WARNING: This answer is NOT technical! ⚠
Plants can get their nutrients from the ground and dirt. But they grow using the carbon around them (Like the carbon dixiode we breathe out).
So given the suggested food chain of algae-snail-sunfish-heron we can conclude that this food chain is heavily dependent on the process of photosynthesis.
The algae is the only of the organism that are directly dependent of the photosynthesis for their survival, while the snail, sunfish, and heron, and indirectly dependent on it.
Since we are talking about a food chain, in essence it means that all organism are connected through one another. So the algae perform photosynthesis for its own survival, the snail is using the algae is a food source, the snail is later eaten by the sunfish, and the sunfish goes on the menu of the heron.
If the algae, by some scenario, are not able to perform photosynthesis, than they will die off, and if they die off, than the snail will die off because of lack of food, if the snail dies off, along with it dies off the sunfish because of lack of food, and if the sunfish is out of the scene, the heron goes as well.
So we can conclude that the process of photosynthesis is of crucial importance for the survival of all four species, be it directly or indirectly.
First stage of photosynthesis in which light energy from the sun is captured and changed into chemical energy that is stored in ATP and NADPH; also known as the light-dependent reactions. ... The splitting of a water molecule to replace electrons used during the light reactions; splitting by light
Many living organisms respond to things in the environment called Stimuli.
