“Pacific Ocean shellfish – the mussels and snails, the clams and cockles – are heading for a mass invasion into the North Atlantic that could alter the entire ecology of both oceans as sea ice vanishes from the warming high Arctic, two California scientists predict.”

But the headline implies too much. Adds, in the first paragraph, to the drumbeat of fear we all feel, in prognosis more benign.

“Studying the fossils of marine organisms from 3.5 million years ago, the two California paleontologists saw that water from the Pacific Ocean must have been flowing north through the Bering Strait and into the Arctic Ocean where the ice had cleared and food was abundant. From there, hundreds of Pacific marine species moved into the warm North Atlantic to “colonize and enrich” the sea there, Vermeij and Roopnarine concluded.

“But a million years later the ice age returned in the far north and put an end to all of that,” Roopnarine said. “The Arctic Ocean, covered densely with ice again, became virtually a desert.”

Now that the northern seas are warming and a new mass migration of marine species is in the offing, “there’s a fair likelihood the invasion might generate new fisheries,” Roopnarine said. “Extinctions are unlikely, and there might be a cascading increase in abundance, perhaps, but that’s not easy to predict.”

Vermeij agreed. “Invasions like this can increase the genetic diversity of many species,” he said, “and in the long run we’ll see a lot of new hybrids.” “