6. Consumers of the Marine and Estuarine Ecosystems

The spectrum of life in the blue soup of the planet Earth starts with the primary producers, which encompass phytoplankton, seaweeds, salt marsh grass, seagrass and mangroves. The energy (through nutrition) and survival of consumers are direct function of the standing stock of primary producers. The consumers of oceans, seas, bays and estuaries feed on primary producers and acquire energy for performing various life processes. Depending on the environmental conditions, the food chains may be short or long. In extreme types of environments like Arctic or Antarctic, very short food chains are observed. Food chains basically represent complex interrelationships among organisms, in which case it is more appropriate to designate the pattern as food web (Fig. 6.1). Species may, however, change levels in the food chain or web at difference stages of their life cycle or consumers may feed more than one level.