Lecture 13 - Carbon

• carbon is the main energy source for all ecosystems
• the two main forms of carbon are inorganic and organic
• dissolving CO2 gas is water can result in a variety of forms including: carbon dioxide, carbonic acid, bicarbonate and carbonate
• inorganic carbons main reservoir is in the atmosphere of carbon dioxide
• an increase of CO2 in the atmosphere increases the acidity of aquatic ecosystems
• greater dissolved bicarbonate = greater buffering capacity
• bicarbonate = around pH 8
• carbonate = around pH 12
• organic carbon can be particulate or dissolved
• organic carbon is carbon chains bonded with other elements (H or O)
• Particulate carbon

  • can be fine or course
  • can be living or dead
  • key source of food for heterotrophic oraganisms
• dissolved carbon can be divided into two classes: humic or non-humic
• Humic -> by products of breakdowns of cellulose, tannins and ligins

  -> harder for organisms to breakdown and not very nutritious
• non-humic -> sugars, carbs, amino acids -> broken-down by heterotrophs to yield humic compounds
• cycling of carbon is dominated by photosynthesis and respiration
• inorganic carbon has three forms in water that are determined by the pH in water
• cycling is different if oxygen is not present