PowerPoint PresentationU6220: Environmental Chem. & Tox. Thursday, July 07 2005Biotic Control over Ecosystems Chapin et al (1997), Science, Vol. 277, p.500-503Slide 4Defining the EcosystemSlide 6Chemical Elements (the Periodic Table) and those essential for lifeChemical Elements - Essential for life CarbonChemical Elements - Essential for life NitrogenChemical Elements - Essential for life PhosphorusChemical Elements - Essential for life Carbon:Nitrogen:Phosphorus RatiosChemical Elements - Essential for lifeO2 solubility and ventilationDissolved O2 and Biological DemandSlide 15Dissolved O2 and lake trophic statusSlide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Slide 27Slide 28Slide 29Slide 30Slide 31Slide 32Slide 33Slide 34Slide 35Chesapeake Bay ProgramNitrogen Loads“Total” Nitrogen Load to the BayNitrogen in the SusquehannaPhosphorus in the SusquehannaFactors Affecting Delivery and TrendsSlide 42““Monday is an awful way to spendMonday is an awful way to spend1/7 of your week…”1/7 of your week…”““A clear conscience is usually a the signA clear conscience is usually a the signof a bad memory”of a bad memory”““I used to have an open mind,I used to have an open mind,but my brains kept falling out”but my brains kept falling out”A)A)Ecosystem functioningEcosystem functioningB)B)Biological Oxygen DemandBiological Oxygen DemandC)C)Detergents and PhosphatesDetergents and Phosphates•Phosphorus control: A US case-studyPhosphorus control: A US case-studyD)D)Coastal Hypoxia: From the Gulf of Mexico to Coastal Hypoxia: From the Gulf of Mexico to the Chesapeakethe ChesapeakeU6220: Environmental Chem. & Tox.Thursday, July 07 2005Biotic Control over EcosystemsChapin et al (1997), Science, Vol. 277, p.500-503Ecosysts Processes: productivity and nutrient cyclingRegional Processes: trace gases and nutrient fluxesCommunity Processes: competition and predationEcosyst Services: benefits to humans from above processesBiotic Control over EcosystemsChapin et al (1997), Science, Vol. 277, p.500-503““Changes in species composition are likely to alter ecosystem Changes in species composition are likely to alter ecosystem processes through changes in functional traits of biota”processes through changes in functional traits of biota”The number of species in a community is a measure of the The number of species in a community is a measure of the probability of the presence of species with particularly probability of the presence of species with particularly important important traitstraitsGreater diversity allows a greater range of traits to be Greater diversity allows a greater range of traits to be represented in the ecosystem providing opportunities for more represented in the ecosystem providing opportunities for more efficient resource use in a efficient resource use in a variable environmentvariable environmentNo two species are ecologically redundant, even if they appear No two species are ecologically redundant, even if they appear similar in their ecosystem effects under one particular set of similar in their ecosystem effects under one particular set of environmental conditions.environmental conditions.Defining the EcosystemBiology is not the sole subject of ecosystem studies Biology is not the sole subject of ecosystem studies  The The flow of energy and flow of energy and materialsmaterials (i.e. water, chemicals) into and out of biological communities (i.e. water, chemicals) into and out of biological communities definesdefines the main theme of ecosystem studies the main theme of ecosystem studiesDefining the EcosystemThere exists an inseparable relationship between the flow of energy and the There exists an inseparable relationship between the flow of energy and the flow of nutrient elements (i.e. N, P, K, Ca, etc)flow of nutrient elements (i.e. N, P, K, Ca, etc)Chemical Elements (the Periodic Table) and those essential for lifeOf the 103 elements in the Periodic Table, only 24 are required by organismsRequired elt Required for some life formsToxic eltMacronutrients: Macronutrients: Required in large Required in large amountamount (“Big Six”: C, (“Big Six”: C, N, P, S, O, H)N, P, S, O, H)Micronutrients: small Micronutrients: small or moderate amountor moderate amountChemical Elements - Essential for lifeCarbonCarbon forms three-dimensional molecules of large size Carbon forms three-dimensional molecules of large size and complexity in organic (carbon-containing) compounds and complexity in organic (carbon-containing) compounds that form large molecules (amino acids, sugars, enzymes, that form large molecules (amino acids, sugars, enzymes, DNA), and other chemicals vital to life on Earth. DNA), and other chemicals vital to life on Earth.Chemical Elements - Essential for lifeNitrogenNitrogen (along with carbon) is the essential element that allows formation of amino acids ( proteins) and DNA.Proteins contain up to 16% NChemical Elements - Essential for lifePhosphorusPhosphorus is the “Phosphorus is the “energy elementenergy element” occurring in ” occurring in compounds called ATP and ADP important for energy compounds called ATP and ADP important for energy transfer processes and DNA.transfer processes and DNA.Chemical Elements - Essential for lifeCarbon:Nitrogen:Phosphorus RatiosOrganisms Organisms activelyactively concentrate certain elements essential for life: concentrate certain elements essential for life:  Algae concentrate Iron (Fe) 100,000 times Algae concentrate Iron (Fe) 100,000 times vsvs. its concentration . its concentration in the Oceanin the Ocean• Most organisms keep a rather Most organisms keep a rather constant chemical composition constant chemical composition  Algae and plankton C:N:P ratio Algae and plankton C:N:P ratio of 106:16:1 (Redfield Ratio)of 106:16:1 (Redfield Ratio) Soil microbes maintain a Soil microbes maintain a relatively constant proportion of relatively constant proportion of nutrients in their biomass (and at nutrients in their biomass (and at higher levels than the OM they higher levels than the OM they decompose)decompose)Chemical Elements - Essential for life• Availability of some elements (particularly N & P) is Availability of some elements (particularly N & P) is often often limitedlimited and the supply of these elements may control the rate and the supply of these elements may