Biotic factors of a pond include all living organisms that make up the pond ecosystem. The biotic factors can be split into different trophic levels, such as autotrophs, heterotrophs, and saprotrophs, depending on their function in the ecosystem.
Autotrophs, also known as producers, include plants likr algae that can convert energy into food. The most common form of energy used is sunlight, which is then converted to food through a process called photosynthesis. Depending on the location of the pond, organisms like bacteria might also use the heat produced in hydrothermal vents to produce food.
Heterotrophs are organisms that cannot produce their own food and can be further split into two kinds, primary consumers and secondary consumers. Primary consumers include organisms like insects and crustaceans, which consume plants. Secondary consumers are typically carnivores and include several kinds of fish, which feed either on heterotrophs, plants or both.
Saprotrophic organisms, more commonly known as decomposers, are responsible for decomposing organic matter into usable nutrients for the autotrophs. They usually include certain types of fungi and bacteria and break down dead organic matter to carbon dioxide, nitrogen and phosphorus. Decomposers are found at the bottom of the ponds, where most of the organic waste can be found.