HOW DOES THE FOOD CHAIN WORK IN THE MANGROVE? - ENVIRONMENT - 2025

The food chain in the mangrove is the set of food interactions between decomposers, consumers and producers that develop in the mangrove ecosystem. The interaction of all these chains forms the mangrove food web.

Mangroves are widely distributed in the tropical and subtropical coastal areas of the world. It is estimated that the total area occupied by mangroves in the world reaches 16,670,000 hectares. Of these, 7,487,000 ha are in tropical Asia, 5,781,000 ha in tropical America and 3,402,000 ha in tropical Africa.

Ardea herodias fishing in the mangrove. Author: I, Acarpentier

Terrestrial, amphibian and aquatic organisms participate in the set of trophic chains or trophic web of a mangrove. The central element is the mangrove species. Depending on the geographical area, they range from 4 species (Caribbean area) to 14-20 species (Southeast Asia).

There are two main food chains in a mangrove. In the detritus the leaves of the mangroves are the primary product. These are transformed into detritus (solid waste from the decomposition of organic matter) by chopping and decomposing organisms. The detritus is consumed by the detritivores. Later the carnivores intervene and finally the decomposers.

The other food chain is known as grazing. In this case the plants (primary producers) are consumed by herbivores. These serve as food for first-order carnivores, then second-order ones participate. Lastly, decomposers act on dead organic matter.

Species

-Vegetation

Mangroves

Globally, 54 species belonging to 20 genera and 16 plant families have been described. The main species belong to five families: Rhizophoraceae, Acanthaceae, Combretaceae, Lythraceae and Palmae or Arecaceae.

Other groups of plants

Up to 20 species of 11 genera and 10 families have been identified as minor components of the mangrove forest.

-Fauna

Mangroves are places of refuge, reproduction and feeding for numerous animal species, both terrestrial, amphibian and aquatic.

Sea birds

In some mangroves, up to 266 species of birds have been identified. Some are permanent inhabitants, others migratory. A variety of herons and wading birds are common. Among them we have the ibis (white, black and scarlet), the spatula heron, the white stork, the cock of the well and the flamingo.

Among the falconids are the peregrine falcon, the mangrove hawk, the caricari or carancho (mainly scavenger). Other birds are kingfishers, frigate birds, seagulls, and pelicans.

Crustaceans

There is a wide variety of crabs, shrimp and amphipods (small crustaceans), in addition to the microscopic crustaceans that are part of the marine zooplankton of the area.

Reptiles

In the terrestrial area of ​​the mangrove iguanas and other species of lizards inhabit. In the water, the mangroves are visited by species of sea turtles that use them for reproduction and food. Depending on the geographical area, different species of snakes also inhabit.

The largest crocodile in existence (Crocodylus porosus) is found in Southeast Asia and the Australian coasts. On the coasts of the Caribbean the coastal caiman (Crocodylus acutus).

Insects and arachnids

There are several species of butterflies whose larvae feed on the mangrove leaves. Odonata larvae are predators of other larvae, tadpoles, adult insects, and even small fish.

Fishes

Mangroves are places of refuge, reproduction and feeding for many species of fish.

Mammals

Mammals include monkeys, crab foxes, the South American raccoon, and the manatee.

Guilds

The ecological guilds or trophic guilds are groups of species that have a similar function within the trophic web. Each guild exploits the same type of resources in a similar way.

-Primary producers

The primary producers in the mangrove are forest plants, aquatic grasses, algae, and cyanobacteria (photosynthetic organisms). These are the first trophic level in both the grazing and detrital chains.

The net primary productivity in a mangrove is greater on land than in the sea, and the fundamental flow of energy goes in that direction. The primary source of food in the mangrove is constituted by detritus or organic particles derived from the decomposition of the plant remains of the mangrove. Especially from the leaves of mangrove species (80-90%).

-Consumers

Detritivores

In mangroves, the main food chain is derived from the detritus of mangrove leaves. These are consumed by terrestrial invertebrates and reused by other detritivores (consumers of fecal matter). Crabs play an important role in fragmenting plant remains.

A relevant portion of this detritus reaches the water. Various mollusks, crustaceans and fish consume the detritus originated in the decomposition process on the forest floor. Another part of the litter falls directly into the water and there undergoes the decomposition process.

Primary (herbivores or second trophic level)

These make up the second link in the grazing chain. Among the primary consumers are a great diversity of organisms that feed on the leaves, flowers and fruits of the mangrove vegetation. In the terrestrial sphere, from insects to reptiles and birds.

On the other hand, fish, crabs and turtles feed on seaweed (including periphyton that cover the submerged roots of mangroves) and aquatic grasses (Thalassia and other aquatic angiosperms). And many fish feed on plankton.

The manatee or sea cow is a herbivorous aquatic mammal. It feeds on herbs such as Thalassia testudinum and mangrove leaves.

Secondary (carnivores of the first order or third trophic level)

Most of the birds present in the mangroves are fishermen. The kingfisher or the stork catch fish. Others feed on crabs that inhabit the roots of mangroves or aquatic mollusks.

In some cases, such as the paddle heron and the flamingo, they filter through mud in search of small crustaceans and other organisms.

Other species of birds, as well as frogs and reptiles, feed on insects that inhabit the forest. Even insect larvae like Odonata behave like first-rate carnivores.

Tertiary (carnivores of the second order or fourth trophic level)

Birds of prey feed on other birds. Larger fish feed on smaller ones. Some mangrove areas are hunting areas for feline species. Saltwater crocodiles inhabit others.

And finally the human being also intervenes as a predator through fishing and capturing turtles, among other prey.

-Decomposers

Soil microorganisms (bacteria, fungi, nematodes) break down the available organic matter. During decomposition the plant remains of the mangrove are progressively enriched with proteins by generating a mixture of bacteria and fungi.

In mangroves in Thailand, up to 59 species of fungi have been identified that decompose the plant remains of the mangrove. Likewise, both aerobic and anaerobic autotrophic bacteria, as well as heterotrophic ones, that participate in decomposition.

In the traditional representation of the food chain the decomposers represent the last level. However, in the mangrove they play an intermediary role between primary producers and consumers.

In the detrital food chain, decomposers generate detritus from mainly mangrove leaves.

Types

In mangrove forests there are two main types of food chains. The grazing chain runs from plants to other organisms at various trophic levels.

Example: Rhizophora mangle leaves - butterfly larvae consume the leaves - bird captures the larvae and feeds its chicks - Boa constrictor (snake) captures the chick - death of organisms: decomposers.

The second is the so-called detrital food chain that begins from detritus and proceeds to other organisms at higher trophic levels.

Example: Rhizophora mangle leaves fall to the ground - decomposers (bacteria and fungi) act - generated detritus is washed into the sea - crustaceans feed on detritus - fish consume crustaceans - kingfisher (bird) consume fish - hawk catches bird - death of organisms: decomposers.

These types of chains, plus smaller ones, are interrelated in an intricate food web of matter and energy flow.

Energy flow

Among tropical marine ecosystems, mangroves are ranked second in importance in terms of gross productivity and sustained tertiary yield. They are second only to coral reefs.

However, unlike other ecosystems, in mangroves the trophic components are spatially separated. The vegetation of the mangrove forest represents the main contribution of primary production, and the aquatic heterotrophs constitute the highest secondary and tertiary yield.

Energy and matter input

As in any ecosystem, the primary source of energy is solar radiation. Being located in tropical and subtropical areas, mangroves receive high solar energy throughout the year.

Tides, rivers, and runoff from nearby highlands carry sediments that represent inputs of matter into the system.

Another relevant source of nutrient entry is the colonies of seabirds that nest in the mangroves. The guano or excreta of these birds mainly contribute phosphorus, nitrates and ammonia.

Outputs of matter and energy

Ocean currents extract materials from the mangrove swamp. On the other hand, many of the species that are part of the trophic web are temporary visitors (migratory birds, deep-sea fish, turtles).

References

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