Normally, a thick meadow of lush algae is what you´d expect to see in healthy, thriving ocean ecosystems, right? Actually, it depends on the species. It´s certainly not a good sign if that green carpet turns out to be Cualerpa taxifolia, one of the deadliest invaders of the Mediterranean.
Known as ´killer algae´, Cualerpa was accidentally released about 25 years ago and has since spread rapidly, crowding out native plants. Toxins in the algae make it poisonous to potential predators, allowing it to grow unchecked. Cualerpa now stretches over more than 130 square kilometres of the Mediterranean, creating ´biological deserts´, and its reach has extended to the U.S. and Australia.
Aquatic invasive species like Cualerpa are becoming more common in marine and coastal areas, due to accidental introductions via the aquarium trade, hulls of recreational boats, or the release of ballast water from commercial ships. Habitat degradation, pollution, and climate change can also create more favourable environments for invasive species to thrive.
Ensuring our oceans are healthy and diverse is one way to prevent invasive species from gaining footholds in sensitive marine ecosystems. Creative minds are finding other solutions – the lionfish, invasive to the Atlantic and Caribbean, is now featured on restaurant menus, including ceviche and even pizza. Perhaps Cualerpa salad will be next?