Taylor Maavara

Editor’s summary River organisms are the most important influence on the transport of carbon and other nutrients from land to sea. These ecosystems have been considered predominantly net heterotrophic, but Maavara et al. reveal that the rivers of the continental US also display a broad range from extreme heterotrophy to autotrophy. Increases in riverine gross primary productivity are particularly sensitive to drought conditions, and more than 70% of river metabolism occurs in the western US.

Abstract Global seafood demand is increasing while oceans continue to receive substantial anthropogenic mercury, heightening concerns about the toxic methylmercury bioaccumulation in seafood. Presently, the fate of mercury in the ocean remains uncertain, hindering comprehensive assessments of marine mercury dynamics and seafood safety.

1 Introduction Methane (CH4) is a potent greenhouse gas contributing 35% of the greenhouse gas-driven warming in 2010–2019 relative to 1850–1900 (IPCC, 2021). Global mean atmospheric concentrations of methane have increased by 160% since pre-industrial levels (1750: 729 ppb; 2021: 1895 ppb) and the global annual increase rate was exceptionally high in 2020–2021 (18.3 ppb yr−1) (Dlugokencky, 2019).