Lecture #35 - Energy/Biogeochemical Cycles

When energy is converted from one form to another

Some energy can be lost as heat

Autotrophs

Can make their own food

Photoautotrophs

Photosynthetic organisms use light as energy source. E.G. plants, algae, cyanobacteria

Chemoautotrophs

Get energy from inorganic chemical reactions. (e.g. hydrogen sulfide gas available at deep sea hydrothermal vents). All are prokaryotes

Heterotrophs

Cannot efficiently make food molecules and must eat chemical bond energy made by other organisms. Animals, fungi, and many prokaryotes are heterotrophs

Biogeochemical Cycles

Elements more between living (biotic) and nonliving (abiotic) parts of the environment

Water Cycle

Water is a compound; it can be broken and remade

Evaporation

Liquid water becomes water vapor (requires energy)

What is a cloud?

Water vapor or frozen water floating in the air

Condensation

Gaseous water vapor becomes liquid or frozen water

How does rain form?

Water vapor cools, condenses and falls out of the sky

Aquifer

Underground layer of rock, sand, or gravel that is often saturated with water (groundwater). Water flows slowly underground (a few inches to a few feet per day) compared to surface water.

Groundwater

Recharged (only 10%) by precipitation. In the US, groundwater provides about 25% of the total water used by humans and about 50% of the drinking water

Unsaturated Zone

Not saturated with water and has air spaces and pores. Water here can flow back into surface water

Saturated Zone

Deeper and saturated with water. Can access with wells

Water Table

Upper part of saturated zone

Watershed

Area of land collects precipitation/groundwater and drains into a common outlet

Photic Zone

Receives enough sunlight to support photosynthesis

Thermocline

Boundary layer between warm surface water and cold water below; warm water floats on cold water. Acts as barrier preventing mixing of oxygenated surface water with oxygen - poor deeper waters (thermal stratification)

Autumn/Spring Turnover

Mixing of warmer and cooler water due to changes in surface temperature, water density, and wind. Also called "lake turnover". Many tropical waters experience a permanent thermocline due to a lack of seasons.

Carbon Cycle

Exists primarily as CO2 and Methane (CH4), except in aquatic ecosystems, where carbon also exists as bicarbonate ion. Parts of carbon cycle move faster/slower, leading to changes in atmosphere CO2

Inorganic Carbon

NOT part of a living organism. Inorganic carbon is removed from atmosphere by photosynthesis

Carbon Fixation

Organisms use atmospheric CO2 to build other carbon - containing compounds

Organic Carbin

Part of a living organism. Organic carbon is returned to atmosphere by cellular respiration/decomposers

CO2/Global Warming

Solar energy reaching Earth is medium - wavelength with enough energy that easily passes through the atmosphere to Heat the Earth; However, CO2 absorbs this heat energy before it leaves the Earth, leading to an increase in Earth's net global temperature. Burning Fossil Fuels is the primary reason atmospheric CO2 is increasing. Methane and nitrous oxide are even more powerful greenhouse gases but are not as abundant.

CO2/Ocean Acidification

CO2 reacts with ocean water to form carbonic acid (H2CO3) that dissociates to form hydrogen and bicarbonate (HCO3-) ions. The extra H+ in the water combines with free carbonate (CO3 2-) ions to form more bicarbonate, reducing the amount of free carbonate in the water needed by shell - building animals

Terrestrial Systems

N and P are limiting nutrients for many plants

Freshwater Systems

P is a limiting nutrient for phytoplankton

Marine Systems

N limits Phytoplankton. Iron is limiting in some oceans

Nitrogen Cycle

The atmosphere is 78% nitrogen by volume, but eukaryotes cannot use N2 gas as a nitrogen source

Nitrogen Fixation

Bacterial nitrogenase enzyme converts N2 gas into usable forms

Denitrification

Prokaryotes turn usable nitrogen back into usable forms

Phosphorus Cycle

In ecosystems as phosphate, (PO4 3-) in liquid or solid form, but does not enter Atmosphere. Weathering/Erosion of rocks releases phosphate into terrestrial ecosystems

Phosphate Remineralization

Decay microbes release phosphate back into soil or water

Hypoxia

Low in oxygen

Anoxia

No oxygen

Oligotrophic

Water is crystal clear, low in algal nutrients (nitrate or phosphate), low in algal biomass, low in dead organic material, and high in dissolved oxygen. Trout are typical fish of these waters

Eutrophic

Water is murky, high in nutrients (nitrate or phosphate), high in algal biomass, high in dead organic material, and low in dissolved oxygen. Carp are typical fish here

Biome

A distinct community of terrestrial plants and animals occupying one or more large geographic regions. Might contain different ecosystems and different habitats within ecosystems. Usually defined by temperature and precipitation

Two most important predictors of terrestrial biomes

1.) Mean Annual Temperature

2.) Mean Annual Precipitation