ChapterChapter 1 13 Clickers Lecture Essentials of Oceanography Eleventh Edition Biological Productivity and Energy Transfer Alan P. Trujillo Harold V. Thurman © 2014 Pearson Education, Inc. Chapter Overview • Primary productivity is photosynthesis. • Productivity is globally and seasonally variable. • Feeding relationships are represented by food chains and food webs. • Oceans are being overfished. © 2014 Pearson Education, Inc. Primary Productivity • 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. © 2014 Pearson Education, Inc. Photosynthesis © 2014 Pearson Education, Inc. Measurement of Primary Productivity • Directly – capture plankton in plankton nets • Measure radioactive carbon in seawater © 2014 Pearson Education, Inc. Measurement of Primary Productivity • Monitor ocean color with satellites – Photosynthetic phytoplankton use green pigment chlorophyll • SeaWiFS (Sea-viewing Wide Field of View Sensor) satellite sensor collected ocean color data 1997–2010 • MODIS (Moderate Resolution Imaging Spectroradiometer) – current – Measures 36 spectral frequencies © 2014 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 © 2014 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) • Enough light for photosynthesis © 2014 Pearson Education, Inc. Light Transmission in Ocean Water • Visible light portion of the electromagnetic spectrum • Blue wavelengths penetrate deepest • Longer wavelengths (red, orange) absorbed first © 2014 Pearson Education, Inc. Transmission of Light in Seawater © 2014 Pearson Education, Inc. Color in the Ocean • Color of ocean ranges from deep blue to yellow-green • Factors – Turbidity from runoff – Photosynthetic pigment (chlorophyll) • Secchi Disk – measures water transparency © 2014 Pearson Education, Inc. Color in the Ocean • Coastal and upwelling areas productive – Light green – Eutrophic • Open ocean lacks productivity – Dark blue – Oligotrophic © 2014 Pearson Education, Inc. SeaWiFS Image of Ocean Chlorophyll © 2014 Pearson Education, Inc. Upwelling and Nutrient Supply • Flow of deep water to surface • Cooler, deeper seawater is nutrient- rich. • Areas of coastal upwelling are sites of high productivity. – Western continental margins © 2014 Pearson Education, Inc. Upwelling and Nutrient Supply © 2014 Pearson Education, Inc. Types of Photosynthetic Marine Organisms • Anthophyta – Seed-bearing plants • Macroscopic (large) algae • Microscopic (small) algae • Photosynthetic bacteria © 2014 Pearson Education, Inc. Anthophyta • Only in shallow coastal waters • Primarily grasses and mangroves © 2014 Pearson Education, Inc. Macroscopic Algae • “Sea Weeds” • Brown algae – Middle latitudes – Colder water © 2014 Pearson Education, Inc. Macroscopic Algae • Green algae – Common in freshwater – Chlorophyll • Red algae – Most abundant and most widespread – Varied colors © 2014 Pearson Education, Inc. Microscopic Algae • Produce food for 99% of marine animals • Most planktonic • Golden algae – Diatoms – tests (shells) made of silica, accumulated shells produce diotomaceous earth – Coccolithophores – plates of calcium carbonate © 2014 Pearson Education, Inc. Microscopic Algae • Dinoflagellates – Red tide (harmful algal bloom) – Toxins – Fish kills – Human illness © 2014 Pearson Education, Inc. Red Tides • Natural conditions may stimulate dinoflagellate productivity. • Some produce toxins inadvertently consumed by fish and shellfish. • Humans who eat affected fish may get paralytic shellfish poisoning (PSP). © 2014 Pearson Education, Inc. Red Tides • April through September most dangerous in N. Hemisphere • Dinoflagellates associated with ciguatera – type of seafood poisoning – Causes most human cases of seafood poisoning © 2014 Pearson Education, Inc. Ocean Eutrophication and Dead Zones • Eutrophication – artificial enrichment of waters by previously scarce nutrient – Can cause harmful algal bloom – Sewage, fertilizer, animal waste © 2014 Pearson Education, Inc. Ocean Eutrophication and Dead Zones • Dead zones – hypoxic (oxygen-poor) water – Mouths of major rivers – Spring runoffs • Suffocates bottom dwellers © 2014 Pearson Education, Inc. Ocean Eutrophication and Dead Zones • Global dead zones – significant increase since 1960s • More than 500 worldwide © 2014 Pearson Education, Inc. Gulf of Mexico Dead Zone • Second largest in world – 22,000 sq. km (8500 sq. mi) • Runoff of nutrients, esp. nitrates – Algal blooms © 2014 Pearson Education, Inc. Photosynthetic Bacteria • Extremely small • May be responsible for half of total photosynthetic biomass in oceans • Exert critical influence on marine ecosystems © 2014 Pearson Education, Inc. Regional Primary Productivity Variations • Values range from 1 gC/m 2/year to 4000 gC/m 2/year – Uneven distribution of nutrients – Changes in availability of sunlight • 90% of biomass from euphotic zone decomposes before descending © 2014 Pearson Education, Inc. Ecosystem Primary Productivity © 2014 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. © 2014 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 © 2014 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 © 2014 Pearson Education, Inc. Polar Ocean Productivity • Isothermal waters – little mixing • Plankton remain at surface • Blue whales migrate to feed on maximum zooplankton productivity. © 2014 Pearson Education, Inc. Polar Ocean Productivity • Blue whales dependent upon zooplankton – Time migration to zooplankton maximum – Fast-growing calves evidence for large biomass in zooplankton © 2014 Pearson Education, Inc. Productivity in Tropical Oceans • Permanent thermocline is barrier to vertical mixing • Low rate of primary productivity – lack of nutrients © 2014 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 © 2014 Pearson Education, Inc. Temperate Ocean Productivity • Productivity limited by – Available sunlight – Available nutrients © 2014 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 © 2014 Pearson Education, Inc. Temperate Ocean Seasonal Cycle © 2014 Pearson Education, Inc. Comparison of Global Productivities © 2014 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. © 2014 Pearson Education, Inc. Energy Flow in Marine Systems • Producers – Nourish themselves with photosynthesis or chemosynthesis – Autotrophic • Consumers – Eat other organisms – Heterotrophic • Decomposers – Break down dead organisms or waste – Heterotrophic © 2014 Pearson Education, Inc. Energy Flow in Marine Systems © 2014 Pearson Education, Inc. Consumers in Marine Ecosystems • Herbivores – eat plants • Carnivores – eat other animals • Omnivores – eat plants and animals • Bacteriovores – eat bacteria © 2014 Pearson Education, Inc. Nutrient Flow in Marine Ecosystems • Detritus – dead remains and waste products • Biogeochemical cycles – chemical parts of matter cycled through ecosystem © 2014 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 © 2014 Pearson Education, Inc. Feeding Strategies © 2014 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 – ratio of energy passed to next higher trophic level divided by energy received from level below © 2014 Pearson Education, Inc. Trophic Levels © 2014 Pearson Education, Inc. Ecosystem Energy Flow and Efficiency © 2014 Pearson Education, Inc. Food Chains • Primary producer • Herbivore • One or more carnivores © 2014 Pearson Education, Inc. Food Webs • Branching network of many consumers • Consumers more likely to survive with alternative food sources © 2014 Pearson Education, Inc. Biomass Pyramid • The number of individuals and total biomass decrease at successive trophic levels. • Organisms increase in size up pyramid. © 2014 Pearson Education, Inc.