Benthic species, the silent guardians of the aquatic ecosystem

In the depths of rivers, lakes, and oceans, where light barely reaches and the hustle and bustle of the surface becomes a distant echo, there is a quiet but essential world. On lake and sea beds, these organisms carry out their task, sustaining life without almost anyone noticing their existence.

The word “benthic” comes from the Greek “bentos,” meaning “bottom,” and is used to describe life that develops in the deepest parts of aquatic ecosystems. At the bottom of rivers, lagoons, and seas live tiny communities, invisible to many, but essential to the health of our aquatic environments. These are benthic species, organisms such as mollusks, crustaceans, algae, and microorganisms that work silently recycling nutrients, sustaining food chains, and providing stability to sediments and habitats. 

They play an essential role in maintaining the health of aquatic ecosystems by forming a key part of the food chain and serving as food for fish, birds, and marine mammals, as well as improving water quality through their ability to filter water. 

Conserving wetlands or coastal areas is not just a matter of protecting landscapes, but also of ensuring that nature can continue to function as it should. A study carried out in the Ebro floodplain showed that both natural and restored ecosystems have greater benthic activity than in open water, confirming the importance of these bottom-dwelling organisms for the overall health of the environment. 

It has also been shown that when these spaces are restored with suitable plants and soils, biodiversity recovers significantly. For example, some wetlands created years ago have once again become home to invertebrates very similar to those found in natural areas, especially when native plant species have been used.

In addition to representing natural heritage, these benthic communities sustain local economies. In Spanish coastal areas, their regeneration helps fishing, aquaculture, and sustainable tourism by ensuring the presence of fish and organisms of commercial value. The European LIFE ECOREST initiative promotes active restoration through the reintroduction of structural benthic species to recover ecosystem functions and thus link science, local fishing, and public management in models that can be replicated in other areas of the Mediterranean.

In Spain, an inspiring example is the CABALGA project, an initiative by the CSIC that has reintroduced thousands of essential organisms such as gorgonians, sponges, and corals in protected areas of the Catalan coast. Thanks to innovative methods and the help of local fishermen, an area equivalent to Andorra was repopulated with nearly 30 structural benthic species. Although these are deep-water habitats, these organisms perform functions comparable to those of trees in a forest: they provide shelter, serve as breeding grounds, and create microhabitats that support entire food chains.

The recovery of benthic organisms also has a powerful educational effect. In educational and environmental projects, bringing schoolchildren and citizens closer to the fascinating world of the seabed or riverbed allows them to understand how the planet works in an interdependent way. In this sense, we can encourage students to explore benthic organisms through water samples, home studies with simple microscopes, or guided tours of wetlands and protected coastlines, where they can directly observe organisms that play a vital role in ecosystems.

When strips of aquatic vegetation return to restored wetlands, when benthic debris disappears from sediments, and when indicator species reappear in a river, not only is there a noticeable improvement in the ecosystem, but also in water quality, local fishing, and communities' enjoyment of nature. It is a simple but profound recognition: to have vibrant oceans, rivers, and wetlands teeming with life, we must also protect those species at the bottom that seem silent but actively contribute to building the environment that sustains us.