A new study released March 28 reports that the iconic Galapagos Islands have been invaded by nearly 10 times the number of alien marine animal species than previously known from its shores.

The study documents 53 species of non-native marine animals in this famed unique UNESCO World Heritage Site, one of the largest marine protected areas on the globe. It was published in in Aquatic Invasions, an open access journal of the International Association for Open Knowledge on Invasive Alien Species (INVASIVESNET) and can be found at http://www.aquaticinvasions.net/2019/issue1.html

The Galapagos lie on the equator 600 miles from Ecuador. Made famous by Charles Darwin's visit in 1835, the Islands have long been recognized for their remarkable biodiversity and have been the subject of extensive preservation efforts both on land and in the sea. But with their fame, traffic has spiked. In 1938, just over 700 people lived on the Galápagos. Today, more than 25,000 people live on the islands, and nearly a quarter-million tourists visit each year.

"This is the greatest reported increase in the recognition of alien species for any tropical marine region in the world," says lead author Dr. James T. Carlton of the Maritime Studies Program of Williams College and Mystic Seaport, USA. The study was a joint effort with Dr. Gregory Ruiz of the Smithsonian Institution's Environmental Research Center and Dr. Inti Keith of the Charles Darwin Foundation. They conducted field surveys on two of the larger Galapagos Islands, Santa Cruz and Baltra, where they hung settlement plates from docks one meter underwater to see what species would grow on them. They also collected samples from mangrove roots, piers, and floating docks and scoured the literature for previous records.

Newly discovered invaders include many species of biofouling sea squirts and moss animals (bryozoans), as well as marine worms and wood-boring mollusks known as shipworms. Most of the introduced species were brought to the Galapagos from tropical seas around the world by ships. Only one species, a mangrove crab, is believed to have been brought directly from the mainland.

The bryozoan Amathia verticillata. Known in other parts of the world for fouling pipes and fishing gear and killing seagrasses, its discovery in the Galapagos is especially concerning for scientists (Credit: Dan Minchin/Marine Organism Investigations).

"This discovery re-sets how we think about what's natural in the ocean around the Galapagos, and what the impacts may be on these high-value conservation areas," says Carlton. “This increase in alien species is a stunning discovery, especially since only a small fraction of the Galapagos Islands was examined in this initial study” adds Ruiz. New research is underway to examine additional areas and is likely to detect many more alien species.

The first goal in this research is to understand just how many invasions there are in the Galapagos. With this baseline, the research team hopes to determine what impact these species are having, especially on rare and endemic species, and how to prevent future invasions.

In an effort to reduce future invasions, the Galapagos Islands in Ecuador have among the most stringent biosecurity management programs in the world. International vessels entering the Galapagos Marine Reserve may only anchor in one of the main ports and must be inspected by divers. If a vessel is found to be transporting alien species, it is requested to leave and return for a second inspection once the hull has been cleaned.

The increase in size of the Panama Canal in 2015 may bring the Indo-Pacific lionfish, which has had significant impacts as a predator in the Caribbean, to the Pacific coast of Central America, carried by ships' ballast water. Once there, it could make its way to the Galapagos, where researchers conclude that the likelihood of its success would be very high. Another possible arrival is the Indo-Pacific snowflake coral, which has already caused extensive mortalities of native corals on the South American mainland.

The researchers suggest that based upon these new Galapagos findings, the number and potential impacts of alien marine species in tropical waters around the world may be significantly underestimated.