IDEAL Center scientists conducted an expedition to the Yendegaia fjord in Tierra del Fuego, in the Magallanes Region, to determine the adaptability of this seaweed species, which provides shelter for hundreds of aquatic organisms.

Daniela Jofré, IDEAL Center: Known as huiro or sargassum, the brown seaweed (Macrocystis pyrifera) is possibly the largest living organism on the planet. With portions that may exceed 70 meters, its distribution extends over almost the entire Pacific Ocean coast of the Southern Hemisphere and in most sub-Antarctic islands. This seaweed (or “macro-algae”) is capable of shaping ecological systems to provide for the feeding, reproduction, and shelter for hundreds of marine species, which coexist in the so-called “huiro forests.”

Although this species represents considerable importance for the marine ecosystem, very little is known about the nature of its adaptability when confronted with change in its environment. But now this is under study by scientists from the Research Center – Dynamics of High Latitude Marine Ecosystems (IDEAL) at the Austral University of Chile (UACh).

In the winter of 2018, a group of researchers conducted an expedition to the Beagle Channel in Tierra del Fuego, in Chile’s Magallanes Region, to evaluate the population dynamics and physiology of these seaweed in the Yendegaia fjord. The study hoped to determine how it responds to variations in environmental factors, including various gradients of glacial influence (temperature, salinity, and sediment) in that area. In July this year, scientists undertook another expedition to the same sector.

Huiro Forests © Mauricio Palacios

“The concept for this campaign was to complement the research that has been done since last year and determine how the huiro “forests” are responding to change factors (environmental stressors). This would result from their ability to produce anti-stress compounds which in turn provide for adjustments in their metabolism to deal with these varying gradients,” reported doctoral candidate Mauricio Palacios, a biologist at the IDEAL Center.

A part of this task involved analysis of phenolic compounds (substances present in brown seaweed). These allows the huiro plant to generate a resistance response to significant variations in environmental conditions such as light, UV radiation, or freshening (a phenomenon involving lower salinity resulting from glacial melting, in response to global warming). These factors are omnipresent challenges in the life of Macrocysti pyrifera.

The research team is headed by Dr. Luis Pardo, who studies the organisms associated with these huiro seaweed “forests.” The study area for the team extended for twelve kilometers.

Palacios emphasized the importance of these huiro seaweed forests for the austral marine ecosystem. “These are stable systems, which allows them to support extensive biological diversity. They work as umbrella species, providing environmental stability (protection and breeding sites) for hundreds of other organisms that live within these communities,” reported Palacios.

In addition to these studies, the team plans to conduct a characterization of seaweed, including detecting coverage and diversity, in an effort to produce the first such estimate of the physiological character of the “macro algae” in the Yendegaia fjord. This data collection involves an underwater drone, operating at depths up to 80 meters, in coordination with the School of Geography and Environment at the University of Oxford. This will allow improvements in remote sensing practices. The work will be undertaken by the doctoral candidate Alejandra Mora, who was part of this scientific expedition.