If you own stock, there are no tax implications until the stock is sold.
If you own mutuals funds that are NOT in a tax-deferred retirement account (IRA, Roth, 401k, SEP, SARSEP, etc...), then you WILL have to pay tax on any dividends or capital gains reported to you by the fund company, whether the fund is worth more or less $$/share.
Your end of year statement from your mutual funds will tell you whether or not any gains/dividends are being posted.