Lava is laying waste to swathes of La Palma but, according to The Guardian, the Canaries’ last volcanic eruption actually helped fertilise the surrounding waters.

As the molten lava reached La Palma’s craggy coastline many marine organisms will have sadly perished. But unlike on land, where life struggles to return amongst the baron fields of igneous rock, recent research shows that marine life can return to the area quickly, and often in better shape. 

A study by researchers at the Spanish Institute of Oceanography and the University of Las Palmas in Gran Canaria studied the after-effects of the Tagoro eruption, which took place underwater near the island of El Hierro in 2011.

Continuing for almost six months, the eruptions caused such extreme changes in temperature, acidity and chemical composition of the water, that all traces of marine life disappeared from the local Mar de las Calmas marine reserve - an area previously popular for recreational diving.

But, according to researchers, within just three years the entire submarine volcano was once again covered with life - with the exception of a 200-metre radius from the crater. Not only was phytoplankton present in bigger quantities, but organisms from the surface of the ocean to the seabed had all also returned - including mature fish, squid and octopus.

The lava is rich in iron, as well as magnesium and silicates, and this supplies nutrients to the water. It’s like a forest fire. It destroys everything, but at the same time provides nutrients for new growth. The difference is that marine life recovers much faster than a forest.- Carolina Santana González, an oceanographer at the University of Las Palmas in Gran Canaria

Incredibly, in El Hierro, the concentration of iron near the volcano’s cone was nearly 30 times the normal level. This is because the surrounding waters were also rich in carbon dioxide, which lowers pH levels and thus helps microorganisms absorb the iron. And, while iron oxidises quickly in water and forms other compounds that sink to the seabed, the continued low-level volcanic activity in El Hierro, simply continued emitting iron.

Another factor involved in the fertilisation of volcanic marine environments is known as “upwelling”, which occurs when lava forces nutrient-rich water from the seabed towards the surface.

“We can’t stop nature, but nature has mechanisms for regeneration that are rapid and effective,” says Eugenio Fraile Nuez, who is in charge of monitoring the La Palma volcano from the Institute of Oceanography’s vessel moored off the stretch of coast where the lava is pouring into the sea. “That’s why it’s not an environmental catastrophe, but quite the opposite: volcanoes are life,” he says.

As eruptions continue around La Palma, the lava now covers more than 20 hectares of sea, reaching depths of 24 metres, and stopping some eight kilometres from a nearby marine reserve that plays host to tropical anemones, sea bream, brown algae, lobsters and sea turtles.

Moving forward, the scientists behind the six year study of El Hierro believe that marine areas with volcanic activity could be used to better understand how the climate crisis could affect oceans.