Large River Floodplain EcologyPowerPoint PresentationSlide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Oxygen Level ControlsSlide 13What is HypoxiaWhy Hypoxia?Slide 16Slide 17Slide 18When and Where Is Hypoxia?Slide 20Three General Types of WaterSlide 22Slide 23Slide 24Slide 25Slide 26Air-Water InterfaceSlide 28Slide 29Slide 30Large River Floodplain EcologyConstruction of levees along the Mississippi River and many of its tributaries has severed the river from over 90% of its floodplain, denying fish and other aquatic species access to millions of acres of foraging, spawning and nursery habitat.Miss. Dept. of Archives and HistoryMiss. Dept. of Archives and Historyhttp://www.lmrcc.org/ARMP%20folio.pdfMaringouin: 6,000 – 7,000 years ago Teche: 5,700 – 3,900 years ago St. Bernard Delta: 4,600 – 1,800 years ago Lafourche Delta: 3,400 - 400Oxygen Level ControlsPhotosynthesis produces oxygen:Solar Energy + CO2 + H20  C6H12O6 + O2Respiration consumes oxygen:C6H12O6 + O2  CO2 + H20 + chemical energy(ATP)EstuariesSwamps and marshesTropical rain forestTemperate forestNorthern coniferous forest (taiga)SavannaAgricultural landWoodland and shrublandTemperate grasslandLakes and streamsContinental shelfOpen oceanTundra (arctic and alpine)Desert scrubExtreme desert800 1,600 2,400 3,200 4,000 4,800 5,600 6,400 7,200 8,000 8,800 9,600Average net primary productivity (kcal/m2/yr)Net Primary Production (measure of produced energy)What is Hypoxia•Dissolved Oxygen less than 2.0 mg/L•Normoxic = DO > 2.0 mg/L•Generally, most fish can not tolerate hypoxic conditions for long periods.–Gar, bowfin (choupique), bullheads canWhy Hypoxia?•During low water times, the dry lands are extremely fertile and grow a lot of plants.•When the spring floods come and temperatures rise, bacteria begin to decompose the vegetation on the floodplain floor.•Bacterial respiration is what removes the oxygen (lack of flushing in backwater habitats contributes).•Respiration rates exceed photosynthetic rates.When and Where Is Hypoxia?•Generally found during high water times when temperatures are warm.•Backwater areas (away from the mainstem river).–Low flowEventually the swamp drains and backwater areas become very productive.Three General Types of Water •Brown–High flow, lots of sediment, fairly high oxygen levels, riverine•Green–Low flow, stratification, very high surface oxygen levels, highly productive, lacustrine•Black–Low flow, very low surface oxygen levels, not productive, swampBackwater Interior Lakes MainstemDecemberJuneAugust6789How Do ‘Unproductive’ Areas Support Living Populations?•Submerged Aquatic Vegetation–Oxygen Refuge–Productive microhabitatsFish and Aquatic Vegetation•Densities of young fish are often greater in aquatic vegetation than in adjacent open water0246810121416GLN GLS INT FL BL SOCDissolved Oxygen (mg/L)OpenPlantNormoxic HypoxicMean Surface Dissolved Oxygen in Open Water and Plants at Each SiteGreenBrown BlackAir-Water InterfaceLow DO WaterAtmospheric oxygen diffuses into waterFish ‘pipe’ at the microsurface layerHow Do ‘Unproductive’ Areas Support Living Populations?•Detritus-Based Production–Decomposers (e.g., bacteria) transfer energy stored in old organic matter to consumers•Insects, crawfish–Low-oxygen tolerant organisms•Gar, bowfin (choupique), bullheadsEnergy flow through an aquatic ecosystem.From Cole 1988, Waveland