Energetics of Marine Ecosystems Part II Section 3

Review primary source of energy for photosynthetic organisms is the sun/light. Food web Food chain Biomass Food web-a network describing the feeding interactions of the species in a defined region Food chain-a linear connection of organisms to show the feeding linkages of predators and prey. Biomass-the amount of living material per unit area of volume; may be expressed as grams of carbon, total dry weight, and so on.

Energy Flow in a Food Chain Hand out the energy flow in an ecosystem handout and work it with them after the video

Gross Primary Production (GPP) calculate the % of incident light energy which appears as energy of newly synthesized organic substances The total energy captured by primary producers = GPP respiration (R) Net primary production (NPP) - Remaining organic substances Transferred to higher trophic levels NPP = GPP – R ~10% energy available at one trophic level is transferred to the next trophic level Use example on restaurant tip handout

Example After this show the food chain example from my paper 3.5%

Energy Losses Along Food Chains Of total energy from Sun, only a small percentage is captured and used for synthesis (NOT ALL ENERGY BECOMES AVAILABLE AS NET PRODUCTION) Reflected back from surfaces Pass straight through a producer – not absorbed Inefficiencies of photosynthesis NPP = GPP – R 3 reasons: Respiration/heat Waste/feces Excretion (feces) or egestion (from cells) Some parts of organism not eaten

BIG reason why RARELY have more than 5 levels Energy losses between trophic levels “loss of heat energy” Insufficient energy available to transfer to more than 5 trophic levels

Efficiency of Energy transfer between trophic levels Net productivity of plants in a food chain is 36,000 kJ/m2 per year Net production of herbivores is 1,700 kJ/m2 per year Efficiency of transfer of energy from the producers to herbivores (1,700 / 36,000) x 100 = 4.72% Energy losses: heat from respiration, losses in urine, undigested plant material (fecal matter) Energy of production of herbivores represent total energy available to carnivores (next trophic level)

Productivity can be measured as mass of carbon incorporated into biological molecules per unit area per unit time The primary productivity of the phytoplankton in this food web is 90 g of carbon per m2 per year. The efficiency of transfer between phytoplankton and herbivores is approximately 10%. Assuming that zooplankton and bottom-feeding herbivores eat equal quantities of phytoplankton, calculate the amount of carbon incorporated into zooplankton per m2 per year. ....................................................... g C m–2 year–1 [2] Answer: 90/10% = 9/2 = 4.5

Ecological Pyramids Graphical representation of food chain Producers at base Horizontal bars represents successive trophic levels Width of bar proportional to numbers, biomass or energy Impossible to have more energy in higher trophic levels Show video (chapter 3 part 4-Ecological pyramids by MrDBioCFC)—8 minutes-as intro to this topic

Ecological Pyramid

Example Draw a pyramid of biomass for the following food chain: Phytoplankton  krill  fish  penguins  killer whales [2] Answer: pyramid with 5 levels; each level named; (trophic)

4th, 5th, 6th, 7th 4th, 5th, 6th 4th, 5th, 6th 3rd, 4th 4th, 5th, 6th 3rd, 4th, 5th 3rd, 4th , 5th 3rd, 4th, 5th 2nd, 3rd 2nd 1st trophic level

4th, 5th 3rd, 4th, 5th 3rd, 4th 3rd 3rd 2nd 2nd 3rd, 4th 1st trophic level