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Chapter 54 Ecosystems Overview Food Chains and Food Webs Productivity Ecological Pyramids Biomagnification Nutrient Cycles Global Warming Ecosystems -The Community along with: Nutrient Cycling Energy Flow Energy Transfer in Ecosystems Food / Energy Pyramid Primary Consumers eat producers, incorporating the energy into the next level. Only 10 % of energy consumed moves to next level Animals loose 90% of the energy at each level Why are Big Fierce Animals so Rare?? Consumers are Heterotrophs Limited by Thermodynamcis Simple Food Chains Trophic Levels Both Marine and Terrestrial Productivity What is it? Season effects varies by ecosystem Productivity –Amount of food in an ecosystem Primary productivity is growth of producers (Biomass) the baseline for the entire ecosystem. Gross productivity is the total amount of food produced or ingested at that trophic level. Net productivity is amount available to next trophic level, after respiration Measured by dry weight or calories Productivity rates: Kelp beds have highest productivity Tropical rainforest highest per sq. meter on land, but only covers 3.3 % of globe Open ocean, one of the lowest, but because it covers 65.0 % it equals rainforest Marsh lands nearly equal tropical rainforest productivity Summary of satellite data on global primary productivity from 1997 to August 2000 Winter NORTH AMERICA SPAIN ATLANTIC OCEAN AFRICA Spring Ocean Currents Upwelling Wind from the north starts surface ocean water moving c. Deep, cold water moves up to replace water moving west Earth's rotational force deflects moving water westward Fig. 55-7 EXPERIMENT B C D E F G Shinnecock Bay Moriches Bay Atlantic Ocean A Phytoplankton density (millions of cells per mL) RESULTS 30 Ammonium enriched 24 Phosphate enriched 18 Unenriched control 12 6 0 A B C D E Collection site F G Table 55-1 Food Webs Energy transfer follows trophic levels Many animals eat at several trophic levels Omnivores: like most of us At salad bar you’re a herbivore Eating a burger makes you a carnivore marsh hawk Higher Trophic Levels Sampling of connections in a Tall grass prairie food web crow upland sandpiper garter snake frog weasel spider Second Trophic Level sparrow earthworms, insects First Trophic Level badger coyote prairie vole grasses, composites pocket gopher ground squirrel Energy Transfer in Ecosystems Food / Energy Pyramid Only 10 % of energy consumed moves to next level Why are Big Fierce Animals so Rare?? Consumers are Heterotrophs Limited by Thermodynamics Laws of Thermodynamics Energy = ability to do work 1st Law = Total amount of energy is a constant 2nd Law = Some energy is lost in every transfer, not 100% efficient Most energy lost as heat Autotrophs about 1% efficient (light–sugar) Heterotrophs about 10% efficient Energy Pyramid Pyramid of Numbers Nutrients Cycle Elements change form, but are not lost No more carbon now than when the dinosaurs lived !! May be trapped in bio-inactive forms Ice, fossil fuels Held together in chemical bonds Breaking bonds – releases energy Uses energy to form bonds Cycles: Nutrient cycles to learn: Water Carbon Nitrogen Carbon Cycle Large reservoirs in rocks (99%), fossil fuels Associated with Greenhouse Effect Build up of CO2 , CH4 etc. in atmosphere Raise sea levels – flooding islands, coasts More severe weather ?? Food chain moves through Carbon cycle Nitrogen Cycle Largest pool is in atmosphere (80%) a generally bio-inactive form Nitrogen fixing bacteria capture it from air Many native plants have nitrogen fixing root nodules After water the most growth-limiting nutrient Nitrogen important for Autotrophs to make protein Protein breakdown releases it back to environment in urine Nitrogen Cycle Always need to replenish agriculture fields with fertilizer. Denitrifying bacteria release it back to atmosphere Tightly cycled in Ecosystems Needed to make amino acids Nitrogen Metabolism In amino acids, nucleotides Nitrogen fixing bacteria (N2 ->NH3) In soil, and some plant root nodules Nitrifying bacteria convert NH3 -> NO2 In soil, or biotower in treatment plant Denitrifying bacteria N02 -(Nitrite) or N03 (Nitrate) to atmospheric N2 In soil, counter-act fertilizers Forests and Nitrogen Cycle Most of nitrogen tied up in a tree’s Biomass Soils tend to be nutrient poor Often highest in later stages of succession Burning trees releases nutrients Soil fertility only lasts a few seasons Nitrogen is leached out with rains Classic problem with Slash and Burn Fig. 31.8 Hubbard Brook Loss of Nitrate from a forest after clear cutting 1620 1850 1850 (pocket only) 1990 Remaining virgin forest Extent of deforestation in the United States Bioaccumulation & Biomagnification Bioaccumulation Build-up of substance within body Lead in humans Calcium from milk to already strong bones Biomagnification build up of of substance along food chain DDT and birds Rachel Carlson’s Silent Spring Build up of DDT along Food Chain Bioaccumulation Biomagnification Fig. 34.1 Peregrine falcon DDT Residues (ppm wet weight of whole live organism) Ring-billed gull fledgling (Larus delawarensis) Herring gull (Larus argentatus) Osprey (Pandion haliaetus) Green heron (Butorides virescens) Atlantic needlefish (Strongylira marina) Summer flounder (Paralychthys dentatus) Sheepshead minnow (Cyprinodon variegatus) Hard clam (Mercenaria mercenaria) Marsh grass shoots (Spartina patens) Flying insects (mostly flies) Mud snail (Nassarius obsoletus) Shrimps (composite of several samples) Green alga (Cladophora gracilis) Plankton (mostly zooplankton) Water Data for a Long Island, NY estuary in 1967 75.5 18.5 13.8 3.57 2.07 1.28 0.94 0.42 0.33 0.30 0.26 0.16 0.083 0.040 0.00005 Greenhouse Effect Gasses trap heat in atmosphere Carbon dioxide, methane, CFC’s Anthropogenic use of these gasses is increasing Earth’s temperature appears to be warming Hard to measure a world temperature Greenhouse Effect Sun’s rays penetrate atmosphere. Enters as light not as heat. Hitting the earth, light changes to heat. Surface radiates heat. Greenhouse gases absorb some heat and radiate it back toward Earth. Increased greenhouse gases trap more heat near Earth’s surface. Correlation in changes in atmospheric CO2 with ice ages and interglacials Fig. 55-21 14.9 390 14.8 380 14.7 14.6 370 Temperature 14.5 360 14.4 14.3 350 14.2 340 14.1 CO2 330 14.0 13.9 320 13.8 310 13.7 13.6 300 1960 1965 1970 1975 1980 1985 Year 1990 1995 2000 2005 Satellite image of an iceberg roughly the same size as Connecticut Antarctica 2000 National Snow and Ice Data Center Fig. 34.6 Fig. 55-24 Chlorine atom O2 Chlorine O3 ClO O2 ClO Cl2O2 Sunlight Fig. 55-24 Chlorine atom O2 Chlorine O3 ClO O2 ClO Cl2O2 Sunlight “Tragedy of the Commons”
