Scientists Research Kelp Forests as Harvesting Increases

algae forest

Bilagay (Cheilodactylus variegatus) and castañeta (Beryx decadactylus) fish swim in a brown algae forest off Pisagua, Chile. Image by Eduardo Sorensen/Oceana.

Translated by Theo Bradford

Michelle Carrere writes in Monga Bay News that a growing industry based on the production of alginate, a common thickener used in the food, textiles and pharmaceutical industries, is driving a boom in kelp harvesting off the coasts of Chile and Peru. At the same time, researchers are warning that large-scale harvesting of kelp forests could have significant ecosystem impacts.

The kelp forests of the oceans are a habitat for a wide range of marine species, rivaling the great tropical forests for sheer richness of biodiversity, according to scientists from the KELPER project, which studies these complex systems. “KELPER” stands for Kelp Ecosystems in Latin America: Pathways to Ecological Resilience.

Alejandro Pérez Matus, assistant professor at the Department of Ecology at the Catholic University of Chile is the main researcher with the KELPER Project. He says one of the project’s priorities is to identify the source or parent colonies that have the ability to provide new specimens. They will also evaluate the resilience of kelp forests and their capacity to bounce back from being harvested.

The species of seaweed strands anchored to rocks on the seafloor are typically Macrocystis pyrifera, or giant kelp, and Lessonia trabeculata, known locally as huiro palo. The largest natural reserves of both species are found off the coast of Chile and southern Argentina, according to the United Nations Food and Agriculture Organization (FAO). Chile is the world’s largest producer of macroalgae with an entire industry dedicated to kelp harvesting.

Increasing demand for alginate

Until 2005, the strands were collected on the beach by fisher-gatherers when, after a swell, the waves pulled them from the seafloor and deposited them on the shore. Since then, increasing demand for alginate — a market estimated at $1 billion a year according to a KELPER Project report — has driven the industry to start harvesting the kelp directly from the source in the sea. The practice is known locally as barreteo. According to the most recent figures published by the Chilean National Fisheries Service (Sernapesca), 40,261 tons of L. trabeculata were cut from the seafloor in 2018.

Amid the boom, however, marine algae remain relatively understudied, and scientists are drawing attention to this information gap. For the KELPER Project, the overarching question is: Can seaweed be extracted in a way that doesn’t harm ecosystems?

“We are trying to find out how long it takes for a forest to recover after extraction events,” Dr. Pérez Matus says. To do this, the research team is also studying which agents speed up and slow down kelp recovery. For example, how does the presence of herbivorous fish that feed on the plants affect recuperation?

The scientists are performing several experiments simultaneously. One of them consists of fertilizing algae in a laboratory at different temperatures to evaluate the impacts of climate change. Another is to cage certain patches of kelp to exclude all fish. Similar caged plots allow some fish in while barring sea urchins and herbivorous invertebrates that feed on the plants.

“The goal is to see which agent inhibits the recovery of these ecosystems,” Dr. Pérez Matus says. This will provide researchers with the necessary data to “propose measures with gatherers to determine where, when and how to extract these algae.”

Having begun in Chile, the project is looking to expand north into Peru to study the connectivity of kelp networks across the Humboldt Current that hugs the coast of both countries.

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