© 2014 pearson education, inc.. primary productivity rate at which energy is stored in organic...
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© 2014 Pearson Education, Inc.
© 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.
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 (106:16:1)
© 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
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Transmission of Light in Seawater
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Types of Photosynthetic Marine Organisms
• Anthophyta– Seed-bearing plants
• Macroscopic (large) algae
• Microscopic (small) algae
• Photosynthetic bacteria
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Anthophyta
• Only in shallow coastal waters
• Primarily grasses and mangroves
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Macroscopic Algae
• “Sea Weeds”• Brown algae
– Middle latitudes– Colder water
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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
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Microscopic Algae
• Dinoflagellates – Red tide (harmful algal
bloom)
– Toxins
– Fish kills
– Human illness
© 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.
Regional Primary Productivity Variations
• Values range from 1 gC/m2/year to 4000 gC/m2/year – Uneven distribution of nutrients
– Changes in availability of sunlight
• 90% of biomass from euphotic zone decomposes before descending
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