Lecture biology Nutrient Cycle

• Through either gaseous or sedimentary cycles • Wetfall- Precipitation takes nutrients from the Inputs to the Cycle atmosphere or as water runs off surfaces • Dryfall- from airborne p

Nutrient Cycles

Physical Environment

DECOMPOSER

– Bio: Processes through living organisms

– Geo: Geological processes

Types of Nutrient Cycles Biogeochemical:

– Geo: Geological processes

– Chemical: Chemical processes (interactions

of chemicals in the environment)

• Gaseous Cycle:

– Main source of nutrients are the atmosphere and ocean (freshwater

to a much lesser extent)

– Have global circulation patterns (follow ocean currents and

Types of Nutrient Cycles Biogeochemical:

– Have global circulation patterns (follow ocean currents and

prevailing weather currents)

General Model of Nutrient Cycling:

•Inputs

•Internal Cycling

•Outputs

• Through either gaseous or sedimentary cycles

• Wetfall- Precipitation takes nutrients from the

Inputs to the Cycle

atmosphere or as water runs off surfaces

• Dryfall- from airborne particles and aerosols

Recycling of nutrients WITHIN an ecosystem

Requires microbial decomposers to transform

Internal Cycling

organic nutrients into mineral forms (Mineralization)

This makes these nutrients available for plant

uptake (Primary production which drives the

ecosystem)

 Loss of nutrients from the ecosystem, inputs must

be equal for the system to not experience a net loss

of nutrients

Internal Cycling

of nutrients

 CO2 cycling in the atmosphere

 Downstream transport in lotic aquatic systems

(River Continuum Concept based on nutrient flow)

 Ecosystems are interrelated and depend upon

processing occurring at larger scales

Atmospheric

cycles (e.g., N)

Nutrients are recycled within an ecosystem

1 Water Cycle

• Condensation of water vapor in the air leads to

precipitation

• Evaporation returns water vapor to the atmosphere

• Infiltration of rainwater replenishes groundwater

supplies

• Surface runoff of rainwater replenishes surface

water supplies

How does the carbon cycle work?

• Carbon is an essential component of cells and

life-sustaining chemical reactions

2 Carbon Cycle

life-sustaining chemical reactions

• Carbon is cycled through living and decaying

organisms, the atmosphere, bodies of water, and soil and rock

2 Carbon Cycle

Carbon moves between stores via six main processes:

1 Photosynthesis: Photosynthesis is a chemical reaction that

converts solar energy and atmospheric carbon dioxide gas

(CO2) into chemical energy

(CO2) into chemical energy

2 Cellular respiration: During cellular respiration, plants and

animals obtain energy by converting carbohydrates and

oxygen (O2) into carbon dioxide and water

3 Decomposition: Decomposers release carbon dioxide into

the atmosphere through the decomposition of carbon-rich

organic matter in soil

2 Carbon Cycle

Carbon moves between stores via six main processes:

4 Ocean processes: Dissolved carbon dioxide is stored in

oceans Marine organisms store carbon-rich carbonate

(CO32_) in their shells, which eventually form sedimentary rock

5 Volcanic eruptions

6 Forest fires

2 Carbon Cycle

How do human activities affect the carbon cycle?

• Human activities, such as fossil fuel combustion and land clearance, quickly introduce carbon into the atmosphere from longer-term stores

•These actions increase the levels of carbon dioxide, a

greenhouse gas that contributes to global climate change

Carbon dioxide Cycle

3 Oxygen Cycle

The Atmosphere is of course the region of gases that lies above the Earth’s surface and it is one of the largest reservoirs

of free oxygen on earth

The Biosphere is the sum of all the Earth’s ecosystems This

The Biosphere is the sum of all the Earth’s ecosystems This also has some free oxygen produced from photosynthesis and other life processes

The largest reservoir of oxygen is the lithosphere Most of this oxygen is not on its own or free moving but part of

chemical compounds such as silicates and oxides

The total amount of free oxygen (O2)

on the earth is 1.5 x 1015 tons

Photosynthetic of plants and algae produce about

4 Nitrogen Cycle

How does the nitrogen cycle work?

 Nitrogen is an important component of DNA and proteins

 Most nitrogen is stored in the atmosphere, where it exists as nitrogen gas (N2) It is also stored in bodies of water, living

organisms, and decaying organic matter

 Most organisms cannot use atmospheric nitrogen gas

 The nitrogen cycle involves four processes, three of which make nitrogen available to plants and animals

4 Nitrogen Cycle

1 Nitrogen fixation: Nitrogen gas is converted into nitrate

(NO3–) and ammonium (NH4+), compounds that are usable by plants Nitrogen fixation occurs mainly through nitrogen-fixing bacteria, and when lightning strikes in the atmosphere

2 Nitrification: Ammonium is converted into nitrate and

nitrite (NO2–) through the work of nitrifying bacteria

4 Nitrogen Cycle

3 Uptake: Useable forms of nitrogen are taken up by plant

roots and incorporated into plant proteins When herbivores and omnivores eat plants, they incorporate nitrogen into their own tissues

4 Denitrification: Denitrifying bacteria convert nitrate back

into atmospheric nitrogen

Nitrogen cycle

Global

How do human activities affect the nitrogen cycle?

Fossil fuel combustion and burning organic matter releasenitrogen into the atmosphere, where it forms acid rain

Chemical fertilizers also contain nitrogen, which escapes

Chemical fertilizers also contain nitrogen, which escapes

into the atmosphere or leaches into lakes and streams

High levels of nitrogen cause eutrophication (too many

nutrients) and increased algal growth in aquatic ecosystems, depriving aquatic organisms of sunlight and oxygen

Schematic representation of the flow of nitrogen through the environment The importance of bacteria in the cycle is

immediately recognized as being a key element in the cycle, providing different forms of nitrogen compounds assimilable

by higher organisms.

Nitrogen fixation

There are four ways to convert N2 (atmospheric nitrogen gas) into more chemically reactive forms:

1 Biological fixation: some symbiotic bacteria (most often

associated with leguminous plants) and some free-living

bacteria are able to fix nitrogen as organic nitrogen

• An example of mutualistic nitrogen fixing bacteria are the

Rhizobium bacteria, which live in legume root nodules

• An example of the free-living bacteria is Azotobacter.

Nitrogen fixation

2 Industrial N-fixation: Under great pressure, at a temperature

of 600OC, and with the use of an iron catalyst, hydrogen and

atmospheric nitrogen can be combined to form ammonia (NH3)

in the Haber - Bosch process which is used to make fertilizer and explosives

3 Combustion of fossil fuels: automobile engines and thermal

power plants, which release various nitrogen oxides (NOx)

4 Other processes: In addition, the formation of NO from N2 and

O2 due to photons and especially lightning, can fix nitrogen.

Nitrogen fixation

When a plant or animal dies,

or an animal expels waste, the

initial form of nitrogen is organic

Bacteria, or fungi in some cases,

convert the organic nitrogen

within the remains back into

ammonium (NH4+), a process

called ammonification or

mineralization

 The conversion of ammonium to nitrate is performed primarily

by soil-living bacteria and other nitrifying bacteria

 In the primary stage of nitrification, the oxidation of ammonium (NH4+) is performed by bacteria such as the Nitrosomonas

(NH4 ) is performed by bacteria such as the Nitrosomonas

species, which converts ammonia to nitrites (NO2-)

 Other bacterial species, such as the Nitrobacter, are

responsible for the oxidation of the nitrites into nitrates (NO3-)

 It is important for the nitrites to be converted to nitrates

because accumulated nitrites are toxic to plant life

Denitrification is the reduction of nitrates back into the

largely inert nitrogen gas (N2), completing the nitrogen cycle

This process is performed by bacterial species such as

Pseudomonas and Clostridium in anaerobic conditions.

They use the nitrate as an electron acceptor in the place of oxygen during respiration

These facultatively anaerobic bacteria can also live in

aerobic conditions

Denitrification

5 Phosphorus Cycle

How does the phosphorus cycle work?

 Phosphorus carries energy to cells It is found in phosphate

(PO43- ) rock and sediments on the ocean floor

 Weathering- through chemical or physical means -breaks down rock,

 Weathering- through chemical or physical means -breaks down rock, releasing phosphate into the soil from longer-term stores.

 Organisms take up phosphorus When they die, decomposers

return phosphorus to the soil

 Excess phosphorus settles on floors of lakes and oceans, eventually forming sedimentary rock It remains trapped for millions of years until

it is exposed through geologic uplift or mountain building.

5 Phosphorus Cycle

How do human activities affect the phosphorus cycle?

 Commercial fertilizers and phosphate-containing

detergents enter waterways and contribute additional

phosphate to the phosphorus cycle

 Slash-and-burn forest clearance reduces phosphate levels,

as phosphate in trees enters soil as ash

 It leaches out of the soil and settles on lake and ocean

bottoms, unavailable to organisms

Phosphorus Cycle in Soil

Phosphorus Cycle in Water

Phosphorus in the biosphere (103 million tons P)

90

Phosphorus flux (million tons P/ yr)

6 Sulfur Cycle

The sulfur cycle are the collection of processes by which sulfur moves to and from minerals (including the waterways) and living systems

 Biogeochemical cycles are important in geology because they

 Biogeochemical cycles are important in geology because they affect many minerals

 Biogeochemical cycles are also important for life because sulfur

is an essential element , being a constituent of many protein and cofactors

 Human activity plays a dominant role in the sulfur cycle We

must include the inputs due to industrial activity

6 Sulfur Cycle

 The ocean represents a major reservoir of sulfur on Earth, with large quantities in the form of dissolved sulfate and sedimentary minerals

 The sulfur cycle has both sedimentary and gaseous phases

 The sulfur cycle has both sedimentary and gaseous phases

 In the long term sedimentary phase, sulfur is tied up in organic and inorganic deposits, released by weathering and

decomposition, and carried to terrestrial ecosystems in salt

solution

 The gaseous phase of the cycle permits sulfur circulation on a global scale

6 Sulfur Cycle

Steps of the sulfur cycle are:

1 Mineralization of organic sulfur into inorganic forms,

such as hydrogen sulfide (H2S), elemental sulfur, as well

as sulfide mineralss

2 Oxidation of hydrogen sulfide, sulfide, and elemental

sulfur (S) to sulfate (SO42–)

3 Reduction of sulfate to sulfide

4 Incorporation sulfide into organic compounds (including

metal-containing derivatives)

Sulfur cycle for the Everglades

Sulfur Cycle in Soil

1 Why is the Water/Carbon/Oxygen/Nitrogen/Phosphorus/

Sulfur /cycle important?

2 How is Water/Carbon/Oxygen/Nitrogen/Phosphorus/

Sulfur / stored?

3 How is Water/Carbon/Oxygen/Nitrogen/Phosphorus/

Sulfur / cycled?

4 Name several human activities that affect the Water/

Carbon/Oxygen/Nitrogen/Phosphorus/ Sulfur / cycle?