Seagrass habitat metabolism increases short-term extremes and long-term offset of CO 2 under future ocean acidification

Significance The impacts of ocean acidification in nearshore estuarine environments remain poorly characterized, despite these areas being some of the most ecologically important habitats in the global ocean. Here, we quantify how rising atmospheric CO2 from the years 1765 to 2100 alters high-frequency carbonate chemistry dynamics in an estuarine seagrass habitat. We find that increasing anthropogenic carbon reduces the ability of the system to buffer natural extremes in CO2 . This reduced buffering capacity leads to preferential amplification of naturally extreme low pH and high pCO2(s.w.) events above changes in average conditions, which outpace rates published for atmospheric and open-ocean CO2 change. Seagrass habitat metabolism drives these short-term extreme events, yet ultimately reduces organismal exposure to harmful conditions in future high-CO2 scenarios.