The Galápagos Islands are facing invasions on multiple fronts, from plastic bags and microplastics to alien species. According to a study recently published in Aquatic Invasions, more than 50 non-native plants and animals have made their way into Galápagos waters. This is close to 10 times as many as previously thought – and even that might not be the whole story.
The paper is the product of a study conducted by scientists at the Smithsonian Environmental Research Center, Williams College, and the Charles Darwin Foundation, who collected field surveys on Santa Cruz and Baltra (two of the larger Galápagos islands). Here, they gathered samples from mangrove roots, floating docks, and general debris and took note of any species that grew on the settlement plates they hung from docks 1 meter (3 feet) below water.
The team tallied up 48 previously unknown non-native species, which when added to the five known invasive species brings the total number to 53. Of these 48, 30 were newly discovered and may have existed on the islands "under the radar" for years. While another 17 were species that were known to live in the Galápagos but had previously been thought of as native. The last remaining species (the bryozoan Watersipora subtorquata) was first collected in 1987. However, it has only just been identified.
"This is the greatest reported increase in the recognition of alien species for any tropical marine region in the world," lead author James Carlton, an emeritus professor of the Maritime Studies Program of Williams College-Mystic Seaport, said in a statement.
The bulk of creatures in the collection were bryozoans, marine worms, and the adorably named sea squirt, so called because of their tendency to squirt water when disturbed. One of the most worrying finds was a species of mussel called Leiosolenus aristatus, which has been spotted boring into local corals.
The study authors say that pretty much all of these non-native species have had a helping hand from human travelers, who have come to the island by boat or (post-WW2) by plane. While precautions taken to protect the islands from invasive organisms are better today than they were in the 16th century, there is still a high risk of animals and plants inadvertently ending up in the Galápagos, the authors say. In particular, they mention the Indo-Pacific lionfish, which may migrate to the Pacific coast of Central America as a result of the 2015 expansion of the Panama Canal, and from there to the Galápagos. The lionfish is a major predator and could threaten native species, they warn.
"This increase in alien species is a stunning discovery, especially since only a small fraction of the Galápagos Islands was examined in this initial study," added Greg Ruiz, a co-author and marine biologist with the Smithsonian Environmental Research Center.
Which means that further investigations may uncover even more.