The oceans are getting warmer and our marine eco-systems are changing in ways that are becoming harder to predict.

Now, new research has found that higher temperatures – which are opening a Northwest Passage in the polar ice – have allowed marine species to travel between the Pacific and Atlantic oceans for the first time in hundreds of thousands of years.

One of these is the algae Neodenticula seminae, which has apparently returned to the Atlantic Ocean after an absence of over 800,000 years.

Experts say that in addition to being a harbinger of climate change, the re-introduction of the algae species could disrupt the balance of Atlantic's ecosystem.

The Northwest Passage is getting easier and easier to navigate

The research is being coordinated by the EU-funded CLAMER project. CLAMER is synthesizing test results on the effects of climate change on marine eco-systems, and draws on research from over 300 projects in 10 European countries.

"There is a mountain of information – not just about marine life, but the currents, the atmosphere. All the things that are part of the marine eco-system," says Katja Philippart, who is working on the project for the Royal Netherlands Institute for Sea Research.

New neighbors

Some of the noted changes are occurring very gradually.

The research has found that copepods, tiny animals that make up part of the diets of herring, cod and mackerel are moving north as their habitat warms in the North Sea and Atlantic.

With their food supplies on the move, so too are the fish and other species that prey upon them.

Although this process has been underway for a number of years, Philippart says some crucial "thresholds" are being passed.

"When things are going gradually, you can predict how things will develop, but if you're passing thresholds, then suddenly a lot of things can change," she says.

One such threshold is the Northwest Passage.

The melting of ice at the North Pole is clearing a path between the Pacific and Atlantic Oceans that has not been opened for millennia.

One of these is the above-mentioned Neodenticula seminae, but that algae isn't the only species roaming our changing oceans. According to CLAMER, a Pacific gray whale was spotted off the coasts of Spain and Israel last year, provoking a flurry of scientific speculation on how it got there and what the event implied.

Other species are not travelling quite so far but their movements are still causing concern among experts. "This is a sign of the acceleration of change," says Philippart. "If this door opens, then a lot of other species might come in, and things might change very rapidly."

Good changes or bad changes?

It is the speed of the change that CLAMER is emphasizing, not necessarily what they mean. It remains a mystery whether these changes will ultimately be positive or negative for humanity.

"We as human beings are dependent on a certain environment, and most of the things we see are generally changes for the worse, assuming that people prefer to eat cod to jellyfish," says Philippart.

"For example, the species of copepod that prefers warmer waters is less nutritious for the larvae of cod, so you end up with less cod, and there's more room for other species."

A Pacific gray whale surfaced in the Mediterranean last year

Complexity breeds unpredictability

But Philippart admits it is very difficult to make any predictions, because the connections between environmental circumstances are so complex.

"Species can change their diet, and if they do that and grow larger, and it's an edible species for humans, then we will benefit from that," says Philippart.

The algae that has just made its comeback in the Atlantic Ocean, is a good example of this double-edged sword in our marine ecosystems.

"It could disrupt the food chain, and potentially we could end up with less sea mammals and fish," says Philippart.

"On the other hand, it could also be beneficial because it is a relatively heavy algae species, which captures carbon dioxide."

"We need to learn much more about what's happening in Europe's seas, but the signs already point to far more trouble than benefit from climate change," says Carlo Heip, director general of the Royal Netherlands Institute for Sea Research.

"Despite the many unknowns, it's obvious that we can expect to find damaging upheaval as we study the workings of a system that's so complex and important," he added.

Project CLAMER concludes with an international conference in Brussels on September 14, which will be attended by representatives of governments from all round the world.

"All we are hoping for is that the people who are responsible for the management of our seas will take this information into account," says Philippart.

Authors: Stuart Tiffen, Ben Knight

Editor: Nathan Witkop