© 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

© 2014 Pearson Education, Inc.

Transmission of Light in Seawater

© 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.

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