The Rise of Gracilaria vermiculophylla
The Invasion Begins
Imagine a thriving ecosystem, undisturbed for centuries, suddenly facing an unexpected intruder. This is the story of Gracilaria vermiculophylla, an invasive seaweed that has made its presence known along the coasts of North America and Europe.
Unlike most invasions, the journey of Gracilaria vermiculophylla didn’t start with malicious intent. It is native to the Northwest Pacific, with its roots firmly embedded in the coasts of Japan, Korea, China, and Vietnam. First described by H. Ohmi in 1956 from Hokkaido, Japan, this seaweed was initially cultivated for its agar, a prized resource (Israel et al. 1999; Rueness 2005; Hommersand and Freshwater 2009).
A Trail of Genetic Signatures
As Gracilaria vermiculophylla gained popularity as a valuable resource, it unintentionally hitched a ride with Pacific Oysters (Crassostrea gigas) from northwest Japan. From there, it spread to different parts of the world through secondary transport by currents, boat fouling, and ballast water (Krueger-Hadfield et al. 2017).
The Invasion Unfolds: North America
The West Coast Chronicles
The invasion of Gracilaria vermiculophylla on the West Coast of North America remains shrouded in mystery. Confusion with similar species made it difficult to determine the exact range and introduction date. However, it was first reported in Ensenada, Mexico in 1979, with subsequent sightings in Elkhorn Slough, California in 1994 (Bellorin et al. 2004; Rueness 2005).
Further evidence emerged when RNA sequences from the collected specimens closely matched those of the Japanese Gracilaria vermiculophylla (Rueness 2005). As years passed, more sightings occurred, including Vancouver Island and the British Columbia mainland (Saunders 2009). Possible vectors of introduction include hull fouling, ballast water, and Pacific Oyster transplants.
The East Coast’s Encounter
Gracilaria vermiculophylla quietly infiltrated the Atlantic Coast of North America before the year 2000. The earliest reported collection was in Hog Island Bay, Virginia, in 1998, followed by observations in Masonboro Sound, North Carolina in 2000 (Gurgel and Frederiq 2004; Thompson 2002). Its presence became increasingly evident, fouling nets, covering intertidal mudflats, and causing problems in power plants (Freshwater et al. 2006).
While the exact vectors of introduction remain unclear, it is speculated that ship fouling, ballast water, or even scattered plantings of Pacific Oysters in the past might have inadvertently led to its arrival (Krueger-Hadfield et al. 2017). Genetic analyses indicate separate introductions, with one staying in southern New England and the other spreading north to Great Bay, New Hampshire, and south to Georgia (Krueger-Hadfield et al. 2017).
The Global Invasion
Gracilaria vermiculophylla’s journey didn’t stop at North America. It soon found its way to Europe, initially appearing in the Netherlands in 1980 and the Ria de Aveiro lagoon, Portugal in 1985 (Rueness 2005; Abreu et al. 2011). The invasion went unrecognized for some time due to its resemblance to native species.
By 2004, this seaweed had spread extensively along the European coasts, from Norway to Spain and Portugal (Rueness 2005). It continued its conquest, reaching Northern Ireland in 2012 and the Baltic Sea coasts of Denmark and Germany between 2003 and 2007 (Nunn and Minchin 2013; Hammann et al. 2013). Gracilaria vermiculophylla even made its way to the lagoons of the Po Delta and the Venice Lagoon on the northern Adriatic Sea (Sfriso et al. 2012; Munari et al. 2015). Its expansion didn’t halt there, as it spread south to the Atlantic coast of Morocco in 2002 (Guillemin et al. 2008).
The Unintended Consequences of Gracilaria vermiculophylla
Gracilaria vermiculophylla’s unintentional invasion showcases the delicate balance of ecosystems and the lasting impact of human activities. Its introduction through unsuspecting transportation methods and subsequent spread due to genetic mixing have disrupted natural habitats and challenged native species.
As stewards of the environment, it is crucial that we learn from experiences like the Gracilaria vermiculophylla invasion. By being cautious of unintended consequences and promoting responsible practices, we can strive to preserve the delicate harmony of our ecosystems.
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