Underwater invaders

by Jessica Howard

Galapagos is leading the charge in marine biosecurity, with one of the most stringent programmes in the world. But, with increasing challenges facing the endemic species of Galapagos, is the ecological door open for marine invasive species to move in?

An invasive species is any living organism that has travelled into an environment in which it isn’t found naturally, causing harm to the local environment, economy or human health. The effects on local populations are wildly unpredictable, but they often disturb native populations either through predation, competition for space and food, or by introducing unfamiliar diseases.

The geographic remoteness of the Galapagos Islands has naturally limited the arrival of new species, giving the animals and plants there the opportunity to evolve in relative isolation, without much competition or predation to worry about. This has resulted in some amazing adaptations that are unique to the Islands, like the endemic algae munching marine iguana.

Wildlife, Marine Iguana 2 ©Simon Pierce
Marine Iguana © Simon Pierce

However, this has left the native species of Galapagos vulnerable to invasions, as they have few natural defences. As such, invasive species are the ultimate threat to Galapagos wildlife, but with most of the awareness surrounding terrestrial invasions, we’re going to dive under the waves to explore the lesser-known world of marine invasive species.

The ocean has always been a dispersal mechanism for non-native species, and through swimming, following currents, or hitching a ride on anything that floats, these species have found new coastlines in which to flourish.

Since humans began traversing the oceans, organisms have found more opportunities to stow away, travelling faster and further around the world. With increasing tourism and a booming local population, ship traffic to the Islands must also increase, bringing food and other goods to the community. Unfortunately, this is how most non-native species infiltrate new marine environments. Ships can introduce new species through ballast water, which can be full of whatever traumatised species got sucked up where the ship was loaded. They can also piggy-back on the outside of boats, either by permanently attaching or by hiding in nooks and crannies, and by hitch-hiking a ride on anything else that floats. These species can also attach to wood, algae, and of increasing concern, plastic pollution. This enables them to travel for even greater distances, as ocean plastic seems to be one of the only habitats that we are not destroying.

In the midst of the climate crisis, natural barriers in water temperature (which have previously limited the spread of non-native species) are breaking down, leaving invasive species better poised to exploit and populate new habitats where they once wouldn’t have been able to. This, when paired with El Niño events potentially increasing in frequency and intensity, will challenge the survival of native species, making them even more susceptible to invasions.

In a recent study from the Smithsonian Environmental Research Center, Williams College and the Charles Darwin Foundation, scientists found 53 non-native marine species living around the Islands, when previously we knew of just five. This study was limited to only one habitat (harbours), between two islands, suggesting that the actual numbers of invasive species could be considerably higher.

The alien species included worms, crabs and mussels, which were observed burrowing into living coral colonies in Galapagos. In 2012, the Charles Darwin Foundation initiated the marine invasive species project, a large-scale monitoring project targeting marine invasive species in Galapagos.

The project, spearheaded by Dr Inti Keith, has developed an early detection scheme through continuous monitoring of settlement plates in Ecuador as well as in Galapagos, devices that allow the controlled collection of data on colonisation by new species. The team is also monitoring a well established invasive alga, Caulerpa racemosa, which is especially dangerous for corals, as the rapid-growing algae may smother them if growth rates increase.

Boats © Dan Wright
Boats in the harbour © Dan Wright

Policy changes have been implemented to prevent future invasions, with every international vessel that enters the Archipelago inspected by divers for nonnative species. If they find any the ship is asked to leave and have its hull cleaned before returning for a second inspection. The generation of a central ‘cargo hub’ has been introduced to consolidate the threat of marine bioinvasions to just two areas of the Archipelago. A third recommendation is that ballast water should not be released in Galapagos, unless it has been exchanged at sea beforehand.

Despite these advances, the risk of marine invasive species remains high. The two biggest and most likely threats at the moment are thought to be the Indopacific lionfish, which may spread from the Caribbean through the Panama Canal and reach Galapagos, where it’s likely to be very successful. Another possible arrival is the snowflake coral, which has already caused widespread death of native corals along the South American coastline.


Now that we have a better understanding of what invasive species have already established themselves in Galapagos, the next steps will be to figure out how they are affecting native populations and how we can prevent further introductions.

This article originally featured in our Autumn Winter 2020 edition of Galapagos Matters.

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