Influence of the dissolved organic matter features on the natural and experimental production levels of hydrogen peroxide (H2O2) in temperate Patagonian lakes

GARCÍA, PATRICA ELIZABETH; GEREA, MARINA; DIÉGUEZ, MARÍA DEL CARMEN

Congreso; ASLO Aquatic Science Virtual MEeting; 2021

ASLO

In the aquatic ecosystems, the dissolved organic matter (DOM) represents the mayor C reservoir, and it is strongly influence by climatic variables that varies the input, production and weathering within the system. The photo- and bio- degradation of DOM produces reactive intermediates substances, including the reactive oxygen species (ROS). Among aquatic environments these ROS can have a direct impact in the biogeochemistry cycles. One of the ROS with a traceable life is the hydrogen peroxide (H2O2). In natural aquatic ecosystems the characteristics of DOM can influence the natural variation of H2O2, due to it can act as source for H2O2 photo-production. Natural H2O2 levels range from 3 to 60 nM in deep lakes (Moreno East and Moreno West), with lower concentration found in Moreno West. The DOC concentration in the water column range from 0.33 to 0.45 mg L-1 in Moreno East and from 0.55 to 0.64 mg L-1 in Moreno West. Vertical H2O2 distribution levels displayed higher levels in the photic zone (surface to ~40 m) compared with the aphotic zone (40 m to ~100 m), supporting the idea of the H2O2-photoproduction. Laboratory experiments were performed in order to assess the abiotic (photoproduction) and the biotic (microbial) production in two contrasting seasons (autumn and summer). Both type of production reach higher levels in summer samples collected in the photic zone. DOM with higher humic content resulted more susceptible to both photo- and bio- degradation, displaying stronger signs of weathering.