Jakarta –
When a new island appeared in the South Pacific in 2015, it opened new horizons not only for geologists and volcanologists, but also for biologists and ecologists.
The emergence of new islands offers an opportunity to study how ecosystems began, starting with pioneering microbes that ‘colonized’ new lands like this, before plants or animals appeared.
Unfortunately, the existence of Hunga Tonga-Hunga Ha’apai (Hunga Tonga), the name of the island, did not last long. After being formed by a volcanic eruption and discovered in 2015, it was destroyed by another eruption in early 2022.
However, over the seven years of its existence, the island has revealed several interesting secrets. In a new study, researchers report evidence of an unexpected microbial community on the island. These microbes metabolize sulfur and atmospheric gases, similar to organisms that occupy very different habitats, namely hot springs or hydrothermal vents in the deep ocean.
“We didn’t see what we expected,” said microbial ecologist Nick Dragone of the University of Colorado, quoted from Science Alert.
“We thought we’d be looking at organisms typically found when glaciers recede, or cyanobacteria, a more typical early colonizer species. But instead, we found a unique group of bacteria that metabolize sulfur and atmospheric gases,” he said.
Dragone and co-researchers collected 32 soil samples from the island, on surfaces from sea level to the top of the crater, which is about 120 meters high. They then extracted and sequenced the DNA from the sample.
Plants colonized the island fairly quickly once it was established, possibly thanks to seeds carried by bird droppings. But the researchers focused on collecting them on non-vegetated surfaces.
They found bacteria and archaea in all samples taken from the volcanic cone, although the microbes were less diverse than those from nearby vegetated areas, and very different.
It makes sense that the first microbes on the new island came from seawater or bird droppings. But apparently, that’s not where these strange bacteria and archaea came from. Instead, the researchers suspect these microbes may have come from underground.
“One of the reasons why we thought we saw these unique microbes is because of a trait associated with volcanic eruptions: lots of gaseous sulfur and hydrogen sulfide, which likely fueled the unique taxa we found,” said Dragone.
“These microbes most closely resemble those found in hydrothermal vents, hot springs such as Yellowstone, and other volcanic systems. Our best guess is that the microbes originate from these types of sources,” he believes.
Having the opportunity to investigate this kind of system was rare. A major eruption is one thing, but being able to witness the ecosystem thriving on a newly formed volcanic island is quite another.
While scientists also flocked to study the arrival of life on newly formed islands, they focused more on plants and animals than microbes.
“This type of volcanic eruption occurs all over the world, but usually doesn’t produce islands,” Dragone said. “We have a very unique opportunity. Never before has anyone comprehensively studied microorganisms in an island system like this at such an early stage,” he continued.
Now, no one will ever have the chance to study the island’s inhabitants again, at least not in person. Seven years after emerging from the Pacific, Hunga Tonga disappeared in spectacular fashion.
When Tonga’s Hunga volcano erupted again in January 2022, its activity resulted in the largest explosive eruption of the 21st century, with the highest plume of steam and ash in history. Hunga Tonga was obliterated. Luckily, scientists have managed to learn interesting details about its short lifespan.
“We were of course disappointed that the island was lost, but now we have a lot of predictions about what will happen if the islands do form,” said Dragone.
“So if something forms again, we’d be happy to go out there and collect more data. We’ll have a strategy on how to study it,” he concluded.
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(rns/afr)
