A couple of the ARK Invest exchange-traded funds managed by ETF superstar Cathie Wood made a significant acquisition on Thursday. The fund purchased roughly 290,000 shares of Roku Inc. (NASDAQ: ROKU) in total, even though the price of these ETFs fell by less than 1% on the day. It's worth noting that some funds have had substantial gains in the last year.

ARK Innovation ETF (NYSEARCA: ARKK) purchased 216,219 Roku shares, while ARK Next Generation Internet ETF (NYSEARCA: ARKW) purchased 71,357. At Thursday's closing price, the total value of this acquisition would have been around $83.2 million. Even though this is only a tiny portion of the total holdings, every little bit helps. The innovation fund increased by 30% last year, while the other has increased by around 37%.

Catherine Wood, the CEO and CIO of ARK Investment Management is a nonvoting minority shareholder in 24/7 Wall St., which owns 247wallst.com.