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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/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