Eutrophication presentation2


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  • Eutrophication presentation2

    1. 1. AQUATIC PLANTS ELODEA TO EMILY: the first 3 slides are the info i got with the websitesunderneath. and my actual slides are the ones after that.
    2. 2. a) • Among the most important for aquatic ecosystems are nitrogen and phosphorous.Nitrogen and phosphorus are particularly critical to aquatic ecosystems because they often control the rates of photosynthesis. This is not because nitrogen andphosphorous are the most abundant constituents of living things - carbon is significantly more abundant than either of them, and oxygen and sulfur are more abundantthat phosphorous. Instead, it is because nitrogen and phosphorous are less available to plants relative to their growth requirements than are other elements.Phosphorus is often in short supply in an aquatic ecosystem and limits plant and algae growth. The primary natural sources of phosphorus to aquatic ecosystems are theslow dissolution of minerals in soil and decomposition of allochthonous organic matter, such as leaf litter, although natural sources also include soil dusting and burning.But human activities have dramatically increased delivery of phosphorus to fresh waters. Primary anthropogenic sources of the nutrient include sewage (whether treatedor not), septic tank leachate, fertilizer runoff, soil erosion, animal waste and industrial discharges.A lack of nitrogen can limit plant growth in both terrestrial and aquatic ecosystems. As with phosphorous, we often add nitrogen to farm fields and gardens in the form offertilizers to increase production of crops and other desirable plants.For example, nitrogen fixation readily occurs in freshwater. When nitrogen availability limits plant or algae growth in freshwater ecosystems, populations of nitrogenfixing organisms (especially cyanobacteria) increase until some other nutrient - often phosphorus - becomes limiting. Because nitrogen fixation is less rapid in marineenvironments, nitrogen is more likely to limit primary production in marine and estuarine environments than in freshwater. Nitrogen can be limiting in phosphorus-richenvironments.akes and streams may also undergo anthropogenic eutrophication, where human inputs of nutrients create excessive algal blooms and result in decreased water clarityand dissolved oxygenIn aquatic ecosystems, it is important to recognize that there are healthy ranges all of these aspects of water chemistry, including water temperature, dissolved oxygen,pH and nutrients. If too little of one of these components is available, the ecosystem will suffer, just as it will if there is too much of another. of water and habitat quality. Nitrogen and phosphorus are essential components of structural proteins, enzymes, cellmembranes, nucleic acids, and molecules that capture and utilize light and chemical energy to support life.Nutrient enrichment of marine waters promotes the growth of algae, either as attached multicellular forms (e.g. sea lettuce) or assuspended microscopic phytoplankton, because algae can grow faster than larger vascular plants. Small increases in algalabundance or biomass have subtle ecological responses that can increase production in food webs sustaining fish and shellfish,even producing higher fish yields. However, over-stimulation of algal growth leads to a complex suite of interconnectedbiological and chemical responses that can severely degrade water quality and threaten human health and sustainability of livingresources in the coastal zone.
    3. 3. hypoxia• Hypoxia, or oxygen depletion, is a phenomenon that occurs in aquatic environments as dissolved oxygen (DO; molecular oxygen dissolved in the water) becomes reduced in concentration to a point where it becomes detrimental to aquatic organisms living in the system. Dissolved oxygen is typically expressed as a percentage of the oxygen that would dissolve in the water at the prevailing temperature and salinity (both of which affect the solubility of oxygen in water; see oxygen saturation and underwater). An aquatic system lacking dissolved oxygen (0% saturation) is termed anaerobic, reducing, or anoxic; a system with low concentration—in the range between 1 and 30% saturation—is called hypoxic or dysoxic. Most fish cannot live below 30% saturation. A "healthy" aquatic environment should seldom experience less than 80%. The ex-aerobic zone is found at the boundary of anoxic and hypoxic zones.-------> wikipedia•
    4. 4. hypothesis of eutrophication • Eutrophication brings about increased dissolved oxygen consumption in lakes progressively lowering dissolved oxygen concentrations. Eutrophic lakes covered with ice and snow, wetlands and northern rivers receiving large quantities of organic matter from their ice and snow, exhibit substantial DO losses during the winter (Likens, 1972). At higher temperatures, water can hold less oxygen when saturated which results in less oxygen directlyavailable and a lower percentage of the metabolic demand being satisfied, since the metabolic rate of organisms increases with increasing temperature (Klaff, 2002). Eutrophication can have both temporary and more irreversible effects on aquatic ecosystems. Significant fluctuations in dissolved oxygen concentrations between day and night can occur in waters where there isenhanced plant growth (Muir, 2001). This can cause problems in the early morning when low oxygen levels, the result of plant respiration, may lead to the death of invertebrates and fish. This process can be compounded when algal blooms, through their decay, further reduce the oxygen content of water. (Klaff, 2002). The growth and/or decay of bottom-dwelling macro-algae can also lead to the deoxygenating of sediments. Certain algal species, particularly freshwater blue-green algae, can produce toxins, which may seriously affect the health of mammals, including humans, fish and birds (Muir, 2001). This occurs either through the food chain, through contact with, or ingestion of, the algae. Algal species also cause fish deaths, for example by physically cloggingor damaging gills, and causing asphyxiation. Eutrophication ultimately detracts from biodiversity, through thedominance of nutrient-tolerant plants and algal species. These tend to displace more sensitive species of higher conservation value, changing the structure of ecological communities (Muir, 2001). Eutrophication can also adversely affect a wide variety of water uses such as water supply (e.g. algae cloggingfilters in treatment works), livestock watering, irrigation, fisheries, navigation, water sports, angling and nature conservation (Hutchinson, 1970). It can give rise to undesirable aesthetic impacts in the form of increased turbidity, discoloration, unpleasant odors, slimes and foam formation (Klaff, 2002).
    5. 5. After examining the consequences of eutrophication we can see there is both temporary, butmore irreversible effects on aquatic ecosystems. It may lead to the death of invertebrates and fish from over-population of algal blooms, and through their decay reducing the oxygen content of water. The deoxygenation of sediments can produce toxins, which may seriously affect the health of mammals, including humans, fish and birds. This may occur either through the food chain, through contact with, or ingestion of the algae or even physically clogging or damaging gills, and causing asphyxiation. Eutrophication ultimately will continue to reduce biodiversity, through the dominance of nutrient-tolerant plants and algal species unless we see a change in agricultural activities. At the rate eutrophication is negativelyeffecting aquatic ecosystems, this will soon begin to have an effect on humans as well. If thebiodiversity decreases even more dramatically than it already is we may find ourselves being responsible for the extinction of many fish and as a result could lose many commerciallyimportant species such as salmon or tuna that are purchased and consumed daily. This couldeliminate many fishing-dependent industries as well. Even recreational fishing could come to an end as fresh water tourist lakes become depleted of aquatic plants.
    6. 6. GROWTH LIMITING FACTORS:Like all ecosystems, aquatic environments thrive best at optimal or “preferable” ranges of certain factors.Specifically aquatic ecosystems are dependent on aspects of water chemistry including water temperature,dissolved oxygen, pH, nutrients, and also sufficient sunlight for plants conducting photosynthesis. Iforganisms cannot properly adapt to environmental changes, it can substantially damage the growth of allsurroundings.Human inputs have been one of the leading causes of altered habitat quality in aquatic ecosystems.Agricultural activities have increased delivery of nitrogen and phosphorus to fresh waters via sewage,fertilizer runoff, soil erosion, animal waste and industrial discharges, Though nitrogen and phosphorusare essential components of structural proteins, enzymes, cell membranes, nucleic acids, etc. and helputilize light/chemical energy they also have many harmful effects. At unnaturally high rates, nitrogen andphosphorous promote the rapid growth of algae. However the over-stimulation of algal growth leads tobiological and chemical responses that can severely decrease water quality & water clarity. Algae drapeover the water surface preventing light to be delivered to the plants below for photosynthesis inhibitingtheir ability to metabolize prevent ing growth or repair. Furthermore, increased production of algae alsoresults in increased dead matter of algae that fuels bacterial growth in bottom waters and sedimentscausing over-consumption of oxygen by bacterial metabolisms. <--- 2011/02/eutrophication.html
    7. 7. WHAT ABOUT BIOMASS? WHAT IS HYPOXIA?In an aquatic system, increases inbiomass of organisms such as algaeduring eutrophication result in increasedproduction in food webs sustaining fishand shellfish, even producing higher fishyields. However, it is common when algalbiomass builds during blooms thatresulting algal dead matter sinks tobottom waters and sediments ignitingbacterial population sizes. With increasedbacteria consuming excessive rates ofalgae there is a high metabolic of oxygen caused by thebacteria. If the rates of oxygen dissolvingin water are slower than bacterialmetabolism consuming it, then bottomwaters become hypoxic. Thisphenomenon occurs when oxygen inreduced in concentration to a point whereit becomes detrimental to aquaticorganisms living in the system. Aquaticsystems lacking dissolved oxygen becomeanaerobic creating conditions stressful oreven lethal for marine invertebrates andfish. Eventually, this can become the birthplace of “Dead Zones” where no livingorganisms can survive or reproduce.
    8. 8. HYPOTHESIS OF EUTROPHICATIONIt may be assumed that with the addition of nutrients such as phosphorous and nitrogen byeutrophication there would be a positive affect on aquatic plants, it is evident that theresulting increased biomass of aquatic plant life results in more negative effects than positiveones. Aquatic plants need proper conditions to survive, however algal blooms diminish theirability to properly metabolize using photosynthesis and without photosynthesis all aquaticlife can only begin to deplete.