Movement of elements Flashcards
Nutrients
elements required by organisms for metabolism and growth
Biogeochemistry
physical, chemical, biological factors that influence the movements and transformation of elements
Assimilation
inorganic → organic
Dissimilation
organic → inorganic
Two abiotic sources of nutrients
- Minerals in rocks
– Potassium, calcium, magnesium, phosphorus
– Weathering - Gases in the atmosphere
– 78% N2, 21% O2, 0.9% argon, 0.039% CO2
– Atmospheric deposition
– Chemical fixation
Mechanical weathering
physical alteration of rocks; freezing, wetting/rewetting, otherwise “broken apart”
Chemical weathering
minerals subjected to chemical processes (e.g. oxidation)
Atmospheric deposition
precipitation, particles, aerosols, and gases move from the atmosphere to the earth’s surface
Hydrologic cycle
The movement of water through ecosystems and atmosphere;
driven by evaporation, transpiration, and precipitation
Detritivores
physically break organic matter into smaller pieces
Decomposers
break dead organic matter into inorganic elements – process called mineralization (a form of dissimilation)
Dry environments→
slow decomposition rates
Moist forests→
relatively high decomposition rates
Water-logged environments
(bogs, swamps, etc.) →
slow
more nitrogen →
faster decomposition
Nitrogen fixation
Converts atmospheric nitrogen into forms
producers can use, N2 → NH3→ NH4 + or NO3-, requires energy
Biotic fixation
free-living and mutualistic bacteria (e.g. rhizobia, frankia)
Abiotic fixation
lightning, wildfires, fossil fuel combustion, fertilizer production
– Fertilizer production: Haber-Bosch process, energy from fossil fuels
Nitrification
conversion of ammonium to nitrate by bacteria
– Nitrates more easily used by plants
Assimilation of nitrogen
incorporation of NH4+ or NO3– into organism tissues
Ammonification
nitrogen in organic matter (feces, dead organisms) converted to ammonia or ammonium
– fungal and bacterial decomposers
– can then be converted back into nitrates (nitrification)
Denitrification
Nitrates are water-soluble and are leached from surface
* nitrates converted into nitrogen gas (N2) by bacteria under anaerobic conditions
1. NO3- to NO
2. NO to N2
* Returns nitrogen to atmosphere
Phosphorus (P) is an essential element
because…
- Needed for bones, scales, teeth, DNA, RNA, ATP, phospholipids in the cell membrane
- Moves as phosphate: PO4 3-
- Often limits productivity
- Excessive phosphorus can cause toxic plant/algae growth
Phosphorous plays a role in —– and —– systems
Terrestrial and Aquatic systems
Atmospheric deposition
Phosphorous moves through the atmosphere as dust
- Sahara provides phosphorous to the Amazon
How do humans alter the hydrologic cycle?
Increase run-off and decrease water in soil:
* Creation of impervious surfaces
* Removal of plant biomass
* Heavy use of ground water
* Climate change → increase evaporation, intense storms → Increased soil erosion and flooding
– Human erosion: 10-15 times faster than
nature
Human and increased N-fixation
3 Processes?
– Haber Bosch process
– Crops- soybeans, alfalfa, peas
– Higher atmospheric N from gaseous emissions: fossil fuel combustion, biomass burning, sewage treatment, livestock, etc.
Human Impacts on N Cycle
Export of nitrate from river systems worldwide as a function of human population in the watershed
Human Impacts on P Cycle
- Use of fertilizers and detergents
- Discharge of sewage and industrial waste
- Increase in terrestrial surface erosion
Increased run-off increases…
nutrient transfer to aquatic systems
Oligotrophic
– Low nutrient levels (nitrogen & phosphorus)
– Low NPP
– Healthy, diverse fish & invertebrate communities
Eutrophic
− Nutrient rich (nitrogen & phosphorus)
− High phytoplankton, algae abundance and turnover
− Oxygen depleted → anaerobic organisms
− Accumulation of detritus, turbid water
− Loss of diversity
Consequences of too much Phosphorous
- Eutrophication
- Hypoxia creates “dead zones”
Example: Grand Lake St. Marys
