(Bloomberg News) John Paulson, the hedge-fund manager enduring the worst year in his career, may be facing a final blow from this month's selloff in gold, an investment that mitigated losses at his $28 billion firm earlier in 2011.

The SPDR Gold Trust exchange-traded fund, of which Paulson was the largest shareholder as of Sept. 30, fell 10 percent from the end of last month, and all eight of his gold stocks slumped with a 9.6 percent decline for bullion. The declines would translate into a $672.1 million paper loss on those securities for Paulson & Co., assuming his holdings haven't changed since the end of the third quarter, when the firm reported its equity stakes in a regulatory filing.

Until this month, gold had been the bright spot for Paulson & Co. clients, who can choose to invest in gold-denominated shares of the hedge funds. Gains in bullion had alleviated losses of 46 percent, in the dollar share class, for one of the firm's biggest funds this year through November. Paulson also offers a dedicated Gold Fund, its best performer this year.

"With the dramatic moves of gold and the recent decline from its peak, I think some investors will be deciding whether they want to continue to invest in that share class," said Don Steinbrugge, managing partner of Agecroft Partners LLC, a Richmond, Virginia-based firm that advises hedge funds and investors.

Paulson, who turned 56 yesterday, has lost money this year on investments including Citigroup Inc., Bank of America Corp. and Sino-Forest Corp., the Chinese forestry company accused by short-seller Carson Block of overstating timberland holdings. Paulson cut the so-called net exposure in his main funds to 30 percent last month and reduced bullish bets across all his funds on stocks including gold companies.

Net exposure is calculated by subtracting the percentage of a fund's short positions, or bets on falling securities, from its longs, or wagers on rising stocks and bonds.

Armel Leslie, a spokesman for Paulson, declined to comment on the firm's potential gold-related losses.

Paulson & Co. held shares of SPDR Gold Trust and eight gold companies in the third quarter, according to its 13F filing. The firm, which uses the ETF to denominate the gold share classes of his funds, pared its stake in the gold trust to 20.3 million shares from 31.5 million as of June 30.

The firm was the largest holder of American depositary receipts in AngloGold Ashanti Ltd., the third-biggest gold producer. Paulson also owned shares or ADRs of Gold Fields Ltd., NovaGold Resources Inc., Randgold Resources Ltd., Agnico-Eagle Mines Ltd., Iamgold Corp., Barrick Gold Corp. and International Tower Hill Mines Ltd.

Gold's plunge to a five-month low sent it below its 200-day moving average for the first time in almost three years, signaling more declines to traders who follow technical analysis. Bullion fell below $1,600 an ounce yesterday to settle at the lowest level in five months as a stronger dollar curbed demand for the metal as an alternative asset. Gold futures for February delivery dropped 4.6 percent to settle at $1,586.90 at 1:44 p.m. on the Comex in New York, the lowest closing level since July 13. The 200-day moving average was near $1,613.