A near miss: invasive non-indigenous mussels and barnacles transported deep into Antarctic waters [short note]

The Southern Ocean around Antarctica remains the only large area on the planet populated by almost entirely native and mainly endemic species. Despite being one of the most constant environments for millions of years and still the least human populated, the polar regions are now hotspots of physical climate change, and this is likely to make the shallow waters less inhospitable to invading non-indigenous species (NIS). A key vector for such potential invasive NIS are ship hulls, and the highest-risk species (likelihood × impact of establishment) are mytilid mussels. Here, we report finding live balanamorph barnacles Amphibalanus improvises and variously sized/aged (3–31 mm) Mytilus cf. chilensis mussels on the water intake grills of a research ship docked at a UK research station at 68°S. The discovery of these NIS shows that they were not just surviving deep into Antarctic waters but included multiple life stages and were actively feeding at ambient (−0.36°C) temperatures. With rising ship traffic and sea temperatures, this discovery should reinforce recent literature showing that some current, regional marine biosecurity monitoring needs urgent reassessment and improvement.