Volcanic carbon cycling in East Lake, Newberry Volcano, Oregon, USA

The carbon cycle in East Lake (Newberry Volcano, Oregon, USA) is fueled by volcanic CO₂ inputs with traces of Hg and H₂S. The CO₂ dissolves in deep lake waters and is removed in shallow waters through largely diffusive surface degassing and photosynthesis. Escaping gas and photosynthate have low δ¹³C values, leading to δ¹³C(DIC) (DIC—dissolved inorganic carbon) as high as +5.7‰ in surface waters, well above the common global lake range. A steep δ¹³C depth gradient is further established by respiration and absorption of light volcanic CO₂ in bottom waters. The seasonal CO₂ degassing starts at >100 t CO₂/day after ice melting in the spring and declines to ∼40 t/day in late summer, degassing ∼11,700 t CO₂/yr. Thus, volcano monitoring through gas fluxes from crater lakes should consider lacustrine processes that modulate the volcanic gas output over time. The flux contribution of a bubbling CO₂ “hotspot” increased from 20% to >90% of the lake-wide CO₂ flux from 2015 to 2019 CE, followed by a “toxic gas alert” in July 2020. East Lake is an active volcanic lake with a “geogenic” ecosystem driven primarily by hydrothermal inputs.