Jumping the Pond: A European Colonist Arrives on American Shores
10 April 2025
Last update: 10/04/25 09:57
The latest Paper of the Month for Journal of the Marine Biological Association of the United Kingdom is First record of the sea anemone Actinia equina (Cnidaria: Anthozoa) on the Mid-Atlantic coast of the United States and is available as open access.
Relocation by container shipping is often a cost-effective option for those moving overseas. Unfortunately, shipping also provides a route for translocation of invasive species – whether transported on the hulls of ships or in their ballast water. The shores of New Jersey, sitting close to the entrances to the busy ports of New York, New Jersey, and Philadelphia, see shipping traffic from all over the world passing close-by, and a plume of water which exits New York runs past these beaches.
It was on rocky groynes on the beaches of New Jersey that Biology student Diederik Boonman noticed in 2023 an unexpected occupant looking out of place amongst the barnacles and blue mussels that make these rocks their home – clusters of pale-green sea anemones could not only be seen but were both patchily abundant and seemed to be outcompeting the usual residents. Taking to the citizen science reporting platform iNaturalist.org to log his find, Diederik noted that similar records for New Jersey had been posted by other contributors to the platform as early as 2021.
Genetic analysis quickly confirmed the initial identification of this new New Jersey anemone as the well-known European beadlet anemone Actinia equina, specifically to populations hailing from the UK and Ireland, where it is familiar to rock poolers and marine biologists. Relatively small and ranging in colour from bright red to green (but also brown and orange), the beadlet anemone is a carnivore, consuming a wide variety of prey, including crustaceans and small fish, on intertidal shores. Long-lived, Actinia equina is also one of the most famous species of sea anemones in the world – one individual, known as Granny, lived for over 60 years in aquaria in England between the 1820s and 1880s! Beadlet anemones are known to reproduce asexually. Poke them (gently) and they may release tiny clonal offspring out of their “mouths”. Perhaps such tiny clones hitched a ride across the Atlantic in a ballast tank or in one of many niches on a ship’s hull. Regardless of the vector, the arrival of European colonists is causing a stir in the local press:
https://www.njpbs.org/programs/nj-spotlight-news/anemone-1741972811/
Beyond just the discovery of this invasive species on New Jersey shores, this study reveals the usefulness of reporting platforms like iNaturalist. Checking kilometers of coastline requires many hours of work – far beyond what is possible for an academic study. But through reporting of sightings, citizen scientists can provide a wealth of useful data. Indeed, since the publication of the paper, the beadlet anemone has now been found to the north in New York State. The colonists are spreading out.
The paper “First record of the sea anemone Actinia equina (Cnidaria: Anthozoa) on the Mid-Atlantic coast of the United States“, by Diederik Boonman, Craig Stephen Wilding, James T. Carlton and Jason E. Adolf, published in Journal of the Marine Biological Association of the United Kingdom, is available as open access.
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