With drone images and field work, scientists from the IDEAL Center and the University of Oxford conduct mapping to obtain a more complete picture of these ecosystems, which will contribute to conservation efforts.

Alejandra Mora and Mauricio Palacios

Daniela Jofré, IDEAL Center. The underwater forests of the giant alga(seaweed) Macrocystispyrifera (also called ‘huiro’ or sargassum) are one of the most extensive and diverse ecosystems of the ocean. These macroalgae – which can extend more than 70 meters – provide refuge and food to countless marine species. Despite its ecological importance, there is still no certainty concerning its complex global distribution, especially in the extreme southern regions of South America, nor how its distribution and abundance patterns have been affected by climate change, due to the logistically complexity in performing field studies that could provide a more complete understanding of these communities.

To address this uncertainty, researchers Alejandra Mora, geographer of the University of Chile and doctoral student of the University of Oxford, and doctoral candidate Mauricio Palacios, of the Research Center: Dynamics of High Latitude Marine Ecosystems (IDEAL) of the Austral University of Chile (UACh) are working on a detection system which will use satellite images, to establish a realistic assessment of the distribution of these underwater forests, particularly those found in the Strait of Magellan.

“Carrying out field work in this area is complex and getting satellite images with clear skies even more so. Out of 500 images obtained in three years, 90% are covered with clouds, so it’s necessary to filter and process a lot of that information,” says Alejandra Mora, who designed an algorithm that is currently using drone overflights and field samplings for validation.

Researcher Mora added that “for the rest of the population these forests are completely unknown, and if they are invisible, there will be no interest in preserving them. Currently, as there is no monitoring system dedicated to this ecosystem, we still do not know exactly where they are or if they have changed the extent of their range in recent years.”

Credit: Mauricio Palacios

Meanwhile, Mauricio Palacios, who has focused his interest on deciphering the physiology of this type of organism, indicated that “for the images recorded by Alejandra, field validation is necessary, and for that reason we are characterizing the population dynamics of these macroalgae [seaweed] in the Strait of Magellan, as well as for those communities located in the Yendegaia Fjord (Beagle Channel), which are exposed to different environmental stressors. The physiological responses, such as carbon productivity and available biomass, will complement the mapping made by the drone, to obtain a complete analysis of this area.”

The researchers are working from the eastern mouth of the Strait of Magellan as far as the San Isidro Lighthouse, which will be complemented by a population analysis, already carried out in the Yendegaia Fjord, and information surveys in other areas of the region. These are conducted in coordination with the Chilean Ichthyological Foundatione – ranging from the Carlos III Island sector to Cape Horn. “This method has many implications for the possibility of making global estimates of the distribution of this ecosystem, which can help protect it on other coasts of the world,” added Mora. This combined effort involving doctoral theses from the Austral University of Chile and the University of Oxford would help to complete a picture of the health of these ecosystems that are part of the largest underwater “huiro” seaweed forests in Patagonian waters.