(22): nitrogen cycle

what are nutrients?

a SUBSTANCE that is essential to all organisms

they are recycled in many ways

the earth is a ____ _____ with respect to matter.

closed system

what are some nutrient cycling fundamentals? (r & f)

reservoirs: HOLDS nutrients for some time (ex: humans)

fluxes: the MOVEMENT of nutrients from one reservoir to another (ex: animals pooping)

what is nitrogen?

an essential nutrient for life

where is nitrogen present?

in the chemical makeup of DNA, proteins, etc.

what does this image show?

the atmosphere is primarily made up of nitrogen, but is not biologically available

(ex: we don’t build proteins by breathing)

what is the first step of the nitrogen cycle?

nitrogen fixation

what is nitrogen fixation?

ATMOSPHERIC NITROGEN is converted into a BIOLOGICALLY AVAILABLE FORM (ammonia)

very energetically expensive to make bioavailable triple bonded nitrogen

as you increase bonds, it gets harder to break it down

cyanobacteria is…

one of the first organisms to evolve and make nitrogen

what is nitrogenase?

 an ENZYME that catalyzes nitrogen fixation

breaks the triple bond apart

what does nitrogenase require? (2)

an anaerobic environment (no O2) and special conditions to fix nitrogen

what are heterocysts?

thick walled, anaerobic cells that ONLY fix nitrogen

what does this picture show?

nitrogen fixing organisms in mutualistic ways

what happened with nitrogen in the early 20th century?

nitrogen became limited in agriculture

what were some agricultural uses for nitrogen-fixing organisms?

CROP ROTATION

corn-hay-soybean crop rotation

hay and soybeans are root nodules and nitrogen to soil.

how does the atmospheric deposition of nitrogen relate to fossil fuel emmision?

fossil fuels burning adds an NOx to the atmosphere

important source of nutrients in some ecosystems

what is the haber-bosch process?

industrial system

required energy and high pressure, CREATED AMMONIA

fed around 2 billion people globally

what are some nitrogen fundamentals? (ammonia)

plants DO NOT uptake ammonia (product of nitrogen fixation)

ammonia chemically interacts with soil, making it hard to absorb

what is nitrification?

ammonia uses oxygen to convert into NITRITE and then NITRATE (transported in soil)

what is step one of the nitrogen cycle?

ammonia (an energy source) produces NITRITE, generates acid, performed by bacteria in the Nitrospira genus

what is step two of the nitrogen cycle?

NITRITE (energy source) produces NITRATE,

performed by bacteria in the Nitropsira genus

what is nitrogen assimilation?

PLANTS take in nitrogen from their root hairs and convert them into DNA, proteins, etc.

uptake is the greatest when availability is low

what is mycorrhizal fungi? (mutalistic)

symbiotic fungi that HELPS PLANTS AND NUTRIENTS GET WATER

fungal hyphae are much finer and better access soil nutrients

are responsible for up to 85% of nitrogen uptake in the Arctic tundra

how is nitrogen use efficient?

plants use nitrogen at different efficiencies

cellulose, tannins, lignin

effects rates of decomposition

what is nitrogen mineralization?

decomposers converts AMMONIA to AMMONIUM and recycles nitrogen in organic matter

depends on the C:N ratio

what is nitrogen denitrification?

the conversion of NITRATE BACK INTO ATMOPSHERIC NITROGEN

occurs under anaerobic (no O2) conditions

produces N2O, strong long lived greenhouse gas

why does denitrification occur?

decomposition in aerobic environments uses oxygen to release energy

electronegative = more energy is released from the element

anaerobic environments require other elements to create energy, no oxygen

what is an example of abiotic denitrification?

pyro denitrification - fires converting assimilated and mineralized nitrogen to N2

what are the effects of human alteration to the global nitrogen cycle?

1. eutrophication (over fertilizing marine envrionments)

2. greenhouse gas addition

3. changes to biodiversity

what is the mass balance for nitrogen?

what comes in has to leave

haber-bosch process has greatly increased available nitrogen

28% of newly fixed N is natural, 72% is from humans

what is eutrophication by nutrient runoff?

aquatic ecosystems are limited by nitrogen

around 50 to 60% of fertilizer applied runs off into streams

large agricultural economy in the mississippi river watershed

what are the four steps of dead zones? the effects of eutrophication?

1. fertilizer is added into marine environment

2. nutrients from fertilizer (N and P) causes algal blooms

3. algae eventually dies and are decomposed by bacteria

4. dead zone is formed (anaerobic), killing organisms that cant escape and breathe

what is the dead zone in algal bloom?

visible from space, blooms are often very large

common across coastal areas with nearby agriculture

large agricultural industries in Michigan and Ohio

what are some examples of dead zones on the eastern U.S. coast?

large MS river watershed + intense agriculture in the Midwestern U.S.

produces large dead zones across the eastern U.S.

what are global coastal dead zones?

a global problem associated with population

greater population density means larger and more numerous dead zones

what are some eutrophic concerns for human health?

RED TIDE: produces harmful toxins to fish, shellfish, and people

other harmful algal blooms also produce various toxins such as neurotoxins

how does species diversity respond to increase nitrogen availability?

MORE NITROGEN = LESS SPECIES RICHNESS

plants limited by nitrogen outcompete other plants with more nitrogen

faster decline when NH4+ is applied as fertilize