The issue there was the sulphur emissions from power plants, industry, and so on. As a result of the research that was done, largely in freshwater systems and in terrestrial systems, it became clear that these emissions needed to be reduced. The response from industry and governments was to ensure that the products being burned had lower sulphuric levels. So that problem—I don't want to say it went away because it still exists in some areas—was significantly moderated. In terms of the impact on the ocean, hydrogen sulphide is one of the components of ocean acidification, but the main component is the increase in partial pressure of CO2.
On February 13th, 2018. See this statement in context.