Environment & Safety Engineering (CH1400)
Ecosystems
Dr. Adhidesh S. Kumawat
Ecosystem
• Ecosystems are communities of organisms that interact with one another and
with their physical environment, including sunlight, rainfall and soil nutrients.
– Organisms within an ecosystem interact with one another to a higher extent compared to
those between different ecosystems
– Examples – a tidal pool (even as small as 2 m diameter), a tropical rainforest
• Habitats – a place where a population of organisms lives
• Characteristics of ecosystem:
1. Matter flows – flow into and out of ecosystem exists but its extent is very small compared to
the amount contained in the ecosystem
2. Changes with time – for ex. Lakes change (naturally or anthropogenic over time. Several
phenomenon such as flooding, droughts, extreme temperature changes and extreme
environmental conditions (e.g. volcanic activity or forest fires)
3. Can be natural or artificial – lakes, tidal pools = natural; constructed wetlands for reducing
storm runoff, agricultural land = artificial ecosystems.
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Human Influence on Ecosystems
– Environmental engineers and scientists have a responsibility to protect ecosystems and the life
residing within them.
– Activities such as release of pesticides, fertilizers and greenhouse gases to environment
– Dams provide a clean, renewable energy source. Further, dam construction can have
detrimental effects on river ecosystems related to fish population, soil erosion and vegetation.
• Human activities can cause ecosystem changes resulting in destruction of
species
– Destruction of rainforest in Mexico threatens existence of Monarch butterfly. If forests are
destroyed to the extent that it looses its winter roosting grounds than global extinction may
result. However, localized destruction of milkweed plants have deprived of its nesting
environment, resulting in local extinction.
– Toxic chemical threaten wildlife such as DDT, petroleum compounds or heavy metals.
– Acid rain is a result of emission from power plants, automobiles and industrial operations.
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There is a strong relationship between oxides of sulfur and nitrogen
Human Influence on Ecosystems
– Agricultural operations in California resulted in increase of concentration of selenium to an
extent that several species of water birds including black – necked stilts became threatened.
– Species could also be threatened by introduction of nonnative (exotic) species in ecosystems.
The introduction of rabbits onto Norfolk Island in 1830 resulted in loss of 13 species of
vascular plants by 1967.
– The zebra musel in inland waters of Ontario and Quebec is assumed to be responsible for the
reduction of about 80 % of mass of phytoplankton in Lake Erie. Because It is an efficient water
filterer of water, its presence significantly increase water clarity, allowing light to penetrate
deeper into the water column, increasing the density of aquatic vegetation, algae and other
organisms.
– Another method by which species can become extinct is excessive hunting. Fr ex. Rhinoceros is
threatened due to poaching, mainly for its horns.
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Energy and Mass Flow
• Primary producers: Sunlight – using organisms; Autotrophic.
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–
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Trophic is the term to describe the level of nourishment
Plants are photoautotrophic – obtain carbon from inorganic sources
6CO2 + 6H2O + 2800 kJ energy from sun (in presence of chlorophyll) –> C6H12O6 + 6O2
Net Primary Productivity (NPP) – rate of production of biomass glucose, cells and other
organic chemicals by primary producers. For ex. Swamps and tropical forests have high NPP but
deserts and arctic tundra does not.
– Photoheterotrophs – they can obtain energy through photosynthesis but are not capable of
reducing CO2. they obtain carbon from reduced carbon compounds generated by other
organisms.
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Ecological and Energy Pyramid
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Energy and Mass Flow
Ex.1. A deer eats 25 kg of herbaceous material per day. The herbaceous matter is approximately 20%
dry matter (DM) and has an energy content of 10 MJ (kg/DM). Of the total energy ingested per day, 25%
is excreted as undigested material. Of the 75% that is digested, 80% is lost to metabolic waste products
and heat. The remaining 20% is converted to body tissue. How many megajoules are converted to body
tissue on a daily basis? Calculate the percentage of energy consumed that is converted to body tissue.
Solution.
The percentage of consumed energy used for
body tissue is =
= (75 MJ/day)/(50 MJ/day) * 100
= 15 %
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Energy and Mass Flow
Ex.2. For every megajoule of energy used by the phytoplankton in Lake Michigan, how many joules of
energy are used in building cell tissue in the lake trout? How many in humans? Use the following
food web path:
Phytoplankton −→ zooplankton −→ alewife −→ lake trout −→ humans
Solution.
•
Given the rule of thumb that only 10% of the energy consumed is converted to biomass, then
Phytoplankton −→ zooplankton −→ alewife −→ lake trout −→ humans
1 MJ
0.1 MJ
0.01 MJ 1000 J
100 J
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Bioaccumulation
•
Bioaccumulation has serious implications for the movement of chemicals in the
environment.
–
Chemicals that are hydrophobic will tend to be lipophilic. As a result, these chemicals will tend to partition
(move into) into the fat tissue of animals. This process results in bioaccumulation.
•
Bioaccumulation is the total uptake of chemicals by an organism from food items (benthos, fish
prey, sediment ingestion, etc.) as well as via mass transport of dissolved chemicals through the gills
and epithelium (Schnoor, 1996).
•
When chemical bioaccumulate, the concentration of a chemical increases over time in an organisms
body relative to the surrounding environment. This occurs because chemical retain in the living
tissues more than the extent to which they are broken down (metabolized) or excreted.
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Biomagnification
•
•
Biomagnification is the process that results
in the accumulation of a chemical in an
organism at higher levels than are found in
its own food.
It occurs when a chemical becomes more
and more concentrated as it moves up
through a food chain.
–
•
For ex. Algae eats chemical… small fish eats that
algea… bigger fish eats that small fish ad finally
human eats that big fish.
If each step results in bioaccumulation, then an
animal at the top of the food chain, through its
regular diet, will accumulate a much greater
concentration of chemical than was present in
organisms lower in the food chain, and
biomagnification will occur.
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Ref. blue-growth.com
Bioaccumulation vs Biomagnification
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Bio-Concentration
•
•
•
bioconcentration—the uptake of chemicals from the dissolved phase.
Through bioconcentration, the concentration of a chemical in an organism becomes
greater than its concentration in the air or water in which the organism lives.
Although the process is the same for both natural and synthetically made chemicals, the
term bioconcentration usually refers to chemicals foreign to the organism.
–
•
•
For fishes, bioconcentration after uptake through the gills (or skin) is the most important bioaccumulation
process.
Bioconcentration factors, the ratio of the concentration of the chemical of interest in the organism
to the concentration in water, are used to measure the tendency of a chemical to accumulate in
lipid tissue and to relate pollutant concentrations in the water column with that in fish using the
following equation:
Concentration in fish = (concentration in water) × (bioconcentration factor)
These factors are important in performing risk assessment calculations for predicting the effect of a
chemical on a target species.
Ex.3. The concentration of the pesticide DDT was found to be 5 g ・ L−1 in the water of a pond. The
bioconcentration factor for DDT is 54,000 L ・ kg−1 (U.S. EPA, 1986). What is the expected
concentration of DDT in the fish living in the pond?
Solution.
Concentration in fish = (5 g ・ L−1)(54,000 L ・ kg−1)
= 270,000 g ・ kg−1, or 270 mg ・ kg−1
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Nutrient Cycles
•
The basic elements of which all organisms
are composed are carbon, nitrogen,
phosphorus, sulfur, oxygen, and hydrogen.
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–
–
•
The first four of these elements are much more
limited in mass and easier to trace than are oxygen
and hydrogen.
Because these elements are conserved, they can
be recycled indefinitely (or cycled through the
environment).
Because the pathways used to describe the
movement of these elements in the environment
are cyclic, they are referred to as the carbon,
nitrogen, phosphorus, and sulfur cycles.
In any particular environment, the nutrient
cycle must be balanced and stable if the
organisms that live in that environment are
to flourish and be maintained in a constant
population (MARTIN 2010).
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Nutrient Cycles disturbance
•
population growth and resulting human
activities such as large-scale farming have
caused some significant changes in nutrient
cycles
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–
•
with the introduction of water-borne sewage, this
cycle was interrupted and replaced by a linear
system that transports nutrients away from soils
and into watercourses
agriculture accelerates land erosion — because
ploughing and tilling disturb and expose the soil —
so more nutrients drains away with runoff
In any particular environment, the nutrient
cycle must be balanced and stable if the
organisms that live in that environment are
to flourish and be maintained in a constant
population (MARTIN 2010).
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–
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Depletion of soils
Depletion of nutrient sources
Affordability and food security
Eutrophication of waterways and dead zones
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Carbon Cycle
•
•
•
Ocean is the greatest reservoir of carbon
(about 85%)
Photosynthesis is the major driving force for
the carbon cycle
Ocean is the major sink of carbon
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–
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Uptake of CO2 is driven by: (1) the solubility and (2)
biological pumps
Solubility pump – dissolution of CO2 into waters
such as polar waters are colder than deeper
regions and have greater capacity of dissolving CO2.
Phytoplankton, Zooplanktons and bacteria make up
the biological pump. They take up carbon and
nutrient from the water resulting in carbon cycling.
Human have affected the carbon cycle significantly
through the combustion of fossil fuels, industrial
activities and burning of materials.
Pmfias.com
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Carbon Cycle
•
•
•
Ocean is the greatest reservoir of carbon
(about 85%)
Photosynthesis is the major driving force for
the carbon cycle
Ocean is the major sink of carbon
–
–
–
–
Uptake of CO2 is driven by: (1) the solubility and (2)
biological pumps
Solubility pump – dissolution of CO2 into waters
such as polar waters are colder than deeper
regions and have greater capacity of dissolving CO2.
Phytoplankton, Zooplanktons and bacteria make up
the biological pump. They take up carbon and
nutrient from the water resulting in carbon cycling.
Human have affected the carbon cycle significantly
through the combustion of fossil fuels, industrial
activities and burning of materials.
Pmfias.com
Pmfias.com
16
Nitrogen Cycle
• Cycling of nitrogen content
• Nitrogen in lakes as nitrate (NO3-) and
taken up by algae and reduced to amino
(NH2–R). Dead algae contains NH3, which
dissolves to form NH4+. Nitrifying bacteria
oxidized this to NO3- to a process called
nitrification.
4NH4+4 + 6O2 = 4NO2− + 8H+ + 4H2O
4NO2− + 2O2 = 4NO3−
• Nitrate is reduced back to N2 by
denitrification.
2NO3- + organic carbon = N2 + CO2 + H2O
• Nitrogen fixation is also accomplished in the
soils by almost all legumes. Nitrogen fixation
occurs in the root nodules that contain bacteria.
Pmfias.com
17
Nitrogen Cycle
•
The basic elements of which all organisms
are composed are carbon, nitrogen,
phosphorus, sulfur, oxygen, and hydrogen.
–
–
–
The first four of these elements are much more
limited in mass and easier to trace than are oxygen
and hydrogen.
Because these elements are conserved, they can
be recycled indefinitely (or cycled through the
environment).
Because the pathways used to describe the
movement of these elements in the environment
are cyclic, they are referred to as the carbon,
nitrogen, phosphorus, and sulfur cycles.
Pmfias.com
18
Phosphorus Cycle
• Cycling of phosphorus content
• It enters unpolluted waters through dust
in precipitate
• Phosphorus is normally present in
watersheds in extremely small amounts,
usually existing dissolved as inorganic
orthophosphate, suspended as organic
colloids, adsorbed onto particulate organic
and inorganic sediment, or contained in
organic water.
• Phosphorus available to plants is the
amount soluble as well as in organic
compounds
• Largely, the permanent removal of
phosphorus from overlying waters to the
sediments depends on the amount of
iron, aluminium, calcium ad clay entering
the lake along with phosphorus
• Excess use of phosphorus fertilizer also
adds in disturbing ecosystem
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Phosphorus Cycle
•
The basic elements of which all organisms
are composed are carbon, nitrogen,
phosphorus, sulfur, oxygen, and hydrogen.
–
–
–
The first four of these elements are much more
limited in mass and easier to trace than are oxygen
and hydrogen.
Because these elements are conserved, they can
be recycled indefinitely (or cycled through the
environment).
Because the pathways used to describe the
movement of these elements in the environment
are cyclic, they are referred to as the carbon,
nitrogen, phosphorus, and sulfur cycles.
Pmfias.com
20
Sulfur Cycle
H. W. Assignment
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Population Dynamics
• It is the study of changes in nos. and composition of individuals in population and factors that affect these
numbers.
• It helps in several ways: (1) how environment changes affects populations; (2) determining resources
needs; (3) predicting bacterial populating in systems; (4) using population as indicator of environmental
quality.
• Reduction in resources => inc. Mortality
• Enables us to utilize mathematical models to understand and predict population dynamics – what, how and
why are the changes in population of a particular species occurring?
• Particular relevant in the studies of mathematical biology – more than 2 centuaries
• Earliest studies – Thomas Robert Malthus
• Malthusian growth model, sometimes called a simple exponential growth model, is essentially
exponential growth based on the idea of the function being proportional to the speed to which the
function grows
– P(t) = P0 ert
– dP/dt = rP
or dP
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Population Dynamics
• Bacteria population Growth:
• Model Growth of bacteria using geometric progression
• Mixed culture growth becomes complicated
• Bacterial growth in pure cultures:
• Lag phase: when bacteria adjusts to their new
environment
• Accelerated growth phase: bacteria begins to divide.
But all organisms do not divide at the same time.
(production by binary fission)
• nth generation growth: P = Po(2)n
• log P = log Po + n log 2 (exponential or log growth)
• Growth rate = straight line with slope “n”
• Stationary phase: balance in death & reproduction
rates due to limitation of resources
• Death phase: die faster than reproduction
• Carrying capacity: point at which decline occurs
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Thank You
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