Understanding Food Webs: Terrestrial and Aquatic Ecosystems

Food Webs

Of course, the real world is much more complicated than a simple food chain. While many organisms have very specialized diets, such as anteaters, in most cases, this is not true. Snakes do not limit their diets to frogs, and frogs and toads eat more than just black ants. Every living thing feeds on different prey types and, in turn, is prey to different predators. In addition, some organisms (like mice and birds) include both plants and animals in their diets. This determines that ecosystems form trophic networks (food webs), which include many food chains and a large number of species: producers, consumers, and decomposers. The only way to untangle the chains is by following the course of a chain back to its source (producers). In short, all the food chains that have common links result in a food web. The following scheme shows a terrestrial food web.

While this type of chain is important, most common food chains are based on detritus, which is rotting at the base.

Aquatic Communities

The marine environment occupies 70% of the planet. The ocean offers its inhabitants (plants and animals) an almost constant environment, with little change, especially in regard to temperature and salinity. Marine living beings can live actively swimming, resting on the bottom of coastal waters or deep, or carried away by water currents where they live at different depths. Thus, swimming on their own, resting on the bottom, or being swept away by the waters are “lifestyles” that have been called nekton, benthos, and plankton, respectively.

Nekton

The set of swimming animals in shallow and deep water, able to withstand the movements of water and swim in a particular direction (e.g., mackerel, sharks, whales).

Benthos

It is the group of animals and plants that live at the bottom of the water, resting on a solid substrate. Examples of plants are green algae, red algae, sea lettuce, etc. Examples of animals include clams, crabs, and mussels.

Plankton

It is the group of microscopic animals and plants that live floating or suspended in the waters near the surface. Plankton almost always moves passively, dragged by the water. When it is plant plankton, it is called phytoplankton. If it is animal, it is called zooplankton.

Communities in Aquatic Food Chains

Marine plankton is made up of tiny plants and animals. Microscopic marine algae (phytoplankton) are the main producers. The microscopic animals (zooplankton) represent primary consumers or first order. In turn, these are the food of small fish and crustaceans, considered secondary consumers, which in turn serve as food for larger fish, aquatic birds, and mammals, which in the food chain take the place of tertiary consumers. At the beginning of all marine food chains are green algae as producers, equivalent to the green plants of terrestrial communities. Examples of marine food chains:

Phytoplankton -> whale (two links)

Phytoplankton -> zooplankton -> penguin (three links)

Phytoplankton -> zooplankton -> anchovy -> human (four links)