Abstract <p>Among the diverse marine phytoplankton, dinoflagellates are of great interest as a group of protists that dominates ocean ecosystems and causes harmful algal blooms (HABs). Information on the impacts of pollutants (cadmium, nickel, copper, mercury, lead, zinc, etc.) on the population dynamics, morphology, biochemical parameters, and photosynthetic activity of this group of microalgae is summarized. The resistance of dinoflagellates to heavy metals (HMs) is considered along with the mechanisms of impact of these substances on microalgae, in particular accumulation and toxicity, oxidative stress, inhibition of enzymatic activity, suppression of photosynthetic processes, and changes in cell morphology. The effects of HMs on ecosystem processes, including the exacerbation of HABs caused by dinoflagellates that produce dangerous toxins, are discussed.</p>