Nutrient Cycles & Thermodynamics

DO NOW Draw the hydrologic cycle Label all parts of your diagram

Biogeochemical Nutrient Cycles

Biogeochemical Nutrient Cycles Hydrologic Carbon-Oxygen Nitrogen Phosphorus Sulfur Rock

Biogeochemical Cycles describe the flow of essential elements from the environment, through living organisms, and back into the environment

Nutrients circulate through ecosystems Physical matter is circulated continually in an ecosystem Nutrient (biogeochemical) cycle = the movement of nutrients through ecosystems Atmosphere, hydrosphere, lithosphere, and biosphere Pools (reservoirs) = where nutrients reside for varying amounts of time Flux = movement of nutrients among pools, which change over time and are influenced by human activities Sources = pools that release more nutrients than they accept Sinks = accept more nutrients than they release 6

Hydrologic Cycle

The hydrologic cycle

Hydrologic Cycle (water cycle) 1. Reservoir – oceans, air (as water vapor), groundwater, lakes and glaciers; evaporation, wind and precipitation (rain) move water from oceans to land 2. Assimilation – plants absorb water from the ground, animals drink water or eat other organisms which are composed mostly of water 3. Release – plants transpire, animals breathe and expel liquid wastes

Reserviors

Residence Times

The carbon-oxygen cycle

Carbon-Oxygen Cycle (carbon is required for building organic compounds) 1. Reservoir – atmosphere (as CO2), fossil fuels (gas, oil, coal), durable organic materials (for example: cellulose). 2. Assimilation – plants use CO2 in photosynthesis; animals consume plants 3. Release – plants and animals release CO2 through respiration and decomposition; CO2 is released as wood and fossil fuels are burned

The carbon cycle Carbon is found in carbohydrates, fats, proteins, bones Carbon cycle = describes the routes that carbon atoms take through the environment Photosynthesis moves carbon from the air to organisms Respiration returns carbon to the air and oceans Decomposition returns carbon to the sediment, the largest reservoir of carbon Ultimately, it may be converted into fossil fuels The world’s oceans are the second largest reservoir of carbon 14

Humans affect the carbon cycle Burning fossil fuels moves carbon from the ground to the air Cutting forests and burning fields moves carbon from organisms to the air Today’s atmospheric carbon dioxide reservoir is the largest in the past 650,000 years The driving force behind climate change The missing carbon sink: 1-2 billion metric tons of carbon are unaccounted for It may be the plants or soils of northern temperate and boreal forests

The nitrogen cycle

Nitrogen Cycle (Nitrogen is required for the manufacture of amino acids and nucleic acids) 1. Reservoir – atmosphere (as N2); soil (as NH4+ or ammonium, NH3 or ammonia, N02- or nitrite, N03- or nitrate

Nitrogen Cycle 2. Assimilation – plants absorb nitrogen as either NH4+ or as N03-, animals obtain nitrogen by eating plants and other animals. The stages in the assimilation of nitrogen are as follows: Nitrogen Fixation: N2 to NH4+ by nitrogen-fixing bacteria (prokaryotes in the soil and root nodules), N2 to N03- by lightning and UV radiation. Nitrification: NH4+ to N02- and N02- to N03- by various nitrifying bacteria.

Nitrogen Cycle 3. Release – Denitrifying bacteria convert N03- back to N2 (denitrification); detrivorous bacteria convert organic compounds back to NH4+ (ammonification); animals excrete NH4+ (or NH3) urea, or uric acid.

The nitrogen cycle Nitrogen comprises 78% of our atmosphere, and is contained in proteins, DNA and RNA Nitrogen cycle = describes the routes that nitrogen atoms take through the environment Nitrogen gas is inert and cannot be used by organisms Nitrogen fixation = Nitrogen gas is combined (fixed) with hydrogen by nitrogen-fixing bacteria to become ammonium Which can be used by plants

Nitrification and denitrification Nitrification = bacteria that convert ammonium ions first into nitrite ions then into nitrate ions Plants can take up these ions Animals obtain nitrogen by eating plants or other animals Denitrifying bacteria = convert nitrates in soil or water to gaseous nitrogen, releasing it back into the atmosphere

Humans affect the nitrogen cycle Haber-Bosch process = synthetic production of fertilizers by combining nitrogen and hydrogen to synthesize ammonia Dramatically changed the nitrogen cycle Humans are fixing as much nitrogen as nature does Increased emissions of nitrogen-containing greenhouse gases Calcium and potassium in soil washed out by fertilizers Acidified water and soils Moved more nitrogen into plants and terrestrial systems Reduced biodiversity of plants adapted to low-nitrogen soils Changed estuaries and coastal ecosystems and fisheries

Human inputs of nitrogen into the environment Fully half of nitrogen entering the environment is of human origin

The phosphorus cycle Phosphorus is a key component of cell membranes, DNA, RNA, ATP and ADP Phosphorus cycle = describes the routes that phosphorus atoms take through the environment No significant atmospheric component Most phosphorus is within rocks and is released by weathering With naturally low environmental concentrations, phosphorus is a limiting factor for plant growth

Phosphorus Cycle (Phosphorus is required for the manufacture of ATP and all nucleic acids) 1. Reservoir – erosion transfers phosphorus to water and soil; sediments and rocks that accumulate on ocean floors return to the surface as a result of uplifting by geological processes 2. Assimilation – plants absorb inorganic PO43- (phosphate) from soils; animals obtain organic phosphorus when they plants and other animals 3. Release – plants and animals release phosphorus when they decompose; animals excrete phosphorus in their waste products

The phosphorus cycle

Humans affect the phosphorus cycle Mining rocks for fertilizer moves phosphorus from the soil to water systems Wastewater discharge also releases phosphorus Runoff containing phosphorus causes eutrophication of aquatic systems

The sulfur cycle

Sulfur Cycle (Sulfur is required for the manufacture of proteins) 1. Reservoir – Earth’s crust as gypsum (CaSO4) and pyrite (FeS2), oceans as sulfate anions, atmosphere as sulfur dioxide (SO2) 2. Assimilation – sulfate (SO4 2–) is reduced by plants, fungi and prokaryotes 3. Release – plants and animals release sulfur when they decompose

The rock cycle Rock cycle = The heating, melting, cooling, breaking and reassembling of rocks and minerals Rocks help determine soil chemistry, which influences ecosystems Helps us appreciate the formation and conservation of soils, mineral resources, fossil fuels, and other natural resources 34

The Nitrogen Cycle Game Questions In the course of the Nitrogen Cycle, are nitrogen atoms themselves ever created? Ever destroyed? Ever changed into other compounds? Explain why or why not. Discuss what moves on the game board represented the following processes of the Nitrogen Cycle: Nitrogen Fixation Nitrification Ammonification Assimilation Denitrification

The Nitrogen Cycle Game Questions Identify what other gases, besides, N2, can be produced during denitrification. For each gas you identify, describe what human activities facilitate the production of these gases. Discuss why a natural ecosystem (assuming no anthropogenic interaction ) is not polluted by nitrogenous wastes from various organisms.

Hypoxia and the Gulf of Mexico’s Dead Zone Observations: low oxygen levels - hypoxia Hypothesis: caused by nutrients (fertilizers) that ran into the Gulf from rivers Experiments: monitoring oxygen (long term), water sampling (N, NaCl. Bacteria, phytoplankton); observed life; analyzed historical data Results: phytoplankton receiving too much phosphorus from farming & sewage treatment plants As the phytoplankton die the decomposers use up available oxygen Solution: reduce amount of phosphorus entering the Gulf – but How?

Newton’s Laws Conservation of Mass – mass cannot be created or destroyed, but can be changed to energy

Newton’s Laws - First Thermodynamics – inertia – an object in motion stays in motion unless acted upon by an outside force

Thermodynamics – entropy– disorder increases Newton’s Laws - Second Thermodynamics – entropy– disorder increases Think of entropy as heat loss We must add more energy to compensate for the heat loss

Energy passes through trophic levels One of the most important species interactions is who eats whom Matter and energy move through the community Trophic levels = rank in the feeding hierarchy Producers Consumers Detritivores and Decomposers 41

Producers: the first trophic level Autotrophs (“self-feeders”) = organisms that capture solar energy for photosynthesis to produce sugars Green Plants Cyanobacteria Algae Chemosynthetic bacteria use the geothermal energy in hot springs or deep-sea vents to produce their food 42

Consumers: organisms that consume producers Primary consumers = second trophic level Organisms that consume producers Herbivores consume plants Deer, grasshoppers Secondary consumers = third trophic level Organisms that prey on primary consumers Carnivores consume meat Wolves, rodents, birds 43

Consumers occur at even higher trophic levels Tertiary Consumers = fourth trophic level Predators at the highest trophic level Consume secondary consumers Are also carnivores Hawks, owls Omnivores = consumers that eat both plants and animals

Detritivores and decomposers Organisms that consume nonliving organic matter Enrich soils and/or recycle nutrients found in dead organisms Detritivores = scavenge waste products or dead bodies Millipedes Decomposers = break down leaf litter and other non-living material Fungi, bacteria Enhance topsoil and recycle nutrients 45

Energy, biomass, and numbers decrease Most energy organisms use is lost as waste heat through respiration Less and less energy is available in each successive trophic level Each level contains only 10% of the energy of the trophic level below it There are far fewer organisms at the highest trophic levels, with less energy available A human vegetarian’s ecological footprint is smaller than a meat-eater’s footprint 46

Pyramids of energy, biomass, and numbers

Food webs show relationships and energy flow Food chain = the relationship of how energy is transferred up the trophic levels Food web = a visual map of feeding relationships and energy flow Includes many different organisms at all the various levels Greatly simplified; leaves out the majority of species 48

Some organisms play big roles Keystone Species = has a strong or wide-reaching impact far out of proportion to its abundance Removal of a keystone species has substantial ripple effects Alters the food chain

Species can change communities Trophic Cascade = predators at high trophic levels can indirectly affect populations of organisms at low trophic levels by keeping species at intermediate trophic levels in check Extermination of wolves led to increased deer populations, which led to overgrazed vegetation and changed forest structure Ecosystem engineers = physically modify the environment Beaver dams, prairie dogs, fungi, insects, phytoplankton