1. Unit 2 The Living World

2. Lesson 3 1.Hydrologic/Water Cycle 2.Oxygen Cycle 3.Oxygen Sag Curve 4.Dissolved Oxygen in Water 5.Nitrogen Cycle 6.Steps to Nitrogen Cycle 7.Dead Zones 8.Human Impacts on Nitrogen Unit 2

3. Hydrologic/Water Cycle Hydrologic cycle - Summarizes how liquid, gaseous and solid water flows through the environment – driven by the sun & gravity Evaporation - Water moves from aquatic and land systems into the atmosphere Condensation - Conversion of water vapor into droplets of liquid – condensation on dust particles creates clouds Transpiration - Release of water vapor by plants Precipitation, Runoff, & Surface Water - water returns to Earth as rain or snow and flows into streams, oceans, etc. Snow Pack - Snowpack is an important water resource that feed streams and rivers as they melt.

4. Human Impacts on Water Cycle ImpactEffect Deforestation Tree roots prevents soil erosion – healthy soil allows water to infiltrate into the ground – prevents flooding Plowing Loss of plants reduces transpiration which recharges the atmosphere to produce rain again – can create desertification Irrigation Depletes rivers, streams, lakes, & aquifers – increases the rate of evaporation due to exposure to atmosphere Damming Increases evaporation and disrupts fish migrations to breeding grounds Pollutants Changes water chemistry – Water flowing between different ecosystems transmits the pollutants Over Drafting Over drafting of aquifers faster than they can recharge for drinking, irrigation, & industrial usage

5. Oxygen Cycle Oxygen is the byproduct of photosynthesis & a reactant in cellular respiration – The 2 nd most abundant gas in atmosphere Oxygen is important in the formation of atmospheric ozone in the stratosphere. Remember: Sunlight breaks water (H 2 O) into hydrogen gas & oxygen. 3 oxygens then bond together to form ozone in the stratosphere. Ozone (O 3 ) layer is a filter for harmful ultraviolet (UV) radiation, especially UV-c. There are 3 types of UV: UV-a, UV-b, & UV-c (completely filtered)

6. Oxygen Cycle Dissolved Oxygen - Oxygen is measured in its dissolved form in water as dissolved oxygen (DO) and is usually in the unit of mg/L. – Bottom feeders, crabs, oysters and worms need minimal amounts of oxygen (1-6 mg/L), while most fish need higher levels (4-15 mg/L). – Microbial decomposition is an important contributor to nutrient recycling. However, if there is an excess of decaying organic material (from dying algae and other organisms), in a body of water with infrequent or no turnover, the oxygen at lower water levels will get used up quicker. The saltier and/or warmer water is, the less oxygen it can hold; therefore, the equator contains less oxygen. Most biomass is located near the poles because it contains more oxygen and nutrients.

7. Oxygen Cycle Biological Oxygen Demand – Is the amount of dissolved oxygen needed by aerobic bacteria in a body of water to break down organic material present in a given water sample at certain temperature over a specific time period. – This is not a precise quantitative test, although it is widely used as an indication of the organic quality of water. – BOD can be used as a gauge of the effectiveness of wastewater treatment plants and for finding sources of organic pollution into an ecosystem.

8. Oxygen Cycle Hypoxia – Hypoxia (Hypo- means BELOW), or oxygen depletion, is an environmental phenomenon where the concentration of dissolved oxygen in the water column decreases to a level that can no longer support living aquatic organisms. Hypoxia is defined as a concentration of dissolved oxygen (DO) around 2 mg/L (2 ppm). Anoxic – (An- means NOT/WITHOUT) Are areas of sea water, fresh water or groundwater that are depleted of DO and are a more severe condition of hypoxia. The concentration is at or less than.5 mg/L. Hypoxic Anoxic

9. Oxygen Sag Curve A graph of the measured concentrations of Dissolved Oxygen in water samples collected – Clean Zone: Head waters/up stream, High DO of 8 mg/L or higher, Low BOD, High biodiversity (including sensitive species like trout, bass, mayfly & stonefly larvae) – Decomposition Zone: Organic matter/nutrients entering ecosystem, Dropping DO, Increasing BOD, Dropping biodiversity (species adapted to hypoxic conditions like blackflies, midge larvae, catfish, gar, and leeches) – Septic Zone: Bacteria reach highest population to decompose organic matter, Low DO of 2 mg/L or lower, High BOD, lowest biodiversity (species adapted to anoxic conditions like sludge worms, blood worms, and mosquito larvae – fish are completely absent) – Recovery Zone: Organic matter/nutrients has been consumed by bacteria, Increasing DO, Dropping BOD, and increasing biodiversity (species adapted to hypoxic conditions) – Clean Zone: High DO of 8 mg/L or higher, Low BOD, High biodiversity

10. Dissolved Oxygen in Water Things to Remember: Photosynthesis & wave action adds oxygen Cold water holds oxygen better than warm water Bacteria uses lots oxygen during decomposition (eutrophication) Video Link: https://www.youtube.com/watch?v=oVW5LAzd7Ec

11. Nitrogen Cycle Nitrogen – N 2 makes up 78% of atmosphere This type of nitrogen is NOT usable by organisms. It must be transformed/converted into a usable nitrogen compound. Nitrogen is essential for life – Create proteins, DNA, RNA, and promotes plant growth Term to know: – Legume: A family of plants that have symbiotic nitrogen-fixing bacteria in structures called root nodules. These bacteria “fix” the unusable nitrogen from the atmosphere into usable nitrogen Examples of Legumes: Beans, Peas, alfalfa, clover, lentils, soy, peanuts

13. Steps to Nitrogen Cycle: “Fix NAAD” (LOL…that’s funny) 1.Nitrogen Fixation: Lightning and Legumes fix nitrogen from N 2 into ammonia (NH 3 ) and then into ammonium (NH 4 + ). 2.Nitrification: Ammonium (NH 4 + ) is changed into nitrites and then into nitrates by other bacteria in the soil. Nitrates are what plants can absorb! 3.Assimilation: This is how plants get nitrogen. They absorb nitrates from the soil into their roots. Then the nitrogen gets turned into amino acids and nucleic acids (DNA & RNA). Animals assimilate nitrogen by eating plants & other animals. 4.Ammonification: This is part of the decaying process. When a plant or animal dies, decomposers like fungi & bacteria turn the organic nitrogen (proteins) back into ammonium so it can be taken up by producers again or denitrified. 5.Denitrification: Special bacteria convert nitrate into N 2 and is released back into the atmosphere.

14. How to Remember Nitrogen Cycle Nitrogen Process Nitrogen Product FIX – Nitrogen fixation Ammonia Nitrification Nitrates Assimilation Proteins Ammonification Ammonia Denitrification Nitrogen

15. Dead Zones Hypoxic zones are areas in the ocean of such low oxygen concentration that animal life suffocates and dies, and as a result are sometimes called "dead zones." One of the largest dead zones forms in the Gulf of Mexico every spring. Each spring as farmers fertilize their lands preparing for crop season, rain washes fertilizer off the land and into streams and rivers, and empties out of the Mississippi River. (Chesapeake Bay is another dead zone in the US) These excess nutrients fertilize the rapid growth of plants like phytoplankton and algae, in a process known as eutrophication. When the phytoplankton use up all the nutrients, they die and sink to the bottom, where they are decomposed by bacteria. The bacteria respire as they decompose the phytoplankton, consuming oxygen. Fish kills occur due to low oxygen levels

16. Dead Zones Other sources of nutrients with the help of rain runoff: – C.A.F.O.s (Concentrated Animal Feeding Operations) – Agricultural operations where animals are kept and raised in confined situations. AFOs congregate animals, feed, manure and urine, dead animals, and production operations on a small land area. Waste management is a serious issue with CAFOs. – Human Sewage – Most developing countries do not have waste treatment systems to process sewage, and developed countries are developing better technology to reduce nutrients in released water. – Suburban Lawn Fertilizers – In the quest for the perfect lawn, home owners often over fertilize their lawns. – Fossil Fuels – Burning fossil fuels release nitrogen into the air that redeposits on land or in water.

17. Dead Zones Video Link: https://www.youtube.com/watch?v=ahOmeTOIrRg

18. Reducing Dead Zones The Harmful Algal Bloom and Hypoxia Research and Control Act (1998) – Called for an assessment of hypoxia in the dead zone Solutions outlined included: – Reduce nitrogen fertilizer use in Midwestern farms – Apply fertilizer at times which minimize runoff (not during rain) – Use alternative crops and manage manure better – Restore wetlands (natural bio-filters) and create artificial ones – Improve sewage treatment technologies that reduce nutrients in released water – Monitor water conditions

19. Artificial Nitrogen (Haber-Bosh) The Haber-Bosch Process is the #1 contributor to new nitrogen in the global cycle. Although the Haber process is mainly used to artificially produce fertilizer today by using industrial processes, during World War I, it provided Germany with a source of ammonia for the production of explosives Usage has grown exponentially in recent decades Without nitrogen fertilizers, about 1/3 of our current agricultural production would be lost

20. Human Impacts on Nitrogen Cycle ImpactEffect Nitric Oxide (NO) Released into atmosphere when any type of fossil fuel is burned. Includes byproducts of internal combustion engines (cars) Nitrous Oxide (N 2 O) Released into the atmosphere through bacterial in livestock waste and commercial fertilizers applied to the soil (eutrophication). Mining Removing nitrogen from the Earth’s crust and soil when we mine nitrogen rich mineral deposits. Municipal Sewage Adds nitrogen to aquatic ecosystems which disrupts the ecosystem & kills fish (eutrophication) Haber-Bosch Process An artificial nitrogen fixation process and is the main industrial procedure for the production of ammonia today Dead Zones Hypoxic areas, usually on the coast, caused by excess nutrients finding its way into the ocean

21. End of Unit 2 Lesson 3