Cycles of Matter
Water, Carbon, Nitrogen, and Phosphorous
S
Biogeochemical Cycles
S What is a biogeochemical cycle?
S Bio – Biology
S Geo – Geology
S Chemical - Chemistry
S A biogeochemical cycle connects all three aspects of the
biosphere
Energy vs. Matter
S Remember, in terms of ENERGY, Earth is an OPEN system.
S Energy is transferred
S Energy comes in from the sun, is transferred and used by plants,
and then transferred and used by consumers
S However, in terms of MATTER, Earth is a CLOSED system.
S Matter is transformed
S Matter is not used up – it is recycled from one form to another
Types of Cycles
S Carbon
S Nitrogen
S Phosphorous
S Water
Nutrient Cycles
Every living organism needs nutrients to build tissues and carry out
essential life functions. Like water, these nutrients are passed
between organisms and the environments through biogeochemical
cycles
S Carbon – key ingredient in living tissue
S Nitrogen – required for amino acids used in protein synthesis
S Phosphorous – required for DNA and RNA
Carbon Cycle
S How does carbon move through its cycle?
S Biological – photosynthesis, respiration, and decomposition take up
and release carbon and oxygen
S Geochemical – erosion and volcanic activity release carbon dioxide
into atmosphere and oceans
S Biogeochemical – decomposition of dead organisms and their
conversion into fossil fuels store carbon underground
S Human activity – mining, cutting/burning forests, and burning fossil
fuels release carbon dioxide into the atmosphere
Carbon Cycle
S How can carbon get into the ocean?
S Respiration by ocean animals
S Precipitation that contains dissolved carbon dioxide
S Erosion of carbonate rocks formed from animal
skeletons and shells
Carbon Facts
S 71% of world’s carbon is in the oceans
S 22% exists as fossils
S 3% contained in dead organic matter and phytoplankton
S 3% held in terrestrial ecosystems.
S Only 1% within the atmosphere as carbon dioxide.
Nitrogen Cycle
S The majority of nitrogen is in the form of nitrogen gas in the
atmosphere.
S Not really usable by most organisms
S How does nitrogen gas become usable?
S Only certain types of bacteria can use this form of nitrogen directly
S Nitrogen fixation - the bacteria convert the nitrogen gas into ammonia
S Other bacteria then convert the ammonia into nitrates and nitrites to be
used by producers
S Producers use the nitrates and nitrites to make proteins.
Nitrogen Cycle
S How does nitrogen get back into the atmosphere?
S When organisms die, decomposers return nitrogen to the
soil as ammonia
S Denitrification - Bacteria in the soil convert the nitrates
back into nitrogen gas
Phosphorus Cycle
S Unlike water, carbon, and nitrogen, phosphorus does not
enter the atmosphere
S Cycles between soil/water and organisms
S Majority of phosphorus is located:
S On land in rocks and soil minerals
S In the ocean as sediment
How Nutrients Effect an Ecosystem
S Primary Productivity – the rate at which organic matter is
created by producers
S Controlled by the amount of available nutrients
S
If a nutrient is in short supply, it will limit an organism’s growth
S Limiting nutrient – substance that limits an ecosystem’s
primary productivity due to limited availability or slow
cycling
How Nutrients Effect an Ecosystem
S When an ecosystem receives a large quantity of its limiting
nutrient, the primary productivity (plant growth) is now
increased
S In the ocean, nitrogen is limiting
S In freshwater, phosphorus is limiting
S Algal bloom - when an aquatic ecosystem receives a surplus of
the limiting nutrient (say, from runoff from a fertilized field),
there is usually an immediate increase in the amount of algae
How Nutrients Effect an Ecosystem
S Algal bloom
S More nutrients are available so the producers can grow and
reproduce more quickly
S Negative effects
S If there are not enough consumers to eat the excess algae, once the
algae die, decomposers take up all of the available oxygen to break
down the dead algae
S Limited oxygen left for the other aquatic animals which can
eventually lead to their death
Water Cycle
S All living things need
water to survive.
S Where does it come from?
S Cycles between the ocean,
atmosphere, and land
Water Cycle
S How does water get into the atmosphere?
S Evaporation – water heats up and changes from liquid to
gas (water vapor)
S Transpiration – water evaporates from plant leaves
S Condensation – water vapor starts to cool and condenses
into small droplets that form clouds
Water Cycle
S How does water return to Earth?
S Precipitation – Droplets that formed clouds become
too large and return the Earth’s surface in the form
of rain, snow, sleet, or hail
Water Cycle
S What happens to the water on land?
S Runoff – Precipitation “runs” along land until it reaches a
body of water
S Seepage – Precipitation “seeps” (moves into) soil to form
ground water below the soil’s surface
S Root uptake – Plants absorb ground water from the soil
through their roots