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What are these cycles? Cycling of atoms, molecules, and ions from the non-living environment to the living organisms and back again. Connect the past, present, and future forms of life. Obey Law of Conservation of Mass Provide for recycling of materials Prevent accumulation of wastes Prevent essential nutrients from running out What is the water/hydrologic cycle? The steps involved in the Water Cycle Evaporation – liquid water in rivers, lakes, oceans, etc. is converted into water vapor Transpiration – the evaporation of water from the leaves of plants Condensation – as water vapor in the air rises with warm air, it cools and forms liquid water, resulting in cloud formation. Precipitation– rain or snow falling from clouds Runoff – precipitation runs over land into bodies of water Groundwater – precipitation infiltrates the ground and ends up in aquifers Ice – precipitation freezes for varying periods of time resulting in glaciers, etc. What are the benefits of the Hydrologic Cycle? Water supplies are replenished Since water is the universal solvent and so many substances dissolve in it, it helps to transport nutrients When water is evaporated, only the water becomes a gas, pollution and particulates are left behind. So this is a natural purification process for water. How do humans affect the Water Cycle? Remove groundwater supplies faster than can be replenished resulting in water shortages. Runoff from erosion pollutes water by adding nutrients (eutrophication) which cause excessive plant growth and fish kills Runoff brings pollutants from land into water like oil and pesticides (non-point source pollution) Removal of forests and other vegetation alters normal rain patterns What is the Sulfur Cycle? It is the cycling of sulfur containing compounds and ions through the atmosphere and rocks. S naturally enters the atmosphere by weathering, volcanic eruptions, sea spray, and sea floor vents. H2S (hydrogen sulfide) is released from the anaerobic (without oxygen) breakdown of organic matter by bacteria in swamps, bogs, and tidal flats. (Smells like rotten eggs). H2S is a greenhouse gas. Sulfur circulates through plants in the form of sulfate (SO42-) or sulfur dioxide (SO2) Where is Sulfur found? It is found in amino acids, insulin, fool’s gold, oceanic deposits, sulfur dioxide, etc. How does sulfur contribute to acid rain? When certain compounds are burned, sulfur dioxide (SO2). is produced. SO2 released in air reacts with oxygen to produce sulfur trioxide which then reacts with water to produce sulfuric acid (H2SO4). SO2 +O2 SO3 SO3 + H2O H2SO4 Sulfuric acid can also form from reactions of DMS (dimethyl sulfide) released by plankton. This lowers the pH of rainfall. Normal rainfall is slightly acidic (5.6) because carbon dioxide in the air and water react to form carbonic acid. Acid rain causes damage to plants, lowers the pH in water which affects fish and other aquatic organisms, damages building, statues, and cars, and can decrease the pH of soils. Acid Rain How do humans affect the sulfur cycle? Burning of fossil fuels containing sulfur causes the release of sulfur dioxide into the air. Smelting (removal of valuable metal from rock) of metal ores containing sulfur releases sulfur dioxide into the air. The use of sulfuric acid in industrial and manufacturing processes releases sulfur containing compounds into the air. What is the Phosphorus Cycle? It is the cycling of P through rocks and soil and living organisms. There is no gaseous component in the P cycle. When P is broken down from rocks and soils, phosphate ions (PO43-) are released and this is the form that plants will pick up through their roots. Most compounds containing phosphate ions are insoluble in water. Because of this the release of P from rocks during weathering is a very SLOW process. As a result P is often a limiting factor (a nutrient or needed factor in short supply) in ecosystems. Where is P found? Living organisms DNA Fats Bones, shells, teeth Rocks Both terrestrial and oceanic formations What is Organic Phosphorus? Inorganic (does not contain C). Organic (contains C). Plants absorb inorganic P in the form of phosphate and convert it to organic forms (such as DNA). Animals take in organic P through the food chain (and use it for making bones, shells, teeth, DNA, etc.). Organic P is broken down by bacteria during cellular respiration. It is then released in urine and wastes. There are large concentrations of P in guano (sea bird poop) since their diet is high in fish which naturally have higher levels of P. How do humans affect the P Cycle? Phosphorus is mined from rocks for use in fertilizers and detergents. Mining phosphate rocks damages the land and pollutes groundwater. P is found in limited quantities in tropical soils so removing forests for agriculture helps to wash away P Runoff from farms and fertilized areas and sewage runoff containing excess P leads to eutrophication in waterways. Results in algae blooms and fish kills. What is the Nitrogen Cycle? It is the cycling of nitrogen and nitrogen containing compounds and ions through the air, soil, water, and living organisms. In living organisms, nitrogen is found in DNA, RNA, proteins, and amino acids. It’s a gaseous cycle. 78% of the atmosphere is N2. What are the steps of the Nitrogen Cycle? Nitrogen fixation – conversion of N2 in the atmosphere into a form usable by plants. N2 cannot be taken up by plants. It must be “fixed”: converted to NH3 or NH4 N2 + H2 ---> NH3 What fixes N2? Lightening cyanobacteria Rhizobium bacteria which live in root nodules on legumes (peas, soybeans, alfalfa) Humans use the Haber process Legumes and Rhizobium Nitrification NH3 or NH4+ are converted to nitrate (NO3-) or nitrite (NO2-) ions. Nitrates are easily taken up by plants, while nitrites are toxic. Assimilation Inorganic forms of nitrogen are converted to organic forms in plants Animals pick up organic forms of nitrogen by eating plants directly or by eating other animals. Ammonification Animal/plant waste or dead organisms are broken down by bacteria. Bacteria convert the organic nitrogen forms back into simpler inorganic forms such as ammonium (NH4+) or ammonia(NH3). Denitrification The “final” process Converts ammonia and ammonium first into nitrates or nitrites and then back into atmospheric nitrogen (N2) or NO2. How do humans affect the Nitrogen Cycle? Humans now control more of the nitrogen cycle than natural processes. 3 human activities have the greatest impact: Use of commercial fertilizer. Increased cultivation of legumes and crops that have nitrogen fixing bacteria. Burning of fossil fuels. HOW DOES NITROGEN IN FERTILIZER HAVE AN IMPACT ON AQUATIC ECOSYSTEMS? Draining of wetlands, burning of forests, etc. also release N Burning fossil fuels releases nitrogen in the form of NOx into atmosphere which reacts with water in the air to form nitric acid (HNO3), a component of acid rain. NOx + H2O HNO3 Nitrous oxide gas (N2O) in the air is a greenhouse gas. Forms by the breakdown of animal waste and commercial fertilizer. Excess N entering waterways can lead to eutrophication, algae blooms, and fish kills. Overfertilization of crops can lead to a decrease in biodiversity. Fixed nitrogen entering ground water and drinking water is a health risk particularly to pregnant women and young children. Prevents blood from taking up enough oxygen. Known as Methemoglobinemia or Blue Baby Syndrome Methemoglobinemia What can be done to decrease human impact on the N cycle? Reduction of commercial fertilizer use and change to more “natural forms” of fertilizers. Reduction in fossil fuel consumption. Methods of removing nitrates from water. Preservation of wildlands. What is the Carbon Cycle? Gaseous cycle. Based on carbon dioxide gas which makes up 0.036% of volume of troposphere. CO2 also found dissolved in water. CO2 helps control the earth’s thermostat. Terrestrial and aquatic producers remove carbon dioxide and convert it into glucose via photosynthesis. CO2 is returned to air and water through aerobic respiration. What is the connection between photosynthesis and aerobic respiration? Photosynthesis CO2 + H2O ---> O2 + C6H12O6 Aerobic respiration O2 + C6H12O6 ---> CO2 + H2O What are the sinks (place where a nutrient is stored for periods of time) for carbon? 1. Sedimentary rocks like limestone (CaCO3), found in deposits on the ocean floor or on continents. The carbon in limestone is released slowly as CO2 by geological processes or by acid rain. This is the largest sink for C. 2. The oceans CO2dissolved in the oceans is 50x greater than in the air. CO2 gets into the oceans from contact with air, aerobic respiration and decomposition, and breakdown of CO32 Some of the CO2 in the water is used by producers during photosynthesis and some will react with water to form carbonate (CO32-) Some marine organisms take up the CO32-, react it with Ca2+ and form calcium carbonate (CaCO3) which becomes shells and skeletons When these creatures die, these shells are buried deep in the ocean where over time they form sedimentary rock (limestone). 3. Fossil fuels form when dead plants and bacteria are pressed between layers of sediment. Time and pressure eventually create what we call fossil fuels. The C they contain is locked up in the fossil fuel until it is burned and carbon dioxide is released. 4. Forests During photosynthesis, trees take in CO2 and convert it into organic matter (glucose). C remains bound up with the tree for long periods of time and is not released until the tree dies or is cut down and burned. How do human activities affect the carbon cycle? Humans increase the amount of CO2 in the atmosphere by Removing vegetation. Combusting fossil fuels. CO2 in atmosphere is considered a greenhouse gas and is linked to global climate change. How is excess CO2 affecting the Oceans? As a result of human activities, more CO2 is entering the atmosphere and at the same time more is entering the oceans. The normal pH levels of the ocean range from 7.5 to 8.5. When CO2 dissolves in water, it reacts with the water to produce carbonic acid: H2O + CO2 ---> H2CO3 This creates a lowering of the pH of the ocean (ocean acidification). This does not necessarily mean that the ocean is becoming an acidic solution, but it is more acidic than normal. How is acidification affecting the Ocean? Studies conducted have found that: increasing acidification of ocean water affects the ability of organisms to make shells. The problem is greatest in colder water regions near the poles because colder waters can hold more carbon dioxide. Pteropods (a form of plankton) are an important base of the food web in polar regions. They cannot grow shells as the water becomes more acidic. May be a serious problem in the coming decades. And in some places, it may already be one. Are corals also affected by acidification? Coral is actually a symbiotic relationship between the coral animal and an algae called zooxanthellae. Because of acidification, the coral animal itself loses its ability to make a calcium carbonate shell. Because of more carbon dioxide in the water, the symbiotic algae goes through more photosynthesis. The symbiotic relationship is disrupted possibly due to greater competition for carbon between the symbiotes. What can be done to reduce carbon dioxide levels? Reduce human activities that put excess CO2 into the atmosphere. Add iron sulfate to oceans to increase phytoplankton growth and photosynthesis Inject carbon dioxide into the deep ocean Direct injection of CO2 underground Problems with injection: May come back up Creates more acidic waters Concern over earthquakes In 1986 at Lake Nyos in Cameroon, 1700 people died when a natural carbon dioxide bubble was released.
