Climate change could be altering northern ecosystems more quickly and profoundly than anyone surmised, suggests a study that focused on a large Arctic lake. "Everything is so intricately connected," said lead author Igor Lehnherr of the University of Toronto. "You warm the region and it has this domino effect on the entire watershed." The study, published recently in the journal Nature Communications, keyed in on Ellesmere Island's Lake Hazen, where summer temperatures have risen by about one degree since 2000. It brought together a large team of scientists to look at effects of the temperature increase on the area's overall ecosystem.

Despite Lake Hazen's size — it holds more water than any other lake in the High Arctic — impacts are already profound and wide-ranging with no precedent for at least the last 300 years. Meltwater and sediment are flowing into the lake at 10 times the historic rate. So are contaminants such as mercury. Large areas of permafrost that were once solid year-round now melt in the summer. Ice-free days have increased and the lake averages three more square kilometres of open water every year. Shorelines have risen by about a metre, and nearly four times as much water is flushing into the river that drains the lake. The lake's food web is changing. Algae are blooming, but Arctic char are deteriorating, perhaps because the water has grown murkier.

"The lake is waking up," said co-author John Smol of Queen's University, who confesses he was surprised at the speed and breadth of the changes despite such a small temperature increase in such a big lake. "Things are really changing fast and it didn't take much." Lake Hazen was an ideal test subject for the unique interdisciplinary study. Despite its remote position at the northern end of Canada's most northern island, scientists have been camping by the lake's frigid shores since the 1950s. That's given them decades of solid data. As well, it's located within Quttinirpaaq National Park, which protects the lake from the direct influence of humans. Lehnherr cautions against concluding all Arctic lakes are going through exactly the same changes as Lake Hazen. Conditions differ across the North and so will the effects of warming. But the basic finding is likely to be widely applicable, he said. "Most of the Arctic lakes are likely representative of fragile ecosystems and are going to be sensitive to warming," Lehnherr said. "They're likely already experiencing impacts. "It didn't take a huge amount of warming to see impacts. One degree was enough."

Smol described the changes as stunning. "Nature doesn't go in slow, gradual changes — it hangs on and then reaches a threshold and goes for something completely different." Climate change makes winners and losers.

"I don't know what a lot of these Arctic lakes are going to look like," said Smol, who's been studying them for more than 30 years. "It's very hard to say what's better or worse. This lake is going from its natural state to a new type of regime. "That worries me. Humans have a very poor record of altering ecosystems."