Influence of dissolved organic matter (DOM) on the field and laboratory production of hydrogen peroxide (H2O2) in temperate deep lakes of Patagonia.

GARCÍA, P.E.; GEREA, M.; DIÉGUEZ, M.C.

Virtual

Congreso; Aquatic Sciences Meeting ASLO 2021; 2021

America Society of Limnology and Oceanography (ASLO)

In the aquatic environment, dissolved organic matter (DOM) represents a mayor C reservoir, and it is properties are shaped by climate variable which drive the amount and timing of allochthonous input, as well as the production and weathering within the system. Photo- and bio-degradation generate intermediate substances such as reactive oxygen species (ROS). Depending on their concentration and reactivity, these ROS may impact certain biogeochemical pathway. Hydrogen peroxide (H2O2) is a potent ROS with a traceable life. In aquatic systems, photochemical weathering of natural DOM can generate H2O2 and this production depends on DOM properties. In this study we assessed natural H2O2 levels in the water column of two connected deep ultraoligotrophic lakes, Moreno East (ME) and Moreno West (MW) of Patagonia. H2O2 levels ranged from 3 to 60 nM with lower values in MW whereas the DOC concentration in the water column ranged from 0.33 to 0.45 mg L-1 in ME and from 0.55 to 0.64 mg L-1 in MW. In both lakes, H2O2 concentration were higher in photic (surface to ~40 m) compared to aphotic (40 m to ~100 m) layers, reflecting the influence of photo-production. Laboratory experiments aimed to assess the abiotic (photoproduction) and biotic (microbial) production in surface and deep water samples collected in contrasting seasons (autumn and summer). Photo- and bio-production yielded higher levels of H2O2 in summer water samples of the photic zone of both lakes. DOM with higher humic content resulted more susceptible to both photo- and bio-degradation, displaying stronger signs of weathering.