Migrating plankton could adversely affect the biodiversity and workings of the Atlantic
IT TOOK 800,000 years but it is back. A microscopic plankton long extinct from the Atlantic Ocean has returned, drifting across from the Pacific because of dramatically reduced ice over the Arctic.
Climate change is being blamed for the loss of ice that has allowed this migration and the arrival of other marine species that could have a negative impact on north Atlantic ecosystems.
The tiny plankton has already been joined by another visitor, a Pacific gray whale that also took the Arctic Ocean shortcut. It was spotted swimming in the mild waters of the Mediterranean Sea, according to research released yesterday by Climate Change and European Marine Ecosystem Research (Clamer).
The discovery was “the first evidence of a trans-Arctic migration in modern times”, according to the UK’s Sir Alister Hardy Foundation for Ocean Science. It is one of 17 marine institutes in 10 European countries that have joined in the project. NUI Galway is the Irish participant in Clamer and along with its Ryan Institute it conducts research into the impact of alien species on established ecosystems, said Mark Johnson, professor of marine environment at NUI Galway.
Researchers recognised an Arctic Ocean route free of ice would mean incoming species, particularly as hitchhikers on ships. An ice-free shipping lane could be there during summer months by 2050, Prof Johnson said. It means species will no longer be blocked by the warm water barrier they now face when moving between the two oceans via the Arctic. Ship hulls carry algae, invertebrates and mollusc species while ballast tanks when discharged may harbour fish eggs and other species, he said.
“If you add species, each is an uncontrolled experiment even if they are later found to cause no harm,” he said.
The returned plankton, Neodenticula seminae, once lived in the Atlantic but has been missing there for 800,000 years. For this reason it is a potential threat because it could have effects on the biodiversity and functioning of the Atlantic marine ecosystems as they now are.
The gray whale has only been missing from the Atlantic for about 300 years, probably hunted out by whalers, but it too could cause unexpected problems with its return.
More migrants are expected as the Arctic ice continues to retreat. The Clamer project will catalogue new arrivals but also detail other changes, for example the displacement of cold-loving fish species that travel north to keep cool or in pursuit of prey.
The project involves scrutinising some 300 EU-funded research projects accumulated over 13 years, all focused on the oceans and near-shore waters.
Sometimes the influx of newcomers to a region increases biodiversity and causes no problems, but things can also go bad as marine habitats change.
Warmer waters encourage plankton species that can cause toxic blooms, killing fish and making edible shellfish poisonous to humans. Jellyfish blooms are occurring more frequently in the northeast Atlantic and often involve venomous warm-water species such as Pelagia noctiluca that force closure of beaches.
Complete strangers can also arrive, for example the deadly Portuguese Man-of-War, Physalia physalis, a sub-tropical jellyfish-like species. Warm water means it can travel further north.
Changes in the sea can have an impact in the air. Alterations in the plankton mix are associated with the collapse of some fish stocks, a loss that causes a decline in fish-eating sea birds along our coastlines, the scientists said.
