2 Ecosystem

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Environmental

Chemistry

Is the study of the sources,

reactions, transport, effects andfates of chemical species in the

water, soil, air and organism in

the environment



What is environmental chemistry?

"What is environmental chemistry? This question is a littledifficult to answer because environmental Chemistryencompasses many different topics. It may involve a study

of Freon reactions in the stratosphere or an analysis of toxic deposits in ocean sediments. It also covers thechemistry and biochemistry of volatile and solubleorganometallic compounds biosynthesized by anaerobic

bacteria. Environmental chemistry is the study of

the sources, reactions, transport, effects, andfates of chemical species in water, soil, and airenvironments."

- Stanley E. Manahan. 1991. Environmental Chemistry,Fifth edition.



What does an environmental chemist do?

Environmental

Chemist

Prevent

Environmental

deterioration

Environmental

Clean-up

Environmental

Research Environmental

Regulation

Environmental

Measurement

& Monitoring



Ecology

A study of interactions of organisms with

each other and with physical environment(both biotic and abiotic).



Examples of interactions

competitions among plants for light

tree and animal disperser

growth of a crop and soil fertility

forests as a sink for atmospheric carbon



Ecosystem:

³a spatially explicit unit of the Earththat includes all of the organisms,

along with all the components of the

abiotic environment within its

boundaries.´

Gene Likens





Ecosystem

the environment within which

interactions take place, subject to

influences both internal and external,with inputs and outputs OF ABIOTIC





Study of ecosystem includes living community

plus physical environment.

a. Living (biotic) components : habitats and

niches.b. Nonliving (abiotic) components: soil, water,

light, inorganic nutrients, and weather



Habitat = organism's place of residence,

where it can be found, such as under a log.

Niche = profession or role of that organism

in the community, factors limiting its life,

and how it acquires food



Producers = autotrophic photosynthetic

organisms.a. In terrestrial ecosystems, producers are

predominantly green plants.

b. In freshwater and marine ecosystems,dominant producers are algae.



C onsumers are heterotrophic organisms

that eat preformed food.a. Herbivores feed directly on green plants;

are primary consumers.

b. Carnivores feed on other animals and are

secondary or tertiary consumers.

c. Omnivores feed on both plants and

animals; for example, humans eat both



d. Decomposers are organisms of decay.i. Mostly are bacteria and fungi.

ii. Break down detritus, nonliving

organic matter, into inorganic matter.

iii. Small soil organisms are critical in

helping bacteria and fungi shred leaf

litter and form rich soil.



Energy Flow and Chemical Cycling

Energy flow in ecosystems based on two

laws of thermodynamics:

(a) First law states energy cannot becreated or destroyed.

(b) Second law asserts that when energy is

transformed from one form to another, someusable energy is lost as heat.



The Food Chain

Figure : A Pond Ecosystem. Each of the roles of producer, consumer, and

decomposer is filled by a number of different organisms in a pond

ecosystem.





A Food Pyramid in the Temperate Rain Forest Biome

Segments of Pyramid Show Relative Biomass at Each Trophic Level



marine environmentmarine environment::

open ocean ± low primary productivity, often limiting N, P, Fe resulting in

low heterotrophic activity

inshore ± nutrient rich resulting in greater productivity

deep sea habitatsdeep sea habitats::

about 75% of ocean water is at depths of greater than 1000 m

mostly dark, cold (2-3ºC), high hydrostatic pressure, very low nutrient

input (marine snow)low microbial activity; inhabitants are psychrotolerant or psychrophilic,

barotolerant or barophilic

sort of a cold, wet desert

..... and then we have hydrothermal vents, analogous to oases in

deserts



hydrothermal venthydrothermal vent

communitiescommunities:

driven by geothermal energy

microbe-animal symbioses

�free-living microorganisms

include S-oxidizing

chemolithotrophs (Thiot hrix,Beggi atoa, Thiobacillus), may

also be H2-, Fe2+-, Mn2+-

oxidizers, methanotrophs,

nitrifiers



tube worms: can be 2 m+ long

� lack mouth, gut, anus

� possess trophosome, spongy tissue packed with S granules and S-oxidizing

bacteria� bacteria grow on H2S, thiosulfate and CO2

� tube worm traps O2, H2S in blood and delivers to bacteria

� dead bacteria, products of bacterial metabolism support tube worm

S A9a



³black smoker´

³snowblower´: tufts of bacterial biomass blown out

of a vent into overlying water

S A9bbacteria (green) & archaea (red) from

black smoker chimney material



the habitats we¶re used to: the hydrothermal vent habitat:

plant

(phototrophic

& autotrophic)

lightlight CO2

carbonenergy

animal

(organotrophic &heterotrophic)

carbon

& energy

cow

S-oxidizing bacterium

(chemolithotrophic &

autotrophic)

tube worm

(organotrophic &heterotrophic)

HH22SS CO2

energy carbon

carbon& energy

� driven by sunlight � driven by geothermal energy

S A9d



Food Chains Become Food Webs

Food chain = simply "who eats what".

Food web = weaves together many food

chains to form a complicated networkof feeding relationships.

Many animals eat more than one thing, and

each link in each chain is important andintegral to the entire system.





Populations Form a Pyramid

Trophic structure of an ecosystem forms anecological pyramid.

Base of pyramid represents producer trophiclevel, apex is highest level consumer or the top

predator. Pyramid of numbers is based on number of

organisms at each trophic level.

Pyramid of biomass is calculated by multiplyingthe average weight for organisms times thenumber of organisms at each trophic level.

Pyramid of energy calculates amounts of energyavailable at each successive trophic level.



The food energy pyramid always shows a

decrease moving up trophic levels because: i. Only a certain amount of food is captured and

eaten by organisms on the next trophic level.

ii. Some of food that is eaten cannot be digested and

exits digestive tract as undigested waste. iii. Only a portion of digested food becomes part of

the organism's body; rest is used as source of energy.

iv. Substantial portion of food energy goes to build up

temporary ATP in mitochondria; ATP energy is thenused to synthesize proteins, lipids, carbohydrates,and fuel contraction of muscles, nerve conduction,etc.



Only about 10% of energy available at a

particular trophic level is incorporated into

tissues at the next level. Example: a larger

population can be sustained by eating grain

than by eating grain-fed animals since 100kg of grain would result in 10 human kgs but

if fed to cattle, the result is 1 human kg.







Although sometimes usedinterchangeably with 'bioaccumulation,'an important distinction is drawnbetween the two.

Bioaccumulation occurs w it hin a

trophic level, and is the increase inconcentration of a substance in anindividuals' tissues due to uptake fromfood and sediments in an aquatic milieu.

Bioconcentration is defined asoccurring when uptake from the water isgreater than excretion.



Barry Commoner

One of Commoner's lasting legacies is his four laws of ecology,as written in The C losing C ircle in 1971. The four laws are:

1. Everything is Connected to Everything Else.

There is one ecosphere for all living organisms and whataffects one, affects all.

2. Everything Must Go Somewhere. There is no "waste" in nature and there is no ³away´ to which

things can be thrown.

3. Nature Knows Best.

Humankind has fashioned technology to improve upon nature,but such change in a natural system is, says Commoner, ³likelyto be detrimental to that system.´

4. There Is No Such Thing as a Free Lunch.

In nature, both sides of the equation must balance, for everygain there is a cost, and all debts are eventually paid.



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2 Ecosystem