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Standard Two: Biological Productivity and Energy Transfer © 2011 Pearson Education, Inc. Overview • Productivity is the same as photosynthesis, which is affected by sunlight and nutrients. • Productivity is globally and seasonally variable. • Feeding relationships are represented by food chains and food webs. • Oceans are being overfished. © 2011 Pearson Education, Inc. Primary Productivity • Primary productivity is the rate at which energy is stored in organic matter. • Photosynthesis uses solar radiation. • Chemosynthesis uses chemical reactions. • 99.9% of the ocean’s biomass relies directly or indirectly on photosynthesis for food. © 2011 Pearson Education, Inc. Photosynthesis © 2011 Pearson Education, Inc. Photosynthesis and chemosynthesis are both processes by which organisms produce food; photosynthesis is powered by sunlight while chemosynthesis runs on chemical energy. © 2011 Pearson Education, Inc. Primary Production • Ecosystems depend upon the ability of some organisms to convert inorganic compounds into food that other organisms can then exploit (or eat!). • In most cases, primary food production occurs in a process called photosynthesis, which is powered by sunlight. • In a few environments, primary production happens though a process called chemosynthesis, which runs on chemical energy. • Together, photosynthesis and chemosynthesis fuel all life on Earth. © 2011 Pearson Education, Inc. Photosynthesis • 1. The Sun gives off energy in the form of light. • 2. Plants absorb sunlight. They take up nutrients from their roots and release Carbon Dioxide through the pores on their leaves. • 3. Plants use solar energy to make organic molecules, aka glucose (sugar). • 4. The plants grow and reproduce. • Example: Photosynthesis takes place on land and in shallow water where sunlight can reach seaweeds. © 2011 Pearson Education, Inc. Chemosynthesis • 1. Hot water gushing from hydrothermal vents is saturated with dissolved chemicals. • 2. Bacteria absorb hydrogen sulfide and carbon dioxide from vent water and oxygen from seawater. • 3. The bacteria use energy released by oxidizing sulfur to make organic molecules. • 4. The bacteria grow and reproduce and are eaten or hosted as internal symbionts by other animals. • Chemosynthesis occurs around hydrothermal vents and methane seeps in the deep sea where sunlight is absent. © 2011 Pearson Education, Inc. In the diagram, mussels and tubeworms are using the hydrogen sulfide released from a hydrothermal vent. The chemical equation given here for chemosynthesis is just one of a number © 2011 Pearson Education, Inc. of possibilities. Instructions: 1. 2. 3. • Create a foldable of chemosynthesis vs. photosynthesis. Construct a hydrothermal vent fauna food web. Critical Thinking Question Marine scientists were stunned to find complex ecosystems based on chemosynthesis flourishing around deep-sea hydrothermal vents. This discovery also caught the attention of space scientists, giving them renewed hope that they might find life elsewhere in the solar system. Explain why chemosynthesis may be more likely to support life on distant worlds than photosynthesis. © 2011 Pearson Education, Inc. Food Web • • • • • Top Order Carnivores: First Order Carnivores: Primary Consumers: Primary Producers: Simple Chemicals: © 2011 Pearson Education, Inc. Measurement of Primary Productivity • Directly – capture plankton in plankton nets • Measure radioactive carbon in seawater • Monitor ocean color with satellites – Green pigment chlorophyll – SeaWiFS © 2011 Pearson Education, Inc. Ocean Chlorophyll – SeaWiFS © 2011 Pearson Education, Inc. Factors Affecting Primary Productivity • Nutrient availability – Nitrate, phosphorous, iron, silica – Most from river runoff – Productivity high along continental margins – Redfield ratio – C:N:P © 2011 Pearson Education, Inc. Factors Affecting Primary Productivity • Solar radiation – Uppermost surface seawater and shallow seafloor – Compensation depth – net photosynthesis becomes zero – Euphotic zone—from surface to about 100 meters (330 feet) © 2011 Pearson Education, Inc. Light Transmission in Ocean Water • Visible light of the electromagnetic spectrum • Blue wavelengths penetrate deepest • Longer wavelengths (red, orange) absorbed first © 2011 Pearson Education, Inc. Transmission of Light in Seawater © 2011 Pearson Education, Inc. Color in the Ocean • Color of ocean ranges from deep blue to yellow-green • Factors – Turbidity from runoff – Photosynthetic pigment (chlorophyll) • Eutrophic • Oligotrophic • Secchi Disk – measures water transparency © 2011 Pearson Education, Inc. Upwelling and Nutrient Supply • Cooler, deeper seawater is nutrient-rich. • Areas of coastal upwelling are sites of high productivity. © 2011 Pearson Education, Inc. Upwelling and Nutrient Supply © 2011 Pearson Education, Inc. Types of Photosynthetic Marine Organisms • Anthophyta –Seed-bearing plants • Macroscopic (large) algae • Microscopic (small) algae • Photosynthetic bacteria © 2011 Pearson Education, Inc. Anthophyta • Only in shallow coastal waters • Primarily grasses and mangroves © 2011 Pearson Education, Inc. Macroscopic Algae • • • • “Seaweeds” Brown algae Green algae Red algae – Most abundant and most widespread – Varied colors © 2011 Pearson Education, Inc. Microscopic Algae • Produce food for 99% of marine animals • Most planktonic • Golden algae – Diatoms – tests made of silica – Coccolithophores – plates of calcium carbonate • Dinoflagellates – Red tide (harmful algal bloom) – Toxins – Fish kills – Human illness © 2011 Pearson Education, Inc. Microscopic Algae © 2011 Pearson Education, Inc. Photosynthetic Bacteria • Extremely small • May be responsible for half of total photosynthetic biomass in oceans • Exert critical influence on marine ecosystems © 2011 Pearson Education, Inc. Regional Primary Productivity Variations • Values range from 1 gC/m2/year to 4000 gC/m2/year based on: – Uneven distribution of nutrients – Changes in availability of sunlight • 90% of biomass from euphotic zone decomposes before descending © 2011 Pearson Education, Inc. Regional Primary Productivity Variations • Only 1% of organic matter is not decomposed in the deep ocean. • Biological pump – moves material from euphotic zone to sea floor • Subtropical gyre thermoclines and pycnoclines prevent the resupply of nutrients to the surface. © 2011 Pearson Education, Inc. Polar Ocean Productivity • Winter darkness • Summer sunlight • Phytoplankton (diatoms) bloom • Zooplankton (mainly small crustaceans) productivity follows • Example: Arctic Ocean’s Barents Sea © 2011 Pearson Education, Inc. Polar Ocean Productivity • Antarctic productivity slightly greater than Arctic • North Atlantic Deep Water upwells near Antarctica • Productivity decrease from UV radiation – ozone hole © 2011 Pearson Education, Inc. Polar Ocean Productivity • Isothermal waters – little mixing • Plankton remain at surface • Blue whales migrate to feed on maximum zooplankton productivity. © 2011 Pearson Education, Inc. Productivity in Tropical Oceans • Permanent thermocline is barrier to vertical mixing • Low rate of primary productivity – lack of nutrients © 2011 Pearson Education, Inc. Productivity in Tropical Oceans • High primary productivity in areas of – Equatorial upwelling – Coastal upwelling – Coral reefs • Symbiotic algae • Recycle nutrients within the ecosystem © 2011 Pearson Education, Inc. Temperate Ocean Productivity • Productivity limited by – Available sunlight – Available nutrients © 2011 Pearson Education, Inc. Temperate Ocean Productivity • Highly seasonal pattern • Winter low – Many nutrients, little sunlight • Spring high – Spring bloom • Summer low – Few nutrients, abundant sunlight • Fall high – Fall bloom © 2011 Pearson Education, Inc. Temperate Ocean Seasonal Cycle © 2011 Pearson Education, Inc. Comparison of Global Productivities © 2011 Pearson Education, Inc. • Upwelling is an oceanographic phenomenon that involves wind-driven motion of dense, cooler, and usually nutrient-rich water towards the ocean surface, replacing the warmer, usually nutrient-depleted surface water. © 2011 Pearson Education, Inc. Learning Target Write the questions: 1. Describe and analyze the limiting factors that influence the primary productivity of the oceans. 2. Antarctic productivity is slightly greater than artic because of ____________. 3. What can an upwelling provide oceans? 4. Why is a spring bloom greater in productivity than a fall bloom? © 2011 Pearson Education, Inc. Energy Flow in Marine Systems • Biotic community – assemblage of organisms in definable area • Ecosystem – biotic community plus environment • Energy flow is unidirectional based on solar energy input. © 2011 Pearson Education, Inc. Energy Flow in Marine Systems • Three categories of organisms: • Producers – Nourish themselves with photosynthesis or chemosynthesis – Autotrophic • Consumers – Eat other organisms – Heterotrophic • Decomposers – break down dead organisms or waste © 2011 Pearson Education, Inc. Energy Flow in Marine Systems © 2011 Pearson Education, Inc. Consumers in Marine Ecosystems • • • • Herbivores – eat plants Carnivores – eat other animals Omnivores – eat plants and animals Bacteriovores – eat bacteria © 2011 Pearson Education, Inc. Nutrient Flow in Marine Ecosystems • Biogeochemical cycling © 2011 Pearson Education, Inc. Feeding Strategies • Suspension feeding or filter feeding – Take in seawater and filter out usable organic matter • Deposit feeding – Take in detritus and sediment and extract usable organic matter • Carnivorous feeding – Capture and eat other animals © 2011 Pearson Education, Inc. Feeding Strategies © 2011 Pearson Education, Inc. Trophic Levels • Feeding stage • Chemical energy transferred from producers to consumers • About 10% of energy transferred to next trophic level • Gross ecological efficiency © 2011 Pearson Education, Inc. Trophic Levels © 2011 Pearson Education, Inc. Ecosystem Energy Flow and Efficiency © 2011 Pearson Education, Inc. Food Chains • Primary producer • Herbivore • One or more carnivores © 2011 Pearson Education, Inc. Food Webs Branching network of many consumers Consumers more likely to survive with alternative food sources © 2011 Pearson Education, Inc. Biomass Pyramid • The number of individuals and total biomass decreases at successive trophic levels. • Organisms increase in size. © 2011 Pearson Education, Inc. Marine Fisheries • Commercial fishing • Most from continental shelves • Over 20% from areas of upwelling that make up 0.1% of ocean surface area © 2011 Pearson Education, Inc. Overfishing • Fish from standing stock – the mass present in the ecosystem at any given time • Overfishing – fish stock harvested too rapidly, juveniles not sexually mature to reproduce • Reduction in Maximum Sustainable Yield (MSY) © 2011 Pearson Education, Inc. Exploitation Status of Marine Fish © 2011 Pearson Education, Inc. Overfishing • 80% of available fish stock fully exploited, overexploited, or depleted/recovering • Large predatory fish reduced • Increased fish production, decreased stocks © 2011 Pearson Education, Inc. Incidental Catch or Bycatch • Non-commercial species are taken incidentally by commercial fishers. • Bycatch may be up to 8 times more than the intended catch. – Birds, turtles, dolphins, sharks © 2011 Pearson Education, Inc. Tuna and Dolphins • Tuna and dolphins swim together • Caught in purse seine net • Marine Mammals Protection Act addendum for dolphins • Driftnets or gill nets banned in 1989 © 2011 Pearson Education, Inc. Purse Seine Net © 2011 Pearson Education, Inc. Fisheries Management • • • • • • Regulate fishing Conflicting interests Human employment Self-sustaining marine ecosystems International waters Enforcement difficult © 2011 Pearson Education, Inc. Fisheries Management • Many large fishing vessels • Governments subsidize fishing • 1995—world fishing fleet spent $124 billion to catch $70 billion worth of fish © 2011 Pearson Education, Inc. Fisheries Management • Northwest Atlantic Fisheries such as Grand Banks and Georges Bank • Canada and United States restrict fishing and enforce bans • Some fish stocks in North Atlantic rebounding • Other fish stocks still in decline (e.g., cod) © 2011 Pearson Education, Inc. Fisheries Management Effectiveness © 2011 Pearson Education, Inc. Fisheries Management • Consumer choices in seafood • Consume and purchase seafood from healthy, thriving fisheries – Examples: farmed seafood, Alaska salmon • Ecosystem-based fishery management • Avoid overfished or depleted seafood – Examples: tuna, shark, shrimp © 2011 Pearson Education, Inc. Seafood Choices © 2011 Pearson Education, Inc. End of CHAPTER 13 Biological Productivity and Energy Transfer © 2011 Pearson Education, Inc.