CEE 210 Environmental Biology for EngineersSouthern Illinois University Carbondale2/15/2010Lecture: HypoxiaInstructor: L.R. Chevalier p. 1CEE 210 ENVIRONMENTAL BIOLOGY FOR ENGINEERSCase Study: HypoxiaInstructor: L.R. ChevalierDepartment of Civil and Environmental EngineeringSouthern Illinois University CarbondaleEnvironmental Biology for EngineersEutrophication The over enrichment of waters by nutrients It threatens and degrades many coastal ecosystems around the world.  The two most acute symptoms of eutrophication are ◦ hypoxia (or oxygen depletion)◦ harmful algal blooms Impact the aquatic ecosystemEnvironmental Biology for EngineersIntroductory VideoEnvironmental Biology for EngineersPhytoplankton Bloom of Vancouver IslandEnvironmental Biology for EngineersEcosystem Balance of Nutrients and Oxygen For most coastal ecosystems, nutrients (plant fertilizers like nitrogen and phosphorus) and delivered to an estuary primarily from the adjacent watershed land.  Nutrients also enter the coastal waters from rain and dust that falls from the air, and in some cases from the ocean. Most of the nutrients entering the estuary are used for the growth of a floating algae called phytoplankton Phytoplankton use nutrients, along with sunlight, carbon dioxide and water, to create energy for growth This process, called photosynthesis, also creates oxygen, but it can only occur in the upper zones of water where there is sufficient lightEnvironmental Biology for EngineersStratification of OceanThe differences in density of freshwater and ocean water create stratification.Freshwater is this picture is warmer and less dense than the colder ocean water.ocean waterriver watermixing boundarysedimentCEE 210 Environmental Biology for EngineersSouthern Illinois University Carbondale2/15/2010Lecture: HypoxiaInstructor: L.R. Chevalier p. 2Environmental Biology for EngineersImportance of Phytoplankton These tiny ocean plants help regulate our atmosphere and the health of our oceans◦ Phytoplankton produce half of the oxygen generated by plants on Earth◦ They also can soften the impacts of climate change by absorbing carbon dioxide, a heat-trapping greenhouse gas◦ In addition, phytoplankton serve as the base of the ocean food chain, so their abundance determines the overall health of ocean ecosystems Typically, phytoplankton only live 2-3 days◦ Biomass sinks to the bottom of the ocean◦ Over geological time, the ocean has become the primary storage sink for atmospheric carbon dioxide◦ About 90 percent of the world's total carbon content has settled to the bottom of the ocean, primarily in the form of dead biomassEnvironmental Biology for EngineersSpring Bloom in New Zealand WatersNorth IslandSouth Island25 kmNacquired August 4, 2009Environmental Biology for EngineersWhat causes a bloom? When surface waters are cold, water from the lower depths can well up to the surface, bringing essential nutrients  Phytoplankton use these nutrients and photosynthesis for growthEnvironmental Biology for EngineersBloom in the Norwegian SeaEnvironmental Biology for EngineersHypoxia – What is it? Dead zones◦ Naturally occurring in marine environment◦ Increasing in numbers due to anthropogenic factors Primarily a problem for estuaries and coastal waters Excess nutrient promotes the growth of phytoplankton (nitrogen and phosphorus)◦ Fertilizers from agriculture, golf courses, and suburban lawns◦ Erosion of soil full of nutrients◦ Discharges from sewage treatment plants◦ Deposition of atmospheric nitrogenEnvironmental Biology for EngineersHypoxia – What is it? Organic matter produced by phytoplankton sinks to the bottom of the ocean Bacteria in the bottom of the ocean break down the organic matter Bacteria use oxygen This oxygen is also needed by other oxygen respiring animals at the bottom◦ Crabs, clams, shrimp, and a host of mud-loving creatures◦ Zooplankton and fish swimming at these depths A growth in the bacteria will reduce these populations, sometimes to the point of deathCEE 210 Environmental Biology for EngineersSouthern Illinois University Carbondale2/15/2010Lecture: HypoxiaInstructor: L.R. Chevalier p. 3Environmental Biology for EngineersUpwelling and Mixing  Stratification◦ Ocean water is denser than fresh water◦ Higher summer temperature of river water increases density difference◦ Sun also warms the surface water In the fall, the temperature of the surface waters cool If cold enough, the top layer can become more dense Coupled with wind, the surface and bottom layers can will mix Brings nutrients to the surface Brings oxygen to the bottom watersEnvironmental Biology for EngineersUpwelling and mixing When surface waters are warm (El Nino), it is harder for colder deeper currents to surface Phytoplankton starve, disrupting the food chain Biomass accumulates at the bottom of the ocean Bottom dwelling organisms feed on this biomass, but also use dissolved oxygen Lack of oxygen kills off other aquatic life, causing dead zonesEnvironmental Biology for EngineersDissolved Oxygen Concentration1 mg/L3 mg/L2 mg/L4 mg/L5 mg/L6 mg/L0 mg/LhypoxiaanoxiaUsually will not support fishStressful to most aquatic organismsUsually required for growth and activityperch oystersStripped bassBlue crabBay anchovywormsEnvironmental Biology for EngineersDead zone off the coast of San DiegoEnvironmental Biology for EngineersOregon Dead Zone Off the coast of Oregon, a large dead has been appearing each summer since 2002 The dead zones appear to be linked to an unusually persistent northerly wind that pushes surface waters away from the coast The cool waters that well up from deeper in the ocean to replace them are rich in nutrients but low in oxygen These high-nutrient, low-oxygen waters pack a one-two punch in creating dead zones The excess nutrients fertilize an overgrowth of algae and other marine phytoplankton When the plants die, bacteria decomposition takes more oxygen out of the already oxygen-poor water Problem related to the phytoplankton bloom near Vancouver shown earlierEnvironmental Biology for EngineersOregon Dead ZoneCEE 210 Environmental Biology for EngineersSouthern Illinois University Carbondale2/15/2010Lecture: HypoxiaInstructor: L.R. Chevalier p. 4Environmental Biology for EngineersCumulative increases in dead zonesEnvironmental Biology for EngineersDead