Chapter 3 Ecosystems and Energy

1. Chapter 3Ecosystems and Energy

2. Chesapeake Bay Salt Marsh Ecosystem • Chesapeake is an estuary (affected by tides) • Tidal marshes are special because they: • Purify water • Protect the coastline • Provide shelter and breeding grounds for aquatic species • Are one of the most productive ecosystems in terms of energy!

3. Chesapeake Ecosystem • Water is salty on the ocean side, brackish in the middle, and fresh water at the head of the bay • Base of the food web is cordgrass (shown in photo). This has an advantage since it can grow under saline conditions and periodic submergence due to tides. • The bay receives high nutrient levels (N,P) from treated human sewage and farm runoff, which promotes algal growth (cordgrass too), which serve as food for other organisms.

5. What is the Chesapeake like? Major kinds of life in the salt marsh ecosystem: • Insects • Millions of mosquitoes and horseflies • Birds • Sparrows, hulls, clapper rails • Shrimp, lobster, crabs, barnacles, worms, clams and snails are all present and seek refuge in the cordgrass. • No amphibians live there (salt) but the terrapin turtle does. • Numerous species of fish call the Chesapeake home…including: • Sea trout, croaker, bluefish, striped bass • Young species enter from the ocean. • Meadow voles live along the shores, and are excellent swimmers too….and they eat leaves, stems and many insects

7. What does the Chesapeake Tell Us? • This ecosystem is interdependent upon human inputs (pollutants such as nitrates, phosphates and others like oil, gas, etc.) and also it’s natural setting. • It remains one of the most productive ecosystems on the planet…but it is in peril! • Too much pollution…overfishing…too many nutrients (eutrophication)…oil spills….growing population…. • It is important to protect our most productive ecosystems!

8. Chesapeake Ecosystem • Chesapeake also serves as an excellent case study in how energy flows through an ecosystem!

10. Overview of Chapter 3 • What is Ecology? • The Energy of Life • Laws of Thermodynamics • Photosynthesis and Cellular Respiration • Flow of Energy Through Ecosystems • Producers, Consumers and Decomposers • Path of Energy Flow: Who Eats Whom • Ecological Pyramids • Ecosystem Productivity

11. Ecology • Ecology • “logy” study of, “eco” house – study of one’s house • The study of interactions among and between organisms in their abiotic environment • Biotic - living environment • Includes all organisms • Abiotic - non living or physical environment • Includes living space, sunlight, soil, precipitation, etc.

12. Ecology • Organisms interact with biotic components, but also effect many physical and chemical processes • Physical – walking on soil • Chemical – CO2, O2, wastes

13. Ecology • Ecologists are interested in the levels of life above that of organism

14. Ecology Definitions • Species - A group of similar organisms whose members freely interbreed to produce fertile offspring • Population - A group of organisms of the same species that live in the same area at the same time • Community - All the populations of different species that live and interact in the same area at the same time • Ecosystem - A community and its physical (abiotic) environment • Landscape - Several interacting ecosystems (ex: bear hunting for salmon in a river, living in adjacent forest)

15. Ecology Part of Earth that contains living organisms Community and physical environment All populations of species in an area Group of same species Individuals

16. Ecology • Coral Reef communities – similar to rainforests for number of species and productivity • Threatened with changing climate • How can communities be protected from warming waters? • What could loss mean?

17. Ecology • Biosphere contains earth’s communities, ecosystems and landscapes, and includes: • Atmosphere- gaseous envelope surrounding earth • Hydrosphere- earth’s supply of water • Lithosphere- soil and rock of the earth’s crust

18. Ecology Atmosphere Lithosphere Hydrosphere

19. Energy of Life • The ability or capacity to do work • Chemical, Thermal, Mechanical, Nuclear, Electrical, and Radiant/Solar (below)

20. Energy of Life • Solar radiation is the primary source of energy on planet Plants turn solar radiation into food

21. Energy of Life • Energy exists as: • Potential energy (stored energy) • Kinetic energy (energy of motion) • Potential energy is converted to kinetic energy as arrow is released from bow

22. Thermodynamics • Study of energy and its transformations • System- the object being studied • Closed System- Does not exchange energy with surroundings (rare in nature) • Open System- exchanges energy with surroundings

23. Laws of Thermodynamics • First Law of Thermodynamics • Energy cannot be created or destroyed; it can change from one form to another • Energy is absorbed by water and plate, but not lost

24. Laws of Thermodynamics • Second Law of Thermodynamics • When energy is converted form one form to another, some of it is degraded to heat • Heat is highly entropic (disorganized) • Water in sunlight will get warmer • Engine converts chemical energy of gasoline into mechanical energy inefficiently

25. Photosynthesis • Biological process by which energy from the sun (radiant energy) is transformed into chemical energy of carbohydrate (sugar) molecules 6 CO2 + 12 H2O + radiant energy Chlorophyll in plants C6H12O6 + 6 H2O + 6 O2

26. Cellular Respiration • The process where the chemical energy captured in photosynthesis is released within cells of plants and animals • This energy is then used for biological work C6H12O6 + 6O2 + 6 H2O 6 CO2 + 12 H2O + energy

27. Photosynthesis and Cellular Respiration

28. Life without Sun • 1970s – discovered hydrothermal vents in deep ocean (200oC or 392oF) • Rich ecosystem supported without light • Bacteria perform chemosynthesis • Similar to photosynthesis, but use chemical (H2S) not sunlight

29. Energy Flow Through Ecosystems • Passage of energy through an ecosystem

30. Food Chains- The Path of Energy Flow • Energy from food passes from one organism to another based on their Trophic Level • Definition: An organism’s position in a food chain, which is determined by its feeding relationships • First Trophic Level: Producers • Second Trophic Level: Primary Consumers • Third Trophic Level: Secondary Consumers • Decomposers are present at all trophic levels

31. Food chains • Autotrophs = Producers • Auto “self” and tropho “nourishment” • Produce own food from inorganic material • Ex: plants via photosynthesis and hydrothermal vent bacteria via chemosynthesis

32. Food chains • Heterotrophs = Consumers • heter “different” and tropho “nourishment” • Uses bodies of other organisms as food • Omnivores – eat both plants and animals

33. Food chains • Consumers of detritus (detritivores) • Eat dead material such as leaves, carcasses, feces • Ex: crabs, worms, millipedes, snails

34. Food chains • Decomposers or saprotrophs • sapro“rotten” and tropho “nourishment” • Breakdown dead organic material • Release inorganic molecules (CO2 and nutrients) that producers can use • Ex: fungus, bacteria • Involved in all aspects of food chains

35. Food Web • Food web visualizes feeding relationships within a community • More complex than food chain • Still simplified compared to nature

37. Humans and Antarctic food web • Base of web is algae, which is eaten by krill • Krill are eaten by many larger organisms • Wastes of whales resupply nutrients for algae and krill • Whaling can remove a critical component for decomposers • Ozone layer depletion allows UV rays to destroy phytoplankton • Climate change is warming the ocean, lowering pH, decreasing dissolved oxygen; altering ecosystem!

39. Ecological Pyramids • Graphically represent the relative energy value of each trophic level • Important feature - large amount of energy is lost as heat between trophic levels • Three main types • Pyramid of numbers • Pyramid of biomass • Pyramid of energy

40. Pyramid of Numbers • Illustrates the number of organisms at each trophic level • Fewer organisms occupy each successive level • Does not indicate: • biomass of organisms at each level • amount of energy transferred between levels

41. Pyramid of Biomass • Illustrates the total biomass at each successive trophic level • Biomass: measure of the total amount of living material • ~90% reduction in biomass through trophic levels • 100 to 10

42. Pyramid of Energy • Illustrates how much energy is present at each trophic level and how much is transferred to the next level • Most energy dissipates between trophic levels • Lost as heat and energy to maintain each level • Explains why there are so few trophic levels

43. Ecosystem Productivity • Gross Primary Productivity (GPP) • Total amount of energy that plants capture and assimilate in a given period of time • Cellular respiration (R) • Plants use some energy of GPP to maintain themselves • Plants respire too • Net Primary Productivity (NPP) • Productivity after respiration losses are subtracted • What is available as food for other organisms

44. Ecosystem Productivity • GPP is similar to gross pay in paycheck • R is similar to taxes • NPP is similar to take home pay Net Primary Productivity (plant growth per area per time) Gross Primary Productivity (total photosynthesis per area per time) Plant Cellular Respiration (per area per time) = -

45. Variation in NPP by Ecosystem • Coral reefs are near tropical rain forests • Humans consume a large amount of global NPP • ~30% but we make up ~0.5% of biomass • This represents a threat to planet’s ability to support both human and non-human inhabitants • See PAGE 52 (bottom)!

46. Energy and Climate Change • Humans use a large portion of global NPP • If we use more biomass as energy rather than fossil fuels, our use of NPP may increase • Corn as fuel, wood for heat • How can we balance our needs with other organisms?

47. ENVIRONEWS • Use of satellite imagery improves biomass estimates of forests • Help protect tropic forests in developing countries • Developed countries pay to keep forests intact • Need to ground truth satellite models with monitoring data from forest