Bitcoin and cryptocurrency markets have been rocked by volatility recently, with around $70 billion wiped from the combined value of the world’s cryptocurrencies in the first week of September.

The bitcoin price has been bouncing around the psychological $10,000 level over the last few days as bullish bitcoin buyers try to maintain what’s been described as “the last zone of defense.”

With nervous investors worried an equity sell-off could spill over to bitcoin and crypto markets, the San Francisco-based Kraken exchange has warned September is historically bitcoin’s worst-performing month—and predicted the market could see monthly returns below -7%.

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“A number of lesser-known market dynamics suggest incremental volatility is likely on the horizon,” Kraken bitcoin and crypto market analysts wrote in their August report this week, adding “with bitcoin under-performing its average monthly returns for most of the year, we could see returns below -7%.”

“Annualized volatility reverted to the mean after falling as low as 15%, while U.S. equities continued to climb. This coincided with a multi-year low for bitcoin’s dominance and a record number of bitcoin remaining untouched for over a year.”

Stock markets in the U.S. and around the world soared to all-time highs in August, fueled by government stimulus spending. However, Kraken warns that “stocks are relatively expensive and could cheapen in the months ahead. Such a correction could have an impact on the bitcoin and broader crypto market.”

Bitcoin dominance, a measure of bitcoin’s value compared to the wider cryptocurrency market, has fallen since the start of 2020, as alternative cryptocurrencies have been stealing market share from bitcoin—with Kraken pointing to the “emergence” of decentralized finance (DeFi) in the second quarter.

“While this trend may continue, we could see an eventual rotation back into bitcoin amid a reclamation of dominance,” Kraken analysts wrote.

Meanwhile, bitcoin’s current volatility could give way to “a new bull market,” with the report suggesting technical analysis shows an unprecedented number of bitcoin “are in the hands of long-term holders”—something that has “historically foreshadowed a new bull market.”

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For now, bitcoin and cryptocurrency market watchers remain focused on the key $10,000 per bitcoin level.

“Given that we haven’t yet seen a significant trend reversal pattern on the smaller chart time frames, a downward spike below $10,000 is not out of the question,” Simon Peters, crypto-asset analyst at brokerage eToro, said via email, adding the recent drop “represents overselling from investors, so buyers may soon step back in again.”

“If we do see a daily candle close below $10,000, then the pessimism will of course creep in. But as long as we remain above that threshold, I remain bullish.”