The Carbon cycle - Rogue Community College

Biology 213 Chapter 55 Ecosystems and the Biosphere

You will be able to… • Compare & contrast food chains, webs, and pyramids • Explain Bioaccumulation & magnification • Describe C cycle, N cycle, P cycle & H2O cycle in the biotic and abiotic environment. • Examine human influence on natural cycles • Describe role of the sun in – Creating seasons – Weather systems – Developing ocean currents – Creating a climate and weather

• Energy flow through an ecosystem – Linear – Sun to producer to consumer to decomposer

Is the sun the only source of energy for food webs?

Energy flow through an ecosystem A food chain

Food chains, webs, & trophic levels.

Food chains, webs, & trophic levels.

Trophic relationships important in endangered wildlife management: e.g. DDT  Bald Eagle & Condors

• Ecological pyramids Express progressive reduction in #’s of: – Organisms – Biomass – energy found in successive trophic levels

Food chains, webs, & trophic levels.

Not all animals or plants are eaten. Portions (beaks, shells, bones, etc.) not digested.

Matter & energy transfer not efficient.

Pyramids of biomass

Usually amount of fixed energy in an ecosystem is measured in quantity of living material = biomass

Generally amount of biomass decreases at successively higher trophic levels. Why?

Pyramid of biomass: If you want to support a lot of humans, what should you feed them?

Pyramids of energy What happens to the energy? • Undigested parts • Entropy • Energy expended in “hunting” & processing food

Bioaccumulation: build up of toxins in an organism Biological magnification: increasing concentration in successive trophic levels

• Gross primary productivity (GPP) – Rate at which photosynthesis captures energy

• Net primary productivity (NPP) – Energy remaining after plants and other producers carry out cellular respiration

What do you think are the most productive ecosystems?

NPP for selected ecosystems Ecosystem

Avg NPP (g dry matter/m2/yr)

Algal beds & reefs Tropical rain forest Swamp & marsh Estuaries Temperate evergreen forest Temperate deciduous forest Savanna Boreal (northern) forest

2,500 2,200 2,000 1,500 1,300 1,200 900 800

NPP for selected ecosystems Ecosystem

Avg NPP (g dry matter/m2/yr)

Woodland & shrubland Agricultural land Temperate grassland Upwelling in oceans Lake and stream Arctic and alpine tundra Open ocean Desert and semi-desert scrubland Extreme desert (rock, sand, ice)

700 650 600 500 250 140 125 90 3

Why is Carbon important in the ecosystem? • What form is carbon used by plants? – CO2 absorbed / O2 released – Sugars (starch) formed – Sugar used for Energy (cellular respiration)

• What form is carbon used by animals? – Sugar used for Energy (cellular respiration) – CO2 released / O2 absorbed (see Joseph Priestly’s experiments) Remember: – C forms the “skeleton” for every biomolecule

How does Carbon cycle in the environment? Biotic factors: • plants and animals: gaseous form • Trees store carbon • Seashells: solid form calcium carbonate Abiotic factors: • Atmospheric gas: circulates globally • Mineral compounds: limestone • Fossil fuels – remnants of ancient plants and marine critters

Biogeochemical Cycles: The Carbon cycle –Carbon dioxide is the most important gas (0.038% of air) • gas phase allows for global circulation –Carbon enters plants as CO2

Biogeochemical Cycles: The Carbon cycle –CO2 returned to the environment: • Cellular respiration • Combustion & volcanoes • Erosion of limestone • Decomposition

Carbon cycle Carbon Reservoirs: in billions of metric tons:

Atmosphere: 720 Ocean: 39,000 Carbonates: 100,000,000

Fossil fuels: 4,000 Soils: 1500 Land plants: 560

• most C is in rocks (carbonates & sediments) • most C not in rocks is dissolved in ocean • ~ 3 x more C in soils than in land plants • Methane hydrates under sea floor

Carbon Cycle

Nitrogen cycle Why is nitrogen important to living things? How is it used? Proteins, DNA, Chlorophyll formation.

• Nitrogen cycle – Five steps: 1. Nitrogen fixation 2. Nitrification 3. Assimilation 4. Ammonification 5. Denitrification

Nitrogen fixation: 2 moles of ammonia produced by prokaryotes from 1 mole of N2 gas N2 + 8H+ + 8e- + 16 ATP = 2NH3 + H2 + 16ADP + 16 Pi

Combustion, volcanoes, industry, and lightning can fix N2 as nitrates & nitrites

Lightning: N2 + O2 --------------> 2 NO (nitric oxide) Nitric oxide free radical combines with O2 to form NO2. 2 NO + O2 ---------------> 2NO2 Nitrogen dioxide dissolves in water to produce nitric and nitrous acids; 2 NO2 + H2O -------> HNO3 + HNO2 These acids readily release NO3 & NO2 ions utilized by plants & micro-organisms. HNO3 --------> H+ + NO3- (nitrate ions) HNO2 --------> H+ + NO2- (nitrite ions)

Nitrification

Ammonia converted to ammonium to nitrate

Assimilation • Roots absorb: – Ammonia (NH3) – Ammonium ions – Nitrate ions

• Make plant proteins, nucleic acids, & chlorophyll

Ammonification • Nitrogen compounds released as wastes: – Urea in urine – Uric acid in bird poop • Compounds are decomposed into ammonia by bacteria

Denitrification • Nitrate ions reduced to gaseous nitrogen by denitrifying bacteria • Reverse nitrogen fixing process • Anaerobic environments: deep soil, swamps, deep ocean

Nitrogen cycle

Both Carbon & Nitrogen cycles involve gas, biological, & geochemical reservoirs

• Phosphorus cycle –Phosphorus erodes from rock as inorganic phosphate –Animals obtain it from their diet

–Plants obtain it from the soil –Does not have a gaseous phase, so cycles more locally

Phosphorus cycle: no gas phase

N and P are the major limiting factors for plant growth

Guano happens! • Sea bird deposits • Bat caves • Used extensively in agriculture as a fertilizer • Used in detergents • Run-off enters streams

Eutrophication: enhanced phytoplankton growth due excess supply of nutrients • High concentrations of nutrients as run-off from – Sewage – Agriculture – Lawns

Eutrophication: enhanced phytoplankton growth due excess supply of nutrients • Phytoplankton “bloom” • Phytoplankton die and are eaten by bacteria • Oxygen levels depleted & fish die

Dr. David Schindler is an ecologist who worked at the Experimental Lakes Project in northern Ontario – performed several experiments on eutrophication that led to ban on phosphates in detergents

Phosphates are the culprit

• Hydrologic cycle – Renews supply of water – Involves exchange of water btwn land, ocean, atmosphere, and organisms – Water enters atmosphere by evaporation and transpiration – Water leaves atmosphere as precipitation – “Distillation” purifies water

Water Basins: Lakes, Oceans, Ice

How much fresh water is there?

Transpiration and Evaporation • Solar energy drives evaporation • Evaporation: ocean surface is main reservoir • Transpiration: plants release over 95% of water they absorb back into air

Condensation and precipitation • Solar E drives surface winds • Winds carry moist air inland and up over mountains • Cooling air loses moisture as condensation • Precipitation: rain, sleet, snow, hail, & fog

Storage: percolation and ground water • Aquifers may take hundreds of years to replenish • Underground aquifers supply water for – Streams – Agriculture – Wells

Ogallala Aquifer: ~95 % used for irrigation. High Plains = 65 % of total irrigated acreage in USA. Overuse: 175,000 wells, irrigating > 15 million acres. Depleted much faster than natural rate of recharge. Some states 40 x higher.

Hydrologic cycle

Bottom-up processes Availability of resources e.g. nutrient minerals controls # of producers, which controls # of herbivores, which controls # of predators, etc.

Top-down processes: Increase in top predators cascades down food web

Sunlight: primary source of energy • Combo of Earth’s spherical shape & axis tilt concentrate solar E at equator. • Inclination of Earth’s axis primarily determines the seasons

Amount of solar radiation reaching Earth • 30% reflected back • 47% absorbed by atmosphere • 23% runs hydrologic cycle • 1% drives wind and ocean currents • 0.02% captured by photosynthesis • 0.0001% used by Culhane for tanning

Seasonal changes in temperature

• Visible light & IR radiation warm surface and lower part of atmosphere • Atmospheric heat produces air movement, which moderates the climate Hadley cells Global wind map

• Coriolis effect – Tendency of moving air or water to be deflected • Right in the Northern Hemisphere • Left in the Southern Hemisphere Does your toilet really flush straight down on the equator?

Atmospheric circulation Trade winds

Doldrums

Oceanic currents • Generated by uneven heating of ocean surfaces • Salinity differences • Surface winds

Major surface ocean currents

Modifies temperatures and affects precipitation patterns

• Regional precipitation differences – Influenced by latitude, elevation, topography, vegetation, distance from large bodies of water, and location – Precipitation greatest where warm air passes over ocean & then cools

Small D in sea surface temp D trade winds, which D sea temp, which continues until atmospheric circulation patterns & precipitation are disrupted across Pacific & Indian Oceans, & surrounding continents

Look at the geography of major deserts

Why are they found in these locations?

Rain shadow

Sierra Nevadas

• California side – Moist and lush

• Nevada side – Dry and desertlike plant communities

Much of the sun’s heat is trapped in the atmosphere by CO2 • • • • • • •

How has man influenced global climate? Increased CO2 from burning fossil fuels What are fossil fuels? CO2 reservoir depleted: deforestation Surface algae polluted What will happen globally? Very complex! What are the alternatives?