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Productivity and Food Webs

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Productivity and Food Webs World Net Primary Productivity . 55.4 see Fig text Lecture 18 Productivity and (Rounded Estimates) in your book NPP World NPP Biomass World Biomass Food Webs Ecosystem (g m-2 y-1) (x1015 g y-1) (g m-2 ) (x1015 g ) Photosynthesis and Respiration on ecosystem Desert 80 0 .5 720 15 Grassland, etc. 500 18 4000 125 scales Cultivated Land 760 8 1000 14 Moist Forest 1000 12 30,000 900 Tropical Forest 2000 18 45,000 750 18 04 LAND TOTAL 56 Analysis of global productivity Estuaries 2000 3 1500 2.6 Energy flow through trophic levels and Continental Shelf 500 5 20 .3 Open Ocean 100 40 3 1.0 ecosystems MARINE TOTAL 48 3.9 Three weeks in the life of a food web (DVD) World NPP = NPP × ∑Area 1015g = 1 Gigaton World Biomass = Biomass × ∑Area World Net Primary Productivity World Net Primary Productivity (Rounded Estimates) % of surface (Rounded Estimates) NPP World NPP Biomass World Biomass NPP World NPP Biomass World Biomass Ecosystem (g m-2 y-1) (x1015 g y-1) (g m-2 ) (x1015 g ) Ecosystem (g m-2 y-1) (x1015 g y-1) (g m-2 ) (x1015 g ) Desert 80 0 .5 720 15 Desert 80 0 .5 720 15 Grassland, etc. 500 18 4000 125 Grassland, etc. 500 18 4000 125 Cultivated Land 760 8 1000 14 Cultivated Land 760 8 1000 14 Moist Forest 1000 12 30,000 900 Moist Forest 1000 12 30,000 900 Tropical Forest 2000 18 45,000 750 Tropical Forest 3.3% 2000 18 45,000 750 18 04 18 04 LAND TOTAL 56 LAND TOTAL 56 Estuaries 2000 3 1500 2.6 Estuaries 2000 3 1500 2.6 Continental Shelf 500 5 20 .3 Continental Shelf 500 5 20 .3 Open Ocean 100 40 3 1.0 Open Ocean 65% 100 40 3 1.0 MARINE TOTAL 48 3.9 MARINE TOTAL 48 3.9 World NPP = NPP × ∑Area World NPP = NPP × ∑Area World Biomass = Biomass × ∑Area World Biomass = Biomass × ∑Area 1 Marine Food Web Shore Birds Sea Bass Flow of Carbon (Energy) Through a R Trophic Level (or organism) Trophic n Level n Blue Crab Barnacle Sea Worms P In An P Zooplankton n -1 n Bn Pn-1 = Productivity of trophic level n-1 Dn Living D = Portion of P not consumed Fn Shore Shrimp n n-1 Biomass Phytoplankton I = Amount Ingested Dead n Organic Fn = Fecal matter produced Matter To Detritus An = Amount assimilated and available Food Web Rn = Respiration B = Biomass in trophic level n Detritus n Photo Source: The Lloyd Center at UMass Pn = Productivity at trophic level n R Marine Food Web Shore Birds Efficiencies n Trophic Sea Bass Exploitation Eff iciency ( EE) Level n EE = I / P × 1 0 0 Blue Crab n n-1 I A Pn -1 n n Pn Barnacle B n Sea Worms Assim ilation Eff iciency ( AE) Dn Living Fn Zooplankton AE = A / I 1 0 0 Biomass n n × Dead Organic Matter Shore Shrimp Production Eff iciency ( PE) To Detritus Phytoplankton Food Web PE = Pn / An × 1 0 0 Ecological Efficiency = (EE)(AE)(PE) (trophic transfer efficiency) = P / P × 100 n n-1 Detritus ≈ 10 % to 20 % Photo Source: The Lloyd Center at UMass 2 Marine Food Web Shore Birds Grazing Food Web RA RH RH RH Primary producers 2nd Carnivore A I A P I GPP NPP 1st herbivores carnivore Sea Worms D D F F Zooplankton POC = Particulate Org anic Carbon Heat DOC = Dissolved Net Ecosystem Production Detritus RH Phytoplankton Org anic Carbon = GPP - RA - ∑ RH RH DOC POC Etc. Etc. Detrivores Microorganisms “Refractory” Carbon Detritus Microbial Food Web Detrivore Food Web Photo Source: The Lloyd Center at UMass Pyramids of Biomass and Energy Another Representation of Energy Flow Through an Ecosystem Biomass See also Energy Flow Fig. 55.7 Process: See also (grams/m2) (calories/m2/day) See also in text Photosynthesis Fig. 55.3 in text Grassland Excretion and Death Biomass in green Digestion, assimilation, & growth plants, accessible to The majority of energy herbivores Respiration Photosynthetic Organisms is lost to respiration and is unavailable to Forest (Our world depends on this for food and fiber) other organisms Detritivores Biomass tied up in wood & unavailable to herbivores Herbivores Open Ocean Primary Respiration carnivores Inverted Pyramid of Biomass Secondary carnivores Producers Herbivores Carnivores 3 Human Appropriation of Photosynthesis Direct Use Diverted Productivity Productive capacity lost by land conversion & Take Home Messages (food, fuel, (crop waste, lumber Take Home Messages desertification or fiber, timber) waste, burning etc) Small% overuse Massive amounts of carbon flow through photosynthesis largest% (open land to cities, forests each year to cropland etc.) Marine and Terrestrial ecosystems roughly same amount Medium% Carbon/energy flows through food webs Detritivores 80-90% dissipated with each trophic transfer In mature ecosystems, nearly all that is produced is eaten Herbivores Humans have co-opted a significant fraction of global primary productivity Between 10 and 55% Primary Respiration has been appropriated carnivores (difficult to estimate) Secondary carnivores Blue Planet DVD Three weeks in the life of a Marine Food Web Think About: • The massive amount of energy and carbon the phytoplankton must be processing to support such a diversity and biomass at higher trophic levels • How the information in DNA could be controlling all of these complex processes 4.
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