LONDON/NEW YORK (Reuters) - Bridgewater Associates' flagship fund Pure Alpha posted a gain of 8.2% in January, in a period when investors navigated a sell-off in AI-related stocks and uncertainties around the incoming U.S. administration, a source familiar with the matter said.

It was not immediately clear what drove the hedge fund performance in January.

Last year, the macro flagship fund, known as Pure Alpha 18% volatility, was up 11.3%.

Tech stocks plunged on Jan. 28 after Chinese AI startup DeepSeek revealed that its model was on a par or better than industry-leading rivals in the U.S. at a fraction of the cost, sending shares in Nvidia down roughly 17%.

Worldwide, stocks also whipsawed amid concerns after U.S. President Donald Trump said he would implement tariffs on Canada, Mexico and China. On Monday, Trump suspended his threat of tariffs on Mexico and Canada, but maintained tariffs on China.

Still, despite all choppiness in January, all main U.S. stock indexes ended the month in the positive territory. The S&P 500 rose 2.7%, while the Nasdaq Composite and the Dow Jones Industrial Average gained 1.64% and 4.7%.

Speaking at a conference in Miami last week, co-chief investment officer Karen Karniol-Tambour said investors should diversify their equity allocations to markets outside the U.S. and also add more bonds to portfolios as a way to protect against a growth downturn.

"The bar for the U.S. (equities) to keep being the outperformer has just really risen relative to what it was because of this period of mass outperformance," she said.