The document summarizes key topics in ecosystems, including: 1) Ecosystems are defined as the sum of all organisms in an area and the abiotic factors they interact with. Energy flows and matter cycles through ecosystems. 2) Gross primary production (GPP) is the amount of light energy converted to chemical energy by autotrophs. Net primary production (NPP) is the amount remaining after respiration. NPP determines the base of the food chain. 3) Pyramids illustrate the transfer of numbers, biomass, and energy between trophic levels, with typically only 10% passing to each higher level.

1. Ch 55 Ecosystems Jeff Jewett ACS June 2010 Ver 1

2. Ecosystem Sum of all organisms in an area AND all the abiotic factors with which they interact Communities PLUS abiotic factors Boundaries are rarely clear-cut, may depend on scale of question

3. Ch 55 Key Topics Conservation of Energy/Mass GPP/NPP and limitations Energy Transfer  pyramids of energy/biomass Biogeochemical Cycles (C, N, H 2 0) Human impact on biogeo. Cycles Global warming, eutrophication, biomagnification, acid rain, ozone hole

4. Energy Flows, Matter Cycles Energy enters (usually as sunlight) Converted to biomass (chemical energy) by autotrophs Passed to heterotrophs (incl. decomposers) Dissipated as heat

5. Energy Flows, Matter Cycles (2) Chemical elements (C, N, P) are cycled between abiotic and biotic parts of ecosystem (Law of Conservation of Mass) Matter continuously cycles (not created or destroyed) 2 nd law of Thermodynamics: Energy conversions are never 100% efficient, therefore some is always lost as heat Ecosystems require constant input of energy

6. Trophic Levels Autotrophs = primary producers (redundant) Photoautotrophs rely on light for energy (by FAR the most common) Chemoautotrophs oxidize naturally occuring inorganic compounds as fuel (common in hot springs, deep-sea volcanic vents) All of the ecosystem depends on autotrophs!

7. Trophic Levels (2) Heterotrophs depend directly or indirectly on autotrophs eat things that are alive or were alive Consumers & decomposers (detritivores) Detritivores – fungus, bacteria, insects (FBI) eat detritus (non-living organic material such as feces, dead critters, fallen leaves, wood) Consumers – primary, secondary, tertiary, quarternary (higher levels rare)

8. http://image.tutorvista.com/content/ecosystem/food-web-terrestrial-aquatic-ecosystem.jpeg

9. 55.2 Energy GPP Gross Primary Production (GPP) = Amount of light energy converted to chemical energy (sugars) per time (rate of photosynthesis) Some of this energy is used by the plant for life (cellular respiration) Some is converted into biomass, such as starch storage or structural components (new growth)

10. NPP – a very important ecological statistic! Net Primary Productivity – amount of sugars left over after respiration, per unit time (rate of new biomass production) NPP = GPP – R Value of NPP gives the size of the base of the food chain (how much total food is there for consumers?) NPP highest where it is warm/wet (tropical rainforest)

11. Global NPP, 2008 NASA Earth Observatory: http://earthobservatory.nasa.gov/IOTD/view.php?id=38889

12. June NPP http://www.uwsp.edu/geo/faculty/lemke/geog101/images/14c_npp_junemap_nasa.jpg

13. December NPP http://www.uwsp.edu/geo/faculty/lemke/geog101/images/14e_npp_decmap_nasa.jpg

14. Human Appropriation of NPP SKIP THIS SLIDE http://sedac.ciesin.columbia.edu/es/hanpp.html http://earthobservatory.nasa.gov/Features/HANPP/hanpp.php

15. Aquatic NPP Limitation Light - <50% of light below 15m (photic zone) Nutrient Limitation (more important) – Nitrogen or Phosporus, tend to sink, rapid uptake by phytoplankton, Iron too Nutrient limitation leads to high NPP in river deltas or areas with upwelling

16. Terrestrial NPP Usually limited by heat or water Evapotranspiration is how much water is evaporated from land and transpired from plants (driven by heat and precipitation)

17. Limiting Nutrient A nutrient that when added to an ecosystem increases NPP Most often N, P (that’s what in fertilizer!), same as aquatic

18. Pyramids! Numbers Biomass Energy http://upload.wikimedia.org/wikipedia/commons/a/af/All_Gizah_Pyramids.jpg

19. Pyramid of Net Production Rule of 10 : only about 10% of the energy is passed up each trophic level

20. Biomass Dry mass of all living material in an area How do you calculate? (Hard) Cut everything, dry it, mass it (below ground very tricky) Measure everything, estimate volume, estimate mass Secondary measures like ocean fish harvest

21. Biomass Pyramid Why do some people eat a vegetarian diet for environmental reasons? http://earth.rice.edu/MTPE/bio/biosphere/topics/energy/biomass_pyramid.gif

22. Biogeochemical Cycles Energy flows, matter cycles!!! Carbon, Nitrogen, Phosphorus, Water

23. Nitrogen Cycle 80% of atm is N 2 , but this inorganic form is not available to eukaryotes Plants use “organic” NH 4 + (ammonium) and NO 3 - (nitrate)

24. Humans have more than doubled “organic”/fixed N supply!!! Fertilizers, combustion, tillage practices, deforestation, legume cultivation all increase fixed N supply Acid rain/deposition, algal blooms, ecosystem changes

25. Harmful Algal Bloom (“Red Tide”) Photo credit: NOAA: http://www.noaanews.noaa.gov/stories2009/20090520_ecosystems.html

26. Eutrophication: Spring phytoplankton bloom off New Zealand Photo courtesy NASA Earth Observatory

27. Eutrophication Lake Valencia, Venezuala NASA Earth Observatory: http://earthobservatory.nasa.gov/IOTD/view.php?id=5001

28. Decomposers recycle nutrients http://en.wikipedia.org/wiki/File:Fungi_in_Borneo.jpg Heterotrophs Saprotrophs (old term): eat dead/dying organisms Fungi, Bacteria, Insects Fungi can digest lignin, so main forest decomposers http://en.wikipedia.org/wiki/File:Earthworm.jpg

29. Eutrophication Nutrient addition (P in inland lakes, N offshore) from sewage, agricultural run-off, detergents, fertilizers Lead to temporary algal bloom Algal die-off leads to massive bloom in decomposing bacteria Bacteria consume all dissolved O 2 Fish kills 

30. Fish Kill at the Salton Sea, CA Image from Encyclopedia of Earth: http://www.eoearth.org/image/SaltonSeaFishKill.jpg

31. Eutrophication, continued Reduce seagrasses (loss of light) Cascading food web effects  loss of fish/shellfish that depend on seagrasses Some algal blooms are toxic Riparian/wetland buffers help (no more straight rivers!) Don’t over-apply fertilizer “ Precision Agriculture” Reduce livestock densities

32. Biomagnification Long-lived (persistent), fat-soluble molecules build up in organism ( bioaccumulation) Concentration of these fat soluble substances increase as you go up trophic levels  biomagnification! DDT, PCBs (“Persistent Organic Pollutants” or POPs) Mercury & other metals Biomagnification Animation

33. Great Lakes Population

34. Great Lakes Biomagnification Peak water PCB concentation in 1994: 0.00000036 ppm Bioaccumulation of 69,000 X Herring Gulls have 3.4 MILLION times more PCB than the water!

35. Ozone O 3 Bad down low (smog), good up high Blocks UV radiation in stratosphere (17-25km up) More UV  skin cancer, cataracts, Decrease up to 50% in Antarctica, up to 10% in mid-latitudes NASA animation

36. Atmospheric (Stratospheric) Ozone Depletion