There are forests that are not visible to the naked eye, but are as important as the others. They are submerged in the cold waters of the South Atlantic, swaying with the tide like a hypnotic jungle. They are the forests of cachiyuyo, giants of brown algae that can grow up to twenty meters and form true underwater cities.
They rise as three-dimensional structures that offer habitat, food, and shelter to a great diversity of marine species. They function as true ecosystem engineers, regulating biological and chemical dynamics in the coastal environment.
They have been compared to terrestrial forests, and it is not an exaggerated metaphor. Like trees, cachiyuyo undergoes photosynthesis, captures CO₂, releases oxygen, and sustains entire life networks. It just does it from below, out of reach of simple observation.
Submarine Forest: the architecture of the sea
In Chubut, these submarine forests appear as corridors or patches near the coast, especially on rocky bottoms. Their fronds—the “leaves” of the algae—extend from depths of 5 to 20 meters to the surface, forming a canopy that can be seen with drones and even from satellites. During some low tides, they timidly come into view, as if wanting to remind us that they are there.
As one moves south, these forests become more abundant and complex. In Tierra del Fuego, for example, they reach their maximum splendor. In Chubut, on the other hand, their presence is more seasonal: they usually reach the coast after completing their life cycle.
What is remarkable is that, despite their discretion, cachiyuyos sustain a universe. “They are engineering species of the coastal marine ecosystem,” explain biologists specializing in CONICET. And it is not a poetic way of saying it: they perform vital functions in the ecological architecture of the sea.
A refuge with thousands of doors
Among their fronds and roots—or more precisely, their holdfasts, which attach to the seabed—a huge number of macroinvertebrates live. Relationships have been found with king crabs in their juvenile stages, with dolphins, mollusks, crustaceans, and fish that find in these algae a home to grow, reproduce, or simply not be eaten.
Moreover, when they decompose, cachiyuyo feeds many of these same species. Their remains become detritus that nourish the seafloor and are part of the carbon cycle. Because in the perfect architecture of the sea, nothing is wasted: what floats is also food.
Breathing thanks to the sea
A large part of the oxygen we breathe comes from the sea, although it is popularly associated with the function of plants. And in that system, algae like cachiyuyo play a key role. They are primary producers: they transform solar energy into energy and, in the process, release oxygen. They also capture CO₂, which makes them natural allies against climate change.
In the case of Chubut, significant impacts of global warming or pollution on these submarine forests have not yet been detected. But scientists warn that it is urgent to have updated information on their dynamics and biology to prevent any damage before it is too late. Protecting these forests is protecting the biodiversity of the Patagonian sea.
Value on the coast and beyond
Today, the collection of cachiyuyo in Argentina is mainly carried out from plants that naturally arrive on the coast. There is no active underwater harvesting, which for now avoids impacts on the forests themselves. However, their possible uses are being studied in industries ranging from food to cosmetics and medicine, due to their bioactive compounds and their capacity to generate biomass at a rapid pace.
The key, explain the researchers, is to balance that economic potential with their enormous ecological value. Because cutting a cachiyuyo is not like picking a leaf: it is altering an entire ecosystem that lives under the sea.
Gastronomic and cosmetic uses
Cachiyuyo, like other seaweed, contains compounds of high industrial and artisanal value in its structure. In gastronomy, its use extends from soups and stews to snacks and dietary supplements, especially in cultures with a long seaweed tradition such as Chilean or Japanese. Although a consolidated seaweed culture does not yet exist in Argentina, its potential as a healthy and sustainable food is beginning to emerge in certain gastronomic circles.
In the cosmetic field, cachiyuyo provides natural gels present in its cell walls, such as alginate, which shares the spotlight with other compounds extracted from red algae such as carrageenan or agar-agar.
These gelling agents are highly valued by the industry for their ability to thicken, hydrate, and stabilize products. Additionally, some species have antioxidant properties that are used in the production of creams, masks, and skin treatments. The link between the sea and personal care, still in its infancy in the country, is projected as a new frontier to explore with awareness and creativity.
By Diego Crova
