- Slides: 24
2. 2 NUTRIENT CYCLES IN ECOSYTEMS
NUTRIENT CYCLES • the flow of nutrients IN and OUT of the land, ocean, atmosphere, and deep rock. • The health of our ecosystems depends on the balance of: Carbon Nitrogen Phosphorus Hydrogen Oxygen C N P H O
NUTRIENT CYCLES • Cycles
CARBON CYCLE • • A. Carbon Facts: • Carbon is found in all living matter • Places where carbon is found are called stores or sinks Short-term stores • living things • rotting tissue • atmosphere • ocean • • Long-term stores underground (oil, gas, natural gas, coal) sedimentary rock (e. g. limestone) ocean floor (old shells)
B. HOW CARBON CHANGES FORM: • 1. Photosynthesis (in plants, algae, and cyanobacteria) • • CO 2 + H 2 O + sunlight C 6 H 12 O 6 + O 2 2. Cellular Respiration (in cells of all living things) • C 6 H 12 O 6 + O 2 CO 2 + H 2 O + ENERGY (energy is used for grown, repair, etc. ) 3. Decomposition (rotting) done by bacteria/fungi cellulose CO 2
HOW CARBON CHANGES FORM (CON’D) • 4. Ocean mixing: moves CO 2 around the world • CO 2 sinks in cold ocean waters; flows to the warm equator and evaporates into the air
HOW CARBON CHANGES FORM (CON’D) • 5. Combustion (burning, engines, volcanoes, forest fires) • fossil fuels + O 2 CO 2 + H 2 O + ENERGY
HUMAN ACTIVITIES & CO 2 • 1. Burning Fossil Fuels • CO 2 in atmosphere has increased 30% in past 160 years. • In the 160, 000 years before that, it only increased 1 - 3%. • Carbon is removed from longterm storage as we mine coal & drill for oil and gas. • CO 2 is also a greenhouse gas, (traps heat in atmosphere)
HUMAN ACTIVITIES AND CO 2 (CON’D) • 2. Removing Trees • • Trees absorb CO 2, so when they are cut down, CO 2 is released into the air. Other crops don’t remove as much CO 2
NITROGEN CYCLE • A. Nitrogen Facts • • • Makes up DNA & proteins (muscle function). Help plants grow. Where Nitrogen is Found: • Atmosphere (78% is N 2) • Oceans • Organic matter in soil • Lakes, marshes, organisms
B. HOW NITROGEN CHANGES FORM • N 2 is not usable by plants or animals, so it has to be converted to other forms. • Rain washes nitrate into soil. (small amount) • Plants can use NO 3 - (nitrate) and NH 4+ (ammonium) • Bacteria in soil (rhizobium) & cyanobacteria in water change N 2 (nitrogen gas) into NH 4+(ammonium). 1. Nitrogen Fixation • – Lightning changes N 2 (nitrogen gas) NO 3(nitrate).
2. NITRIFICATION • This is done by nitrifying bacteria: NH 4+ (ammonium) NO 2(nitrite) NO 3(nitrate) The nitrate is what plants want. NH 4+ is useless to them.
3. UPTAKE • NO 3 - is sucked into plants & used for growth. • Herbivores eat plants & use N for making proteins & DNA.
4. DENITRIFICATION • (done by denitrifying bacteria& volcanic eruptions) NO 3(nitrate) N 2 (nitrogen gas)
C. HUMAN ACTIVITIES AFFECT THE NITROGEN CYCLE • The amount of nitrogen in the ecosystem has doubled in the last 50 yrs due to • 1. Burning fossil fuels & sewage treatment • NO & NO 2 are byproducts
HUMAN ACTIVITIES (CON’D) • 2. Land Clearing by burning • • acid rain is formed which contains nitric acid (HNO 3) • 3. Overfertilization NH 4+ & NO 3 - leach into soil and waterways • Huge growth in aquatic algae = eutrophication These algal blooms use up all CO 2 & O 2, block sunlight, & produce neurotoxins which poison and kill many aquatic organisms
THE PHOSPHORUS CYCLE • Phosphorus (P) facts • P is a part of the molecule that carries energy in cells (ATP) • P helps root growth, stem strength, and seed production • In animals, P is important for strong bones. • P is NOT found in the atmosphere, but in phosphate rocks (PO 43 -, HPO 42 -, H 2 PO 4 -) and sediments on the ocean floor
B. HOW PHOSPHORUS CHANGES FORM 1. Weathering A. Chemical weathering: acid rain on lichens releases phosphates (PO 43 -) B. Physical Weathering: wind, water, and freezing release the phosphates
B. HOW PHOSPHORUS CHANGES FORM (CON’D) 2. Uptake: plants suck up PO 43 - then are eaten by animals. 3. Decomposition: Bacteria break down organic matter and P is returned to soil. 4. Geologic Uplift: When rocks (containing P) under the ground are pushed up mountains weathering.
C. HUMAN ACTIVITIES AFFECT THE PHOSPHORUS CYCLE • Mining: increases P in ecosystems quickly. • Slash-and-burn forest practices: turns P into ash, which runs in waterways.
HOW CHANGES IN NUTRIENT CYCLES AFFECT BIODIVERSITY • Any significant changes to any of these nutrients (C, H, O, N, P) can greatly impact biodiversity. 1. Carbon cycle changes climate change & global warming. 2. Too much N can allow certain plant species to out-compete other species. 3. Decreased levels of P slow growth of algae (NB producers)