Aquatic ecology and Biodiversity

Unit 2- Ecosystem ecology

2.3.1. Types of food chain
There are two basic types of food-chains in aquatic ecosystems
• Grazing food chain
• Detritus food chain
Grazing food chain
The grazing food chain starts with green plants and ends with carnivores via herbivores. The producers synthesize their own food in the presence of sunlight. The herbivorous eat the producers and the carnivores are eaten by the top carnivores. Thus, the grazing food chain starts with primary producers and ends with carnivores. This food chain starts from plants goes through the herbivore and the carnivores.
Types of grazing food chain

• Predator food chain
• Parasitic food chain

Predator food chain
In the predator food chain, one animal captures and devours another animal. In this food chain one animal kills and eat the other animal. The animal which kills other animals for food is called a predator. This act of hunting is called predation. Animals that are caught and eaten by a predator are called prey. Predators that only eat the meat of prey are carnivores
Parasitic food chain
The plants and animals of the grazing food chain are affected by parasites. Parasites derive their energy from their hosts. Thus, the parasitic chain is formed with in the grazing food chain.

Detritus food chain
Detritus food chain starts from the dead organic matter and ends with inorganic matter. This consists of decomposers such as bacteria and fungi. These live on the dead matter and decompose the organic matter and convert to inorganic matter, which is helpful for plants to prepare their food.
However, these two food chains cannot function separately and are interconnected with each other at different levels. The organisms of detritus food chain may serve as food for the organisms of grazing food chains.
Detritus starts from dead organic matter and ends in inorganic compounds. Certain groups of organisms feed excessively on dead bodies of animals and plants are called as “detrivores” (consists of algae, bacteria, fungi). The groups of detrivores includes Protozoans; Insects; Polychaete worms; Crustaceans – Crab, Shrimps, Amphipods; Molluscans – Clams; Nematode worms etc.
The energy from the detritus is trapped and the remainder is excreted in the form of simple organic compounds by detrivores. These organic compounds are again used by another set of detrivores until the organic compounds are converted in to CO₂ and water.