How Chemosynthesis Allows for Life Without Sunlight

Photosynthesis is the process by which plants convert sunlight into chemical energy in order to sustain themselves. Chemosynthesis is just like photosynthesis in the sense that it allows organisms to produce their own food and source of energy. Except for one major factor, -- chemosynthesis eliminates the need for sunlight! This rare phenomenon can be found occurring in marine life (primarily bacteria) found around hydrothermal vents (where geothermally heated water is discharged from - just like hot springs on the ocean bed!), meters beneath the surface. 

Chemosynthesis was discovered first in 1977, when an ocean research expedition took place near the Galapagos Islands. Researchers observed entire communities of sea life flourishing besides the hydrothermal vents, with zero access to sunlight. Further scientific experiments concluded that it was, in fact, the process that they then named ‘chemosynthesis’, that was responsible for this.  

Here's how chemosynthesis occurs: 

Water emerges through the hydrothermal vents. These vents are essential as large sums of chemosynthetic bacteria depend on the chemicals present in the water, primarily minerals such as sulfides. Compounds like carbon dioxide and hydrogen sulfide go on to react with oxygen which releases chemical energy: 

H₂S                       +  2O₂        →    SO₄²⁻           +  2H⁺                    + energy 

(hydrogen sulfide)   (oxygen)          (sulfate ion)    (hydrogen ion )

Chemosynthetic microbes take advantage of the energy produced in the reactions and harness it. 

They then utilize the chemical energy that was recently formed via the carbon fixation process in order to convert inorganic carbon to organic molecules (food) of glucose sugars:

CO₂                     →     C₆H₁₂O₆

(carbon dioxide)             (glucose)

The bacteria grow as they feed on the organic molecules and reproduce, increasing their populations. They eventually die, either of natural causes where they become a part of the ocean bed, or in most cases, where they are eaten or hosted as internal symbionts by other creatures like tubeworms and mussels. 

… And that is how chemosynthesis works! Not only is this process essential for bacteria to sustain themselves, but it also upholds an entire ecosystem that depends on the bacteria to thrive. The food web the bacteria supports includes shrimp, clams, fish, octopods and so many more!

By Vedica Mehta