“Brown Algae: The Submerged Forests That Sustain Life in the Sea”.

By: Maria Court y Tatiana Pavez

Silent and unknown, the brown kelp forests stretch across the fjords and channels of Chilean Patagonia, forming an interconnected network that sustains marine life, captures carbon, and holds ancient secrets of our origins as a species.

Silent and largely unknown, the kelp forests stretch across the fjords and channels of Chilean Patagonia, forming an interconnected network that sustains marine life, captures carbon, and holds ancient secrets of our origins as a species.

In the fjords and channels of Patagonia, we find one of the most uniquely important interconnected networks of kelp on the planet. These aquatic forests support much of the region’s marine life: they form a structuring habitat, offering shelter and food for a vast number of species, improving water quality, and playing a vital role in climate change mitigation and adaptation. Since ancient times, kelp forests have sustained coastal communities and provided food and medicine for the first human settlements in Patagonia.

When we talk about “kelp,” we often group together very different organisms under the same name. In reality, algae belong to different kingdoms and evolutionary lineages: they don’t form a single biological group, even though they share certain characteristics, such as living in aquatic environments and performing photosynthesis thanks to chlorophyll.

There are microalgae, invisible to the naked eye but fundamental, since they produce a large part of the planet’s oxygen. There are also macroalgae, visible and familiar on the Chilean coast—like cochayuyo and luche—which are classified into three main groups according to their pigments: green, red, and brown.

But regardless of the type of algae, they are fundamental to our lives and to the conservation of ecosystems; so much so, that we wouldn’t exist without them.

“Algae are responsible for the origin of life as we know it today.” “More than 3 billion years ago, the first cyanobacteria began releasing oxygen into the atmosphere, forever changing the planet’s conditions,” says researcher Erasmo Macaya, a prominent Chilean phycologist and professor at the University of Concepción (UdeC), who directs the Laboratory of Algal Studies (Algalab), focused on the ecology, diversity, and molecular biology of macroalgae.

Without these primitive algae, animals—and humans—would never have existed. “In fact, there is an event called the Great Oxygenation Event, which is precisely the great abundance of these organisms that causes the planet’s structure to begin changing, the atmosphere to form, the amount of oxygen to increase, and organisms that depend on it to appear,” Macaya adds.

Thousands of years later, algae also played a leading role in human history. The Kelp Highway theory posits that the first inhabitants of the Americas migrated along the coast, feeding on the resources offered by the underwater forests of brown algae. Archaeological evidence In Monteverde, near Puerto Montt, evidence shows that 14,000 years ago, cochayuyo and red algae were already being consumed, not only as food but possibly also as medicine, the phycologist mentions.

Brown Kelp Forests: Sustainers of Life

Brown kelp forests are extensive clusters of macroalgae that grow from the seabed and rise to the surface. They function similarly to terrestrial forests: they generate oxygen, capture carbon, absorb nitrogen and dissolved phosphorus, accumulate heavy metals, and offer shelter, food, and breeding grounds to a vast diversity of marine species. They are key ecosystems for the balance of life on the planet, for the health of the ocean, and as a crucial source of sustenance for coastal communities and global economies.

In Chile, brown kelp forests are mainly composed of three representative genera: Lessonia (black kelp and palo), Macrocystis (sargassum or canutillo), and Durvillaea (cochayuyo).

“Kelly forests perform practically the same function as trees on land; they are very important for maintaining biogeochemical levels in the carbon cycle, the oxygen cycle, and many other cycles,” says Laura Ramajo, a biologist with a doctorate specializing in global change and an adjunct researcher at the Center for Climate Science and Resilience (CR2) in Chile.

Laura explains that kelp forests play a key role in combating climate change. Although they are not plants, they photosynthesize, which allows them to produce oxygen and absorb CO₂, helping to mitigate ocean acidification and regulate pH in sensitive areas such as fjords. Furthermore, their extensive structures act as natural barriers that reduce the force of storm surges and even the effects of tsunamis, protecting the coast from erosion and infrastructure destruction.

“Kelly seagrass (Macrocystis pyrifera) forests are tens of meters deep, and the fronds are enormous. It has been observed that when these disappear, the effects of tsunamis and storm surges generate erosion and loss of vegetation.