Autotrophic carbon fixation in the oceans

Question 1

What are the methods of carbon fixation?

Answer 1

• Autotrophic carbon fixation
• Calvin-Benson-Bassham cycle
• Alternative pathways
• reductive Tricarboxylic Acid cycle (krebs)

Question 2

What is the carbon cycle?

Answer 2

• Autotrophic organisms have the ability to build all cell material solely from inorganic carbon
• These processes are a crucial component of the global carbon cycle – they provide the organic carbon used by heterotrophs
• Heterotrophs oxidise organic carbon back to inorganic carbon – completing the carbon cycle
• The underlying balance between autotrophy and heterotrophy is key in regulating CO2 and O2 concentrations in the atmosphere
• The standing stock of primary producers is smaller in the ocean yet 50% of global primary production occurs in the ocean due to high turnover of biomass

Question 3

In the ocean most primary production occurs …

Answer 3

in the photic zone by cyanobacteria (Prochlrococcus, Synechococcus) and eukaryotic algae (diatoms and coccolithophores)

They use the Calvin-Benson-Bassham (CBB) cycle to fix inorganic carbon and oxygenic photosynthesis to conserve energy (Raven, 2009, Aquat. Microb. Ecol. 56: 177-192)

This makes the CBB cycle the most significant carbon fixation pathway on today’s earth