Primary producers - Biotic Components
The major primary producers of aquatic ecosystems (freshwater and marine) are various species of algae. In terrestrial ecosystems the major primary producers are predominantly herbaceous and woody plants. Some photosynthetic prokaryotic organisms such as blue green algae and a few bacteria are also called primary producers. Besides the green plants there are certain chemosynthetic bacteria that are also autotrophic. But they obtain the energy for the synthesis of organic compounds (amino acids, proteins) from sources other than solar energy. Some of these sources are: ammonia (NH3), methane (CH4), and hydrogen sulphide (H2S).
Figure: Marine algae a) Laminaria agardhii b) Nereocystis luetkeana
You can surely make a long list of animals that obtain their food from green plants. Can you also name a few organisms that depend on the chemosynthetic bacteria for nutrition? We give you a few examples of the same. Organisms like crabs, molluscs and giant worms, that are present at or near the oceanic floor where sunlight cannot penetrate, get their food from chemosynthetic bacteria.