RECYCLING IN THE BIOSPHERE

Biogeochemical Cycles:1. water cycle2. carbon cycle3. nitrogen cycle4. phosphorus

The Carbon Cycle

http://earthobservatory.nasa.gov/Library/CarbonCycle/carbon_cycle4.html

Movement of carbon into plants for photosynthesis

• Stomata – openings on the underside of leaves, guard cells control opening

• What comes in through stomata that the plant needs?• What goes out through the stomata that the plant needs?

GtC = gigatons of carbon

Four main types of processes that move carbon through the carbon cycle:1. biological processes – PS, CR, decomposition2. geochemical processes – erosion, volcanic activity3. mixed biogeochemical processes – burial and decomposition of dead organisms fossil fuels4. human activities – burning fossil fuels, cutting/burning forests

World map of photosynthetic activity

Interpret the map:• What areas of the world have the highest rate of photosynthetic

activity in December? Explain what environmental factors cause this pattern.

• What would the map look like in June?

Atmospheric carbon dioxide varies over time

• The long-term record of atmospheric carbon dioxide obtained from Antarctic ice cores shows huge fluctuations over the past 150,000 years. Periods of low carbon dioxide concentration correspond to ice ages, while higher carbon dioxide concentrations are linked to warmer periods. The last ice age ended 10,000 to 20,000 years ago, as carbon dioxide levels rose from below 200 parts per million to about 280 parts per million. Current atmospheric carbon dioxide levels are above 370 parts per million because of the burning of fossil fuels. This has raised concern in the scientific community that average global temperatures may rise as a result. (Graph by Robert Simmon, based on data from Lorius, C., J. Jouzel, C. Ritz, L. Merlivat, N.I. Barkov, Y.S. Korotkevitch, and V.M. Kotlyakov. 1995. A 150,000-year climatic record from Antarctic ice. Nature 316:591-596

Atmospheric carbon dioxide levels 1960-2000

Graph interpretation:• What is happening to the level of carbon dioxide in the atmosphere?• Carbon dioxide contributes to the greenhouse effect. How does a

rise in atmospheric carbon dioxide effect our climate?

• This graph shows annual mean global temperature anomalies over the period 1880-2001. The zero line represents the long term mean temperature from 1880-2001, and the red and blue bars are showing annual departures from that mean.

As is evident in the graph, 2001 was second only to 1998 in terms of global temperature, and the trend has been toward increasing temperatures at least since the beginning of the 20th century. Land temperatures have greater anomalies than the ocean, which is to be expected since land heats up and cools down faster than water.

Global Warming?

The Nitrogen Cycle Living organisms use nitrogen to make DNA, RNA, proteins

Definitions:

• N2 is nitrogen gas (atmosphere)

• Forms plants can use:

ammonia (NH3) nitrate (NO3-) nitrite (NO2

-)

• Nitrogen fixation – when bacteria take up N2 and convert it into the forms plants can use

• Denitrification – when bacteria convert nitrates into N2

• Eutrophication – process in which bodies of water receive excess nutrients (such as nitrates from fertilizers) that stimulate aquatic plant growth (if algae, then it is called an algal bloom); when these plants die and decompose, oxygen in the water is used up, which can hurt fish and other animals

The Nitrogen Cycle

The Phosphorus Cycle

• Phosphorus is used by living organisms in DNA, RNA, ATP

• Phosphorus is not common in the biosphere and therefore, is a limiting factor in ecosystems

• Unlike CO2 and N2, phosphorus does not go into the atmosphere

• Phosphorus in fertilizers and livestock waste can lead to eutrophication of aquatic ecosystems

Phosphorus Cycle

Eutrophication

• Too much fertilizer (nitrogen or phosphorus) in the ecosystem leads to overproduction of algae and other aquatic plants

Algal bloomSatellite image of eutrophicationof the northern Caspian Sea

Review of Biogeochemical Cycling

• What are the major cycles that occur in our biosphere?

• How does the atmosphere play a role in each?• What are global warming and eutrophication and

how have humans contributed to both?• Which of the cycles, if thrown off balance, would

have the most immediate catastrophic affect to the biosphere? Can you pick ONE or all they all important and intertwined?