Primary Producers in the Sea
We use the term “primary producers” to include a large variety of organisms that manufacture organic compounds, by either photosynthesis or chemosynthesis. Photosynthetic primary producers use light-derived energy to convert carbon dioxide into organic carbon compounds that are integrated into cells. Chemosynthetic primary producers use energy stored in inorganic compounds, such as H2S, methane, ammonia, nitrite, sulfur, hydrogen gas, or ferrous iron, to fix carbon dioxide into organic matter. A variety of terms have been used to refer to these different kinds of primary production. Producers that use light to self-(auto-)fix inorganic carbon (CO2) have been called photoautotrophs or photolithotrophs. Chemosynthetic producers that use energy in reduced compounds to fix inorganic carbon have been called chemolithotrophs. In this chapter, we first deal primarily with marine organisms that fix inorganic carbon into organic compounds using external sources of energy, then follow with a short section on chemosynthesis.