Mangroves convert sunlight into plant tissue by a process called and are thus a food source for estuarine animals. However, most of the animals do not graze directly on the mangroves. Instead, they eat plant material which has by a slow process known as the detrital food chain. This begins when (fragments of dead leaves, bark and fruit) falls from the mangroves. The soluble nutrients are leached out of it by the rain and tides and it is colonised by microscopic fungi and bacteria. The resulting decomposed material () is eaten by small animals such as prawns and crabs.

These animals the undigested plant material. which is then recolonised by fungi and bacteria. The cycle continues until even the most resistant tissues are broken down. The detritus-feeders are then eaten by the larger fish and birds of the estuary.