Experts emphasize the importance of protecting these fragile ecosystems and hope the newly discovered forests will be considered in the reserve's management plan.
The first thing the researchers noticed from their boat were red spots below the surface of the water during one of their expeditions. This detail led them to carry out a sampling in the Kawésqar National Reserve, a marine protected area in Chile's extreme south.
At 1.2 meters (3.9 feet) depth, they found a large number of red hydrocorals, which are colonial marine animals that resemble, but are distinct from, the more familiar reef-building corals. The discovery attracted their attention because, until then, this species, Errina antarctica, had never been recorded in areas so shallow, much less at such southern latitudes.
However, the discovery wasn't made by chance. The researchers, from the Chilean non-profit Fundación Rewilding Chile and the Spanish Institute of Oceanography, had spent several months analyzing previous marine investigations done between Puerto Montt and Cape Horn to detect gaps in the record. "We checked the entire terrestrial mapping, as well as maps from the SHOA [Hydrographic and Oceanographic Service of the Chilean Navy], which includes the depths and descriptions of banks of certain species," said Ingrid Espinoza León, director of conservation with Fundación Rewilding Chile and co-author of a paper describing the discovery published in April in the journal Scientific Reports.
The researchers' goal was to identify the most unexplored areas and to determine which locations were of greatest interest to explore. To achieve this, they interviewed local residents familiar with the territory.
The next step involved sending divers and underwater robots on an expedition. It was then that the researchers discovered colonies of red hydrocorals at four of the 23 sampling sites.
The colonies of E. antarctica, which looks like a coral but isn't exactly, are the southernmost and shallowest documented in the world, the researchers wrote in the paper.
This study is part of a series of investigations that Fundación Rewilding Chile's marine program is carrying out at different points in the parks of Chilean Patagonia. The goal is to gather information about the marine biodiversity there to later use in the creation of marine parks or marine protected areas.
Corals are tiny animals, known individually as polyps, which when united form the colonies that build and inhabit marine reefs. Apart from their larval stage, corals spend their whole lives motionless, rooted to the ocean floor.
Hydrocorals look almost exactly like corals, but there's a big difference. These species have two main phases in their life cycle: the polyp phase, in which they are stuck to the ocean floor, and the medusa phase, in which they are jelly-like organisms in the water column, explained Mathias Hüne, director of Fundación Rewilding Chile's marine program.
In taxonomy, corals are classified under the class Anthozoa along with sea anemones, while hydrocorals classified belong to the class Hydrozoa.
This is why the red hydrocoral colonies in Kawésqar Marine Reserve are not considered coral reefs but marine animal forests (MAF).
Individual hydrocorals tend to specialize within their own colonies, according to Ana de la Torriente, a researcher at the Spanish Institute of Oceanography and the paper's lead author. "Some Errina antarctica have the ability to capture the plankton that exist in the water, and others are in charge of reproduction. In this way they share different roles," she said.
De la Torriente highlighted the quantity of red hydrocorals the team discovered in Kawésqar Marine Reserve. "There is a high density; there are a lot of colonies together," she said. The importance of this is that, like a coral reef, these MAFs form a three-dimensional structure that is home to a great variety of species, she said.
The red hydrocorals the scientists found in the marine reserve cover up to 28.5% of the substrate of Angostura Toms -- one of the sounds in the Strait of Magellan -- at depths ranging from 1.23 m to at least 33 m (4 to 108 ft). This sets them apart significantly from red hydrocorals elsewhere. According to de la Torriente, in other places, they have been documented at depths of up to 770 m (2,500 ft).
"Generally, they are a deep-sea species. The fact that they appear in the Patagonian fjords in very shallow areas is ecologically significant," de la Torriente said.
The Kawésqar National Reserve borders the Strait of Magellan, considered to be "the most important channel in southern Patagonia that connects the Pacific and Atlantic oceans," according to the study about the discovery. Several micro-basins intersect its 550-kilometer (340-mile) length. "The area is influenced by saline water masses from the Pacific, Atlantic and Southern oceans that mix with freshwater from rainfall, river inputs and snowmelt, generating an estuarine system," the paper states.
José Luis Iriarte, an oceanographer at the Austral University of Chile and principal investigator at the Center for Dynamic Research of High Latitude Marine Ecosystems, said these oceanographic characteristics allow the circulation of two layers of water with different densities. While the fresh portion flows towards the surface, the salty portion sinks to the depths, and this causes a constant renewal and circulation of water, according to Iriarte.
From a chemical point of view, the freshwater that comes from the continent via rivers has high levels of oxygen, while the water from the ocean is rich in nutrients. This promotes biodiversity, Iriarte said.
Iriarte added that the variety in living species may be promoted by the blooming of microalgae that happens in spring, generating increased photosynthesis and biomass production.
The presence of red hydrocorals also indicates the good health of the ecosystem, said Ignacio Garrido, a marine biologist and director of the Austral University of Chile's coastal laboratory.
"They are bioindicators. Because they're species that can't move, they're super sensitive to any changes in the environmental conditions, but they're species that haven't been researched that much physiologically," Garrido said. "We know, more or less, the number of species there are, but we don't know much about their tolerance to environmental pressures."
According to the Chilean regulation for the classification of wild species, red hydrocorals are in a vulnerable state of conservation. Their sensitivity, Garrido said, is in part due to their necessity to set calcium carbonate to generate their skeletons, a component that is in danger due to the climate crisis. "With climate change and the acidification of the oceans, they have less capacity to set the calcium carbonate," he said.
However, that is not the only thing that worries the scientists. As explained in their study, the region where they found the red hydrocorals is threatened by pollution, eutrophication, or the excess supply of nutrients, and the introduction of invasive species, among other stressors.
In fact, in Kawésqar Marine Reserve has more than 60 concessions for salmon farming, even though scientists and civil society organizations have been asking for a cleanup of the area for years. They say the presence of this industry in the protected area worries them because science has abundantly documented its negative impacts on the environment.
In 2006, a study published by Austral University of Chile scientists Verena Häussermann and Günter Försterra showed accumulations of large colonies of Errina antarctica on slopes less than 10 m (32.8 ft) deep at the bottom of Copihue Channel in the Madre de Dios archipelago in southern Chile. Unfortunately, when the researchers went back in 2013, these colonies were dead, they reported in a separate study.
Although they weren't able to establish the precise cause of the mortality, Häussermann told Mongabay Latam that the clues they gathered pointed to a possible brown tide, a phenomenon caused mainly by the presence of microalgae with brown pigments. Although brown tides can occur naturally, scientists say they can also occur due to pollution associated with the salmon industry.
"[B]enthic [seabed] communities are largely unknown and likely contain numerous undiscovered species and unknown animal forest locations," states the paper describing the red hydrocoral discovery. "This lack of knowledge of the marine ecosystem hampers our ability to design effective and suitable long-term sustainable management programs and meet international targets."
That's why co-author Espinoza said the first step would be to generate more information. "To be able to make protection and conservation proposals you need to know what is there, and in the case of the sea, there is little enough information about which species these are," she says.
Data is key to the development of the management plan for Kawésqar National Reserve, which still does not have a date of execution, as the Indigenous consultation process is paralyzed by the Court of Appeals of Santiago.
The need for conservation actions to ensure the survival of the wealth of species and biodiversity associated with benthic communities and specifically with marine animal forests in Chile's Patagonian waters "must include concrete and effective tools," Espinoza said. For example, she added, now-extraction zones should be established and the need to remove aquaculture concessions in protected areas must be resolved to ensure the conservation of biodiversity in the long term.
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De la Torriente, A., Espinoza-León, I. M., Valenzuela-Lobos, L. A., Antolinez, A., & Serrano, A. (2024). The southernmost Errina Antarctica hydrocoral Savannah in patagonian waters. Scientific Reports, 14(1). doi:10.1038/s41598-024-60207-2
Häussermann, V., & Försterra, G. (2006). Extraordinary abundance of hydrocorals (Cnidaria, hydrozoa, Stylasteridae) in shallow water of the patagonian fjord region. Polar Biology, 30(4), 487-492. doi:10.1007/s00300-006-0207-5
Häussermann, V., & Försterra, G. (2013). Vast reef-like accumulation of the hydrocoral Errina Antarctica (Cnidaria, hydrozoa) wiped out in central Patagonia. Coral Reefs, 33(1), 29-29. doi:10.1007/s00338-013-1088-z