield for land-based ecosystems, buffering
them from hurricanes, floods, storms. Also, it provides shelter to support life.
The marine ecosystems are getting affected by following Human Interactions.
Overfishing:
o Disturbs food web by loss of some key stone species
o Promotes algal growth by reducing marine algal grazing
Over-harvesting of coral
o Damages to reefs which acts as shelter for various marine organisms
Nutrient rich Effluent releasing
o increases acidification which promotes Algal bloom which in turn releases bio
toxins causing fish poisoning
o increases water temperatures which promotes proliferation of waterborne
disease causing microbes
o causes eutrophication which covers the water surface affecting light penetration
Disturbs Global/Local Water Cycle
o SOx and NOx vapours in atmosphere causes acid rain and thereby soil erosion
Accumulation of toxins in marine food webs
o Causes damage to marine organisms, altering the ecosystem's equilibrium.
o Causes Loss of keystone species resulting the structure to collapse.
Oil spills
o Causes chemical toxicity (organ/tissue damages)
o Causes coating resulting in inability to swim/fly increasing predation chances
o Damages breeding/migration habitats
Coastal Urbanization:
o Causes encroachment over Salt marshes, sea grasses, and mangroves
Tourism
o Increases trash, littering and water/air/noise pollution

5. Assignments based on discussion Page 5
AS A CASE OF BANGALORE, HOW COULD WE MATCH THE DEMAND VS SUPPLY IN
BACKGROUND OF POPULATION GROWTH & THE AVAILABILITY OF WATER?
Bangalore Background
As Bangalore is also becoming one of the leading technology promoting & harbouring cities in
India, it is facing rapid urban developments, influx of migrants, improvements in living
standards of existing population. These factors are creating strain on existing environmental
resources like Water. Water is essential commodity in day to day life from drinking purpose to
industrial purpose. We will consider population growth data to assess the water demand
against available Natural resources like rivers, reservoirs and planned resource creation
capacity by Rain Water Harvesting or Recycle/Reuse/Sewage Treatment.
Bangalore Population Growth and Water Demand
Water Resources Scenario:
As we have seen the role of Water Cycle; rain water and ground water are important
components of the hydrological cycle. Bangalore receives average rainfall at an average rainfall
of 750mm per year. At this average rainfall the total available rain water will be 35 TMC in
about 1300 sq.km. area of Bangalore city.
The increasing population of city had been burdening the natural resources and old planned
resources of city as here in 2 Reservoirs: Chamarajendra & Chamaraja Sagar reservoir. Then,
city established Cauvery Water Supply Scheme through its 4 phases to meet increasing water
demand. Presently, about 1350 MLD water is drawn from Stages 1, 2, 3 and 4.
For supporting population of more than 1 Crore, the city is dependent upon following
source: Demand = 1700 MLD, Supply = 1500MLD; SHORTFALL = 200MLD.
1350 MLD from Cauvery
184 MLD installed capacity from Arkavathi
70 MLD from groundwater
THIS DECADE SOURCE: CENSUS
Current 2016 11,556,907
2015 10,839,725
2014 10,178,146
2013 9,556,945
2011 8,425,970
2001 5,379,000

6. Assignments based on discussion Page 6
Existing Supply & Distribution System as per ‘Bangalore Water Supply & Sewerage Board’
Present Supply from Cauvery source 1350 MLD
Total length of water supply pipelines 8,746 kms
Number of Ground Level Reservoirs 57 ( 885 ML) No.s
Number of Over Head Tanks 36 (33 ML) No.s
Booster pumping stations 62 No.s
Public taps providing free water 7,477 No.s
Water tanker lorries 62 No.s
Quantity of water supplied/month 42,200 ML
Average per capita consumption 65 L/day
Average cost of water 28 Rs/kL
Demand trend: PROPORTIONALLY ESTIMATED FOR CASE STUDY
Year
Population
(Million)
Water Demand
(MLD)
2011 8.499 1400
2016 11.556 1700
2021 13000 1900
THUS, CITY HAS TO PLAN FOR EXISTING SHORTFALL OF ABOUT 200 MLD PLUS ATLEAST
NEXT 5 YEARS’S ADDITIONAL DEMAND OF 400MLD; TOTALLING ABOUT 600-800 MLD.
Scope of Water Conservation/Recycle/Water Self Sustainable approach:
Effective Wastewater collection, transmission to avoid leakage: +400 MLD
o City uses about 93% of surface sources; thus should be well monitored to avoid
every possible leakage losses
o Leakage loss 40%; wasting about 300-400 MLD.
o Controlling losses by introduction of Economic instruments like increasing
water tariffs, recycle water usage subsidies, water consumption reduction
subsidies
o Proper Metering of taps

7. Assignments based on discussion Page 7
Rain water harvesting: +100 MLD
o City receives average rainfall average rainfall of 750mm per year.
o 35 TMC water will get in available catchment area of Bangalore city.
Groundwater Recharge: +100 MLD
o City uses about 7% of ground water sources, which needs to recharge & be kept
uncontaminated
o Disposal of treated wastewater at 4 valley areas or 6 lakes series will recharge
the groundwater and will ensure availability of water in future.
Sewage Treatment: + 370 MLD
o Current Sewage generation – 1400 MLD as per CPCB
o Sewage treatment capacity – 721 MLD (14 plants); regular monitoring of
operation at full capacity against current about 350 MLD only. working at half
capacity
o Average treatment – 520 MLD
Lakes (water bodies) protection
o No. Of lakes: 379/246 (1973/1996) with 6 lake series
o Restricting encroachment over catchment areas of lakes
o disposal of treated water to recharge
Reuse of water for multipurpose usages with different modes and strategies
o Through Effective Public outreach programme to implement the above.