BIEB132_L3_ProdPhytoplankton

BIEB132_L3_ProdPhytoplankton - Primary Productivity and...

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Primary Productivity and Phytoplankton BIEB 132: Lecture 3, 10/1/09 I. Primary Production A. Ocean responsible for almost 50% of global total annual primary production II. Phytoplankton A. Responsible for >90% of ocean primary productivity B. Prokaryotes and eukaryotes C. Mitigation strategies using phytoplankton Reading: Levinton pp. 169-171, 234-235, Chapter 10, pp. 582-585 I. Primary Production A. Defined as the rate of production of organic carbon from inorganic carbon 1. Photosynthesis 1. Sunlight as source of energy for primary production 2. Major contributor to ocean primary production 3. Chemosynthesis 4. Chemical energy for primary production, e.g., sulfur-oxidizing bacteria in hydrothermal vent systems 5. Minor contributor to ocean primary production 6. Autotrophs – organisms that perform primary production B. Photosynthesis 1. Formation of carbohydrates – occurs in the chloroplast 6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2 2. Carbon is dissolved in seawater mostly as bicarbonate (HCO 3 - ) a) Pump HCO 3 - across cell membrane and chloroplast membrane into chloroplast b) Enzyme carbonic anhydrase – converts HCO 3 - to CO 2 HCO 3 - + H + CO 2 + H 2 O 3. Photosynthesis reactions a) Light reaction – uses 4 photons of light, make ATP, donate electrons to NADP + , form O 2 2H 2 O + 2ADP + 2P i + 2NADP + O 2 + 2ATP + 2NADPH + 2H + b) Dark reaction – requires 12 NADPH, 18 ATP, 12 H + , forms carbohydrates from CO 2 in the Calvin-Benson cycle c) Carbohydrates – stable storage form of chemical energy Phytoplankton p. 1 of 9
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d) Summary – 1 st form electrical energy from light energy (light reaction), then convert electrical to stable chemical bond energy (dark reaction) 4. Gross primary production – total carbon fixed during photosynthesis a) Net primary production – carbon available to higher trophic levels (photosynthesis – respiration) Box Figure 9.1: Light and dark reactions of photosynthesis C. Forms of inorganic carbon in the ocean 1. Dissolved inorganic carbon (DIC) H 2 O + CO 2 H 2 CO 3 H + + HCO 3 - 2H + + CO 3 -2 carbonic acidbicarbonate carbonate 2. Form of DIC depends on pH a) Normal pH 8–8.3 b) Seawater – 2200 µM DIC (at equilibrium with the atmosphere at pH 8.2 and 25˚C) H 2 O + CO 2 H 2 CO 3 H + + HCO 3 - 2H + + CO 3 -2 1% 90% 9% c) Form of DIC depends on pH (1) pH decrease more DIC as CO 2 (2) At pH 1 all DIC is CO 2 Figure: 1990’s DIC map created by Global Ocean Data Analysis Project (GLODAP) D. Ocean acidification 1. Atmospheric levels of CO 2 are increasing Figures: atmospheric CO 2 and Al Gore projection 2. Since 1800 about 142 billion tons CO 2 entered ocean a) 2 billion tons per year b) 1/3 of CO 2 released into atmosphere 3. CO 2 ends up in oceans as DIC, dissolved as carbonic acid a) Causes decrease in ocean pH (more acidic) – “the other CO 2 problem” 4. Continued increase in CO 2 can lead to pH decrease greater than in past 300 million years a) Decrease 0.1 units since 1800 b) Year 2100 – pH decrease 0.5 units 5.
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